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MICHAEL SHORT: I
wanted to give you guys

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a survey of radiation
utilizing technology

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00:00:26,012 --> 00:00:28,470
and tell you a little bit about
the way this department has

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changed the way it teaches.

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It used to be in our department
and probably everywhere else

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around the country
that first we teach you

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the theory of how things go
down and understand them,

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and then we can
teach you the context

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in which they're placed.

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This resulted in a rather boring
curriculum, in my opinion,

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having been one of
the ones that went

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through this actual curriculum.

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So for those who don't
know, I was an undergrad

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in this department.

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And while I learned a lot
of great things from folks,

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I also kept some mental notes
on what I would do differently,

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and now's the chance to do this.

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So instead, we've adopted
a context first theory

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second approach, which
means we tell you

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where we're going to show you
why should you pay attention

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00:01:05,489 --> 00:01:07,020
to the rest of the semester.

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Then we fill out the rest of
the theory and fill in the gaps

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and then revisit the context
to show you what you've learned

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and how you can understand it.

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That's why today is going
to be a rather light class.

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00:01:17,310 --> 00:01:20,257
So don't take any notes, just
listen, enjoy, ask questions.

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00:01:20,257 --> 00:01:22,590
And I'm going to show you
some of the applications where

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we use radiation and
the principles of NSE

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and technology today.

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And for recitation
today since we

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haven't gone over any
technical material,

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we're going to be
heading to my lab

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00:01:32,220 --> 00:01:34,890
to demonstrate one of these
things, a sputter coder which

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is a controlled system
for radiation damage

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00:01:37,410 --> 00:01:39,870
which applies one material
to the other via the process

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00:01:39,870 --> 00:01:43,980
of sputtering or actual nuclear
or ionic collisions that blast

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material, in this case,
gold, onto whatever

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you want to coat,
which in this case

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is a pile of pocket change.

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So we're going to make
some gold change today.

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So the motivation
today is really

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00:01:54,660 --> 00:01:57,720
to get over two questions
is how can radiation

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00:01:57,720 --> 00:02:01,170
be used for benefit and what
is the physics behind how

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it can be used?

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I'll be using a zircaloy fuel
rod, the same kinds that you'd

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see in a nuclear
reactor as the pointer

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because I'm not a fan of lasers.

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And this is actually
incredibly light.

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I can hold it out at the
end, not much visible shaking

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and I wanted you guys to see
and feel and try and bend

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what zircaloy actually is like.

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That's a piece the same diameter
and dimensions and stuff

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that you would see
in a nuclear reactor.

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So give it a slight bend.

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If you try really
hard, you can bend it.

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But notice how light it is.

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Notice how strong it is.

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It's about midway in density
between stainless steel

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and aluminum, but it's a hell
of a lot stronger than aluminum.

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It also has the added
benefit that it basically

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doesn't absorb neutrons.

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The real reason we use
zircaloys, zirconium alloys

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and reactors is that they
have very low interaction

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probabilities or cross-sections.

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And for those who don't know
what those are, in a couple

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of weeks we'll be defining
what a cross-section is.

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This stuff's pretty cool.

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Also what makes this
nuclear grade zircaloy

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and not just
regular zirconium is

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that there's no hafnium in it.

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Hafnium is chemically
very similar to zirconium,

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it also happens to be one of the
highest cross-section elements

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that there is.

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So you hide the
stuff that you need

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to be neutronically
transparent in reactors.

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It happens to be found in the
ground with the last thing

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you'd want in your
fuel cladding.

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In fact, you can use hafnium as
a control rod or control blade.

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So the difference in
chemistry and in cost

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between nuclear zirconium
what you've got there,

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and regular zirconium
is the hafnium

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has been taken out by some very
painful chemical separation.

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Usually you'd find
about 3% or 4% hafnium.

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So there's all sorts of
technologies that we use,

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the principles of nuclear
science and engineering.

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I'm just going to
say NSE from now on.

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You're all probably
pretty familiar with power

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and maybe familiar with
some of these other ones.

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00:03:52,240 --> 00:03:54,420
Like medical isotopes
are the backbone

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of a lot of imaging
techniques to find and treat

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00:03:57,240 --> 00:03:58,650
different maladies.

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Space is basically a giant
maelstrom of radiation

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so you can both use it and
have to shield from it.

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We'll go over some
of the crazier

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ways of shielding from space
radiation, actually today.

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Semiconductors.

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The way that the MIT
reactor made about 60%

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00:04:13,350 --> 00:04:15,600
of its operating
budget until recently

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00:04:15,600 --> 00:04:19,410
was by irradiating crystals of
silicon single, crystal bools

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or ingots of silicon, to
make what's called an n type

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semiconductor, via
the following reaction

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if I can find an eraser.

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I'm going to use the shorthand
that we talked about last time.

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Normally you would take
silicon and you add a neutron

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and you end up
forming phosphorus.

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I've not memorized the masses
of the isotope, but in the end

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this is actually a neutron
capture reaction, and then

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a resulting decay,
which produces

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phosphorus, which is what's
also known as an n type dopant.

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It's a sort of extra negative--

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what is it? --a
negative charge type

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00:05:03,830 --> 00:05:06,170
dopant that changes
the conductivity

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of the semiconductor.

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00:05:07,580 --> 00:05:10,280
There's lots of different
ways of doping semiconductors.

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One of the best
and most uniform is

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to stick things in the reactor.

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So back when silicon
ingots were smaller,

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like 4 or 6 inches
in diameter, there

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was a constant train of
these things traveling

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through the reactor
getting irradiated

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and being sold and then cut up
into wafers to make devices.

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And it used to be
students or Europe jobs

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to load and unload those
things from the reactor.

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Now, it's not that dangerous.

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As long as you use the
right handling procedures,

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like put them on a cart,
pull the cart at arm's length

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and push like that,
your dose is very low.

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And that's because for a
given point source emitter,

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the dose you receive drops off
as 1 over r or the distance

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00:05:46,700 --> 00:05:49,270
squared, which means
that your arm's length,

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let's say your arm
is about a meter,

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you can drop the
dose by quite a bit

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compared to what's
called the contact dose.

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Well, this poor fool held
the silicon ingots up

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to their chests like that.

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They were OK.

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They got about 10 months
of their yearly allowable

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radiation dose that won't induce
any additional risk of cancer.

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But to ensure that they would
not exceed that allowable dose,

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they became the administrative
assistant for the reactor

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for the next 10 months.

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So their job at the
reactor was to answer

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the phone, which is not
a radioactive activity,

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including at the reactor.

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First nuclear power.

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The reason why I know a
number of you guys are here

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is pretty simple.

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It's just a hot bucket of water.

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The way we make that
bucket of water hot

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is by putting uranium or other
fuel into these rods assembling

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a lot of them in a small
space where they then heat up

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by producing nuclear
fission, capturing

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the resultant kinetic energy
of the fission products

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and neutrons and everything
else that comes out

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and using it to either
heat up or boil water,

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that's then just driven through
a heat exchanger and a turbine.

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So aside from
everything on this side,

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it looks basically like any
other water cooled power plant.

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The difference is things get
toasty in a radioactive sense,

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but also pretty
well under control.

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And what's inside a reactor--

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if you say this is the diagram
of a typical Pressurized Water

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Reactor or PWR where the
water is pressurized enough so

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as to stop boiling
from occurring, keeping

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the water liquid which has a
number of safety implications,

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you've got the core of
the reactor right here--

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and these things right here
are called steam generators.

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It's nothing more than a heat
exchanger that generates steam.

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--and the steam generated in
here goes off somewhere else

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and drives the turbine.

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If you look inside
this reactor you'll

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notice a lot of different
fuel assemblies or fuel rods,

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including things like control
rods or shut down rods,

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rods made of neutron
absorbers like hafnium

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that we talked about,
or gadolinium or boron

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4 carbide or any other
material with a high capture

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cross-section, meaning a high
probability for capturing

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a neutron rather than
letting it go from one fuel

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00:07:59,030 --> 00:08:01,550
element to another to
produce more fission,

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00:08:01,550 --> 00:08:03,380
to produce more heat.

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That's effectively
how a reactor works.

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00:08:06,427 --> 00:08:08,260
So we went over a little
bit about the fuel.

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The fission and the
energetics is kind of cool.

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So let's say you start
off with uranium,

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00:08:15,730 --> 00:08:20,010
probably the
fissile isotope 235,

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and you send in one neutron--

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think it's 92.

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Don't quote me on that though.

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--and instead of undergoing
some sort of a capture reaction

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or something else, it can
split into what we call

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different fission products.

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And plus, anywhere
between two or three

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neutrons the usually
accepted number

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is an average of about 2.44
neutrons plus gamma rays,

202
00:08:47,090 --> 00:08:52,160
plus antineutrinos,
plus other energy

203
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and some occasional other stuff.

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The main point here is
these fission products--

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if let's say you had
a uranium nucleus

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and it were to split in
half, fission products

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00:09:02,680 --> 00:09:06,940
go in other directions,
they carry with them

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00:09:06,940 --> 00:09:08,665
quite a lot of kinetic energy.

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00:09:08,665 --> 00:09:11,290
And what we'll be doing a lot in
the second half of this course

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00:09:11,290 --> 00:09:15,070
is watching to see how do
these highly energetic nuclei

211
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or atoms--

212
00:09:15,877 --> 00:09:17,710
when they slam into
other atoms, how quickly

213
00:09:17,710 --> 00:09:18,970
do they lose energy?

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00:09:18,970 --> 00:09:20,800
How far do they tend to go?

215
00:09:20,800 --> 00:09:23,890
These fission products
tend to stop in the fuel.

216
00:09:23,890 --> 00:09:26,680
Their range is going to be
on the order of nanometers.

217
00:09:26,680 --> 00:09:29,020
I don't even think
it reaches microns.

218
00:09:29,020 --> 00:09:30,850
But the neutrons
however, as we saw

219
00:09:30,850 --> 00:09:32,800
from looking at
Chadwick's paper,

220
00:09:32,800 --> 00:09:35,500
they can go pretty far,
usually on the order

221
00:09:35,500 --> 00:09:38,710
of around 10 centimeters
in a reactor before they

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00:09:38,710 --> 00:09:39,610
go do something else.

223
00:09:39,610 --> 00:09:42,640
So it might make it
a few fuel rods over,

224
00:09:42,640 --> 00:09:46,720
and chances are get captured by
another uranium nucleus making

225
00:09:46,720 --> 00:09:50,620
more fission, more neutrons,
and some other fun stuff

226
00:09:50,620 --> 00:09:53,680
like gamma rays and neutrinos.

227
00:09:53,680 --> 00:09:56,690
Anyone not know
what a neutrino is?

228
00:09:56,690 --> 00:09:59,950
So a neutrino is a
very, very low mass

229
00:09:59,950 --> 00:10:04,120
but not massless as was found
I think like last year; almost

230
00:10:04,120 --> 00:10:05,800
speed of light particle
that's released

231
00:10:05,800 --> 00:10:07,870
as part of radioactive decay.

232
00:10:07,870 --> 00:10:10,060
They basically don't
interact with matter,

233
00:10:10,060 --> 00:10:12,010
but once in a while they do.

234
00:10:12,010 --> 00:10:13,978
What that means is that
they travel straight

235
00:10:13,978 --> 00:10:14,770
through everything.

236
00:10:14,770 --> 00:10:16,930
It's been estimated that
trillions of neutrinos

237
00:10:16,930 --> 00:10:19,480
from space are passing
through us per second

238
00:10:19,480 --> 00:10:21,850
and on average you won't
get a single interaction

239
00:10:21,850 --> 00:10:22,960
during a day.

240
00:10:22,960 --> 00:10:25,000
In fact, to detect
neutrinos they've

241
00:10:25,000 --> 00:10:27,460
had to fill old hollowed
out salt mines with water

242
00:10:27,460 --> 00:10:30,340
and fill them with photo
tubes in the hopes of catching

243
00:10:30,340 --> 00:10:31,780
two or three a day.

244
00:10:31,780 --> 00:10:34,210
What that means is if
someone turns on a reactor

245
00:10:34,210 --> 00:10:36,670
somewhere anywhere
in the world, it's

246
00:10:36,670 --> 00:10:39,005
releasing tons and
tons of neutrinos

247
00:10:39,005 --> 00:10:40,630
and if all of a sudden
you start to see

248
00:10:40,630 --> 00:10:42,640
two or three coming from
the same place, that's

249
00:10:42,640 --> 00:10:43,990
a rare event.

250
00:10:43,990 --> 00:10:46,600
That's something with some
statistical significance.

251
00:10:46,600 --> 00:10:50,470
And there's been projects in
our department using neutrino

252
00:10:50,470 --> 00:10:53,500
detectors to try and detect
where reactors are turning

253
00:10:53,500 --> 00:10:55,030
on anywhere in the world.

254
00:10:56,070 --> 00:10:58,660
So we've been able to sense that
the MIT reactor is next door

255
00:10:58,660 --> 00:10:59,827
from the building next door.

256
00:10:59,827 --> 00:11:01,827
I don't know how well
this is going to work when

257
00:11:01,827 --> 00:11:03,430
you get to farther distances.

258
00:11:03,430 --> 00:11:06,040
But the physics is
pretty much there.

259
00:11:06,040 --> 00:11:08,660
It's an engineering problem
to figure out, well,

260
00:11:08,660 --> 00:11:11,020
how do you detect
enough neutrinos to get

261
00:11:11,020 --> 00:11:13,210
a statistically
significant signal?

262
00:11:13,210 --> 00:11:15,760
That, far as I know,
has not been solved.

263
00:11:15,760 --> 00:11:19,120
Hopefully, by this
time next year it will.

264
00:11:19,120 --> 00:11:20,910
There's also control rods--

265
00:11:20,910 --> 00:11:23,680
rods filled with absorbers,
like I mentioned before.

266
00:11:23,680 --> 00:11:26,310
If you want to stop
this nuclear reaction,

267
00:11:26,310 --> 00:11:30,420
you send in something like
hafnium or gadolinium or boron.

268
00:11:30,420 --> 00:11:33,960
So let's say, Boron-11,
like Chadwick knew,

269
00:11:33,960 --> 00:11:36,888
would be able to
capture a neutron.

270
00:11:36,888 --> 00:11:39,180
And then it would turn into--
what's the next one over?

271
00:11:39,180 --> 00:11:40,300
Well, sorry.

272
00:11:40,300 --> 00:11:42,270
That's a one and a zero.

273
00:11:42,270 --> 00:11:43,800
That's a five.

274
00:11:43,800 --> 00:11:46,140
That should turn into carbon-12.

275
00:11:46,140 --> 00:11:48,420
And then you've
captured the neutron

276
00:11:48,420 --> 00:11:50,730
instead of letting it
get into more uranium

277
00:11:50,730 --> 00:11:52,465
and cause additional fissions.

278
00:11:52,465 --> 00:11:54,090
So when something's
going wrong, or you

279
00:11:54,090 --> 00:11:56,250
want to control the power
level in the reactor,

280
00:11:56,250 --> 00:11:58,360
you insert control rods.

281
00:11:58,360 --> 00:12:00,090
They soak up the
neutrons, and make

282
00:12:00,090 --> 00:12:01,770
the reactor go subcritical.

283
00:12:01,770 --> 00:12:05,160
And we'll go over what all
these words mean in due time--

284
00:12:05,160 --> 00:12:07,350
various points in the course.

285
00:12:07,350 --> 00:12:09,510
There's also coolant and
what's called moderation.

286
00:12:09,510 --> 00:12:13,030
Does anyone know what I mean
by moderation of neutrons?

287
00:12:13,030 --> 00:12:14,012
Yeah?

288
00:12:14,012 --> 00:12:14,720
What do you mean?

289
00:12:14,720 --> 00:12:17,102
AUDIENCE: It thermalizes them.

290
00:12:17,102 --> 00:12:18,560
MICHAEL SHORT: It
thermalizes them.

291
00:12:18,560 --> 00:12:20,870
And in other words,
it slows them down.

292
00:12:20,870 --> 00:12:24,230
Because the probability
that each uranium nucleus

293
00:12:24,230 --> 00:12:28,200
can capture a neutron depends
on the energy of the neutron.

294
00:12:28,200 --> 00:12:29,900
The cross sections
for interaction,

295
00:12:29,900 --> 00:12:33,860
which we give the symbol sigma
for the microscopic or sort

296
00:12:33,860 --> 00:12:37,000
of mass independent
cross section,

297
00:12:37,000 --> 00:12:38,240
they're functions of energy.

298
00:12:38,240 --> 00:12:40,970
They're extremely strong
functions of energy,

299
00:12:40,970 --> 00:12:43,310
over the energy ranges
we're interested in.

300
00:12:43,310 --> 00:12:46,640
Because we're interested in an
extremely large energy range.

301
00:12:46,640 --> 00:12:49,985
These neutrons tend to be
born at around 1 to 10 MeV,

302
00:12:49,985 --> 00:12:51,770
or Megaelectron Volts.

303
00:12:51,770 --> 00:12:54,980
And by the time they thermalize,
like you said, or reach roughly

304
00:12:54,980 --> 00:12:57,950
room temperature, kinetic
energy is of about 2,200 meters

305
00:12:57,950 --> 00:13:00,590
per second, they can be--

306
00:13:00,590 --> 00:13:05,690
what is it-- a 40th or 0.025 eV,
fraction of an electron volt.

307
00:13:05,690 --> 00:13:09,620
So we're interested in nine
orders of magnitude of energy.

308
00:13:09,620 --> 00:13:11,960
And the cross
sections vary wildly

309
00:13:11,960 --> 00:13:13,860
over these nine
orders of magnitude.

310
00:13:13,860 --> 00:13:16,970
And I'll show you what some of
these look like pretty soon.

311
00:13:16,970 --> 00:13:19,220
And in this case, in the
case of light water reactors,

312
00:13:19,220 --> 00:13:22,190
like the PWR we saw, the
coolant and the moderator

313
00:13:22,190 --> 00:13:24,560
are basically the same thing.

314
00:13:24,560 --> 00:13:26,780
You guys remember how when
Chadwick put the paraffin

315
00:13:26,780 --> 00:13:29,270
in front of the neutron
source, he started

316
00:13:29,270 --> 00:13:31,310
to see more ionizations.

317
00:13:31,310 --> 00:13:34,280
That's because the paraffin
is a great source of hydrogen.

318
00:13:34,280 --> 00:13:35,880
So is water.

319
00:13:35,880 --> 00:13:37,580
Water is an ideal
coolant because it

320
00:13:37,580 --> 00:13:40,790
takes a lot of energy to heat
it up, and a lot to boil it.

321
00:13:40,790 --> 00:13:43,250
So you can store a lot of energy
with less of a temperature

322
00:13:43,250 --> 00:13:44,360
difference in water.

323
00:13:44,360 --> 00:13:48,050
And it's full of hydrogen.
And kinematically, it's

324
00:13:48,050 --> 00:13:51,950
easier for something
the size of a neutron

325
00:13:51,950 --> 00:13:56,150
and the mass of a neutron
to slow a neutron down.

326
00:13:56,150 --> 00:13:58,040
Because a neutron
hitting a proton

327
00:13:58,040 --> 00:14:01,880
can transfer up to all of
its energy ballistically.

328
00:14:01,880 --> 00:14:04,910
Then that proton won't move
very far because it's also

329
00:14:04,910 --> 00:14:07,990
got charge on it.

330
00:14:07,990 --> 00:14:09,640
If a neutron hits
something heavier,

331
00:14:09,640 --> 00:14:12,010
like stainless steel or
other stuff in the reactor,

332
00:14:12,010 --> 00:14:14,740
it cannot, by conservation
of energy and momentum,

333
00:14:14,740 --> 00:14:16,300
transfer all of its energy.

334
00:14:16,300 --> 00:14:18,800
That fraction is
actually pretty small.

335
00:14:18,800 --> 00:14:19,712
So you'll see.

336
00:14:19,712 --> 00:14:21,670
We'll actually calculate
what that fraction is.

337
00:14:21,670 --> 00:14:24,430
But it drops off
pretty precipitously

338
00:14:24,430 --> 00:14:26,860
as you start to get
heavier than hydrogen.

339
00:14:26,860 --> 00:14:29,530
And finally, there's
reflection and shielding.

340
00:14:29,530 --> 00:14:32,080
We'll get into shielding
in terms of how much stuff

341
00:14:32,080 --> 00:14:34,840
and how much matter does
it take to stop radiation

342
00:14:34,840 --> 00:14:36,190
from getting through.

343
00:14:36,190 --> 00:14:38,200
In some cases, you
can stop it all.

344
00:14:38,200 --> 00:14:41,320
In some cases, like gammas,
you technically never can.

345
00:14:41,320 --> 00:14:44,260
You'll just get what's called
attenuation or continuous

346
00:14:44,260 --> 00:14:45,940
removal of gamma rays.

347
00:14:45,940 --> 00:14:48,430
But chances are, you can't
remove every single photon

348
00:14:48,430 --> 00:14:49,420
from getting out.

349
00:14:49,420 --> 00:14:53,028
It's only a matter of how much
do you need it to get down to.

350
00:14:53,028 --> 00:14:54,070
And there's a neat aside.

351
00:14:54,070 --> 00:14:58,228
Who here has looked down into
a nuclear reactor before?

352
00:14:58,228 --> 00:14:58,770
Three of you.

353
00:14:58,770 --> 00:14:58,970
Wow.

354
00:14:58,970 --> 00:14:59,470
Four.

355
00:14:59,470 --> 00:15:00,300
OK.

356
00:15:00,300 --> 00:15:02,385
What did you see?

357
00:15:02,385 --> 00:15:03,385
AUDIENCE: Not that much.

358
00:15:03,385 --> 00:15:04,593
MICHAEL SHORT: Not that much.

359
00:15:04,593 --> 00:15:06,270
This is a particularly
powerful reactor

360
00:15:06,270 --> 00:15:08,820
known as the Advanced
Test Reactor, or ATR,

361
00:15:08,820 --> 00:15:10,545
at the Idaho
National Laboratory.

362
00:15:10,545 --> 00:15:12,420
You won't see any others
that look like this.

363
00:15:12,420 --> 00:15:15,270
One, because these
crazy-shaped fuel elements

364
00:15:15,270 --> 00:15:16,980
are not that easy to make.

365
00:15:16,980 --> 00:15:19,290
This is a test or
a research reactor

366
00:15:19,290 --> 00:15:20,460
where things get irradiated.

367
00:15:20,460 --> 00:15:22,740
It's about 125 megawatts.

368
00:15:22,740 --> 00:15:24,450
And the blue light
being produced

369
00:15:24,450 --> 00:15:27,450
is called Cherenkov radiation.

370
00:15:27,450 --> 00:15:30,840
It's from electrons
and things moving,

371
00:15:30,840 --> 00:15:33,390
or beta particles,
electrons, moving faster

372
00:15:33,390 --> 00:15:35,682
than the speed of
light in water.

373
00:15:35,682 --> 00:15:37,890
Now, as you know, you can't
exceed the speed of light

374
00:15:37,890 --> 00:15:39,240
in a vacuum.

375
00:15:39,240 --> 00:15:41,520
But things can move
through other media

376
00:15:41,520 --> 00:15:44,640
faster than the speed of light
in that medium, effectively

377
00:15:44,640 --> 00:15:47,400
producing optical
shock waves given off

378
00:15:47,400 --> 00:15:50,250
as little blue cones of
light for each particle.

379
00:15:50,250 --> 00:15:52,197
So when folks say, oh,
am I going to go green

380
00:15:52,197 --> 00:15:53,280
when I get near radiation?

381
00:15:53,280 --> 00:15:56,870
You can say, no,
you'll glow blue.

382
00:15:56,870 --> 00:16:00,130
They've just got the wrong
color on all the TV shows.

383
00:16:00,130 --> 00:16:01,520
And then onto fusion energy.

384
00:16:01,520 --> 00:16:03,640
Since most of us tend
to talk about fission

385
00:16:03,640 --> 00:16:05,432
a lot of the time, but
how many of you here

386
00:16:05,432 --> 00:16:08,150
are interested in
going into fusion?

387
00:16:08,150 --> 00:16:09,890
Usually, it's at
least half the class.

388
00:16:09,890 --> 00:16:13,985
And so I figured this used to
be a fairly fission-centric

389
00:16:13,985 --> 00:16:15,360
teaching style in
the department.

390
00:16:15,360 --> 00:16:17,180
And I think fusion
deserves equal time.

391
00:16:17,180 --> 00:16:18,680
Because about an
equal number of you

392
00:16:18,680 --> 00:16:20,930
want to go into fusion
to make it a reality.

393
00:16:20,930 --> 00:16:23,960
These reactors are laid
out fairly differently.

394
00:16:23,960 --> 00:16:26,660
What they'll be is a big,
hollow vacuum chamber

395
00:16:26,660 --> 00:16:29,030
that's shaped like
a donut or a torus,

396
00:16:29,030 --> 00:16:33,020
and lots of magnets
to confine a plasma

397
00:16:33,020 --> 00:16:36,530
or sort of a charged mess of
separated ions and electrons

398
00:16:36,530 --> 00:16:39,590
that whirls around in
millions of meters per second.

399
00:16:39,590 --> 00:16:43,130
Once in a while, these ions
and electrons, or especially

400
00:16:43,130 --> 00:16:45,620
these nuclei, will
collide with each other

401
00:16:45,620 --> 00:16:48,950
and undergo a fusion reaction,
or one of a few fusion

402
00:16:48,950 --> 00:16:51,450
reactions that I've
written up here for you.

403
00:16:51,450 --> 00:16:54,770
So in this case, there's no
elements with a symbol d or t.

404
00:16:54,770 --> 00:16:57,770
We're just using those to
refer to deuterium or tritium

405
00:16:57,770 --> 00:16:58,670
as a visual aid.

406
00:16:58,670 --> 00:17:00,920
But you should know that
they're deuterium and tritium

407
00:17:00,920 --> 00:17:03,560
from their atomic numbers.

408
00:17:03,560 --> 00:17:06,050
One, which means it's
an isotope of hydrogen.

409
00:17:06,050 --> 00:17:07,740
And their mass
numbers, two and three,

410
00:17:07,740 --> 00:17:11,200
which is not the mass
number for normal hydrogen.

411
00:17:11,200 --> 00:17:14,270
And in this case, when you
fuse deuterium and tritium,

412
00:17:14,270 --> 00:17:17,150
you can produce helium
and another neutron.

413
00:17:17,150 --> 00:17:19,430
And so then those
neutrons can be

414
00:17:19,430 --> 00:17:21,980
used to hit lithium,
which they'll usually

415
00:17:21,980 --> 00:17:25,260
have in what's called a breeder
blanket around the outside,

416
00:17:25,260 --> 00:17:27,589
which releases more tritium.

417
00:17:27,589 --> 00:17:30,740
So fusion reactors actually
can produce their own fuel.

418
00:17:30,740 --> 00:17:33,830
The trick is they're
radioactive gases, so containing

419
00:17:33,830 --> 00:17:36,140
them can be kind of tricky.

420
00:17:36,140 --> 00:17:40,220
You also need a way to get
the helium out of the reactor.

421
00:17:40,220 --> 00:17:42,020
But we have one of
these on campus.

422
00:17:42,020 --> 00:17:44,150
We have one of the only
three in the country.

423
00:17:44,150 --> 00:17:45,470
It's called the Alcator C-Mod.

424
00:17:45,470 --> 00:17:49,030
Have any of you guys seen
a tour of this place yet?

425
00:17:49,030 --> 00:17:49,870
Almost all of you.

426
00:17:49,870 --> 00:17:52,540
So for ever who hasn't,
do it this year.

427
00:17:52,540 --> 00:17:55,090
Because this may be the
last year of Alcator C-Mod's

428
00:17:55,090 --> 00:17:56,120
operation.

429
00:17:56,120 --> 00:17:58,120
That's not to say there
won't be the next fusion

430
00:17:58,120 --> 00:18:00,710
device on campus, but
there's one here right now.

431
00:18:00,710 --> 00:18:03,140
And it might be a while
before the next one's built.

432
00:18:03,140 --> 00:18:06,100
So if you haven't seen it yet,
go and see it this semester,

433
00:18:06,100 --> 00:18:08,440
definitely.

434
00:18:08,440 --> 00:18:10,090
The reason why
fission and fusion

435
00:18:10,090 --> 00:18:12,940
work from an
energetic standpoint,

436
00:18:12,940 --> 00:18:16,240
is if we look at the
binding energy per nucleon--

437
00:18:16,240 --> 00:18:19,510
remember, last time we
mentioned the binding energy

438
00:18:19,510 --> 00:18:20,720
is the difference in energy.

439
00:18:20,720 --> 00:18:24,610
If you were to take, let's
say, a proton and a neutron

440
00:18:24,610 --> 00:18:29,050
from infinitely far away,
and bring them together

441
00:18:29,050 --> 00:18:31,910
to create a nucleus
of deuterium--

442
00:18:34,850 --> 00:18:37,440
we'll call this D--

443
00:18:37,440 --> 00:18:40,400
these two, the
energy of the proton

444
00:18:40,400 --> 00:18:43,940
plus the energy of the neutron,
the rest mass energies, rather,

445
00:18:43,940 --> 00:18:46,820
would be greater than the
energy of just deuterium.

446
00:18:46,820 --> 00:18:48,770
And that little bit
of mass that's changed

447
00:18:48,770 --> 00:18:49,880
is converted into energy.

448
00:18:49,880 --> 00:18:52,250
And this is what's known
as the binding energy.

449
00:18:52,250 --> 00:18:54,860
If we look at the binding
energy per nucleon

450
00:18:54,860 --> 00:18:57,200
or per proton or
neutron, we can get

451
00:18:57,200 --> 00:19:02,000
a relative ranking of how
tightly bound each nucleus is.

452
00:19:02,000 --> 00:19:04,550
So for the light
isotopes, smashing

453
00:19:04,550 --> 00:19:08,140
them together should liberate
excess binding energy--

454
00:19:08,140 --> 00:19:10,880
or sorry, excess energy--
because you'll gain

455
00:19:10,880 --> 00:19:15,050
back some of that energy by the
conversion of mass to energy.

456
00:19:15,050 --> 00:19:17,720
Same thing over on this
side, just not as extreme

457
00:19:17,720 --> 00:19:18,900
of a gradient.

458
00:19:18,900 --> 00:19:21,000
If you were to split
apart heavy nuclei,

459
00:19:21,000 --> 00:19:25,370
like uranium-235, you can
release a little bit of energy

460
00:19:25,370 --> 00:19:26,420
in fission.

461
00:19:26,420 --> 00:19:28,400
And once you get
up here to iron,

462
00:19:28,400 --> 00:19:30,590
you can't go either
way, which is

463
00:19:30,590 --> 00:19:33,200
why, if you think about the
biggest fusion reactors that

464
00:19:33,200 --> 00:19:36,133
exist in the universe--
anyone know what they are?

465
00:19:36,133 --> 00:19:36,800
AUDIENCE: Stars.

466
00:19:36,800 --> 00:19:38,330
MICHAEL SHORT: Stars, right.

467
00:19:38,330 --> 00:19:40,340
They tend to hit cores
of iron before they

468
00:19:40,340 --> 00:19:42,920
either die out or
go all gravity crazy

469
00:19:42,920 --> 00:19:45,140
and become black
holes of supernovas,

470
00:19:45,140 --> 00:19:46,310
or whatever you will.

471
00:19:46,310 --> 00:19:48,170
This is kind of
the energetic limit

472
00:19:48,170 --> 00:19:50,300
for normal nuclear processes.

473
00:19:50,300 --> 00:19:51,800
Or if they become
a neutron star,

474
00:19:51,800 --> 00:19:54,680
then things get beyond
the scope of this course.

475
00:19:54,680 --> 00:19:57,840
I won't be explaining
neutron stars.

476
00:19:57,840 --> 00:19:59,718
There's a lot of medical
uses of radiation.

477
00:19:59,718 --> 00:20:02,010
I don't know if any of you
guys have seen these things.

478
00:20:02,010 --> 00:20:04,830
It's the only time I'll show
a tricky looking biology

479
00:20:04,830 --> 00:20:07,740
diagram, because it's kind
of interesting to note.

480
00:20:07,740 --> 00:20:10,020
These are what's called
brachytherapy seeds,

481
00:20:10,020 --> 00:20:13,440
little seeds of isotopes
that remit a certain type

482
00:20:13,440 --> 00:20:16,650
and energy of radiation selected
for their applicability,

483
00:20:16,650 --> 00:20:19,170
that can be implanted in the
body at the site of a tumor

484
00:20:19,170 --> 00:20:22,380
to deliver localized
radiation treatment.

485
00:20:22,380 --> 00:20:25,240
You can either go in through
existing ports on the human,

486
00:20:25,240 --> 00:20:27,660
and not having to drill
or cut a hole in someone,

487
00:20:27,660 --> 00:20:30,358
or they can be implanted
laparoscopically or surgically.

488
00:20:30,358 --> 00:20:32,400
So this way, if you don't
want to subject someone

489
00:20:32,400 --> 00:20:35,400
to a whole body radiation
dose or chemotherapy,

490
00:20:35,400 --> 00:20:38,340
or if you want to use it in
conjunction with chemotherapy,

491
00:20:38,340 --> 00:20:41,370
you can implant a tiny little
seed of a radioactive material

492
00:20:41,370 --> 00:20:44,040
in there to deliver a
certain dose to a tumor,

493
00:20:44,040 --> 00:20:45,330
and then take it out.

494
00:20:45,330 --> 00:20:47,250
And that way you
know very, very well

495
00:20:47,250 --> 00:20:49,830
what the dose is going to
be, because you can measure

496
00:20:49,830 --> 00:20:52,710
the activity or the number
of decays per second

497
00:20:52,710 --> 00:20:54,570
of that brachytherapy seed.

498
00:20:54,570 --> 00:20:56,830
And you know how it's
going to change over time.

499
00:20:56,830 --> 00:20:58,830
Because you know the
half-life of the particular

500
00:20:58,830 --> 00:21:01,290
isotope that you've looked at.

501
00:21:01,290 --> 00:21:03,180
There's also things
like imaging.

502
00:21:03,180 --> 00:21:05,850
You can have someone
ingest an isotope

503
00:21:05,850 --> 00:21:10,260
like technetium-99 metastable,
to highlight certain organs

504
00:21:10,260 --> 00:21:11,910
or things in the body
that you can then

505
00:21:11,910 --> 00:21:15,788
image later by their decay
gamma rays or other phenomena.

506
00:21:15,788 --> 00:21:18,330
It's also one of those reasons
why when you go in an airport,

507
00:21:18,330 --> 00:21:20,538
you have to tell them if
you've had a medical imaging

508
00:21:20,538 --> 00:21:21,540
procedure.

509
00:21:21,540 --> 00:21:23,910
Because a lot of these places
have radiation detectors.

510
00:21:23,910 --> 00:21:27,120
And if you are radioactive
and don't identify yourself,

511
00:21:27,120 --> 00:21:29,070
you will quickly be
identified and taken

512
00:21:29,070 --> 00:21:30,910
into the back room
to the probulator,

513
00:21:30,910 --> 00:21:32,910
or whatever they're going
to do at the airports.

514
00:21:32,910 --> 00:21:33,452
I don't know.

515
00:21:33,452 --> 00:21:36,540
I've never been searched I
don't plan on that happening.

516
00:21:36,540 --> 00:21:38,490
There's also X-ray
and proton therapy

517
00:21:38,490 --> 00:21:43,020
sending in well-known, well
energy-characterized radiation

518
00:21:43,020 --> 00:21:45,120
to fry tumors or other things.

519
00:21:45,120 --> 00:21:48,510
In the case of X-rays,
you're relying on what's

520
00:21:48,510 --> 00:21:50,700
called exponential attenuation.

521
00:21:50,700 --> 00:21:53,520
If you look at the
distance into a material,

522
00:21:53,520 --> 00:21:56,060
and you look at the
intensity of the X-rays--

523
00:21:58,880 --> 00:22:04,410
say, at x equals zero,
this is your X-ray source.

524
00:22:04,410 --> 00:22:06,930
This is your incoming intensity.

525
00:22:06,930 --> 00:22:10,615
It falls off exponentially
with distance.

526
00:22:10,615 --> 00:22:12,240
You might then ask
yourself, all right,

527
00:22:12,240 --> 00:22:16,290
if my tumor is this deep, and
I apply that radiation dose

528
00:22:16,290 --> 00:22:19,842
to the tumor, what
about the rest?

529
00:22:19,842 --> 00:22:21,800
What about the part of
the body that the X-rays

530
00:22:21,800 --> 00:22:25,670
have to travel through in
order to get to that site?

531
00:22:25,670 --> 00:22:28,070
Anyone know how you would
deliver more X-rays to a tumor

532
00:22:28,070 --> 00:22:31,190
than the surrounding tissue?

533
00:22:31,190 --> 00:22:32,362
Anyone have any ideas?

534
00:22:32,362 --> 00:22:32,862
Yeah?

535
00:22:32,862 --> 00:22:34,410
AUDIENCE: Go from
different angles

536
00:22:34,410 --> 00:22:36,362
so the rays intersect
on the tumor.

537
00:22:36,362 --> 00:22:37,320
MICHAEL SHORT: Exactly.

538
00:22:37,320 --> 00:22:39,570
Go from different
angles so the rays

539
00:22:39,570 --> 00:22:41,490
would intersect on the tumor.

540
00:22:41,490 --> 00:22:45,570
I'll have a better diagram,
but I'll draw one for now.

541
00:22:45,570 --> 00:22:49,900
Let's say, that's the
eyes and that's the tumor.

542
00:22:49,900 --> 00:22:53,200
You can wear this helmet
where X-rays can come in

543
00:22:53,200 --> 00:22:55,970
from all different angles.

544
00:22:55,970 --> 00:22:58,480
And the X-ray emitter
would have to come in

545
00:22:58,480 --> 00:23:01,630
from different angles, so that
as all the rays intersect,

546
00:23:01,630 --> 00:23:05,225
this part gets fried the
most, while keeping you

547
00:23:05,225 --> 00:23:07,600
from getting too much radiation
to the rest of your brain

548
00:23:07,600 --> 00:23:09,890
and ceasing to function.

549
00:23:09,890 --> 00:23:11,110
There's also radio tracers.

550
00:23:11,110 --> 00:23:13,670
I think I already covered those.

551
00:23:13,670 --> 00:23:16,540
So imaging, we already showed an
image of what this looks like.

552
00:23:16,540 --> 00:23:19,545
The first X-ray
back in 1895 didn't

553
00:23:19,545 --> 00:23:20,920
have that good
resolution, but it

554
00:23:20,920 --> 00:23:22,503
was kind of striking
in that you could

555
00:23:22,503 --> 00:23:25,300
see the difference in contrast
between bones and tissue.

556
00:23:25,300 --> 00:23:27,610
I should replace this
with the X-ray of my foot

557
00:23:27,610 --> 00:23:30,220
that was my signing
bonus at MIT.

558
00:23:30,220 --> 00:23:32,200
My first day on
the job I went down

559
00:23:32,200 --> 00:23:35,080
to clean one of the old
rooms in Northwest 13,

560
00:23:35,080 --> 00:23:36,820
which is now where my labs are.

561
00:23:36,820 --> 00:23:38,530
And I moved a bunch
of boxes aside,

562
00:23:38,530 --> 00:23:43,000
and a 200-pound steel plate,
jagged cut with plasma torch,

563
00:23:43,000 --> 00:23:45,580
went down and smashed down
on the bones in my foot.

564
00:23:45,580 --> 00:23:49,400
And I had one of those temporary
feats of superhuman strength

565
00:23:49,400 --> 00:23:50,525
and was able to lift it up.

566
00:23:50,525 --> 00:23:53,108
I went back to try to lift it
up and couldn't move it an inch.

567
00:23:53,108 --> 00:23:54,790
I don't know how I
got out of the plate.

568
00:23:54,790 --> 00:23:57,130
The next thing I remember,
I was crawling up the stairs

569
00:23:57,130 --> 00:23:58,750
to go to the hospital.

570
00:23:58,750 --> 00:24:00,580
But I did get an
X-ray, and they were

571
00:24:00,580 --> 00:24:02,380
able to sense that
the pain in my foot

572
00:24:02,380 --> 00:24:03,850
was due to a hairline fracture.

573
00:24:03,850 --> 00:24:06,730
It was like a fracture in the
bones that basically came back

574
00:24:06,730 --> 00:24:07,700
together.

575
00:24:07,700 --> 00:24:10,900
But the improvement in
contrast resolution in X-rays

576
00:24:10,900 --> 00:24:12,370
is what differentiates
the ability

577
00:24:12,370 --> 00:24:14,920
to see a hairline fracture
from just the ability

578
00:24:14,920 --> 00:24:16,420
to see that you contain bones.

579
00:24:18,970 --> 00:24:20,620
And the reason for
this, and we'll

580
00:24:20,620 --> 00:24:22,960
be looking at a lot of
these curves in this course,

581
00:24:22,960 --> 00:24:26,110
is the differential absorption
or attenuation of X-rays,

582
00:24:26,110 --> 00:24:28,990
or any photons of any energy
through different types

583
00:24:28,990 --> 00:24:30,225
of matter.

584
00:24:30,225 --> 00:24:31,600
And so, for example,
here we have

585
00:24:31,600 --> 00:24:34,930
the ICRU standardized
average soft tissue

586
00:24:34,930 --> 00:24:37,960
attenuation, as well as bone.

587
00:24:37,960 --> 00:24:40,060
And you notice that
there's a few differences

588
00:24:40,060 --> 00:24:40,750
in these curves.

589
00:24:40,750 --> 00:24:43,747
So also, there's
some similarities.

590
00:24:43,747 --> 00:24:45,830
I'll note that these
actually have the same access

591
00:24:45,830 --> 00:24:48,410
to the same units.

592
00:24:48,410 --> 00:24:51,365
What do you guys notice that's
the same about these curves?

593
00:24:57,830 --> 00:24:59,360
How about the value?

594
00:24:59,360 --> 00:25:01,820
They're basically the same--

595
00:25:01,820 --> 00:25:05,090
mass averaged with very
little differences.

596
00:25:05,090 --> 00:25:08,930
If you look at where it hits
the y-axis, about 3 times 10

597
00:25:08,930 --> 00:25:11,240
to the 3rd, 3 times
10 to the 3rd.

598
00:25:11,240 --> 00:25:15,380
The curves follow
basically the same shape.

599
00:25:15,380 --> 00:25:16,730
What's the differences?

600
00:25:16,730 --> 00:25:18,068
So Sean, what do you think?

601
00:25:18,068 --> 00:25:18,610
AUDIENCE: Oh.

602
00:25:18,610 --> 00:25:20,910
That little jagged
[INAUDIBLE] out there.

603
00:25:20,910 --> 00:25:23,070
MICHAEL SHORT: These
jagged edges right here.

604
00:25:23,070 --> 00:25:25,185
Anyone have any idea why?

605
00:25:25,185 --> 00:25:26,873
And these reasons
go back to what

606
00:25:26,873 --> 00:25:28,290
you learned in
high school in 8.02

607
00:25:28,290 --> 00:25:30,540
in terms of atomic
transitions, not nuclear.

608
00:25:33,560 --> 00:25:36,570
Anyone here remember the
k lines or the l lines?

609
00:25:36,570 --> 00:25:38,930
Or what was it-- the--

610
00:25:38,930 --> 00:25:40,928
which emission series
were they called--

611
00:25:40,928 --> 00:25:42,470
the different emission
lines that you

612
00:25:42,470 --> 00:25:45,080
can get from emission
or absorption spectra?

613
00:25:45,080 --> 00:25:48,530
It all has to do with
allowable electron transitions.

614
00:25:48,530 --> 00:25:53,000
And notice the units here are
in centimeters squared per gram.

615
00:25:53,000 --> 00:25:56,792
What's the main difference
between soft tissue and bone?

616
00:25:56,792 --> 00:25:58,740
AUDIENCE: Density.

617
00:25:58,740 --> 00:26:00,770
MICHAEL SHORT: Say it
loud enough so I can hear.

618
00:26:00,770 --> 00:26:01,080
AUDIENCE: Density.

619
00:26:01,080 --> 00:26:02,038
MICHAEL SHORT: Density.

620
00:26:02,038 --> 00:26:05,890
Bone tends to be a fair bit
denser than soft tissue.

621
00:26:05,890 --> 00:26:08,070
So these are mass--

622
00:26:08,070 --> 00:26:10,540
what is it-- mass
normalized curves.

623
00:26:10,540 --> 00:26:13,740
But the fact is, if you have a
bone that has a higher density,

624
00:26:13,740 --> 00:26:16,530
then you're going to end
up with more absorption.

625
00:26:16,530 --> 00:26:19,770
In addition, you can use some of
these features and differences

626
00:26:19,770 --> 00:26:21,310
to your advantage.

627
00:26:21,310 --> 00:26:25,830
Like, if you choose a
photon with energy here,

628
00:26:25,830 --> 00:26:28,620
it might not be nearly as
absorbing in soft tissue

629
00:26:28,620 --> 00:26:29,790
as it would in bone.

630
00:26:29,790 --> 00:26:31,890
So by selecting the
mass of the thing

631
00:26:31,890 --> 00:26:33,960
you're trying to image
which you don't control,

632
00:26:33,960 --> 00:26:36,750
and the energy of the photon
which you can control,

633
00:26:36,750 --> 00:26:38,820
you can produce as
much possible contrast

634
00:26:38,820 --> 00:26:41,570
as you can between
two different things.

635
00:26:41,570 --> 00:26:44,480
Is everyone clear on
how that could work?

636
00:26:44,480 --> 00:26:45,110
Cool.

637
00:26:45,110 --> 00:26:47,450
We'll be going over why the
curves have these shapes,

638
00:26:47,450 --> 00:26:52,140
especially these jagged
edges pretty soon.

639
00:26:52,140 --> 00:26:54,640
And like you said,
this is how you

640
00:26:54,640 --> 00:26:56,750
irradiate a tumor with X-rays.

641
00:26:56,750 --> 00:26:59,570
Because you can't quite
control the amount of dose

642
00:26:59,570 --> 00:27:02,210
to any one part
unless you split it up

643
00:27:02,210 --> 00:27:05,600
into a whole bunch
of different rays.

644
00:27:05,600 --> 00:27:07,250
Proton therapy is
quite different.

645
00:27:07,250 --> 00:27:08,780
It's a newer technology.

646
00:27:08,780 --> 00:27:12,050
And it relies on very
well-known and distinct ranges

647
00:27:12,050 --> 00:27:14,270
of charged particles
to enter the body

648
00:27:14,270 --> 00:27:16,550
with very little
damage, stop and do

649
00:27:16,550 --> 00:27:19,520
their damage in the tumor, and
not come out the other side.

650
00:27:19,520 --> 00:27:22,970
They just require significantly
more expensive hardware.

651
00:27:22,970 --> 00:27:25,430
There's one of these at Mass
General Hospital, or MGH,

652
00:27:25,430 --> 00:27:26,590
down the road.

653
00:27:26,590 --> 00:27:30,170
It consists of a cyclotron or
a particle accelerator, which

654
00:27:30,170 --> 00:27:34,065
injects and speeds up protons so
that they're moving very fast,

655
00:27:34,065 --> 00:27:35,690
then sends it in a
beam through a bunch

656
00:27:35,690 --> 00:27:38,810
of bending magnets
and up to deliver

657
00:27:38,810 --> 00:27:41,510
the protons to the patient.

658
00:27:41,510 --> 00:27:45,350
The way this works is you
start injecting the beam.

659
00:27:45,350 --> 00:27:47,480
And as it goes through
these two magnets,

660
00:27:47,480 --> 00:27:49,460
or what's called dees,
every time it moves

661
00:27:49,460 --> 00:27:51,560
through the magnet,
it's a charged particle

662
00:27:51,560 --> 00:27:53,250
and a magnetic field.

663
00:27:53,250 --> 00:27:55,010
It has a fixed curvature.

664
00:27:55,010 --> 00:27:58,280
But every time it's accelerated
through this electric field

665
00:27:58,280 --> 00:28:00,660
it speeds up, so the curvature
gets greater and greater

666
00:28:00,660 --> 00:28:01,160
and greater.

667
00:28:01,160 --> 00:28:03,410
And it spins
outwards in a spiral

668
00:28:03,410 --> 00:28:05,120
until they exit the beam.

669
00:28:05,120 --> 00:28:07,082
And by deciding how
long they get to spin,

670
00:28:07,082 --> 00:28:08,915
you get to choose the
energy of the protons.

671
00:28:11,450 --> 00:28:13,752
Why does proton therapy work?

672
00:28:13,752 --> 00:28:15,710
This has to do with a
difference in interaction

673
00:28:15,710 --> 00:28:19,640
between charged particles and
photons, which have no charge.

674
00:28:19,640 --> 00:28:22,250
Charged particles
will lose their energy

675
00:28:22,250 --> 00:28:24,950
in a very well-known way,
what's called the stopping power

676
00:28:24,950 --> 00:28:28,670
formula, until they
actually stop in the matter

677
00:28:28,670 --> 00:28:30,290
that they are going through.

678
00:28:30,290 --> 00:28:33,960
Photons either scatter or
attenuate, or they don't.

679
00:28:33,960 --> 00:28:36,230
And you can't stop them all.

680
00:28:36,230 --> 00:28:40,310
So I want to run a quick Monte
Carlo simulation for you guys,

681
00:28:40,310 --> 00:28:43,610
and show you what protons
stopping in matter looks like.

682
00:28:43,610 --> 00:28:45,320
So this is a
program called SRIM,

683
00:28:45,320 --> 00:28:47,480
or the Stopping Range
of Ions and Matter.

684
00:28:47,480 --> 00:28:50,240
It uses the formulas that we'll
be deriving and developing

685
00:28:50,240 --> 00:28:53,960
in this class to calculate
the trajectory of protons

686
00:28:53,960 --> 00:28:55,370
in anything.

687
00:28:55,370 --> 00:28:58,550
So let's say, you are
made basically of water.

688
00:28:58,550 --> 00:29:03,800
So let's say, you consist
of hydrogen and oxygen

689
00:29:03,800 --> 00:29:05,870
in a stoichiometric
ratio of two to one.

690
00:29:05,870 --> 00:29:08,420
I think water approximates
humans pretty well.

691
00:29:08,420 --> 00:29:11,300
So we'll find out what the
range of these actual protons

692
00:29:11,300 --> 00:29:13,980
is in humans.

693
00:29:13,980 --> 00:29:17,570
So what we do know is that
it's a proton accelerator.

694
00:29:17,570 --> 00:29:19,580
And I know that
the MGH accelerator

695
00:29:19,580 --> 00:29:28,300
has an energy of 250 MeV, or
250,000 kiloelectron volts.

696
00:29:28,300 --> 00:29:30,910
And finally, we decide
how thick is the person?

697
00:29:30,910 --> 00:29:34,780
So how thick is a
person, typically?

698
00:29:34,780 --> 00:29:38,140
How many-- what units do we get?

699
00:29:38,140 --> 00:29:42,620
How many centimeters thick
is the average person?

700
00:29:42,620 --> 00:29:44,728
AUDIENCE: Forward
or from the side?

701
00:29:44,728 --> 00:29:46,770
MICHAEL SHORT: Let's go
the shortest distance in,

702
00:29:46,770 --> 00:29:48,570
so front to back.

703
00:29:48,570 --> 00:29:49,660
Maybe 10?

704
00:29:49,660 --> 00:29:51,560
Right?

705
00:29:51,560 --> 00:29:53,150
10 centimeters?

706
00:29:53,150 --> 00:29:53,840
Not that much?

707
00:29:53,840 --> 00:29:55,343
Can it get halfway through you?

708
00:29:55,343 --> 00:29:57,260
Only has to go halfway,
because you can always

709
00:29:57,260 --> 00:29:58,540
lie in your stomach.

710
00:29:58,540 --> 00:29:59,040
All right.

711
00:29:59,040 --> 00:30:00,620
Let's go 10 centimeters.

712
00:30:05,330 --> 00:30:07,640
Most of the protons go
screaming right through you.

713
00:30:07,640 --> 00:30:10,430
You notice they don't
actually stop in the person.

714
00:30:10,430 --> 00:30:14,920
So you don't tend to irradiate
people with 250 MeV protons

715
00:30:14,920 --> 00:30:15,890
directly.

716
00:30:15,890 --> 00:30:17,630
You'll actually slow
down their energy

717
00:30:17,630 --> 00:30:21,290
to something a little more
reasonable, maybe 50 MeV.

718
00:30:24,430 --> 00:30:26,770
And then you can actually
watch each of these charged

719
00:30:26,770 --> 00:30:29,260
particle tracks being computed.

720
00:30:29,260 --> 00:30:33,520
As it hits, let's say,
imaginary nuclei or electrons,

721
00:30:33,520 --> 00:30:36,010
the paths will be
slightly deflected.

722
00:30:36,010 --> 00:30:37,600
But what's really
striking is they

723
00:30:37,600 --> 00:30:40,125
all tend to stop at
about the same place.

724
00:30:40,125 --> 00:30:42,250
That's the really cool
thing about charged particle

725
00:30:42,250 --> 00:30:46,130
interactions, is if you know the
charge, you know the nucleus,

726
00:30:46,130 --> 00:30:48,490
you know the energy, you
can calculate the range

727
00:30:48,490 --> 00:30:50,530
to within a very narrow margin.

728
00:30:50,530 --> 00:30:52,120
And what this is
doing is just flying.

729
00:30:52,120 --> 00:30:54,490
Looks like it's
done 70 ions so far.

730
00:30:54,490 --> 00:30:59,070
And it will keep on flying them
until either you hit the end--

731
00:30:59,070 --> 00:31:00,970
let's say, we set it
to do 100,000 atoms--

732
00:31:00,970 --> 00:31:04,537
or you just tell it to stop.

733
00:31:04,537 --> 00:31:06,370
Also, when you don't
have to draw the lines,

734
00:31:06,370 --> 00:31:07,790
it goes way faster.

735
00:31:07,790 --> 00:31:10,570
So let's let it get
maybe 300 or 400 ions,

736
00:31:10,570 --> 00:31:13,210
and we'll show you what the
average range of the protons

737
00:31:13,210 --> 00:31:14,050
looks like.

738
00:31:14,050 --> 00:31:16,880
How far do they go
before they stop?

739
00:31:16,880 --> 00:31:20,970
If we look at the
ion distribution

740
00:31:20,970 --> 00:31:22,380
it's pretty striking.

741
00:31:22,380 --> 00:31:25,110
All of the protons, except
it looks like one of them,

742
00:31:25,110 --> 00:31:29,790
stopped at a very fixed
depth of 41.9 millimeters

743
00:31:29,790 --> 00:31:35,130
with very little straggle, maybe
0.6 millimeters on either side.

744
00:31:35,130 --> 00:31:36,690
So depending on
the depth of the--

745
00:31:36,690 --> 00:31:41,190
you can even get a deep, very
shallow, very small tumor

746
00:31:41,190 --> 00:31:42,750
if you get the
distance just right

747
00:31:42,750 --> 00:31:44,460
and the proton
energy just right.

748
00:31:44,460 --> 00:31:46,410
This is why proton
therapy centers are

749
00:31:46,410 --> 00:31:48,250
popping up all over the world.

750
00:31:48,250 --> 00:31:50,970
This is a much more
effective, though expensive,

751
00:31:50,970 --> 00:31:55,050
treatment for certain
types of tumors.

752
00:31:55,050 --> 00:31:57,270
At the same time, since
we're nuclear engineers,

753
00:31:57,270 --> 00:31:58,890
we may be concerned
with the amount

754
00:31:58,890 --> 00:32:03,545
of radiation damage being
done to different materials.

755
00:32:03,545 --> 00:32:05,670
And so this is kind of a
measure of how much energy

756
00:32:05,670 --> 00:32:08,370
the protons are losing
as they travel through.

757
00:32:08,370 --> 00:32:09,960
Notice, it's not zero.

758
00:32:09,960 --> 00:32:11,670
As soon as the protons
enter the person,

759
00:32:11,670 --> 00:32:14,070
they start to scatter
around, undergoing

760
00:32:14,070 --> 00:32:15,600
some different interactions.

761
00:32:15,600 --> 00:32:19,200
But they mostly don't lose much
energy until they reach almost

762
00:32:19,200 --> 00:32:20,545
their target depth.

763
00:32:20,545 --> 00:32:22,170
And what's called
the stopping power is

764
00:32:22,170 --> 00:32:25,890
very low at high energies, very
high at low energies, which

765
00:32:25,890 --> 00:32:29,280
means once they get slow
enough, they almost all

766
00:32:29,280 --> 00:32:32,370
stop right there at what's
called the Bragg peak.

767
00:32:32,370 --> 00:32:34,200
And that's the basis
behind proton therapy.

768
00:32:34,200 --> 00:32:36,990
And you'll be able to understand
why every feature of this curve

769
00:32:36,990 --> 00:32:39,660
looks the way it does by
the end of this course--

770
00:32:39,660 --> 00:32:42,710
probably by the
end of this month.

771
00:32:42,710 --> 00:32:46,160
So let me stop that simulation
because we really could go

772
00:32:46,160 --> 00:32:49,930
on forever, but we won't.

773
00:32:49,930 --> 00:32:52,900
Then the question is, what do
you do if the tumor is too big?

774
00:32:52,900 --> 00:32:55,720
If the tumor is larger
than that straggling,

775
00:32:55,720 --> 00:32:58,390
you actually have to sweep
the energy of the proton beam.

776
00:32:58,390 --> 00:33:00,370
So you can vary the
energy continuously

777
00:33:00,370 --> 00:33:02,890
in what's called
intensity-modulated radiation

778
00:33:02,890 --> 00:33:05,920
therapy, where you change
the energy of the proton,

779
00:33:05,920 --> 00:33:07,658
sweep it back and
forth across the tumor

780
00:33:07,658 --> 00:33:08,700
to cover the whole thing.

781
00:33:08,700 --> 00:33:12,550
So you can sweep out in 3D
space the size of whatever you

782
00:33:12,550 --> 00:33:15,070
want to die, without
affecting the stuff that you

783
00:33:15,070 --> 00:33:18,163
don't want to die.

784
00:33:18,163 --> 00:33:19,580
So in this case,
let's say, you'll

785
00:33:19,580 --> 00:33:22,490
apply protons of a certain
energy for some point,

786
00:33:22,490 --> 00:33:24,710
and then another energy,
and then another energy.

787
00:33:24,710 --> 00:33:28,130
And you can maximize the
dose to a pretty flat level,

788
00:33:28,130 --> 00:33:31,190
while minimizing the rest
of the dose to the patient.

789
00:33:31,190 --> 00:33:33,670
So even while changing
energies, the most dose

790
00:33:33,670 --> 00:33:35,810
is done to the tumor,
and as little as possible

791
00:33:35,810 --> 00:33:37,227
is done to the
rest of the person.

792
00:33:39,730 --> 00:33:41,380
We already talked
about brachytherapy,

793
00:33:41,380 --> 00:33:43,157
but we didn't say why it works.

794
00:33:43,157 --> 00:33:44,740
This is the first
major topic we'll be

795
00:33:44,740 --> 00:33:46,240
talking about in this course.

796
00:33:46,240 --> 00:33:48,880
It relies on natural
radioactive decay.

797
00:33:48,880 --> 00:33:50,320
And for natural
radioactive decay,

798
00:33:50,320 --> 00:33:53,590
you need to understand
decay diagrams, which

799
00:33:53,590 --> 00:33:56,620
are energy level diagrams
of which isotopes turn

800
00:33:56,620 --> 00:33:59,500
into which others, by
which methods, and how

801
00:33:59,500 --> 00:34:02,470
much energy they release
in each type of decay.

802
00:34:02,470 --> 00:34:05,930
So for example, the
common one is iridium-192,

803
00:34:05,930 --> 00:34:09,310
a pretty biocompatible isotope
because it's, well, it's

804
00:34:09,310 --> 00:34:10,630
like a noble metal.

805
00:34:10,630 --> 00:34:15,280
And iridium-192 can decay
by one of three pathways

806
00:34:15,280 --> 00:34:20,330
and become platinum-192,
gaining a proton.

807
00:34:20,330 --> 00:34:22,887
Gaining a proton--
what has to happen

808
00:34:22,887 --> 00:34:23,929
for that to be conserved?

809
00:34:23,929 --> 00:34:25,100
So let's think about this.

810
00:34:32,020 --> 00:34:37,949
Let's say we have platinum-192,
which decays naturally

811
00:34:37,949 --> 00:34:41,820
into iridium-192.

812
00:34:41,820 --> 00:34:44,760
I can tell you, because we've
drawn the diagram to the right,

813
00:34:44,760 --> 00:34:47,469
it's going up one atomic number.

814
00:34:47,469 --> 00:34:49,920
So let's just say
that it had n protons,

815
00:34:49,920 --> 00:34:53,670
and it now has n plus 1.

816
00:34:53,670 --> 00:34:56,107
How do we balance
this nuclear reaction?

817
00:34:56,107 --> 00:34:56,940
What are we missing?

818
00:35:00,336 --> 00:35:00,836
Yep?

819
00:35:00,836 --> 00:35:02,297
AUDIENCE: [? Can the ?]
[? neutron ?] [? turn into ?]

820
00:35:02,297 --> 00:35:03,163
a [? proton? ?]

821
00:35:03,163 --> 00:35:04,330
MICHAEL SHORT: Can the neu--

822
00:35:04,330 --> 00:35:04,830
OK.

823
00:35:04,830 --> 00:35:07,130
So there's a neutron
somewhere in this nucleus

824
00:35:07,130 --> 00:35:08,583
that turns into a proton.

825
00:35:08,583 --> 00:35:10,250
What are the three--
what are the things

826
00:35:10,250 --> 00:35:12,560
that we have to conserve
in any nuclear reaction?

827
00:35:15,250 --> 00:35:15,750
Yep?

828
00:35:15,750 --> 00:35:16,833
AUDIENCE: Just a question.

829
00:35:16,833 --> 00:35:18,775
Doesn't it go from
iridium to platinum,

830
00:35:18,775 --> 00:35:20,050
not platinum to iridium?

831
00:35:20,050 --> 00:35:20,842
MICHAEL SHORT: Yes.

832
00:35:20,842 --> 00:35:21,870
Thank you.

833
00:35:21,870 --> 00:35:23,157
I got that backwards.

834
00:35:23,157 --> 00:35:24,240
But the numbers are right.

835
00:35:24,240 --> 00:35:25,260
The symbols are wrong.

836
00:35:28,350 --> 00:35:30,300
Something else I'll
mention about this class.

837
00:35:30,300 --> 00:35:33,420
Please do stay on your toes to
correct silly things like that.

838
00:35:33,420 --> 00:35:35,430
I don't do scripts because
you didn't come here

839
00:35:35,430 --> 00:35:37,200
to see me read off
a piece of paper.

840
00:35:37,200 --> 00:35:38,333
Everything's live.

841
00:35:38,333 --> 00:35:40,500
All the derivations are
going to be live because its

842
00:35:40,500 --> 00:35:41,208
more interesting.

843
00:35:41,208 --> 00:35:42,792
It's certainly more
interesting for me

844
00:35:42,792 --> 00:35:44,510
to teach, so thank
you for catching that.

845
00:35:44,510 --> 00:35:46,802
And please do stay on your
toes if you something silly,

846
00:35:46,802 --> 00:35:49,200
especially if it's just not
the same as on the screen.

847
00:35:49,200 --> 00:35:53,070
So like Luke said,
we made a proton,

848
00:35:53,070 --> 00:35:55,170
or a neutron turned
into a proton.

849
00:35:55,170 --> 00:35:57,090
What's not conserved
in this reaction?

850
00:36:02,880 --> 00:36:03,385
Yep?

851
00:36:03,385 --> 00:36:03,740
AUDIENCE: Charge.

852
00:36:03,740 --> 00:36:04,657
MICHAEL SHORT: Charge.

853
00:36:04,657 --> 00:36:07,850
How do we balance that?

854
00:36:07,850 --> 00:36:09,860
Well, let's add some
other particles.

855
00:36:09,860 --> 00:36:13,320
There's got to be some
sort of radioactive decay.

856
00:36:13,320 --> 00:36:17,120
So what are our
choices of particles?

857
00:36:17,120 --> 00:36:17,620
Yep?

858
00:36:17,620 --> 00:36:19,060
AUDIENCE: An electron.

859
00:36:19,060 --> 00:36:19,893
MICHAEL SHORT: Sure.

860
00:36:19,893 --> 00:36:20,710
An electron.

861
00:36:20,710 --> 00:36:24,790
Or more specifically, we'll
call it a beta particle.

862
00:36:24,790 --> 00:36:26,830
Just like a gamma
ray is a photon that

863
00:36:26,830 --> 00:36:29,380
originates in the
nucleus, a beta particle

864
00:36:29,380 --> 00:36:31,750
is an electron that
originates in a nucleus.

865
00:36:31,750 --> 00:36:35,020
You can't tell it's a beta
particle just by looking at it.

866
00:36:35,020 --> 00:36:36,640
An electron is an electron.

867
00:36:36,640 --> 00:36:39,580
The only way you'd know
is either by its energy,

868
00:36:39,580 --> 00:36:42,640
or by because they're another
source of electrons nearby.

869
00:36:42,640 --> 00:36:48,055
So in this case,
we get beta decay.

870
00:36:48,055 --> 00:36:49,180
This looks fairly balanced.

871
00:36:52,510 --> 00:36:54,940
One thing that I'll
put in is beta decay

872
00:36:54,940 --> 00:36:57,790
is accompanied by
an antineutrino,

873
00:36:57,790 --> 00:36:59,560
but I did not expect
anyone to know that.

874
00:36:59,560 --> 00:37:02,000
I just wanted to make sure
it's up there for completeness.

875
00:37:02,000 --> 00:37:05,860
So what we're relying
on is the movement

876
00:37:05,860 --> 00:37:10,210
of these electrons, which are
high charge and low mass, which

877
00:37:10,210 --> 00:37:11,920
means they're very low range.

878
00:37:11,920 --> 00:37:14,500
Which means when you
implant a brachytherapy seed

879
00:37:14,500 --> 00:37:17,470
into a person, the
irradiation volume

880
00:37:17,470 --> 00:37:20,950
is only as large as the
energy of that beta particle

881
00:37:20,950 --> 00:37:22,330
will allow.

882
00:37:22,330 --> 00:37:24,760
The maximum energies
for these beta particles

883
00:37:24,760 --> 00:37:27,520
are given by the differences
between the starting

884
00:37:27,520 --> 00:37:29,450
and the ending energy.

885
00:37:29,450 --> 00:37:31,060
The way these diagrams
are constructed

886
00:37:31,060 --> 00:37:33,910
is your ending energy is
usually at an energy of zero,

887
00:37:33,910 --> 00:37:37,090
which we refer to as the
ground state of that isotope.

888
00:37:37,090 --> 00:37:39,450
And all of these are
relative energies

889
00:37:39,450 --> 00:37:41,920
in MeV, or megaelectron volts.

890
00:37:41,920 --> 00:37:46,360
So for example, this
iridium-192 has a 40% chance

891
00:37:46,360 --> 00:37:50,800
of decaying by beta
to platinum-192,

892
00:37:50,800 --> 00:37:56,380
which means the electron
can have up to 1.4597 MeV.

893
00:37:56,380 --> 00:37:59,980
And if we know its energy,
we know its maximum range.

894
00:37:59,980 --> 00:38:02,710
So selecting the right
isotope and the right activity

895
00:38:02,710 --> 00:38:04,870
for the right tumor
is quite important.

896
00:38:04,870 --> 00:38:06,550
Notice that there's
also other ways

897
00:38:06,550 --> 00:38:08,410
in which this thing can decay.

898
00:38:08,410 --> 00:38:11,710
It might release a beta
particle of a lower energy

899
00:38:11,710 --> 00:38:16,510
and reach what's called an
excited state of platinum-192,

900
00:38:16,510 --> 00:38:20,440
which can then decay by just
giving off this extra 612

901
00:38:20,440 --> 00:38:23,248
keV of energy to
the ground state.

902
00:38:23,248 --> 00:38:24,790
So let's write that
nuclear reaction.

903
00:38:24,790 --> 00:38:29,920
Let's say we have
platinum-192, and I'll

904
00:38:29,920 --> 00:38:39,020
put a star to mention that it's
excited, becomes platinum-192.

905
00:38:39,020 --> 00:38:40,804
Where did the energy go?

906
00:38:40,804 --> 00:38:41,637
AUDIENCE: Gamma ray.

907
00:38:41,637 --> 00:38:42,512
MICHAEL SHORT: Gamma.

908
00:38:42,512 --> 00:38:43,832
So why do you say a gamma ray?

909
00:38:43,832 --> 00:38:46,620
AUDIENCE: Uh, because
that just seems to me

910
00:38:46,620 --> 00:38:49,244
like the biggest source
of energy that's released

911
00:38:49,244 --> 00:38:51,197
in a reaction like this?

912
00:38:51,197 --> 00:38:53,030
MICHAEL SHORT: So you
said it's because it's

913
00:38:53,030 --> 00:38:55,197
the biggest source of energy
that could be released?

914
00:38:55,197 --> 00:38:58,398
AUDIENCE: Well, it seems to
me, yeah, like, intuitively

915
00:38:58,398 --> 00:38:59,750
that would make sense.

916
00:38:59,750 --> 00:39:00,500
MICHAEL SHORT: OK.

917
00:39:00,500 --> 00:39:01,465
What do you think?

918
00:39:01,465 --> 00:39:03,720
AUDIENCE: Isn't it a
thing when an electron

919
00:39:03,720 --> 00:39:07,463
loses energy or drops an energy
level to release the proton?

920
00:39:07,463 --> 00:39:08,380
MICHAEL SHORT: Indeed.

921
00:39:08,380 --> 00:39:11,090
If an electron drops
down in energy levels,

922
00:39:11,090 --> 00:39:13,520
you'll have released
an X-ray or a photon.

923
00:39:13,520 --> 00:39:14,690
But that's not a gamma ray.

924
00:39:14,690 --> 00:39:16,065
It's not coming
from the nucleus.

925
00:39:16,065 --> 00:39:16,681
Yep?

926
00:39:16,681 --> 00:39:17,598
AUDIENCE: [INAUDIBLE].

927
00:39:17,598 --> 00:39:20,038
Doesn't it have to be a
gamma ray because of-- like,

928
00:39:20,038 --> 00:39:22,480
that's the only way it can
conserve mass [? momentum? ?]

929
00:39:22,480 --> 00:39:23,438
MICHAEL SHORT: Exactly.

930
00:39:23,438 --> 00:39:26,800
So the question with this is,
what do we have to conserve?

931
00:39:26,800 --> 00:39:28,870
Mass momentum energy charge.

932
00:39:28,870 --> 00:39:32,350
If we have platinum-192
go into platinum-192,

933
00:39:32,350 --> 00:39:34,960
the mass is pretty
much the same.

934
00:39:34,960 --> 00:39:35,460
Yep.

935
00:39:35,460 --> 00:39:36,020
Question, Luke?

936
00:39:36,020 --> 00:39:37,510
AUDIENCE: What does it
mean to put platinum

937
00:39:37,510 --> 00:39:38,635
in the excited [INAUDIBLE]?

938
00:39:38,635 --> 00:39:42,412
MICHAEL SHORT: It means it's at
a higher energy nuclear state.

939
00:39:42,412 --> 00:39:44,620
It means that there is excess
energy in this nucleus.

940
00:39:44,620 --> 00:39:46,930
So the difference between
ground state or whatever

941
00:39:46,930 --> 00:39:50,560
of iridium-192 and the
ground state of platinum-192

942
00:39:50,560 --> 00:39:53,500
is 1.4597 MeV.

943
00:39:53,500 --> 00:39:54,850
Notice I'm not rounding.

944
00:39:54,850 --> 00:39:56,380
Don't round.

945
00:39:56,380 --> 00:39:59,110
And we can end up with a beta
particle that doesn't quite

946
00:39:59,110 --> 00:40:01,780
release all that energy, leaving
some in the nucleus in what's

947
00:40:01,780 --> 00:40:03,190
called an excited state.

948
00:40:03,190 --> 00:40:05,500
It's analogous to
if you have, let's

949
00:40:05,500 --> 00:40:09,708
say, an atom of a, whatever
that happens to be.

950
00:40:09,708 --> 00:40:12,250
And since you started talking
about different electron energy

951
00:40:12,250 --> 00:40:16,210
levels, maybe this
atom is helium.

952
00:40:16,210 --> 00:40:18,640
And it only has two electrons.

953
00:40:18,640 --> 00:40:24,230
And one of them gained some
energy becoming excited up

954
00:40:24,230 --> 00:40:25,760
to the next energy level.

955
00:40:25,760 --> 00:40:28,730
Same thing, but on
the nuclear level,

956
00:40:28,730 --> 00:40:30,980
these excitations are
not in the eV range,

957
00:40:30,980 --> 00:40:32,570
they're in the MeV range.

958
00:40:32,570 --> 00:40:35,210
But you can think of it as a
precisely analogous process

959
00:40:35,210 --> 00:40:36,290
for the time being.

960
00:40:36,290 --> 00:40:38,660
There are excited
nuclear energy levels,

961
00:40:38,660 --> 00:40:41,600
and they can also decay
by photon emission--

962
00:40:41,600 --> 00:40:46,680
in this case, gamma emission
because the masses are

963
00:40:46,680 --> 00:40:47,850
basically the same.

964
00:40:47,850 --> 00:40:49,350
Remember that the
rest mass energies

965
00:40:49,350 --> 00:40:52,110
might be slightly different,
but the charge is the same.

966
00:40:52,110 --> 00:40:53,790
There's no real
change in momentum

967
00:40:53,790 --> 00:40:56,280
because this is a nucleus
that started at rest.

968
00:40:56,280 --> 00:40:59,480
And this way the energy
can be conserved.

969
00:40:59,480 --> 00:41:00,693
Yeah, Sean?

970
00:41:00,693 --> 00:41:03,040
AUDIENCE: [INAUDIBLE] in
different cases, if they're

971
00:41:03,040 --> 00:41:06,550
excited, can they just go
through another decay process?

972
00:41:06,550 --> 00:41:07,860
MICHAEL SHORT: Absolutely.

973
00:41:07,860 --> 00:41:11,290
So there are multiple isomeric
transitions or gamma rays.

974
00:41:11,290 --> 00:41:13,840
So let's chart one of
the paths through here.

975
00:41:13,840 --> 00:41:17,010
There's a 14% chance that
iridium decays to this excited

976
00:41:17,010 --> 00:41:19,740
state, and it can then
decay by gamma ray

977
00:41:19,740 --> 00:41:23,340
to another excited state,
and then decay to ground.

978
00:41:23,340 --> 00:41:25,800
So there are lots of
different possible pathways.

979
00:41:25,800 --> 00:41:28,530
I've chosen a particularly
simple isotope

980
00:41:28,530 --> 00:41:29,898
because it fits on the slide.

981
00:41:29,898 --> 00:41:31,440
In your homework,
you're going to get

982
00:41:31,440 --> 00:41:35,190
to look at the decay
diagram for plutonium-239.

983
00:41:35,190 --> 00:41:37,470
There are not enough
pixels in this projector

984
00:41:37,470 --> 00:41:39,660
to show the full
complexity of that.

985
00:41:39,660 --> 00:41:41,740
So you'll have to
zoom in a little bit.

986
00:41:41,740 --> 00:41:43,770
But I'm not going to
ask you to do anything

987
00:41:43,770 --> 00:41:45,930
with it except for
look at the three

988
00:41:45,930 --> 00:41:50,730
most likely transitions out
of dozens, maybe scores,

989
00:41:50,730 --> 00:41:52,080
who knows?

990
00:41:52,080 --> 00:41:52,930
You guys will see.

991
00:41:52,930 --> 00:41:53,670
So that's a good question.

992
00:41:53,670 --> 00:41:54,210
Yeah.

993
00:41:54,210 --> 00:41:57,072
It can decay from an excited
state, to an excited state,

994
00:41:57,072 --> 00:41:58,780
to an excited state,
to an excited state,

995
00:41:58,780 --> 00:42:02,700
to an excited state and so on,
until it reaches the ground

996
00:42:02,700 --> 00:42:03,200
state.

997
00:42:03,200 --> 00:42:04,783
AUDIENCE: But does
it lose its energy,

998
00:42:04,783 --> 00:42:06,838
like, not by going
to ground state,

999
00:42:06,838 --> 00:42:10,902
but by decaying in some
more fission products?

1000
00:42:10,902 --> 00:42:12,860
MICHAEL SHORT: It wouldn't
be fission products,

1001
00:42:12,860 --> 00:42:14,527
but everything else
you said is, yes, it

1002
00:42:14,527 --> 00:42:17,480
can continue to lose energy
by continuously undergoing

1003
00:42:17,480 --> 00:42:19,130
radioactive decay.

1004
00:42:19,130 --> 00:42:22,220
And we're going to go some of
this when we explore the early

1005
00:42:22,220 --> 00:42:25,100
origins of the universe to say,
if you just started off with

1006
00:42:25,100 --> 00:42:27,890
a soup of protons
and other things,

1007
00:42:27,890 --> 00:42:30,170
you'd start to form all
the isotopes possible,

1008
00:42:30,170 --> 00:42:33,050
and the shortest half-life
ones would then decay--

1009
00:42:33,050 --> 00:42:36,350
successive decays,
maybe multiple gammas

1010
00:42:36,350 --> 00:42:39,590
or multiple betas or multiple
alphas at the same time--

1011
00:42:39,590 --> 00:42:41,120
I'm sorry-- in
sequence, until it

1012
00:42:41,120 --> 00:42:44,360
reached something that was
stable, or stable enough

1013
00:42:44,360 --> 00:42:46,280
that it's still around now.

1014
00:42:46,280 --> 00:42:49,550
For example, there's no
stable isotope of uranium.

1015
00:42:49,550 --> 00:42:53,420
There's no isotope of
uranium that will not undergo

1016
00:42:53,420 --> 00:42:56,480
alpha or spontaneous fission.

1017
00:42:56,480 --> 00:42:58,520
It's just that the
half-life is so long,

1018
00:42:58,520 --> 00:43:02,020
that there's still some left
since the universe began.

1019
00:43:02,020 --> 00:43:03,577
There's still a fair bit left.

1020
00:43:03,577 --> 00:43:05,410
But you guys are going
to actually calculate

1021
00:43:05,410 --> 00:43:08,440
as part of your homework
later in the course, how

1022
00:43:08,440 --> 00:43:11,620
much uranium-235 was there
when the earth was born?

1023
00:43:11,620 --> 00:43:13,060
And how much has
just disappeared

1024
00:43:13,060 --> 00:43:15,320
because of the passage of time?

1025
00:43:15,320 --> 00:43:20,320
So right now, it's
typically about 0.7% U-235

1026
00:43:20,320 --> 00:43:21,910
by isotopic composition.

1027
00:43:21,910 --> 00:43:24,730
It was not the case
when the earth was born.

1028
00:43:24,730 --> 00:43:26,770
But you guys will be
able to figure that out.

1029
00:43:26,770 --> 00:43:28,840
Yeah, so good question.

1030
00:43:28,840 --> 00:43:33,300
And have a rant from me,
I guess, in response.

1031
00:43:33,300 --> 00:43:35,610
I'll try and keep my
answers a little shorter.

1032
00:43:35,610 --> 00:43:37,350
Oh, here's a crazy one--

1033
00:43:37,350 --> 00:43:39,240
not particularly crazy, though.

1034
00:43:39,240 --> 00:43:42,570
So this is molybdenum
99 decaying

1035
00:43:42,570 --> 00:43:46,590
to technetium-99 metastable.

1036
00:43:46,590 --> 00:43:51,060
There's lots of possible
decays, but the most likely one

1037
00:43:51,060 --> 00:43:52,080
is right here.

1038
00:43:52,080 --> 00:43:55,530
The state above the ground
state at about 140 keV,

1039
00:43:55,530 --> 00:43:59,090
a fairly low-energy and
therefore more easy to detect

1040
00:43:59,090 --> 00:44:00,600
photon.

1041
00:44:00,600 --> 00:44:03,720
So if you notice, almost all
the other excited states,

1042
00:44:03,720 --> 00:44:05,670
with a couple
exceptions, decay down

1043
00:44:05,670 --> 00:44:10,830
to this 0.14 MeV excited
state, at which point

1044
00:44:10,830 --> 00:44:13,020
you get decays to
the ground state.

1045
00:44:13,020 --> 00:44:14,760
Those also have a
rather long half-life.

1046
00:44:14,760 --> 00:44:16,140
It's a few days.

1047
00:44:16,140 --> 00:44:18,390
So you can make
moly-99 in a reactor,

1048
00:44:18,390 --> 00:44:21,570
transport it to a hospital,
feed it to someone,

1049
00:44:21,570 --> 00:44:24,570
and use these 140
keV gamma rays,

1050
00:44:24,570 --> 00:44:26,220
because they come
from the nucleus,

1051
00:44:26,220 --> 00:44:30,740
to image whatever the
technetium will bond to.

1052
00:44:30,740 --> 00:44:31,690
Yep, Carson?

1053
00:44:31,690 --> 00:44:33,070
AUDIENCE: [INAUDIBLE]?

1054
00:44:33,070 --> 00:44:35,278
MICHAEL SHORT: The M
stands for metastable.

1055
00:44:35,278 --> 00:44:36,320
Now, where do you see it?

1056
00:44:36,320 --> 00:44:37,480
This one.

1057
00:44:37,480 --> 00:44:37,980
Yep.

1058
00:44:37,980 --> 00:44:39,900
Because the direct decay--

1059
00:44:39,900 --> 00:44:44,280
you don't-- you never go from
molybdenum-99 to technetium-99

1060
00:44:44,280 --> 00:44:45,570
at the ground state.

1061
00:44:45,570 --> 00:44:48,713
The M stands for metastable,
so it's an excited state.

1062
00:44:48,713 --> 00:44:50,130
And metastable
tells you that it's

1063
00:44:50,130 --> 00:44:52,420
got a pretty long half-life.

1064
00:44:52,420 --> 00:44:55,240
All of these other states
are excited states.

1065
00:44:55,240 --> 00:44:57,880
Metastable means it's
kind of, sort of, stable

1066
00:44:57,880 --> 00:45:00,290
on, like, a human
time scale of things.

1067
00:45:00,290 --> 00:45:02,610
It's not technically
stable, because stable

1068
00:45:02,610 --> 00:45:06,000
would mean infinite
half-life or close enough.

1069
00:45:06,000 --> 00:45:07,590
But metastable means
long enough to be

1070
00:45:07,590 --> 00:45:10,440
detected or used, or
significantly longer

1071
00:45:10,440 --> 00:45:12,930
than the others.

1072
00:45:12,930 --> 00:45:16,032
Any other questions
before I move on?

1073
00:45:16,032 --> 00:45:18,430
Cool.

1074
00:45:18,430 --> 00:45:22,070
So you can use these to image
where something is in the body.

1075
00:45:22,070 --> 00:45:24,790
For example, you can
use this to highlight

1076
00:45:24,790 --> 00:45:27,460
certain organs,
highlight anything that

1077
00:45:27,460 --> 00:45:29,320
will absorb technetium.

1078
00:45:29,320 --> 00:45:32,230
Or if you attach, let's say, the
technetium to a type of sugar

1079
00:45:32,230 --> 00:45:34,450
or something else that will
be uptaken by the body,

1080
00:45:34,450 --> 00:45:36,230
you can see where it goes.

1081
00:45:36,230 --> 00:45:38,050
And you can use
gamma ray imagers

1082
00:45:38,050 --> 00:45:40,690
to make kind of heat
maps or radiation maps

1083
00:45:40,690 --> 00:45:43,120
of where the technetium's
going to find what

1084
00:45:43,120 --> 00:45:46,510
could be causing the problem.

1085
00:45:46,510 --> 00:45:48,520
The problem is--
well, our main problem

1086
00:45:48,520 --> 00:45:51,700
is there are huge
moly-99 shortages.

1087
00:45:51,700 --> 00:45:53,890
Right now the only
economically viable way

1088
00:45:53,890 --> 00:45:56,567
to make molybdenum-99
is in reactors.

1089
00:45:56,567 --> 00:45:58,900
And there's only a few of
these places in the world that

1090
00:45:58,900 --> 00:46:00,250
actually make them.

1091
00:46:00,250 --> 00:46:04,000
And I don't see any on the US.

1092
00:46:04,000 --> 00:46:05,830
We get ours from Canada.

1093
00:46:05,830 --> 00:46:09,740
And these are slowly getting
closed down as we go.

1094
00:46:09,740 --> 00:46:11,200
So the question
is, with millions

1095
00:46:11,200 --> 00:46:13,680
of these diagnostic
procedures per year,

1096
00:46:13,680 --> 00:46:16,195
where is the moly-99
going to come from?

1097
00:46:16,195 --> 00:46:18,070
That might be where some
of you guys come in.

1098
00:46:18,070 --> 00:46:19,945
If you can use the
knowledge from this course

1099
00:46:19,945 --> 00:46:22,450
to figure out an energetically
and economically feasible

1100
00:46:22,450 --> 00:46:26,490
way to make more
moly-99, you're rich.

1101
00:46:26,490 --> 00:46:30,710
That's, you know,
life goal achieved.

1102
00:46:30,710 --> 00:46:32,840
Space applications--
if we ever want

1103
00:46:32,840 --> 00:46:35,290
to get off this earth for a
significant amount of time,

1104
00:46:35,290 --> 00:46:37,040
we have to deal with
the fact that there's

1105
00:46:37,040 --> 00:46:39,740
no atmosphere in
space to shield us

1106
00:46:39,740 --> 00:46:42,530
from the high-energy protons
and other cosmic rays that would

1107
00:46:42,530 --> 00:46:45,380
otherwise, well, destroy life.

1108
00:46:45,380 --> 00:46:47,690
So there's a lot of
interesting ideas,

1109
00:46:47,690 --> 00:46:50,000
and a lot of problems
with astronaut shielding.

1110
00:46:50,000 --> 00:46:52,640
One of them is that the
protons are so heavy--

1111
00:46:52,640 --> 00:46:56,210
I'm sorry-- the protons are
so energetic that they're

1112
00:46:56,210 --> 00:47:01,680
difficult to shield just
by mass attenuation.

1113
00:47:01,680 --> 00:47:04,480
And the trick here is,
well, different radiation

1114
00:47:04,480 --> 00:47:06,688
has different penetrating power.

1115
00:47:06,688 --> 00:47:08,230
It depends on its
energy, but it also

1116
00:47:08,230 --> 00:47:10,420
depends a lot on its charge.

1117
00:47:10,420 --> 00:47:14,170
For example, alpha particles can
be stopped by a sheet of paper.

1118
00:47:14,170 --> 00:47:17,357
These are the MeV
level helium nuclei.

1119
00:47:17,357 --> 00:47:19,690
Like, if you hold an alpha
particle source in your hand,

1120
00:47:19,690 --> 00:47:23,170
the dead skin on your hand stops
the alphas from getting in.

1121
00:47:23,170 --> 00:47:25,930
Remember that, because I'm going
to be asking you a question

1122
00:47:25,930 --> 00:47:28,510
later on to see who your
friends are and who they aren't.

1123
00:47:28,510 --> 00:47:30,800
I don't know if anyone knows
what I'm talking about.

1124
00:47:30,800 --> 00:47:32,980
But if you do,
don't give it away.

1125
00:47:32,980 --> 00:47:37,210
Beta particles or electrons have
low mass and half the charge

1126
00:47:37,210 --> 00:47:38,470
of an alpha particle.

1127
00:47:38,470 --> 00:47:40,360
They can be able to
get through paper, even

1128
00:47:40,360 --> 00:47:41,990
through a little bit of plastic.

1129
00:47:41,990 --> 00:47:44,080
But a small bit of
metal can stop them.

1130
00:47:44,080 --> 00:47:46,060
Gamma rays go right through.

1131
00:47:46,060 --> 00:47:48,070
And notice that they've
been drawn not quite

1132
00:47:48,070 --> 00:47:49,810
being stopped by
the concrete, which

1133
00:47:49,810 --> 00:47:51,550
is a great shielding material.

1134
00:47:51,550 --> 00:47:54,010
Because like I said before,
you can exponentially

1135
00:47:54,010 --> 00:47:55,720
attenuate gamma rays.

1136
00:47:55,720 --> 00:48:00,240
You can't with all certainty
stop every single one.

1137
00:48:00,240 --> 00:48:02,790
So then how do you stop these
high-energy charged particles

1138
00:48:02,790 --> 00:48:06,270
if the more energetic they
are, the more range they are?

1139
00:48:06,270 --> 00:48:08,980
Boost your
electromagnetic field.

1140
00:48:08,980 --> 00:48:11,790
So it's actually been
proposed to have spaceships

1141
00:48:11,790 --> 00:48:15,360
with enormous magnetic fields
or electromagnetic fields

1142
00:48:15,360 --> 00:48:17,610
around them to deflect
the protons away

1143
00:48:17,610 --> 00:48:19,110
or around the ship.

1144
00:48:19,110 --> 00:48:21,750
Because if you can't stop it
by putting matter in the way,

1145
00:48:21,750 --> 00:48:23,292
rely on the fact
that they're charged

1146
00:48:23,292 --> 00:48:26,540
particles, and will
curve around whatever

1147
00:48:26,540 --> 00:48:28,860
has got a high electric
field around it.

1148
00:48:28,860 --> 00:48:30,240
So this is one
way of, let's say,

1149
00:48:30,240 --> 00:48:31,860
shielding deep space missions.

1150
00:48:31,860 --> 00:48:34,640
If you can't put more stuff in
there because stuff is heavy,

1151
00:48:34,640 --> 00:48:37,440
and launching stuff
into space is expensive,

1152
00:48:37,440 --> 00:48:39,820
rely on electromagnetism.

1153
00:48:39,820 --> 00:48:43,210
And there are also RTGs, or
Radio Thermal Generators,

1154
00:48:43,210 --> 00:48:46,460
or Radio Isotope
Thermoelectric Generators,

1155
00:48:46,460 --> 00:48:49,780
which are little balls of things
like plutonium or strontium

1156
00:48:49,780 --> 00:48:51,830
that give off so
many alpha particles.

1157
00:48:51,830 --> 00:48:54,100
And the alpha particles
have very low range.

1158
00:48:54,100 --> 00:48:57,160
They deposit their kinetic
energy as heat in the material,

1159
00:48:57,160 --> 00:48:59,500
and cause them to
glow on their own.

1160
00:48:59,500 --> 00:49:02,410
If you produce enough heat,
if something's glowing red,

1161
00:49:02,410 --> 00:49:06,340
you can use thermal electric
generators to capture that heat

1162
00:49:06,340 --> 00:49:09,140
and turn it directly
into electricity.

1163
00:49:09,140 --> 00:49:12,130
This is how things like
Voyager and, let's see,

1164
00:49:12,130 --> 00:49:15,760
all the other space probes with
interesting names are powered.

1165
00:49:15,760 --> 00:49:18,640
Once you're too far from the
sun for solar power to work,

1166
00:49:18,640 --> 00:49:21,070
you need something
that doesn't turn off.

1167
00:49:21,070 --> 00:49:23,890
So you can use RTGs,
which have long

1168
00:49:23,890 --> 00:49:27,160
enough half-lives to produce
significant amounts of power

1169
00:49:27,160 --> 00:49:30,010
for a long time, but
short enough half-lives so

1170
00:49:30,010 --> 00:49:31,870
that their activity
is pretty high.

1171
00:49:31,870 --> 00:49:34,450
And they release a lot
of energy as radiation.

1172
00:49:34,450 --> 00:49:36,940
And that radiation is
heavy charged particles

1173
00:49:36,940 --> 00:49:39,680
which you can capture as heat.

1174
00:49:39,680 --> 00:49:42,370
So yeah, an actual little sphere
of plutonium that produces

1175
00:49:42,370 --> 00:49:44,260
100 watts just sitting there.

1176
00:49:44,260 --> 00:49:46,770
There is no way to turn it off.

1177
00:49:46,770 --> 00:49:48,500
That's the end of the sentence.

1178
00:49:48,500 --> 00:49:50,640
It's plutonium.

1179
00:49:50,640 --> 00:49:53,160
And finally, there's
nuclear rockets.

1180
00:49:53,160 --> 00:49:56,040
If you think about using a
reactor for thrust instead

1181
00:49:56,040 --> 00:49:58,860
of electrical energy,
the design of the reactor

1182
00:49:58,860 --> 00:50:00,060
gets very different.

1183
00:50:00,060 --> 00:50:02,940
For example, you can start
to let things get a whole lot

1184
00:50:02,940 --> 00:50:06,150
hotter when there's no oxygen
in space to oxidize things.

1185
00:50:06,150 --> 00:50:07,770
And your propellant
maybe would be

1186
00:50:07,770 --> 00:50:10,292
liquid hydrogen that
doesn't burn, but goes

1187
00:50:10,292 --> 00:50:12,750
through the reactor and gets
accelerated, turned into a gas

1188
00:50:12,750 --> 00:50:14,588
with a high kinetic
energy, to fire out

1189
00:50:14,588 --> 00:50:17,130
the back of the rocket nozzle
and provide the thrust that you

1190
00:50:17,130 --> 00:50:18,010
need.

1191
00:50:18,010 --> 00:50:19,920
And so it's nuclear
rockets that would really

1192
00:50:19,920 --> 00:50:22,770
be the only feasible way without
bending space time, which

1193
00:50:22,770 --> 00:50:25,500
I don't think we've
really done yet, in order

1194
00:50:25,500 --> 00:50:26,970
to get to very distant stars.

1195
00:50:26,970 --> 00:50:30,170
Like that planet they just found
orbiting Proxima Centauri--

1196
00:50:30,170 --> 00:50:31,200
four light years away.

1197
00:50:31,200 --> 00:50:32,820
Pretty close, right?

1198
00:50:32,820 --> 00:50:33,780
No.

1199
00:50:33,780 --> 00:50:34,715
Not really.

1200
00:50:34,715 --> 00:50:38,550
And if you think about how a
nuclear rocket mission would

1201
00:50:38,550 --> 00:50:42,630
work, well, it doesn't have
to have nearly as much thrust,

1202
00:50:42,630 --> 00:50:44,880
especially if you
start from orbit.

1203
00:50:44,880 --> 00:50:47,690
Maybe use a chemical rocket
to launch yourself into orbit,

1204
00:50:47,690 --> 00:50:51,900
and then spend half your journey
accelerating very, very slowly.

1205
00:50:51,900 --> 00:50:54,060
And then turn the
rocket around, spend

1206
00:50:54,060 --> 00:50:58,300
the other half of the journey
decelerating very, very slowly.

1207
00:50:58,300 --> 00:51:01,530
So you need a long, constant
but low-level thrust

1208
00:51:01,530 --> 00:51:04,470
for these long-live
nuclear missions.

1209
00:51:04,470 --> 00:51:06,030
I'm going to stop
here because it's

1210
00:51:06,030 --> 00:51:07,740
five minutes before the hour.

1211
00:51:07,740 --> 00:51:10,050
We only have a few more of
these things to go through.

1212
00:51:10,050 --> 00:51:11,853
But what I will ask
is you guys hang tight

1213
00:51:11,853 --> 00:51:13,770
for the next few minutes
while these guys take

1214
00:51:13,770 --> 00:51:14,850
the cameras apart.

1215
00:51:14,850 --> 00:51:16,320
We're going to go
to my lab and see

1216
00:51:16,320 --> 00:51:18,700
an application of nuclear
which, like I said,

1217
00:51:18,700 --> 00:51:19,800
is plasma sputter coating.

1218
00:51:24,827 --> 00:51:25,660
All right, everyone.

1219
00:51:25,660 --> 00:51:27,270
So welcome to my laboratory.

1220
00:51:27,270 --> 00:51:29,765
This is the Mesoscale
Nuclear Materials group,

1221
00:51:29,765 --> 00:51:31,140
where we make and
break materials

1222
00:51:31,140 --> 00:51:34,290
for nuclear technology,
usually not in that order.

1223
00:51:34,290 --> 00:51:35,160
But whatever.

1224
00:51:35,160 --> 00:51:36,570
We get it done somehow.

1225
00:51:36,570 --> 00:51:39,038
And this is Reid Tanaka, one
of my graduate students, who

1226
00:51:39,038 --> 00:51:40,830
has actually repaired
and going to show you

1227
00:51:40,830 --> 00:51:42,900
the physical principles
and operation

1228
00:51:42,900 --> 00:51:44,640
of a sputter coater,
which is nothing

1229
00:51:44,640 --> 00:51:47,250
more than a controlled
radiation damage machine.

1230
00:51:47,250 --> 00:51:49,380
And he'll be making
some interesting door

1231
00:51:49,380 --> 00:51:51,630
prizes for you guys.

1232
00:51:51,630 --> 00:51:53,980
REID TANAKA: Well, as
Professor Mike Short said,

1233
00:51:53,980 --> 00:51:56,020
this is Professor Mike Short's.

1234
00:51:56,020 --> 00:51:57,480
He calls it something else.

1235
00:51:57,480 --> 00:52:00,650
I call it the home--
the rehabilitative home

1236
00:52:00,650 --> 00:52:05,095
for old, orphaned equipment
and old graduates.

1237
00:52:05,095 --> 00:52:05,595
All right.

1238
00:52:05,595 --> 00:52:08,720
And so this is-- actually,
this piece of gear here,

1239
00:52:08,720 --> 00:52:10,790
I did a little
research on it, and I

1240
00:52:10,790 --> 00:52:16,030
think it was built
about the same time

1241
00:52:16,030 --> 00:52:21,400
as I was entering
college 35 years ago.

1242
00:52:21,400 --> 00:52:25,570
So about 1978, maybe 1980.

1243
00:52:25,570 --> 00:52:27,015
That's how old this thing is.

1244
00:52:27,015 --> 00:52:32,460
And now, so Professor Short
goes around, as all of us,

1245
00:52:32,460 --> 00:52:34,990
and we scrounge and we scab
and we put stuff together.

1246
00:52:34,990 --> 00:52:38,200
And you'll see that really
indeed, we do that a lot.

1247
00:52:38,200 --> 00:52:40,390
So this part, we
put together out

1248
00:52:40,390 --> 00:52:43,390
of a bunch of pieces of parts.

1249
00:52:43,390 --> 00:52:46,250
If you look at it, and I'll
talk [? to it ?] a little bit.

1250
00:52:46,250 --> 00:52:48,760
But there's a procedure
that we've got [? rigged ?]

1251
00:52:48,760 --> 00:52:51,485
[? output. ?] But we
don't know [INAUDIBLE],,

1252
00:52:51,485 --> 00:52:53,110
so we just sort of
throw them together.

1253
00:52:53,110 --> 00:52:55,910
So what you're going to see
is a little demonstration

1254
00:52:55,910 --> 00:52:57,460
of what a sputter coater is.

1255
00:52:57,460 --> 00:52:59,305
You're going to see
a little [INAUDIBLE]..

1256
00:52:59,305 --> 00:53:00,270
AUDIENCE: Could you
scoot in here, so we can

1257
00:53:00,270 --> 00:53:00,770
[? hear your mic? ?]

1258
00:53:00,770 --> 00:53:03,220
REID TANAKA: It's under vacuum
right now, vacuum pressure.

1259
00:53:03,220 --> 00:53:04,260
This is our vacuum [? off. ?]

1260
00:53:04,260 --> 00:53:04,970
AUDIENCE: Let me just--

1261
00:53:04,970 --> 00:53:06,553
here-- come right
here so you can see.

1262
00:53:06,553 --> 00:53:09,760
REID TANAKA: [INAUDIBLE] Again,
there is another pressure

1263
00:53:09,760 --> 00:53:11,210
indication, but
we don't actually

1264
00:53:11,210 --> 00:53:15,400
trust that one [? too much. ?]
All right, without further ado,

1265
00:53:15,400 --> 00:53:16,442
I'm going to power it on.

1266
00:53:16,442 --> 00:53:18,608
We're going to [INAUDIBLE]
[? center ?] [? a ?] high

1267
00:53:18,608 --> 00:53:19,240
voltage.

1268
00:53:19,240 --> 00:53:20,500
It's argon in here.

1269
00:53:20,500 --> 00:53:24,080
We've got argon supplies
in that bottle over there.

1270
00:53:24,080 --> 00:53:32,330
And [INAUDIBLE] I just turn up
the high voltage power supply.

1271
00:53:32,330 --> 00:53:33,170
Turning it up--

1272
00:53:33,170 --> 00:53:34,040
MICHAEL SHORT: Should
we get the lights, Reid?

1273
00:53:34,040 --> 00:53:34,950
REID TANAKA: Voltage.

1274
00:53:34,950 --> 00:53:35,450
Yeah.

1275
00:53:35,450 --> 00:53:36,710
We can kill the lights.

1276
00:53:36,710 --> 00:53:38,900
MICHAEL SHORT: I'll go get them.

1277
00:53:38,900 --> 00:53:41,370
I'll just get them right
over where you are.

1278
00:53:41,370 --> 00:53:45,020
REID TANAKA: And if you
see through this glass jar,

1279
00:53:45,020 --> 00:53:46,997
it's going to be a
little bit of a glow.

1280
00:53:46,997 --> 00:53:48,830
Some of you might be
able to see it already.

1281
00:53:54,070 --> 00:53:55,150
MICHAEL SHORT: Oh, yeah.

1282
00:53:55,150 --> 00:53:56,025
Come a little closer.

1283
00:53:56,025 --> 00:53:59,930
From where I am, you start to
see the glowing purple plasma.

1284
00:53:59,930 --> 00:54:02,080
So that's the ionization
of the argon causing

1285
00:54:02,080 --> 00:54:03,640
it to electrostatically
accelerate

1286
00:54:03,640 --> 00:54:05,710
towards the gold target.

1287
00:54:05,710 --> 00:54:07,510
And that's blasting
off gold items

1288
00:54:07,510 --> 00:54:09,820
that are then coating the
stuff that Reid's coating

1289
00:54:09,820 --> 00:54:11,500
that you'll see in a sec.

1290
00:54:11,500 --> 00:54:13,210
But this is a
controlled application

1291
00:54:13,210 --> 00:54:17,080
of ionization and radiation
damage using a couple

1292
00:54:17,080 --> 00:54:19,812
of kilovolt argon ion--

1293
00:54:19,812 --> 00:54:22,270
don't know if you call it a
beam, but at least in argon ion

1294
00:54:22,270 --> 00:54:22,770
plasma.

1295
00:54:30,887 --> 00:54:32,470
So there's a few
other things to note.

1296
00:54:32,470 --> 00:54:34,678
Remember how we talked about
charged particles having

1297
00:54:34,678 --> 00:54:36,400
a certain range in matter?

1298
00:54:36,400 --> 00:54:38,410
Well, charged particles
in, let's say,

1299
00:54:38,410 --> 00:54:41,080
low-energy particles
in the kV range

1300
00:54:41,080 --> 00:54:43,090
do not have a very
high range even

1301
00:54:43,090 --> 00:54:46,990
in gases, which is why Reid
has this vacuum pump connected.

1302
00:54:46,990 --> 00:54:49,090
Otherwise, the argon
wouldn't make it

1303
00:54:49,090 --> 00:54:51,220
to where it has
to do the damage.

1304
00:54:51,220 --> 00:54:53,170
So when there's too
much gas in there--

1305
00:54:53,170 --> 00:54:54,245
shuts off.

1306
00:54:54,245 --> 00:54:55,870
When there's not
enough argon in there,

1307
00:54:55,870 --> 00:54:57,850
there's no argon
to do the damage.

1308
00:54:57,850 --> 00:55:01,090
So we're actually exciting
about two kV ions.

1309
00:55:01,090 --> 00:55:02,980
And their range is
higher than the distance

1310
00:55:02,980 --> 00:55:04,855
they have to travel, so
they actually make it

1311
00:55:04,855 --> 00:55:06,166
where they're supposed to go.

1312
00:55:06,166 --> 00:55:09,250
And this is a kind of
direct application of NSE,

1313
00:55:09,250 --> 00:55:12,570
along with a fair bit of
high voltage electronics.

1314
00:55:12,570 --> 00:55:14,320
And that's pretty much
all there is to it.

1315
00:55:14,320 --> 00:55:14,755
REID TANAKA: OK.

1316
00:55:14,755 --> 00:55:17,344
So we have about two minutes if
you want to take a closer look

1317
00:55:17,344 --> 00:55:18,040
and just [INAUDIBLE].

1318
00:55:18,040 --> 00:55:18,802
MICHAEL SHORT: Yeah.

1319
00:55:18,802 --> 00:55:19,586
REID TANAKA: It's not
going to hurt you.

1320
00:55:19,586 --> 00:55:19,980
MICHAEL SHORT: No.

1321
00:55:19,980 --> 00:55:20,772
Get right in there.

1322
00:55:25,040 --> 00:55:26,970
Do you want to see--
if you look underneath,

1323
00:55:26,970 --> 00:55:29,370
you'll actually see
that blue glowing ring.

1324
00:55:29,370 --> 00:55:32,580
That's actually a ring of gold
that's being hit by the plasma.

1325
00:55:32,580 --> 00:55:35,250
And that's causing gold ions
to fire onto the target.

1326
00:55:52,540 --> 00:55:55,235
REID TANAKA: You guys all took
chemistry at some point, right?

1327
00:55:55,235 --> 00:55:57,658
Well, they tell you that
one of the great mysteries

1328
00:55:57,658 --> 00:55:59,158
of the [? world ?]
[? as ?] [? we ?]

1329
00:55:59,158 --> 00:56:01,116
[? know it's ?]
[? been solved-- ?] [INAUDIBLE]

1330
00:56:01,116 --> 00:56:03,640
take something and
turn it into gold.

1331
00:56:03,640 --> 00:56:08,350
Well, you should know that
only the nukes can do that.

1332
00:56:08,350 --> 00:56:08,850
Right?

1333
00:56:08,850 --> 00:56:11,932
Really, you got to get away
from all the electrons and all

1334
00:56:11,932 --> 00:56:13,890
that other chemistry
stuff, and only the nukes.

1335
00:56:13,890 --> 00:56:17,000
So if you really want to
turn something to gold,

1336
00:56:17,000 --> 00:56:19,810
you got to join the
nuclear department.

1337
00:56:19,810 --> 00:56:21,390
Just so you know that.

1338
00:56:21,390 --> 00:56:22,190
Keep that in mind.

1339
00:56:25,333 --> 00:56:27,000
MICHAEL SHORT: Has
everyone had a chance

1340
00:56:27,000 --> 00:56:27,960
to get a close-up look?

1341
00:56:31,463 --> 00:56:33,880
REID TANAKA: And I think we
got about another minute or so

1342
00:56:33,880 --> 00:56:35,080
to let it run.

1343
00:56:35,080 --> 00:56:36,680
MICHAEL SHORT: OK.

1344
00:56:36,680 --> 00:56:39,480
Anyone have any questions
about what you're seeing here?

1345
00:56:39,480 --> 00:56:42,400
AUDIENCE: Is it getting,
like, super hot in there, or--

1346
00:56:42,400 --> 00:56:43,983
MICHAEL SHORT: That's
a good question.

1347
00:56:43,983 --> 00:56:46,060
The temperature does
not go up that much.

1348
00:56:46,060 --> 00:56:48,570
There's certainly kinetic energy
turned into thermal energy

1349
00:56:48,570 --> 00:56:50,610
as the argon hits the
gold, and the gold

1350
00:56:50,610 --> 00:56:52,560
hits whatever you're
trying to coat.

1351
00:56:52,560 --> 00:56:55,080
But the total amount of
energy, the density of that gas

1352
00:56:55,080 --> 00:56:56,640
is extremely low.

1353
00:56:56,640 --> 00:56:58,950
That's another reason
why in fusion reactors,

1354
00:56:58,950 --> 00:57:01,710
the plasma is up to like
millions or tens of millions

1355
00:57:01,710 --> 00:57:02,820
of Kelvin.

1356
00:57:02,820 --> 00:57:04,262
There's just not a lot of it.

1357
00:57:04,262 --> 00:57:06,720
So if you look at the total
amount of stored thermal energy

1358
00:57:06,720 --> 00:57:09,300
in a fusion reactor,
it's quite low,

1359
00:57:09,300 --> 00:57:11,523
even though the
temperature or the relation

1360
00:57:11,523 --> 00:57:13,440
to the average kinetic
energy of the molecules

1361
00:57:13,440 --> 00:57:14,580
is extremely high.

1362
00:57:18,052 --> 00:57:19,050
So yeah.

1363
00:57:19,050 --> 00:57:19,650
Good question.

1364
00:57:19,650 --> 00:57:24,738
If you want, put your hand
up inside of the chamber.

1365
00:57:24,738 --> 00:57:26,232
Is it warm?

1366
00:57:26,232 --> 00:57:32,208
AUDIENCE: [INAUDIBLE]

1367
00:57:32,208 --> 00:57:33,607
AUDIENCE: It's not warm at all.

1368
00:57:33,607 --> 00:57:34,690
MICHAEL SHORT: Not at all.

1369
00:57:34,690 --> 00:57:35,190
Yep.

1370
00:57:44,890 --> 00:57:47,292
AUDIENCE: The
plasma is the argon?

1371
00:57:47,292 --> 00:57:50,126
And where's the
gold coming from?

1372
00:57:50,126 --> 00:57:51,425
From in that [? ring ?]

1373
00:57:51,425 --> 00:57:52,593
MICHAEL SHORT: There we go.

1374
00:57:52,593 --> 00:57:53,420
REID TANAKA: [INAUDIBLE]
we'll show you.

1375
00:57:53,420 --> 00:57:53,570
MICHAEL SHORT: Yeah.

1376
00:57:53,570 --> 00:57:54,810
We'll open it up and show you.

1377
00:57:54,810 --> 00:57:55,650
So I'll get the lights on now.

1378
00:57:55,650 --> 00:57:56,317
REID TANAKA: OK.

1379
00:57:56,317 --> 00:57:57,060
[INAUDIBLE]

1380
00:58:02,700 --> 00:58:06,468
AUDIENCE: Why isn't the
pressure [INAUDIBLE]??

1381
00:58:06,468 --> 00:58:07,510
REID TANAKA: What's that?

1382
00:58:07,510 --> 00:58:08,802
AUDIENCE: The pressure changed.

1383
00:58:08,802 --> 00:58:09,670
[INAUDIBLE]

1384
00:58:12,940 --> 00:58:14,550
REID TANAKA: Yeah.

1385
00:58:14,550 --> 00:58:17,520
From the point that we-- when
you walked in and saw that?

1386
00:58:17,520 --> 00:58:18,240
AUDIENCE: Yeah.

1387
00:58:18,240 --> 00:58:19,270
REID TANAKA: OK.

1388
00:58:19,270 --> 00:58:21,240
The first thing--
so this had a sort

1389
00:58:21,240 --> 00:58:24,910
of a static amount
of argon in it.

1390
00:58:24,910 --> 00:58:29,040
And when I turned on the
voltage, the high voltage,

1391
00:58:29,040 --> 00:58:30,510
that's to create the plasma.

1392
00:58:30,510 --> 00:58:31,970
But then it has to get fed.

1393
00:58:31,970 --> 00:58:34,303
And so what I ended up doing
with this little knob here,

1394
00:58:34,303 --> 00:58:36,790
I probably should explain that,
is I was feeding it argon.

1395
00:58:36,790 --> 00:58:40,025
That argon bottle from over here
it's going into this chamber.

1396
00:58:40,025 --> 00:58:42,525
When you're feeding the argon
in, then the pressure came up.

1397
00:58:42,525 --> 00:58:45,230
And if the pressure comes up
too high on this particular

1398
00:58:45,230 --> 00:58:47,780
instrument, then it has an
automatic cut-off [? when ?]

1399
00:58:47,780 --> 00:58:51,390
the high voltage [? cuts out. ?]
Because otherwise, you know,

1400
00:58:51,390 --> 00:58:54,240
one of the reasons why it works
is because we have so few atoms

1401
00:58:54,240 --> 00:58:55,524
in there.

1402
00:58:55,524 --> 00:58:56,508
[INAUDIBLE]

1403
00:58:56,508 --> 00:59:15,240
AUDIENCE: [? Good. ?]

1404
00:59:15,240 --> 00:59:17,780
REID TANAKA: [INAUDIBLE] what
atmospheric pressure is in

1405
00:59:17,780 --> 00:59:18,280
[? total? ?]

1406
00:59:18,280 --> 00:59:19,280
AUDIENCE: 760.

1407
00:59:19,280 --> 00:59:20,780
REID TANAKA: 760.

1408
00:59:20,780 --> 00:59:23,780
[INAUDIBLE]

1409
00:59:23,780 --> 00:59:28,390
Maybe we [? actually ?] have
a little bit of a [INAUDIBLE]..

1410
00:59:28,390 --> 00:59:30,570
So this is that--

1411
00:59:30,570 --> 00:59:33,675
that's the gold ring.

1412
00:59:33,675 --> 00:59:37,100
AUDIENCE: [? Neat. ?]

1413
00:59:37,100 --> 00:59:38,475
REID TANAKA: And
in the chamber--

1414
00:59:40,160 --> 00:59:42,660
MICHAEL SHORT: You can put the--
you can put the ring facing

1415
00:59:42,660 --> 00:59:43,770
down for stability if you want.

1416
00:59:43,770 --> 00:59:44,290
REID TANAKA: What's that?

1417
00:59:44,290 --> 00:59:45,748
MICHAEL SHORT: I
said, you can just

1418
00:59:45,748 --> 00:59:48,074
put the ring lying flat down
if you want for stability.

1419
00:59:48,074 --> 00:59:50,534
Yeah.

1420
00:59:50,534 --> 00:59:52,010
REID TANAKA: And
in the chamber--

1421
00:59:55,454 --> 00:59:58,790
the purpose of having this,
actually, this machine,

1422
00:59:58,790 --> 01:00:01,085
the main reason
that we use this for

1423
01:00:01,085 --> 01:00:02,460
is if you have
something that you

1424
01:00:02,460 --> 01:00:06,770
want to put into a scanning
electron microscope, and--

1425
01:00:10,492 --> 01:00:11,950
MICHAEL SHORT:
We're actually going

1426
01:00:11,950 --> 01:00:14,708
to use one of those
in class, so--

1427
01:00:14,708 --> 01:00:16,110
yeah.

1428
01:00:16,110 --> 01:00:19,450
REID TANAKA: You need to have
some kind of conductive coating

1429
01:00:19,450 --> 01:00:21,122
on it.

1430
01:00:21,122 --> 01:00:23,080
So if you're looking at--
[? especially ?] like

1431
01:00:23,080 --> 01:00:27,370
[? biologic ?] [? stuff, ?] you
actually coat it with something

1432
01:00:27,370 --> 01:00:29,350
that's conductive.

1433
01:00:29,350 --> 01:00:34,480
So there you see, it has a gold
coat of about, I would guess,

1434
01:00:34,480 --> 01:00:36,190
I think for as long
as we did it for,

1435
01:00:36,190 --> 01:00:41,398
something on the level
of 200 [INAUDIBLE]..

1436
01:00:41,398 --> 01:00:42,928
It's a pretty thin coat.

1437
01:00:42,928 --> 01:00:44,720
MICHAEL SHORT: That's
all you need, though.

1438
01:00:44,720 --> 01:00:45,500
REID TANAKA: Right.

1439
01:00:45,500 --> 01:00:46,880
MICHAEL SHORT: Remember,
after quiz number one,

1440
01:00:46,880 --> 01:00:48,770
we will be piloting--
well, two of you

1441
01:00:48,770 --> 01:00:51,230
guys we'll be piloting a
scanning electron microscope

1442
01:00:51,230 --> 01:00:52,358
down in the basement.

1443
01:00:52,358 --> 01:00:54,650
And before we look at whatever
samples you want to see,

1444
01:00:54,650 --> 01:00:57,260
whether it's one of your
eyelashes, dust on the floor,

1445
01:00:57,260 --> 01:00:59,070
or a bug you found
or something, we'll

1446
01:00:59,070 --> 01:01:00,980
want to coat in gold,
so that the electrons

1447
01:01:00,980 --> 01:01:03,428
that we use for imaging
will have a place to go.

1448
01:01:03,428 --> 01:01:05,720
We'll have a conductive path,
and they won't charge up,

1449
01:01:05,720 --> 01:01:06,470
ruining the image.

1450
01:01:06,470 --> 01:01:07,428
REID TANAKA: All right.

1451
01:01:07,428 --> 01:01:08,277
I have a question.

1452
01:01:08,277 --> 01:01:09,110
MICHAEL SHORT: Yeah?

1453
01:01:09,110 --> 01:01:12,020
REID TANAKA: Is anybody--
was anybody here born

1454
01:01:12,020 --> 01:01:14,140
this Millennium?

1455
01:01:14,140 --> 01:01:15,200
Anyone?

1456
01:01:15,200 --> 01:01:17,310
2000 or later?

1457
01:01:17,310 --> 01:01:17,820
Nobody.

1458
01:01:17,820 --> 01:01:21,120
Anyone in 1999?

1459
01:01:21,120 --> 01:01:23,194
Nobody in 1999?

1460
01:01:23,194 --> 01:01:26,255
[INAUDIBLE]

1461
01:01:26,255 --> 01:01:28,110
How about '98?

1462
01:01:28,110 --> 01:01:29,130
You were born in '98?

1463
01:01:29,130 --> 01:01:30,330
MICHAEL SHORT: There we go.

1464
01:01:30,330 --> 01:01:31,920
REID TANAKA: All right.

1465
01:01:31,920 --> 01:01:33,580
That would be--

1466
01:01:33,580 --> 01:01:35,970
[INAUDIBLE] brought my glasses.

1467
01:01:35,970 --> 01:01:39,980
I've got that 1998 dime here.

1468
01:01:39,980 --> 01:01:43,390
It's now gold-coated.

1469
01:01:43,390 --> 01:01:45,110
And you can have it.

1470
01:01:45,110 --> 01:01:47,920
[INAUDIBLE] [? too ?]
[? bad. If ?] [? somebody ?]

1471
01:01:47,920 --> 01:01:51,738
[? wanted ?] [INAUDIBLE]
you got a quarter.

1472
01:01:51,738 --> 01:01:54,280
You [? could lie ?] [? and ?]
[? say-- ?] But I guess you are

1473
01:01:54,280 --> 01:01:55,410
the youngest [INAUDIBLE].

1474
01:01:55,410 --> 01:01:55,950
Yeah.

1475
01:01:55,950 --> 01:01:57,100
All right.

1476
01:01:57,100 --> 01:02:00,210
So you win this.

1477
01:02:00,210 --> 01:02:02,128
Now, it'll rub off.

1478
01:02:02,128 --> 01:02:02,670
AUDIENCE: OK.

1479
01:02:02,670 --> 01:02:03,620
REID TANAKA: So
[INAUDIBLE] you--

1480
01:02:03,620 --> 01:02:04,110
AUDIENCE: [? I'll ?]
[? probably ?] keep it

1481
01:02:04,110 --> 01:02:05,900
in a plastic bag.

1482
01:02:05,900 --> 01:02:06,720
REID TANAKA: And--

1483
01:02:06,720 --> 01:02:07,770
MICHAEL SHORT:
[? Gold ?] [? change. ?]

1484
01:02:07,770 --> 01:02:09,228
REID TANAKA: I
guess the other ones

1485
01:02:09,228 --> 01:02:11,446
go to people that [INAUDIBLE].

1486
01:02:16,180 --> 01:02:17,180
Oh, no '97.

1487
01:02:17,180 --> 01:02:19,090
How about a '96?

1488
01:02:19,090 --> 01:02:20,930
You're a '96?

1489
01:02:20,930 --> 01:02:21,760
[INAUDIBLE]

1490
01:02:21,760 --> 01:02:23,260
AUDIENCE: [? There's ?]
[? three. ?]

1491
01:02:23,260 --> 01:02:23,790
REID TANAKA: What's that?

1492
01:02:23,790 --> 01:02:24,710
AUDIENCE: There's three '96s,

1493
01:02:24,710 --> 01:02:25,980
REID TANAKA: Oh,
there's three '96s?

1494
01:02:25,980 --> 01:02:26,480
OK.

1495
01:02:26,480 --> 01:02:28,898
You get the-- you
get the [INAUDIBLE]..

1496
01:02:28,898 --> 01:02:41,282
AUDIENCE: [INAUDIBLE]
over a year old.

1497
01:02:41,282 --> 01:02:42,240
REID TANAKA: All right.

1498
01:02:42,240 --> 01:02:43,815
Who wants the
nickel that's a '96?

1499
01:02:43,815 --> 01:02:45,225
AUDIENCE: [INAUDIBLE].

1500
01:02:45,225 --> 01:02:47,100
REID TANAKA: You going
to arm wrestle for it?

1501
01:02:47,100 --> 01:02:47,410
MICHAEL SHORT: There you go.

1502
01:02:47,410 --> 01:02:47,980
Right in front of you, Reid.

1503
01:02:47,980 --> 01:02:48,940
REID TANAKA: Well,
there's three of them.

1504
01:02:48,940 --> 01:02:49,440
OK.

1505
01:02:49,440 --> 01:02:50,356
MICHAEL SHORT: OK.

1506
01:02:50,356 --> 01:02:51,398
REID TANAKA: [INAUDIBLE].

1507
01:02:51,398 --> 01:02:52,382
AUDIENCE: Thank you.

1508
01:02:52,382 --> 01:02:54,215
REID TANAKA: And who
are the other two '96s?

1509
01:02:57,340 --> 01:02:58,840
You're going to
have to arm wrestle.

1510
01:02:58,840 --> 01:03:01,010
One gets a quarter,
but one gets the dime.

1511
01:03:01,010 --> 01:03:02,160
MICHAEL SHORT: [INAUDIBLE].

1512
01:03:02,160 --> 01:03:02,590
Yep.

1513
01:03:02,590 --> 01:03:03,640
REID TANAKA: That's the
only fair way of doing

1514
01:03:03,640 --> 01:03:03,910
[? it, I think. ?]

1515
01:03:03,910 --> 01:03:06,040
MICHAEL SHORT: That's not a
nuclear thing, but if it's fun.

1516
01:03:06,040 --> 01:03:07,090
REID TANAKA: [INAUDIBLE].

1517
01:03:09,510 --> 01:03:10,510
Here you go [INAUDIBLE].

1518
01:03:10,510 --> 01:03:10,940
AUDIENCE: [INAUDIBLE].

1519
01:03:10,940 --> 01:03:12,416
REID TANAKA: And there is
the quarter [INAUDIBLE]..

1520
01:03:12,416 --> 01:03:13,124
AUDIENCE: Thanks.

1521
01:03:13,124 --> 01:03:14,260
AUDIENCE: [INAUDIBLE]

1522
01:03:14,260 --> 01:03:14,590
MICHAEL SHORT: This one?

1523
01:03:14,590 --> 01:03:15,220
AUDIENCE: [INAUDIBLE].

1524
01:03:15,220 --> 01:03:16,570
AUDIENCE: Yes. [? Because ?]
[? it ?] [? was ?] [INAUDIBLE]..

1525
01:03:16,570 --> 01:03:17,810
MICHAEL SHORT: [INAUDIBLE]
actually [INAUDIBLE]..

1526
01:03:17,810 --> 01:03:18,570
It's just--

1527
01:03:18,570 --> 01:03:20,690
AUDIENCE: It's
[? memorable ?] [INAUDIBLE]..

1528
01:03:20,690 --> 01:03:21,590
REID TANAKA: OK.

1529
01:03:21,590 --> 01:03:22,090
Yeah?

1530
01:03:22,090 --> 01:03:24,070
AUDIENCE: So is that gold
deposited anywhere else

1531
01:03:24,070 --> 01:03:24,700
in that chamber?

1532
01:03:24,700 --> 01:03:25,450
REID TANAKA: Yeah.

1533
01:03:25,450 --> 01:03:28,040
If you look-- actually, if you
look in the chamber, I mean,

1534
01:03:28,040 --> 01:03:30,130
this is all- this is all
[? from it ?] [? being ?]

1535
01:03:30,130 --> 01:03:31,960
[? sputtered. ?] And
if you look around--

1536
01:03:31,960 --> 01:03:34,835
I can turn this a little.

1537
01:03:34,835 --> 01:03:35,650
Look at the glass.

1538
01:03:35,650 --> 01:03:39,060
It gets on the glass, too.

1539
01:03:39,060 --> 01:03:41,920
So it actually gets--
it gets everywhere.

1540
01:03:41,920 --> 01:03:45,344
But it's mostly directed to that
area that you saw [INAUDIBLE]..

1541
01:03:49,140 --> 01:03:50,015
I have another offer.

1542
01:03:53,280 --> 01:03:54,582
Are you guys all nukes?

1543
01:03:54,582 --> 01:03:56,540
You guys are all going
to be in the department?

1544
01:03:56,540 --> 01:03:57,670
MICHAEL SHORT: All but one.

1545
01:03:57,670 --> 01:03:58,000
REID TANAKA: Ah.

1546
01:03:58,000 --> 01:03:59,090
AUDIENCE: [? Not me. ?]

1547
01:03:59,090 --> 01:04:00,965
MICHAEL SHORT: But we
have a nuke enthusiast.

1548
01:04:00,965 --> 01:04:02,850
So-- otherwise, wouldn't
be in this class.

1549
01:04:02,850 --> 01:04:05,810
And anyone scared of nuclear
is probably not in this class.

1550
01:04:05,810 --> 01:04:08,400
REID TANAKA: So obviously, it
was pretty easy for us to do.

1551
01:04:08,400 --> 01:04:10,305
We have this machine here.

1552
01:04:10,305 --> 01:04:12,180
If you're going to be
part of our department,

1553
01:04:12,180 --> 01:04:14,790
if you want to just come
in, we can make you a--

1554
01:04:14,790 --> 01:04:18,295
we can make you a quarter, OK?

1555
01:04:18,295 --> 01:04:19,670
I mean, I could
even supply them.

1556
01:04:19,670 --> 01:04:22,032
I feel rich [? enough ?]
I can [INAUDIBLE],,

1557
01:04:22,032 --> 01:04:24,240
because all this grad
student-- graduate school money

1558
01:04:24,240 --> 01:04:25,126
I'm getting.

1559
01:04:25,126 --> 01:04:26,900
MICHAEL SHORT: Nice.

1560
01:04:26,900 --> 01:04:29,132
REID TANAKA: But--
anything else?

1561
01:04:29,132 --> 01:04:34,096
MICHAEL SHORT: Any questions
for Reid on what you just saw?

1562
01:04:34,096 --> 01:04:36,050
The goal is to sort of
give you a real life,

1563
01:04:36,050 --> 01:04:38,360
you know, learn 22.01,
you'll understand

1564
01:04:38,360 --> 01:04:40,970
how these things work, and
how you can modify them,

1565
01:04:40,970 --> 01:04:42,580
create new stuff.

1566
01:04:42,580 --> 01:04:44,002
That's the general idea.

1567
01:04:44,002 --> 01:04:45,710
Same thing behind
looking at the electron

1568
01:04:45,710 --> 01:04:49,790
microscope for the focused ion
beam, EDX elemental analysis.

1569
01:04:49,790 --> 01:04:51,770
I want to bring what
we're teaching you to life

1570
01:04:51,770 --> 01:04:53,433
as often as we can.

1571
01:04:53,433 --> 01:04:55,100
Since we only got one
recitation a week,

1572
01:04:55,100 --> 01:04:56,810
we'll be doing it
about that much.

1573
01:04:56,810 --> 01:04:59,478
Once in a while I may
schedule some extra stuff

1574
01:04:59,478 --> 01:05:00,770
as long as folks are available.

1575
01:05:00,770 --> 01:05:02,210
But we're going
to try all we can

1576
01:05:02,210 --> 01:05:04,543
to have days like this, where
you get to see what you're

1577
01:05:04,543 --> 01:05:05,970
learning in real life.

1578
01:05:05,970 --> 01:05:07,670
AUDIENCE: It was
called a sputter?

1579
01:05:07,670 --> 01:05:08,880
REID TANAKA: Sputter coater.

1580
01:05:08,880 --> 01:05:09,780
AUDIENCE: Sputter coater.

1581
01:05:09,780 --> 01:05:10,970
REID TANAKA: Sputter coater.

1582
01:05:10,970 --> 01:05:13,470
MICHAEL SHORT: It's because the
process of the argon hitting

1583
01:05:13,470 --> 01:05:15,870
the gold is actually
known as sputtering,

1584
01:05:15,870 --> 01:05:17,490
which is the blasting
off of surface

1585
01:05:17,490 --> 01:05:19,400
atoms by energetic particles.

1586
01:05:19,400 --> 01:05:22,446
It's a controlled form
of radiation damage.

1587
01:05:22,446 --> 01:05:24,820
AUDIENCE: What's that Swagelok?

1588
01:05:24,820 --> 01:05:26,774
MICHAEL SHORT: Swagelok.

1589
01:05:26,774 --> 01:05:27,630
AUDIENCE: Swagelok.

1590
01:05:27,630 --> 01:05:28,778
REID TANAKA: Yeah.

1591
01:05:28,778 --> 01:05:31,668
AUDIENCE: So what's a Swagelok?

1592
01:05:31,668 --> 01:05:32,460
REID TANAKA: Well--

1593
01:05:32,460 --> 01:05:34,230
MICHAEL SHORT: Do we
have any pieces here?

1594
01:05:34,230 --> 01:05:34,700
Let's see.

1595
01:05:34,700 --> 01:05:35,966
REID TANAKA: [? We ?] [? have ?]
[? lots. ?] [INAUDIBLE] if you

1596
01:05:35,966 --> 01:05:38,480
go back [? around ?] [INAUDIBLE]
tubing that you see back

1597
01:05:38,480 --> 01:05:38,980
in there.

1598
01:05:38,980 --> 01:05:41,570
They're connected so
they don't [INAUDIBLE]..

1599
01:05:41,570 --> 01:05:43,350
[INAUDIBLE] [? piping ?]
[INAUDIBLE]..

1600
01:05:43,350 --> 01:05:44,873
It's proprietary--

1601
01:05:44,873 --> 01:05:46,290
MICHAEL SHORT:
They're all in use.

1602
01:05:46,290 --> 01:05:47,360
REID TANAKA: --made by
the Swagelok companies

1603
01:05:47,360 --> 01:05:48,070
to [INAUDIBLE].

1604
01:05:48,070 --> 01:05:49,800
MICHAEL SHORT: Oh, here we go.

1605
01:05:49,800 --> 01:05:51,939
REID TANAKA: So I
don't know if Mike's

1606
01:05:51,939 --> 01:05:53,154
going to take you around.

1607
01:05:53,154 --> 01:05:54,821
AUDIENCE: [? Absolutely ?]
[INAUDIBLE]..

1608
01:05:57,540 --> 01:05:59,460
MICHAEL SHORT: This
is Swagelok tubing.

1609
01:05:59,460 --> 01:06:02,620
It's got a two piece
ferrule, which [INAUDIBLE]

1610
01:06:02,620 --> 01:06:05,070
a metal-to-metal seal
for moving liquid or gas.

1611
01:06:05,070 --> 01:06:07,513
And it takes an
insanely high pressure.

1612
01:06:07,513 --> 01:06:09,930
So actually, over in the next
room, we can look on our way

1613
01:06:09,930 --> 01:06:12,300
out, we've built a
reactor simulator,

1614
01:06:12,300 --> 01:06:15,090
like an experimental
reactor that

1615
01:06:15,090 --> 01:06:17,970
replicates all the conditions
except for the radiation.

1616
01:06:17,970 --> 01:06:20,550
We had to make it entirely
out of Swagelok tubing,

1617
01:06:20,550 --> 01:06:23,050
because this stuff can hold the
pressure and the temperature

1618
01:06:23,050 --> 01:06:25,560
without deforming too much.

1619
01:06:25,560 --> 01:06:29,090
So when you want to make it
absolutely airtight seal,

1620
01:06:29,090 --> 01:06:29,840
use things--

1621
01:06:29,840 --> 01:06:31,517
Swagelok or things like it.

1622
01:06:31,517 --> 01:06:32,850
AUDIENCE: Is it stainless steel?

1623
01:06:32,850 --> 01:06:33,720
MICHAEL SHORT: This
is stainless steel.

1624
01:06:33,720 --> 01:06:34,220
Yep.

1625
01:06:34,220 --> 01:06:36,570
But they make it out of
titanium or other things, too.

1626
01:06:36,570 --> 01:06:38,837
But stainless
steel works for us.

1627
01:06:38,837 --> 01:06:39,754
AUDIENCE: That's cool.

1628
01:06:39,754 --> 01:06:42,550
AUDIENCE: In a PWR, how
much pressure is there?

1629
01:06:42,550 --> 01:06:45,820
MICHAEL SHORT: In a PWR, there's
150 atmospheres of pressure.

1630
01:06:45,820 --> 01:06:47,500
It's also 150
atmospheres of pressure

1631
01:06:47,500 --> 01:06:49,060
over in the room next door.

1632
01:06:49,060 --> 01:06:49,935
AUDIENCE: [INAUDIBLE]

1633
01:06:49,935 --> 01:06:52,268
MICHAEL SHORT: Like I said,
it's all the same conditions

1634
01:06:52,268 --> 01:06:53,912
as a reactor except
the radiation.

1635
01:06:53,912 --> 01:06:55,870
The pressure is what
makes it really dangerous.

1636
01:06:55,870 --> 01:06:57,076
AUDIENCE: [INAUDIBLE]

1637
01:06:57,076 --> 01:06:57,909
MICHAEL SHORT: Yeah.

1638
01:06:57,909 --> 01:07:00,635
We'll look through one of the
few bulletproof glass shields.

1639
01:07:00,635 --> 01:07:02,260
Because if anything
blows on that loop,

1640
01:07:02,260 --> 01:07:05,200
it's like a proj--
it is a projectile.

1641
01:07:05,200 --> 01:07:07,120
We've only had one explosion.

1642
01:07:07,120 --> 01:07:08,890
There was no
temperature at the time,

1643
01:07:08,890 --> 01:07:11,290
but it sounded like
a shotgun blast

1644
01:07:11,290 --> 01:07:12,910
over the side of your shoulder.

1645
01:07:12,910 --> 01:07:14,150
It was loud.

1646
01:07:14,150 --> 01:07:15,515
AUDIENCE: You in the room?

1647
01:07:15,515 --> 01:07:17,140
MICHAEL SHORT: The
loop was right here,

1648
01:07:17,140 --> 01:07:18,160
and we were right
in front of it.

1649
01:07:18,160 --> 01:07:19,760
Then the loop jumped
up maybe an inch.

1650
01:07:19,760 --> 01:07:22,210
And we jumped up
about three feet.

1651
01:07:22,210 --> 01:07:23,950
We got scared.

1652
01:07:23,950 --> 01:07:25,690
That was what happens
when you improperly

1653
01:07:25,690 --> 01:07:27,070
torque a high-pressure fitting.

1654
01:07:27,070 --> 01:07:29,320
Because you've actually got
to tighten these nuts down

1655
01:07:29,320 --> 01:07:32,050
to not too low and not
too high of a torque,

1656
01:07:32,050 --> 01:07:33,683
otherwise, they don't seal.

1657
01:07:33,683 --> 01:07:35,350
And usually, you only
find out that they

1658
01:07:35,350 --> 01:07:36,850
don't seal when
they're approaching

1659
01:07:36,850 --> 01:07:38,022
close to their rated thing.

1660
01:07:38,022 --> 01:07:38,980
And you're like, great.

1661
01:07:38,980 --> 01:07:39,897
It's at half pressure.

1662
01:07:39,897 --> 01:07:40,720
It's OK.

1663
01:07:40,720 --> 01:07:43,505
You reach 99%
pressure and kaboom.

1664
01:07:43,505 --> 01:07:44,380
That's what happened.

1665
01:07:48,529 --> 01:07:49,210
Cool.

1666
01:07:49,210 --> 01:07:50,960
Thanks a lot, Reid,
for showing this to us

1667
01:07:50,960 --> 01:07:52,540
and taking time out of your day.

1668
01:07:52,540 --> 01:07:53,540
REID TANAKA: No problem.

1669
01:07:53,540 --> 01:07:54,275
Anytime.

1670
01:07:54,275 --> 01:07:56,025
MICHAEL SHORT: I hope
you guys enjoyed it.

1671
01:07:56,025 --> 01:07:58,220
So no problems to work
through this week.

1672
01:07:58,220 --> 01:08:01,672
That's going to change
starting Tuesday, next class.

1673
01:08:01,672 --> 01:08:02,630
So have a good weekend.

1674
01:08:02,630 --> 01:08:06,200
And I'll see you guys all
on Tuesday in Room 24-115,

1675
01:08:06,200 --> 01:08:09,090
next to the room
where we were just in.