WEBVTT 00:00:00.000 --> 00:00:02.430 align:middle line:90% [SQUEAKING] 00:00:02.430 --> 00:00:04.374 align:middle line:90% [RUSTLING] 00:00:04.374 --> 00:00:11.190 align:middle line:90% [CLICKING] 00:00:11.190 --> 00:00:15.590 align:middle line:84% JACK HARE: Let's talk a little bit about plasma diagnostics. 00:00:15.590 --> 00:00:21.100 align:middle line:84% So this very word, diagnostic, is pretty interesting. 00:00:21.100 --> 00:00:23.620 align:middle line:84% Gnostic here is coming from knowledge, 00:00:23.620 --> 00:00:25.670 align:middle line:84% and dia is a word sort of meaning through. 00:00:25.670 --> 00:00:28.360 align:middle line:84% So these are objects that we gain knowledge through. 00:00:28.360 --> 00:00:31.450 align:middle line:84% And we're trying to gain knowledge about our plasma. 00:00:31.450 --> 00:00:34.352 align:middle line:84% This is the whole purpose of this class. 00:00:34.352 --> 00:00:36.810 align:middle line:84% We're trying to gain knowledge about the plasma indirectly. 00:00:36.810 --> 00:00:38.550 align:middle line:84% We can't directly look at a plasma 00:00:38.550 --> 00:00:41.375 align:middle line:84% and measure its density, or its temperature, or its velocity, 00:00:41.375 --> 00:00:43.500 align:middle line:84% or any of the other quantities we're interested in. 00:00:43.500 --> 00:00:46.042 align:middle line:84% Instead, we're inferring it from some sort of physical effect 00:00:46.042 --> 00:00:48.120 align:middle line:84% the plasma has on something else. 00:00:48.120 --> 00:00:51.480 align:middle line:84% And we're used to this kind of measurement 00:00:51.480 --> 00:00:53.040 align:middle line:90% with more basic diagnostics. 00:00:53.040 --> 00:00:57.030 align:middle line:84% If we think about something like a thermometer, 00:00:57.030 --> 00:00:59.370 align:middle line:84% and it's filled with mercury, what's 00:00:59.370 --> 00:01:00.900 align:middle line:84% the physical principle that allows 00:01:00.900 --> 00:01:03.750 align:middle line:84% us to measure temperature using a thermometer, a liquid metal 00:01:03.750 --> 00:01:04.750 align:middle line:90% thermometer? 00:01:04.750 --> 00:01:05.250 align:middle line:90% Yeah. 00:01:05.250 --> 00:01:08.110 align:middle line:90% 00:01:08.110 --> 00:01:08.610 align:middle line:90% Yeah. 00:01:08.610 --> 00:01:11.130 align:middle line:84% So the thermal expansion of this metal, which moves it 00:01:11.130 --> 00:01:13.840 align:middle line:84% up and down here, and we can calibrate this, 00:01:13.840 --> 00:01:15.340 align:middle line:84% and then we can measure temperature. 00:01:15.340 --> 00:01:16.620 align:middle line:84% So this is an example of something 00:01:16.620 --> 00:01:17.970 align:middle line:84% that we are relatively familiar with. 00:01:17.970 --> 00:01:19.380 align:middle line:84% Thermal expansion of metal, it's something 00:01:19.380 --> 00:01:20.350 align:middle line:90% we can see with our eyes. 00:01:20.350 --> 00:01:21.558 align:middle line:90% We can pick up a thermometer. 00:01:21.558 --> 00:01:22.530 align:middle line:90% We can touch it. 00:01:22.530 --> 00:01:25.380 align:middle line:84% This is rarely the case with something like a plasma. 00:01:25.380 --> 00:01:26.860 align:middle line:90% Our intuition usually fails us. 00:01:26.860 --> 00:01:28.860 align:middle line:84% And so we have to fall back on mathematics, 00:01:28.860 --> 00:01:31.260 align:middle line:84% or we have to build our intuition for plasma 00:01:31.260 --> 00:01:33.630 align:middle line:84% in the same way that we built our intuition for things 00:01:33.630 --> 00:01:37.310 align:middle line:84% like thermometers as we were growing up. 00:01:37.310 --> 00:01:39.202 align:middle line:84% For example, here we were talking 00:01:39.202 --> 00:01:40.410 align:middle line:90% about the expansion of metal. 00:01:40.410 --> 00:01:42.860 align:middle line:84% But in a plasma, we may be looking at something as obscure 00:01:42.860 --> 00:01:45.212 align:middle line:84% as the polarization of a beam of light 00:01:45.212 --> 00:01:47.420 align:middle line:84% telling us something about magnetic fields, something 00:01:47.420 --> 00:01:50.030 align:middle line:84% that immediately it isn't obvious that these things are 00:01:50.030 --> 00:01:51.830 align:middle line:90% linked at all. 00:01:51.830 --> 00:01:54.080 align:middle line:84% We're going to be assuming very good plasma physics 00:01:54.080 --> 00:01:55.650 align:middle line:90% knowledge in this class. 00:01:55.650 --> 00:01:57.470 align:middle line:84% So the prerequisite for this class 00:01:57.470 --> 00:01:59.960 align:middle line:84% is for students who have taken 22.611. 00:01:59.960 --> 00:02:02.810 align:middle line:84% So that's a class that uses Francis Chen's Introduction 00:02:02.810 --> 00:02:04.040 align:middle line:90% to Plasma Physics textbook. 00:02:04.040 --> 00:02:07.040 align:middle line:84% And we'll be drawing extensively from that without redoing 00:02:07.040 --> 00:02:07.940 align:middle line:90% any derivations. 00:02:07.940 --> 00:02:11.360 align:middle line:84% This is a very hard class to take at the same time as 22.611. 00:02:11.360 --> 00:02:13.700 align:middle line:84% I recommend you don't try, but I know that some of you 00:02:13.700 --> 00:02:14.390 align:middle line:90% are going to. 00:02:14.390 --> 00:02:15.380 align:middle line:90% And that's fine. 00:02:15.380 --> 00:02:16.850 align:middle line:84% But just as a warning, it's going 00:02:16.850 --> 00:02:18.050 align:middle line:90% to be very, very difficult. 00:02:18.050 --> 00:02:21.650 align:middle line:84% If you are a little bit shaky in your plasma physics, 00:02:21.650 --> 00:02:25.190 align:middle line:84% I suggest revising your electromagnetism, your waves 00:02:25.190 --> 00:02:27.740 align:middle line:84% in plasmas, and things like Landau damping, especially 00:02:27.740 --> 00:02:30.910 align:middle line:84% later on when we get on to Thomson scattering. 00:02:30.910 --> 00:02:32.320 align:middle line:90% Any questions on any of that? 00:02:32.320 --> 00:02:40.730 align:middle line:90% 00:02:40.730 --> 00:02:44.000 align:middle line:84% So why do we bother with diagnostics in the first place? 00:02:44.000 --> 00:02:46.870 align:middle line:84% Well, there's no point in making a plasma that you can't actually 00:02:46.870 --> 00:02:47.450 align:middle line:90% measure. 00:02:47.450 --> 00:02:50.702 align:middle line:84% So we could have a huge tokamak, or a giant laser, 00:02:50.702 --> 00:02:52.660 align:middle line:84% or a big pulse power machine, and we could make 00:02:52.660 --> 00:02:53.975 align:middle line:90% the world's greatest plasma. 00:02:53.975 --> 00:02:55.600 align:middle line:84% But if we don't know anything about it, 00:02:55.600 --> 00:02:56.950 align:middle line:90% it's completely pointless. 00:02:56.950 --> 00:02:59.980 align:middle line:84% And so plasma experiments really goes hand in hand 00:02:59.980 --> 00:03:01.610 align:middle line:90% with plasma diagnostics. 00:03:01.610 --> 00:03:03.610 align:middle line:84% And these diagnostics are extremely important 00:03:03.610 --> 00:03:07.090 align:middle line:84% in the history of fusion and in the history of plasma physics. 00:03:07.090 --> 00:03:10.450 align:middle line:84% So one example that I told the students about in fusion energy 00:03:10.450 --> 00:03:12.370 align:middle line:84% last semester that they'll probably remember 00:03:12.370 --> 00:03:13.930 align:middle line:90% is the zeta pinch. 00:03:13.930 --> 00:03:19.540 align:middle line:84% So this was a toroidal Z-pinch type device that was built 00:03:19.540 --> 00:03:22.980 align:middle line:90% in the UK in the '50s. 00:03:22.980 --> 00:03:26.340 align:middle line:84% And the Brits got very excited, because when they cranked up 00:03:26.340 --> 00:03:27.870 align:middle line:84% the current on their toroidal pinch, 00:03:27.870 --> 00:03:29.730 align:middle line:84% they started measuring bursts of neutrons. 00:03:29.730 --> 00:03:30.600 align:middle line:90% And they said, aha! 00:03:30.600 --> 00:03:31.410 align:middle line:90% We see neutrons. 00:03:31.410 --> 00:03:33.480 align:middle line:90% Therefore, we're getting fusion. 00:03:33.480 --> 00:03:35.010 align:middle line:84% Now, there was a problem with this, 00:03:35.010 --> 00:03:36.927 align:middle line:84% because when they looked at it in more detail, 00:03:36.927 --> 00:03:39.180 align:middle line:84% they realized that the neutron burst they were getting 00:03:39.180 --> 00:03:41.550 align:middle line:84% was not isotropic, so it couldn't be thermonuclear 00:03:41.550 --> 00:03:44.040 align:middle line:84% in origin, and also, the temperature of their plasma 00:03:44.040 --> 00:03:45.270 align:middle line:90% was far too low. 00:03:45.270 --> 00:03:47.185 align:middle line:84% So they didn't have sufficient diagnostics 00:03:47.185 --> 00:03:48.810 align:middle line:84% to realize that these neutrons were not 00:03:48.810 --> 00:03:51.420 align:middle line:84% coming from a thermonuclear fusion process, but were, 00:03:51.420 --> 00:03:54.780 align:middle line:84% in fact, coming from MHD instabilities within the plasma. 00:03:54.780 --> 00:03:58.200 align:middle line:84% This was extremely embarrassing, but the upshot of it 00:03:58.200 --> 00:04:00.840 align:middle line:84% was that this team developed a technique called 00:04:00.840 --> 00:04:03.780 align:middle line:84% Thomson scattering, which uses a focused laser beam to measure 00:04:03.780 --> 00:04:05.190 align:middle line:90% the temperature of a plasma. 00:04:05.190 --> 00:04:07.512 align:middle line:84% And they developed it just in time for the Russians 00:04:07.512 --> 00:04:08.970 align:middle line:84% to announce their new device, which 00:04:08.970 --> 00:04:11.610 align:middle line:84% they called a tokamak, which they claimed 00:04:11.610 --> 00:04:14.460 align:middle line:84% had temperatures over a kiloelectron volt, which 00:04:14.460 --> 00:04:16.649 align:middle line:84% was about 10 times higher than any other device 00:04:16.649 --> 00:04:19.910 align:middle line:84% that anyone had been trying to do fusion with at the time. 00:04:19.910 --> 00:04:22.037 align:middle line:84% This, again, caused a huge furor because lots 00:04:22.037 --> 00:04:24.120 align:middle line:84% of groups from around the world didn't believe it. 00:04:24.120 --> 00:04:25.787 align:middle line:84% They said, how have the Russians managed 00:04:25.787 --> 00:04:28.370 align:middle line:84% to get such an incredible result from their machine? 00:04:28.370 --> 00:04:30.920 align:middle line:84% And so the team from the UK who had worked on ZETA 00:04:30.920 --> 00:04:32.630 align:middle line:84% and then worked on Thomson scattering 00:04:32.630 --> 00:04:34.657 align:middle line:84% flew over to Moscow with their ruby laser 00:04:34.657 --> 00:04:36.740 align:middle line:84% and made the first Thomson scattering measurements 00:04:36.740 --> 00:04:39.290 align:middle line:84% on a tokamak, confirming that it had temperatures 00:04:39.290 --> 00:04:40.910 align:middle line:90% of a kiloelectron volt. 00:04:40.910 --> 00:04:42.363 align:middle line:90% And the rest is kind of history. 00:04:42.363 --> 00:04:44.030 align:middle line:84% Immediately everywhere around the world, 00:04:44.030 --> 00:04:47.030 align:middle line:84% people started converting their other machines into tokamaks. 00:04:47.030 --> 00:04:49.190 align:middle line:84% The Princeton Model C stellarator, 00:04:49.190 --> 00:04:51.590 align:middle line:84% they cut off all the long loopy bits 00:04:51.590 --> 00:04:53.120 align:middle line:84% and just shoved two halves together, 00:04:53.120 --> 00:04:55.910 align:middle line:84% and it became the Princeton Model C tokamak instead. 00:04:55.910 --> 00:04:57.290 align:middle line:90% And this happened overnight. 00:04:57.290 --> 00:05:00.260 align:middle line:84% And we're still living in a post-Thomson scattering, 00:05:00.260 --> 00:05:02.960 align:middle line:84% post-tokamak world, because all of our major devices 00:05:02.960 --> 00:05:05.880 align:middle line:90% now are tokamaks. 00:05:05.880 --> 00:05:09.297 align:middle line:84% Another good example is the National Ignition Facility. 00:05:09.297 --> 00:05:11.130 align:middle line:84% The National Ignition Facility was carefully 00:05:11.130 --> 00:05:12.840 align:middle line:84% designed using the best simulations 00:05:12.840 --> 00:05:16.170 align:middle line:84% available-- these incredible radiation hydrodynamics 00:05:16.170 --> 00:05:18.510 align:middle line:84% multigroup, everything you can think of all the best 00:05:18.510 --> 00:05:19.540 align:middle line:90% physics in the world. 00:05:19.540 --> 00:05:20.880 align:middle line:84% And they were very confident that when 00:05:20.880 --> 00:05:22.560 align:middle line:84% they turned on the National Ignition Facility 00:05:22.560 --> 00:05:23.850 align:middle line:90% they were going to get ignition. 00:05:23.850 --> 00:05:25.267 align:middle line:84% They were so confident they put it 00:05:25.267 --> 00:05:26.740 align:middle line:90% in the name of the experiment. 00:05:26.740 --> 00:05:29.340 align:middle line:84% And so back in 2009 or so, they started 00:05:29.340 --> 00:05:30.953 align:middle line:90% running the first experiments. 00:05:30.953 --> 00:05:33.120 align:middle line:84% And they said, we don't really need any diagnostics, 00:05:33.120 --> 00:05:34.245 align:middle line:90% because it's going to work. 00:05:34.245 --> 00:05:35.070 align:middle line:90% It's obvious. 00:05:35.070 --> 00:05:36.450 align:middle line:84% We know exactly what's happening. 00:05:36.450 --> 00:05:39.030 align:middle line:84% We'll just have, basically, some neutron 00:05:39.030 --> 00:05:41.070 align:middle line:84% counters so that we can go ding, we 00:05:41.070 --> 00:05:44.508 align:middle line:84% got to ignition, and tick the box, and move on. 00:05:44.508 --> 00:05:45.300 align:middle line:90% This didn't happen. 00:05:45.300 --> 00:05:47.922 align:middle line:84% When they turned on NIF, the signal was barely measurable. 00:05:47.922 --> 00:05:50.130 align:middle line:84% There was almost no neutrons at all coming out of it, 00:05:50.130 --> 00:05:51.432 align:middle line:90% and they had no idea why. 00:05:51.432 --> 00:05:52.890 align:middle line:84% And the reason they had no idea why 00:05:52.890 --> 00:05:55.170 align:middle line:84% is because they didn't have any diagnostics to tell them 00:05:55.170 --> 00:05:56.170 align:middle line:90% what was actually happening. 00:05:56.170 --> 00:05:58.295 align:middle line:84% They only had diagnostics to tell them whether they 00:05:58.295 --> 00:05:59.290 align:middle line:90% were successful or not. 00:05:59.290 --> 00:06:01.140 align:middle line:90% And the answer was they weren't. 00:06:01.140 --> 00:06:02.820 align:middle line:84% So no one knew what was going on, 00:06:02.820 --> 00:06:05.220 align:middle line:84% but a decade later, they now have very good diagnostics 00:06:05.220 --> 00:06:05.770 align:middle line:90% at NIF. 00:06:05.770 --> 00:06:07.550 align:middle line:84% And it's no coincidence that, of course, 00:06:07.550 --> 00:06:09.850 align:middle line:84% we now have ignition as well, because they understand 00:06:09.850 --> 00:06:12.800 align:middle line:84% a great deal about the physics going on inside this experiment. 00:06:12.800 --> 00:06:15.250 align:middle line:84% So you really need to have good diagnostics 00:06:15.250 --> 00:06:18.665 align:middle line:84% to do good plasma physics and to build good fusion reactors as 00:06:18.665 --> 00:06:19.165 align:middle line:90% well. 00:06:19.165 --> 00:06:21.720 align:middle line:90% 00:06:21.720 --> 00:06:24.190 align:middle line:84% Who needs to know about diagnostics? 00:06:24.190 --> 00:06:26.130 align:middle line:84% Well, obviously, experimenters, we kind of-- 00:06:26.130 --> 00:06:28.080 align:middle line:84% I imagine many of the people in this room 00:06:28.080 --> 00:06:29.760 align:middle line:84% are doing experimental plasma physics. 00:06:29.760 --> 00:06:30.550 align:middle line:90% And that's why they're here. 00:06:30.550 --> 00:06:33.008 align:middle line:84% They want to understand the plasmas that their machines are 00:06:33.008 --> 00:06:33.700 align:middle line:90% producing. 00:06:33.700 --> 00:06:35.700 align:middle line:84% They want to probe the mysteries of the universe 00:06:35.700 --> 00:06:37.770 align:middle line:84% and get unlimited clean renewable energy and all 00:06:37.770 --> 00:06:38.770 align:middle line:90% that sort of stuff. 00:06:38.770 --> 00:06:41.203 align:middle line:84% But they also want to understand the uncertainty involved 00:06:41.203 --> 00:06:42.120 align:middle line:90% in their measurements. 00:06:42.120 --> 00:06:44.520 align:middle line:84% When someone says to you, the temperature on this tokamak 00:06:44.520 --> 00:06:47.080 align:middle line:84% is 1 kiloelectron volt, what does that mean? 00:06:47.080 --> 00:06:48.960 align:middle line:90% Where is it 1 kiloelectron volt? 00:06:48.960 --> 00:06:50.280 align:middle line:90% What's the error bars on that? 00:06:50.280 --> 00:06:52.140 align:middle line:84% Does that true for the entire discharge? 00:06:52.140 --> 00:06:54.570 align:middle line:84% There's huge limitations in the diagnostics we have. 00:06:54.570 --> 00:06:56.790 align:middle line:84% And we need to understand those limitations. 00:06:56.790 --> 00:06:58.950 align:middle line:84% If you're doing computational work, 00:06:58.950 --> 00:07:00.367 align:middle line:84% if you're doing large simulations, 00:07:00.367 --> 00:07:01.992 align:middle line:84% you might be interested in diagnostics, 00:07:01.992 --> 00:07:04.500 align:middle line:84% because they serve as a primary way of validating your code. 00:07:04.500 --> 00:07:06.630 align:middle line:84% Your code is only really worthwhile 00:07:06.630 --> 00:07:09.820 align:middle line:84% if it makes predictions that agree with reality. 00:07:09.820 --> 00:07:12.540 align:middle line:84% And so you may want to understand how diagnosticians 00:07:12.540 --> 00:07:14.400 align:middle line:84% are making these measurements so that they 00:07:14.400 --> 00:07:16.750 align:middle line:84% can understand whether your code is right or not. 00:07:16.750 --> 00:07:19.230 align:middle line:84% And you may also be motivated to make useful outputs 00:07:19.230 --> 00:07:20.430 align:middle line:90% from a computer simulation. 00:07:20.430 --> 00:07:22.930 align:middle line:84% You may get a very large amount of data that's 00:07:22.930 --> 00:07:24.280 align:middle line:90% very hard to distill down. 00:07:24.280 --> 00:07:26.920 align:middle line:84% One way to distill that down is to think about the diagnostics 00:07:26.920 --> 00:07:29.260 align:middle line:84% that experimentalists use and reduce your data 00:07:29.260 --> 00:07:31.450 align:middle line:84% set so it looks a bit more like those diagnostics. 00:07:31.450 --> 00:07:34.090 align:middle line:84% That gives you an easier way of comparing your data 00:07:34.090 --> 00:07:35.653 align:middle line:90% with reality. 00:07:35.653 --> 00:07:37.570 align:middle line:84% If you're a theorist, I think you should still 00:07:37.570 --> 00:07:38.440 align:middle line:90% know about diagnostics. 00:07:38.440 --> 00:07:40.150 align:middle line:84% I think you should be very skeptical about 00:07:40.150 --> 00:07:41.230 align:middle line:90% your experimental colleagues. 00:07:41.230 --> 00:07:42.130 align:middle line:84% I don't think you should believe them 00:07:42.130 --> 00:07:44.797 align:middle line:84% when they say the temperature is 1 kiloelectron volt. You should 00:07:44.797 --> 00:07:47.290 align:middle line:84% ask where, and when, and how sure are you? 00:07:47.290 --> 00:07:49.540 align:middle line:84% Because these people are trying to tell you something, 00:07:49.540 --> 00:07:51.190 align:middle line:84% and you're going to go out and tell all your colleagues 00:07:51.190 --> 00:07:52.570 align:middle line:84% that your theory has been proved. 00:07:52.570 --> 00:07:53.530 align:middle line:84% And if they were wrong, you're going 00:07:53.530 --> 00:07:55.000 align:middle line:90% to be very, very embarrassed. 00:07:55.000 --> 00:07:57.250 align:middle line:84% You might also be motivated to design theories which 00:07:57.250 --> 00:07:58.900 align:middle line:90% have testable predictions. 00:07:58.900 --> 00:08:00.597 align:middle line:84% So a lot of theoretical work is phrased 00:08:00.597 --> 00:08:02.680 align:middle line:84% in a language which is very different from the way 00:08:02.680 --> 00:08:03.847 align:middle line:90% that experimentalists speak. 00:08:03.847 --> 00:08:05.555 align:middle line:84% And that means that when experimentalists 00:08:05.555 --> 00:08:08.030 align:middle line:84% read your papers, they don't understand what's going on. 00:08:08.030 --> 00:08:10.448 align:middle line:84% And they also don't know how exactly 00:08:10.448 --> 00:08:11.740 align:middle line:90% they can test your predictions. 00:08:11.740 --> 00:08:14.080 align:middle line:84% If you know how diagnosticians think, 00:08:14.080 --> 00:08:16.090 align:middle line:84% you can write papers which are clearer for them. 00:08:16.090 --> 00:08:18.040 align:middle line:84% They can go test your theory, prove it right, 00:08:18.040 --> 00:08:20.050 align:middle line:84% and then you can go collect your Nobel Prize. 00:08:20.050 --> 00:08:23.835 align:middle line:84% So it's pretty important to know how diagnostics work there. 00:08:23.835 --> 00:08:25.460 align:middle line:84% All right, I've been talking for a bit. 00:08:25.460 --> 00:08:27.710 align:middle line:84% So I'll pause and see if there's any questions so far. 00:08:27.710 --> 00:08:39.100 align:middle line:90% 00:08:39.100 --> 00:08:40.659 align:middle line:90% So what sort of things-- 00:08:40.659 --> 00:08:46.770 align:middle line:90% 00:08:46.770 --> 00:08:48.980 align:middle line:90% there we are. 00:08:48.980 --> 00:08:50.000 align:middle line:90% What can we measure? 00:08:50.000 --> 00:09:07.940 align:middle line:90% 00:09:07.940 --> 00:09:10.010 align:middle line:84% Before we get onto what can we measure, 00:09:10.010 --> 00:09:11.630 align:middle line:90% what would we like to measure? 00:09:11.630 --> 00:09:13.400 align:middle line:84% What would a theorist like to ask us for? 00:09:13.400 --> 00:09:15.710 align:middle line:90% So what can we measure? 00:09:15.710 --> 00:09:19.505 align:middle line:90% What do we want? 00:09:19.505 --> 00:09:24.690 align:middle line:90% 00:09:24.690 --> 00:09:26.870 align:middle line:84% Well, if it's not too much to ask, 00:09:26.870 --> 00:09:28.670 align:middle line:84% we'd like to know the position and velocity 00:09:28.670 --> 00:09:30.620 align:middle line:84% of every single particle in the plasma 00:09:30.620 --> 00:09:32.335 align:middle line:84% at every point in space and time. 00:09:32.335 --> 00:09:34.460 align:middle line:84% So this would be the Klimontovich type distribution 00:09:34.460 --> 00:09:34.960 align:middle line:90% here. 00:09:34.960 --> 00:09:37.700 align:middle line:84% We'd have sort of f of x as a vector. 00:09:37.700 --> 00:09:39.110 align:middle line:90% v is a vector-- 00:09:39.110 --> 00:09:39.710 align:middle line:90% time. 00:09:39.710 --> 00:09:42.200 align:middle line:84% And this would simply look like the sum 00:09:42.200 --> 00:09:44.690 align:middle line:84% of a series of delta functions, which 00:09:44.690 --> 00:09:54.970 align:middle line:84% are the position of particle i, the velocity of particle i, 00:09:54.970 --> 00:09:58.460 align:middle line:84% and both of those should be functions of time as well. 00:09:58.460 --> 00:09:59.980 align:middle line:84% And our full distribution function 00:09:59.980 --> 00:10:02.690 align:middle line:84% is just a sum over all of these particles. 00:10:02.690 --> 00:10:06.520 align:middle line:84% So this is three dimensional, three velocity vectors 00:10:06.520 --> 00:10:07.315 align:middle line:90% plus time. 00:10:07.315 --> 00:10:09.830 align:middle line:90% 00:10:09.830 --> 00:10:12.330 align:middle line:84% Now, of course, the theorists might tell you they want that, 00:10:12.330 --> 00:10:13.247 align:middle line:90% but they don't really. 00:10:13.247 --> 00:10:14.020 align:middle line:90% No one wants that. 00:10:14.020 --> 00:10:15.687 align:middle line:84% It's absolutely impossible to work with. 00:10:15.687 --> 00:10:16.510 align:middle line:90% This is a mess. 00:10:16.510 --> 00:10:18.780 align:middle line:84% So what theorists really want is they want 00:10:18.780 --> 00:10:20.230 align:middle line:90% some sort of moments of this. 00:10:20.230 --> 00:10:22.562 align:middle line:84% They would like to have a simplified version of this. 00:10:22.562 --> 00:10:25.020 align:middle line:84% At best, they'd like to have a distribution function, which 00:10:25.020 --> 00:10:25.650 align:middle line:90% is smooth. 00:10:25.650 --> 00:10:28.900 align:middle line:84% This one is very, very spiky and hard to work with. 00:10:28.900 --> 00:10:31.050 align:middle line:84% But they may also be willing to get away 00:10:31.050 --> 00:10:33.390 align:middle line:84% with letting you give them some thermodynamic variables, 00:10:33.390 --> 00:10:36.220 align:middle line:84% some variables where we've taken moments over this. 00:10:36.220 --> 00:10:41.300 align:middle line:84% So if we look at some of the moments that we can take here, 00:10:41.300 --> 00:10:45.300 align:middle line:84% we would have things like the density. 00:10:45.300 --> 00:10:48.300 align:middle line:84% And this is an integral over the velocity 00:10:48.300 --> 00:10:52.170 align:middle line:84% part of your distribution function, d3v. 00:10:52.170 --> 00:10:58.730 align:middle line:90% 00:10:58.730 --> 00:11:00.080 align:middle line:90% That's the density. 00:11:00.080 --> 00:11:03.320 align:middle line:84% Or you might want to know things like the average velocity 00:11:03.320 --> 00:11:04.490 align:middle line:90% of your particles. 00:11:04.490 --> 00:11:13.970 align:middle line:90% 00:11:13.970 --> 00:11:17.450 align:middle line:84% And you can keep going with this by multiplying your distribution 00:11:17.450 --> 00:11:19.310 align:middle line:84% function by larger and larger powers of v. 00:11:19.310 --> 00:11:22.190 align:middle line:84% And you start getting tensors and all sorts of exciting things 00:11:22.190 --> 00:11:23.037 align:middle line:90% like that. 00:11:23.037 --> 00:11:25.370 align:middle line:84% So I'm just going to put et cetera before we get carried 00:11:25.370 --> 00:11:26.570 align:middle line:90% away and forget ourselves. 00:11:26.570 --> 00:11:30.850 align:middle line:84% You might also want to know things like magnetic fields. 00:11:30.850 --> 00:11:33.070 align:middle line:84% These are pretty important in plasmas 00:11:33.070 --> 00:11:36.340 align:middle line:84% because plasmas move in response to magnetic fields. 00:11:36.340 --> 00:11:40.850 align:middle line:84% These magnetic fields are caused by currents, fundamentally, 00:11:40.850 --> 00:11:44.360 align:middle line:84% electric currents, and those electric currents 00:11:44.360 --> 00:11:45.740 align:middle line:90% can be external. 00:11:45.740 --> 00:11:48.260 align:middle line:84% So they could be provided by a large set of magnets 00:11:48.260 --> 00:11:49.550 align:middle line:90% that surround your plasma. 00:11:49.550 --> 00:11:53.930 align:middle line:90% 00:11:53.930 --> 00:11:55.070 align:middle line:90% Or they could be internal. 00:11:55.070 --> 00:11:57.948 align:middle line:84% They could be provided by the plasma motion itself-- probably 00:11:57.948 --> 00:11:59.240 align:middle line:90% getting a little bit low there. 00:11:59.240 --> 00:11:59.855 align:middle line:90% Let's go up. 00:11:59.855 --> 00:12:05.030 align:middle line:90% 00:12:05.030 --> 00:12:07.170 align:middle line:84% They're clearly very, very important. 00:12:07.170 --> 00:12:12.310 align:middle line:84% Now, in reality, even if we can measure density and velocity 00:12:12.310 --> 00:12:14.290 align:middle line:84% and magnetic fields, we're not really 00:12:14.290 --> 00:12:16.960 align:middle line:84% going to be able to get them at every point in space and time. 00:12:16.960 --> 00:12:17.840 align:middle line:90% We're quite limited. 00:12:17.840 --> 00:12:34.870 align:middle line:84% So diagnostic limitations, we're going 00:12:34.870 --> 00:12:42.390 align:middle line:84% to end up things which are sparse in space. 00:12:42.390 --> 00:12:45.340 align:middle line:84% I'm just going to use vector x for space and time. 00:12:45.340 --> 00:12:46.950 align:middle line:84% So we don't have it all the time. 00:12:46.950 --> 00:12:49.710 align:middle line:84% This may be because our diagnostic only measures 00:12:49.710 --> 00:12:51.900 align:middle line:84% at a single point as a function of time, 00:12:51.900 --> 00:12:55.170 align:middle line:84% or it may be a picture which measures spatial variation 00:12:55.170 --> 00:13:00.080 align:middle line:84% at a single time, or it may be some combination of those here. 00:13:00.080 --> 00:13:05.640 align:middle line:84% Our diagnostic is often going to be what we call line integrated. 00:13:05.640 --> 00:13:08.550 align:middle line:84% This is especially true for diagnostics which use light. 00:13:08.550 --> 00:13:11.467 align:middle line:84% Light famously mostly traveling in straight lines 00:13:11.467 --> 00:13:13.800 align:middle line:84% means that you don't get to choose where the light comes 00:13:13.800 --> 00:13:14.940 align:middle line:90% from that you're measuring. 00:13:14.940 --> 00:13:16.560 align:middle line:84% It's going to be along some cord. 00:13:16.560 --> 00:13:18.060 align:middle line:84% So we could say what we're measuring 00:13:18.060 --> 00:13:23.400 align:middle line:84% is not the density, but the density along a cord dl 00:13:23.400 --> 00:13:29.193 align:middle line:84% here, which is the path of our ray of light through the plasma. 00:13:29.193 --> 00:13:31.610 align:middle line:84% So that means as opposed to knowing n as a specific point, 00:13:31.610 --> 00:13:33.770 align:middle line:84% you know the integral of n over some points. 00:13:33.770 --> 00:13:36.200 align:middle line:84% If you happen to know some symmetry about your plasma, 00:13:36.200 --> 00:13:38.540 align:middle line:84% then maybe you can work out what n is locally. 00:13:38.540 --> 00:13:41.240 align:middle line:84% But otherwise, you're kind of stuck with this measurement 00:13:41.240 --> 00:13:43.660 align:middle line:90% instead. 00:13:43.660 --> 00:13:45.250 align:middle line:84% Almost certainly your measurement 00:13:45.250 --> 00:13:47.360 align:middle line:84% is going to be filtered in some way. 00:13:47.360 --> 00:13:51.450 align:middle line:84% And I'm using the word filtered here very broadly. 00:13:51.450 --> 00:13:53.970 align:middle line:84% This means that your instrument is in some way 00:13:53.970 --> 00:13:55.900 align:middle line:84% an imperfect measurement of the world. 00:13:55.900 --> 00:13:58.500 align:middle line:84% And so there is some sort of response function 00:13:58.500 --> 00:14:02.370 align:middle line:84% that you have to convolve or deconvolve from your instrument 00:14:02.370 --> 00:14:04.890 align:middle line:84% or convolve your synthetic data with in order 00:14:04.890 --> 00:14:06.750 align:middle line:90% to understand what it does. 00:14:06.750 --> 00:14:09.000 align:middle line:84% This could be things like a frequency response, 00:14:09.000 --> 00:14:10.320 align:middle line:90% if you're measuring voltages. 00:14:10.320 --> 00:14:12.510 align:middle line:84% This could be things like a resolution 00:14:12.510 --> 00:14:15.610 align:middle line:84% if you're taking images with a camera, that sort of thing. 00:14:15.610 --> 00:14:19.420 align:middle line:84% So almost everything has some sort of response function. 00:14:19.420 --> 00:14:23.520 align:middle line:84% And it's also probably going to depend on physics that we just 00:14:23.520 --> 00:14:29.030 align:middle line:84% don't understand very well, so depend 00:14:29.030 --> 00:14:30.905 align:middle line:90% on poorly understood physics. 00:14:30.905 --> 00:14:36.060 align:middle line:90% 00:14:36.060 --> 00:14:40.080 align:middle line:84% A great example of this is spectroscopy, so atomic data. 00:14:40.080 --> 00:14:43.730 align:middle line:90% 00:14:43.730 --> 00:14:45.320 align:middle line:84% Anyone who's ever done spectroscopy 00:14:45.320 --> 00:14:48.072 align:middle line:84% will know that there's a lot of electrons. 00:14:48.072 --> 00:14:49.530 align:middle line:84% There's lots of places they can be. 00:14:49.530 --> 00:14:51.097 align:middle line:84% They can interact in lots of ways. 00:14:51.097 --> 00:14:52.680 align:middle line:84% And so it's very hard to actually make 00:14:52.680 --> 00:14:55.350 align:middle line:84% predictions for the spectrum of even something as simple 00:14:55.350 --> 00:14:56.470 align:middle line:90% as helium. 00:14:56.470 --> 00:14:59.395 align:middle line:84% And so if we're trying to understand spectroscopy, 00:14:59.395 --> 00:15:01.020 align:middle line:84% we need to use this atomic data, but we 00:15:01.020 --> 00:15:03.750 align:middle line:84% should be cautious of the atomic data, which is mostly 00:15:03.750 --> 00:15:05.530 align:middle line:90% provided by theorists as well. 00:15:05.530 --> 00:15:06.930 align:middle line:90% So we should be cautious anyway. 00:15:06.930 --> 00:15:08.910 align:middle line:84% But we should be cautious of the atomic data 00:15:08.910 --> 00:15:11.140 align:middle line:84% because it forms part of our interpretation. 00:15:11.140 --> 00:15:12.913 align:middle line:84% So we may not just have errors due to some 00:15:12.913 --> 00:15:13.830 align:middle line:90% of these other things. 00:15:13.830 --> 00:15:16.403 align:middle line:84% We may have errors due to how we interpret this. 00:15:16.403 --> 00:15:18.570 align:middle line:84% So we should always be on the lookout for like, hmm, 00:15:18.570 --> 00:15:19.470 align:middle line:90% that looks weird. 00:15:19.470 --> 00:15:20.970 align:middle line:84% I wonder why that's going on and see 00:15:20.970 --> 00:15:23.342 align:middle line:84% if we can check whether this is a model dependent effect 00:15:23.342 --> 00:15:25.425 align:middle line:84% or whether it's to do with our diagnostic instead. 00:15:25.425 --> 00:15:28.710 align:middle line:90% 00:15:28.710 --> 00:15:32.630 align:middle line:84% So in this lecture course, we are focusing on the principles. 00:15:32.630 --> 00:15:34.880 align:middle line:84% Professor Hutchinson put this in the title of his book 00:15:34.880 --> 00:15:36.650 align:middle line:84% after teaching this course for many years. 00:15:36.650 --> 00:15:39.680 align:middle line:84% And he explains what he means by principles in the introduction. 00:15:39.680 --> 00:15:41.060 align:middle line:84% And I think it's very, very wise. 00:15:41.060 --> 00:15:42.710 align:middle line:84% He says that we're not going to focus 00:15:42.710 --> 00:15:45.530 align:middle line:84% on the practical implementations of diagnostics. 00:15:45.530 --> 00:15:47.097 align:middle line:90% Those things change over time. 00:15:47.097 --> 00:15:48.680 align:middle line:84% There's always a new camera that works 00:15:48.680 --> 00:15:50.510 align:middle line:90% in a new way that's better. 00:15:50.510 --> 00:15:53.120 align:middle line:84% But what doesn't change is what a plasma is, 00:15:53.120 --> 00:15:55.910 align:middle line:84% the equations that govern it, and some of the techniques 00:15:55.910 --> 00:15:56.803 align:middle line:90% that we can use. 00:15:56.803 --> 00:15:58.220 align:middle line:84% Now, there's always new techniques 00:15:58.220 --> 00:15:59.512 align:middle line:90% that people are coming up with. 00:15:59.512 --> 00:16:00.950 align:middle line:84% This is a very, very lively field. 00:16:00.950 --> 00:16:03.283 align:middle line:84% There's a conference every year, High Temperature Plasma 00:16:03.283 --> 00:16:06.380 align:middle line:84% Diagnostics, which is well worth going to where people present 00:16:06.380 --> 00:16:08.330 align:middle line:84% new diagnostics, new interpretations, 00:16:08.330 --> 00:16:09.950 align:middle line:90% new ways of measurement. 00:16:09.950 --> 00:16:11.190 align:middle line:90% And it's very, very dynamic. 00:16:11.190 --> 00:16:13.783 align:middle line:84% There are lots of different ways to try and measure a plasma. 00:16:13.783 --> 00:16:15.950 align:middle line:84% There are some techniques which are very successful, 00:16:15.950 --> 00:16:18.410 align:middle line:84% but have only been implemented in one or two institutions, 00:16:18.410 --> 00:16:19.743 align:middle line:90% just simply because of the cost. 00:16:19.743 --> 00:16:21.743 align:middle line:84% There's some techniques that are very successful 00:16:21.743 --> 00:16:23.510 align:middle line:84% and have only been implemented because 00:16:23.510 --> 00:16:26.000 align:middle line:84% of institutional inertia, because of the specialized 00:16:26.000 --> 00:16:27.007 align:middle line:90% knowledge to be used. 00:16:27.007 --> 00:16:29.340 align:middle line:84% So it's always worth reading up some papers you'll never 00:16:29.340 --> 00:16:30.382 align:middle line:90% find-- you'll never know. 00:16:30.382 --> 00:16:32.465 align:middle line:84% You'll probably find that the Russians did it back 00:16:32.465 --> 00:16:33.072 align:middle line:90% in the '70s. 00:16:33.072 --> 00:16:35.530 align:middle line:84% This is true with almost every diagnostic you can think of. 00:16:35.530 --> 00:16:37.447 align:middle line:84% And they published it in some obscure journal. 00:16:37.447 --> 00:16:40.110 align:middle line:84% So it's worth looking out to see whether someone's already 00:16:40.110 --> 00:16:42.850 align:middle line:84% tried to do what you're trying to do before. 00:16:42.850 --> 00:16:48.087 align:middle line:84% So any questions on this sort of introduction? 00:16:48.087 --> 00:16:50.170 align:middle line:84% Then we can have an interactive part of the class. 00:16:50.170 --> 00:16:55.870 align:middle line:90% 00:16:55.870 --> 00:16:57.085 align:middle line:90% Yes. 00:16:57.085 --> 00:17:00.993 align:middle line:90% AUDIENCE: [INAUDIBLE] 00:17:00.993 --> 00:17:01.660 align:middle line:90% JACK HARE: Yeah. 00:17:01.660 --> 00:17:04.270 align:middle line:84% Imagine you've got a plasma, which is glowing. 00:17:04.270 --> 00:17:05.387 align:middle line:90% So it's emitting light. 00:17:05.387 --> 00:17:06.220 align:middle line:90% And I have a camera. 00:17:06.220 --> 00:17:07.540 align:middle line:90% And I'm looking at this plasma. 00:17:07.540 --> 00:17:09.040 align:middle line:90% And the plasma is not uniform. 00:17:09.040 --> 00:17:11.200 align:middle line:84% Maybe the core of it is very hot, like a tokamak. 00:17:11.200 --> 00:17:13.060 align:middle line:90% And the edge is very cold. 00:17:13.060 --> 00:17:16.240 align:middle line:84% But that means along the line of sight between the plasma 00:17:16.240 --> 00:17:19.480 align:middle line:84% and your camera over there, you are adding up the emission 00:17:19.480 --> 00:17:21.893 align:middle line:84% from each little blob of plasma along your line of sight. 00:17:21.893 --> 00:17:24.310 align:middle line:84% So you're adding up emission from some hot bits of plasma, 00:17:24.310 --> 00:17:25.819 align:middle line:90% some cold bits of plasma. 00:17:25.819 --> 00:17:27.462 align:middle line:84% So if you look at the spectrum of that, 00:17:27.462 --> 00:17:29.170 align:middle line:84% you're going to see lines that correspond 00:17:29.170 --> 00:17:31.750 align:middle line:84% to a cold plasma and a hot plasma simultaneously. 00:17:31.750 --> 00:17:32.917 align:middle line:90% That doesn't make any sense. 00:17:32.917 --> 00:17:34.667 align:middle line:84% So you need to know that that's happening. 00:17:34.667 --> 00:17:36.170 align:middle line:84% It gets worse than that, of course. 00:17:36.170 --> 00:17:38.253 align:middle line:84% Different bits of plasma can be absorbing as well. 00:17:38.253 --> 00:17:40.503 align:middle line:84% And so you may have attenuation of some of those lines 00:17:40.503 --> 00:17:41.530 align:middle line:90% as it goes through. 00:17:41.530 --> 00:17:42.940 align:middle line:84% This becomes radiation transport, 00:17:42.940 --> 00:17:44.343 align:middle line:90% and it's like a whole mess. 00:17:44.343 --> 00:17:45.760 align:middle line:84% So that's one simple example there 00:17:45.760 --> 00:17:47.650 align:middle line:84% that just as you look through a plasma, 00:17:47.650 --> 00:17:49.030 align:middle line:84% you're going to get very different properties, 00:17:49.030 --> 00:17:50.740 align:middle line:84% all contributing to your final measurement. 00:17:50.740 --> 00:17:52.365 align:middle line:84% This isn't the case of something that's 00:17:52.365 --> 00:17:54.970 align:middle line:84% very local, like a Langmuir probe, or a B-dot probe, 00:17:54.970 --> 00:17:56.080 align:middle line:90% or Thomson scattering. 00:17:56.080 --> 00:17:58.240 align:middle line:84% But it's very much the case for, I would say, 00:17:58.240 --> 00:17:59.440 align:middle line:84% about half the diagnostics we're going 00:17:59.440 --> 00:18:00.280 align:middle line:90% to talk about in this course. 00:18:00.280 --> 00:18:02.238 align:middle line:84% They're going to suffer from light integration. 00:18:02.238 --> 00:18:05.290 align:middle line:84% And the reason is plasma is electromagnetic. 00:18:05.290 --> 00:18:06.460 align:middle line:90% Light is electromagnetic. 00:18:06.460 --> 00:18:08.072 align:middle line:84% So we use light to probe plasmas, 00:18:08.072 --> 00:18:10.030 align:middle line:84% and light has this problem of line integration. 00:18:10.030 --> 00:18:12.530 align:middle line:84% So it almost always comes up, no matter what you try and do. 00:18:12.530 --> 00:18:16.270 align:middle line:90% 00:18:16.270 --> 00:18:17.356 align:middle line:90% Other questions? 00:18:17.356 --> 00:18:22.638 align:middle line:90% 00:18:22.638 --> 00:18:23.680 align:middle line:90% How's it going, Columbia? 00:18:23.680 --> 00:18:26.570 align:middle line:90% 00:18:26.570 --> 00:18:27.530 align:middle line:90% Good. 00:18:27.530 --> 00:18:29.880 align:middle line:90% Thumbs up. 00:18:29.880 --> 00:18:32.212 align:middle line:90% So what I like to do-- 00:18:32.212 --> 00:18:34.170 align:middle line:84% I found when I taught this class before there's 00:18:34.170 --> 00:18:37.890 align:middle line:84% a huge array of people who take it, which is super exciting. 00:18:37.890 --> 00:18:40.000 align:middle line:84% And they all work on very different things. 00:18:40.000 --> 00:18:41.910 align:middle line:84% And this is my opportunity to find out 00:18:41.910 --> 00:18:45.300 align:middle line:84% some of the stuff you work on as we play 00:18:45.300 --> 00:18:47.110 align:middle line:90% pin your plasma to the board. 00:18:47.110 --> 00:18:51.330 align:middle line:84% So as you can all see, we have a temperature scale on the side 00:18:51.330 --> 00:18:53.760 align:middle line:84% here that goes from 0.1 eV-- and yeah, 00:18:53.760 --> 00:18:55.260 align:middle line:90% you can still get plasma there-- 00:18:55.260 --> 00:18:58.553 align:middle line:84% up to 10 keV and above, whatever. 00:18:58.553 --> 00:18:59.970 align:middle line:84% And then we've got densities here. 00:18:59.970 --> 00:19:01.470 align:middle line:84% If you thought that was logarithmic, 00:19:01.470 --> 00:19:05.730 align:middle line:84% they go from 10 to 16 particles per cubic meter 00:19:05.730 --> 00:19:08.980 align:middle line:84% to 10 to the 32 particles per cubic meter here. 00:19:08.980 --> 00:19:10.220 align:middle line:90% So 16 orders of magnitude. 00:19:10.220 --> 00:19:11.970 align:middle line:84% And yet we're all sitting in the same room 00:19:11.970 --> 00:19:13.262 align:middle line:90% trying to learn the same stuff. 00:19:13.262 --> 00:19:15.150 align:middle line:84% That's one of the reasons why this topic is 00:19:15.150 --> 00:19:18.630 align:middle line:84% very fascinating, and also quite hard to teach at times. 00:19:18.630 --> 00:19:22.350 align:middle line:84% I've also tried to get the third dimension to you guys. 00:19:22.350 --> 00:19:24.240 align:middle line:90% We're going to be using color. 00:19:24.240 --> 00:19:26.740 align:middle line:84% And we're looking at the magnetic field here. 00:19:26.740 --> 00:19:28.200 align:middle line:84% So I've got a magnetic field going 00:19:28.200 --> 00:19:30.210 align:middle line:84% from 0.01, which I think most of us 00:19:30.210 --> 00:19:33.525 align:middle line:84% agree is basically 0, all the way up to 100 tesla 00:19:33.525 --> 00:19:35.400 align:middle line:84% or so, which I know some places where you get 00:19:35.400 --> 00:19:37.080 align:middle line:90% 100 tesla in plasma physics. 00:19:37.080 --> 00:19:40.960 align:middle line:84% I don't know whether anyone working here works on those. 00:19:40.960 --> 00:19:44.038 align:middle line:84% But the idea is you're either going to volunteer, 00:19:44.038 --> 00:19:45.330 align:middle line:90% or I'm going to start pointing. 00:19:45.330 --> 00:19:48.330 align:middle line:84% And you're going to come up, if you're here in the room, 00:19:48.330 --> 00:19:51.570 align:middle line:84% or you're going to tell me if you're over there in Columbia, 00:19:51.570 --> 00:19:53.910 align:middle line:84% where your plasma falls on this board. 00:19:53.910 --> 00:19:55.600 align:middle line:84% So we'll just draw little circles. 00:19:55.600 --> 00:19:57.540 align:middle line:84% So say you've got a plasma that is 100 tesla 00:19:57.540 --> 00:19:59.703 align:middle line:84% and it lives up in this corner here. 00:19:59.703 --> 00:20:01.620 align:middle line:84% You would just draw a little blob, being like, 00:20:01.620 --> 00:20:02.880 align:middle line:90% that's my plasma. 00:20:02.880 --> 00:20:06.223 align:middle line:84% You'd put a number in, and by the side of it, 00:20:06.223 --> 00:20:08.140 align:middle line:84% you'd maybe write something about your plasma. 00:20:08.140 --> 00:20:11.710 align:middle line:84% Maybe it's a magnetized ICF implosion on NIF. 00:20:11.710 --> 00:20:14.200 align:middle line:84% And you'd maybe dot down a couple of diagnostics 00:20:14.200 --> 00:20:15.040 align:middle line:90% that you work on. 00:20:15.040 --> 00:20:16.960 align:middle line:84% If you don't work on any diagnostics at the moment, 00:20:16.960 --> 00:20:17.460 align:middle line:90% that's fine. 00:20:17.460 --> 00:20:19.600 align:middle line:84% Maybe just mention a diagnostic you know is used. 00:20:19.600 --> 00:20:21.190 align:middle line:84% And you don't have to be exhaustive. 00:20:21.190 --> 00:20:22.420 align:middle line:84% If you mention the tokamak, you don't 00:20:22.420 --> 00:20:24.837 align:middle line:84% have to list every diagnostic on the tokamak, just the one 00:20:24.837 --> 00:20:25.690 align:middle line:90% that you work on. 00:20:25.690 --> 00:20:27.670 align:middle line:84% And let someone else have a go at mentioning 00:20:27.670 --> 00:20:28.640 align:middle line:90% some of the other ones. 00:20:28.640 --> 00:20:30.917 align:middle line:84% So I'm going to erase that now, because I 00:20:30.917 --> 00:20:32.500 align:middle line:84% think that's slightly optimistic, even 00:20:32.500 --> 00:20:36.160 align:middle line:90% for a magnetized ICF shot. 00:20:36.160 --> 00:20:38.950 align:middle line:84% And I'm now going to turn around and see someone with their hand 00:20:38.950 --> 00:20:40.900 align:middle line:84% up as the first willing volunteer. 00:20:40.900 --> 00:20:43.820 align:middle line:90% 00:20:43.820 --> 00:20:44.320 align:middle line:90% Good. 00:20:44.320 --> 00:20:49.890 align:middle line:90% 00:20:49.890 --> 00:20:54.770 align:middle line:84% As you're walking up, what's your name and your department? 00:20:54.770 --> 00:20:57.488 align:middle line:84% AUDIENCE: I've worked with Nathan Howard and Pablo 00:20:57.488 --> 00:21:03.630 align:middle line:90% Rodriguez Fernandez. 00:21:03.630 --> 00:21:05.130 align:middle line:84% JACK HARE: Can the folks at Columbia 00:21:05.130 --> 00:21:08.040 align:middle line:84% hear him OK if I stand nearby or is it very quiet? 00:21:08.040 --> 00:21:09.300 align:middle line:90% Oh, dear. 00:21:09.300 --> 00:21:10.618 align:middle line:90% You should have this then. 00:21:10.618 --> 00:21:11.160 align:middle line:90% AUDIENCE: OK. 00:21:11.160 --> 00:21:12.090 align:middle line:90% Let's pull you up. 00:21:12.090 --> 00:21:12.760 align:middle line:90% AUDIENCE: Hello, everybody. 00:21:12.760 --> 00:21:13.290 align:middle line:90% I'm Vince. 00:21:13.290 --> 00:21:16.800 align:middle line:84% I work with Nathan Howard and Pablo Rodriguez Fernandez 00:21:16.800 --> 00:21:20.760 align:middle line:84% on modeling turbulent transport in the Spark reactor. 00:21:20.760 --> 00:21:23.910 align:middle line:84% I don't remember off the top of my head the particle density. 00:21:23.910 --> 00:21:26.580 align:middle line:90% I think it's in this range. 00:21:26.580 --> 00:21:28.200 align:middle line:90% Just a circle you said? 00:21:28.200 --> 00:21:28.705 align:middle line:90% Or like-- 00:21:28.705 --> 00:21:30.705 align:middle line:84% JACK HARE: Yeah, where's my little [INAUDIBLE]?? 00:21:30.705 --> 00:21:36.587 align:middle line:90% 00:21:36.587 --> 00:21:37.920 align:middle line:90% I have 10 to the 20 [INAUDIBLE]. 00:21:37.920 --> 00:21:38.260 align:middle line:90% AUDIENCE: 10 to the 20. 00:21:38.260 --> 00:21:38.845 align:middle line:90% OK. 00:21:38.845 --> 00:21:41.070 align:middle line:90% JACK HARE: 10 to the 20. 00:21:41.070 --> 00:21:41.970 align:middle line:90% Yeah, cool. 00:21:41.970 --> 00:21:46.800 align:middle line:90% 00:21:46.800 --> 00:21:47.300 align:middle line:90% Cool. 00:21:47.300 --> 00:21:49.250 align:middle line:84% But put a little number on it like one, 00:21:49.250 --> 00:21:50.833 align:middle line:84% and then just write on the side what's 00:21:50.833 --> 00:21:53.033 align:middle line:90% your diagnostic [INAUDIBLE]. 00:21:53.033 --> 00:21:54.700 align:middle line:84% Yeah, I should not have made it so high. 00:21:54.700 --> 00:22:01.780 align:middle line:90% 00:22:01.780 --> 00:22:04.110 align:middle line:90% AUDIENCE: Let's see. 00:22:04.110 --> 00:22:06.400 align:middle line:84% I don't work with any diagnostics at the moment. 00:22:06.400 --> 00:22:11.740 align:middle line:84% I work with heat flux data that's 00:22:11.740 --> 00:22:20.325 align:middle line:84% generated via simulation code, like TGLF and gyrokinetic 00:22:20.325 --> 00:22:20.825 align:middle line:90% [INAUDIBLE]. 00:22:20.825 --> 00:22:29.390 align:middle line:84% JACK HARE: Anyone else know [INAUDIBLE]?? 00:22:29.390 --> 00:22:30.698 align:middle line:90% AUDIENCE: I don't-- 00:22:30.698 --> 00:22:32.198 align:middle line:84% I don't know off the top of my head. 00:22:32.198 --> 00:22:33.813 align:middle line:90% 00:22:33.813 --> 00:22:36.230 align:middle line:84% JACK HARE: Well, let's go for that, like a Langmuir probe. 00:22:36.230 --> 00:22:42.182 align:middle line:90% 00:22:42.182 --> 00:22:44.168 align:middle line:84% AUDIENCE: Is that how you spell it? 00:22:44.168 --> 00:22:45.710 align:middle line:84% JACK HARE: All right, next volunteer. 00:22:45.710 --> 00:22:47.252 align:middle line:84% Let's have one from Columbia, please. 00:22:47.252 --> 00:22:49.710 align:middle line:90% 00:22:49.710 --> 00:22:51.730 align:middle line:90% Hey, Nigel. 00:22:51.730 --> 00:22:52.810 align:middle line:90% AUDIENCE: Hello. 00:22:52.810 --> 00:22:55.630 align:middle line:84% I work with plasmas that are 10 to the 19 00:22:55.630 --> 00:23:02.320 align:middle line:84% density, 100 eV with a magnetic field of 0.1 00:23:02.320 --> 00:23:03.970 align:middle line:90% on that order of magnitude. 00:23:03.970 --> 00:23:05.137 align:middle line:90% JACK HARE: So what was that? 00:23:05.137 --> 00:23:06.550 align:middle line:90% 10 to 19, and 100 eV. 00:23:06.550 --> 00:23:07.390 align:middle line:90% AUDIENCE: Yes. 00:23:07.390 --> 00:23:09.010 align:middle line:84% JACK HARE: So kind of about here? 00:23:09.010 --> 00:23:11.320 align:middle line:90% AUDIENCE: Yeah. 00:23:11.320 --> 00:23:13.330 align:middle line:84% JACK HARE: And so what's this plasma? 00:23:13.330 --> 00:23:14.740 align:middle line:90% AUDIENCE: That's the HBT plasma. 00:23:14.740 --> 00:23:17.800 align:middle line:84% That's the tokamak that we have at Columbia. 00:23:17.800 --> 00:23:21.130 align:middle line:84% And I work with Langmuir probe arrays, Mirnov coils, 00:23:21.130 --> 00:23:24.880 align:middle line:84% and tangential extreme electromag-- 00:23:24.880 --> 00:23:26.500 align:middle line:90% extreme ultraviolet light. 00:23:26.500 --> 00:23:27.122 align:middle line:90% So TUV. 00:23:27.122 --> 00:23:30.490 align:middle line:90% 00:23:30.490 --> 00:23:33.100 align:middle line:84% JACK HARE: And Mirnov, which I'm just going to write as B-dot. 00:23:33.100 --> 00:23:34.058 align:middle line:90% AUDIENCE: Yeah, B-dots. 00:23:34.058 --> 00:23:35.990 align:middle line:84% JACK HARE: They're sort of B-dots. 00:23:35.990 --> 00:23:36.490 align:middle line:90% Great! 00:23:36.490 --> 00:23:39.090 align:middle line:90% A volunteer from in the room. 00:23:39.090 --> 00:23:39.590 align:middle line:90% Come on up. 00:23:39.590 --> 00:23:43.400 align:middle line:90% 00:23:43.400 --> 00:23:45.400 align:middle line:84% I don't know if I can have both of these working 00:23:45.400 --> 00:23:46.108 align:middle line:90% at the same time. 00:23:46.108 --> 00:23:47.590 align:middle line:90% I think there are spares. 00:23:47.590 --> 00:23:49.418 align:middle line:90% There you go. 00:23:49.418 --> 00:23:49.960 align:middle line:90% AUDIENCE: Hi. 00:23:49.960 --> 00:23:50.920 align:middle line:90% My name is Amelia. 00:23:50.920 --> 00:23:55.180 align:middle line:84% I do some work with DIII-D on a Lyman-alpha diagnostic, 00:23:55.180 --> 00:23:59.410 align:middle line:84% and that's roughly here-ish in operating space. 00:23:59.410 --> 00:24:04.720 align:middle line:90% 00:24:04.720 --> 00:24:06.180 align:middle line:90% JACK HARE: Is it that low? 00:24:06.180 --> 00:24:08.070 align:middle line:84% AUDIENCE: I think it's like a little higher. 00:24:08.070 --> 00:24:10.830 align:middle line:90% It's like four to five often. 00:24:10.830 --> 00:24:11.970 align:middle line:90% It's good enough for me. 00:24:11.970 --> 00:24:12.553 align:middle line:90% JACK HARE: OK. 00:24:12.553 --> 00:24:19.697 align:middle line:90% 00:24:19.697 --> 00:24:22.280 align:middle line:84% AUDIENCE: And then Lyman-alpha, the spectral line of hydrogen, 00:24:22.280 --> 00:24:23.720 align:middle line:90% as we mentioned. 00:24:23.720 --> 00:24:32.422 align:middle line:90% 00:24:32.422 --> 00:24:33.130 align:middle line:90% JACK HARE: Great. 00:24:33.130 --> 00:24:33.790 align:middle line:90% Thank you. 00:24:33.790 --> 00:24:35.290 align:middle line:84% We've got a volunteer from Columbia. 00:24:35.290 --> 00:24:40.683 align:middle line:90% 00:24:40.683 --> 00:24:42.100 align:middle line:84% AUDIENCE: Do I need raise my hand? 00:24:42.100 --> 00:24:42.725 align:middle line:90% Or can I just-- 00:24:42.725 --> 00:24:43.558 align:middle line:90% JACK HARE: Oh, yeah. 00:24:43.558 --> 00:24:44.170 align:middle line:90% Please, start. 00:24:44.170 --> 00:24:45.818 align:middle line:90% Please go for it. 00:24:45.818 --> 00:24:46.360 align:middle line:90% AUDIENCE: Hi. 00:24:46.360 --> 00:24:47.770 align:middle line:90% I'm Jacob. 00:24:47.770 --> 00:24:48.760 align:middle line:90% I'm at Columbia. 00:24:48.760 --> 00:24:52.840 align:middle line:84% I just got done working with some DIII-D plasmas as well. 00:24:52.840 --> 00:24:53.710 align:middle line:90% JACK HARE: Nice. 00:24:53.710 --> 00:24:56.620 align:middle line:84% AUDIENCE: Roughly the same area, I'd say. 00:24:56.620 --> 00:24:58.802 align:middle line:84% And I was working with bolometers. 00:24:58.802 --> 00:25:00.010 align:middle line:90% JACK HARE: Bolometers-- cool! 00:25:00.010 --> 00:25:02.032 align:middle line:90% What do bolometers measure? 00:25:02.032 --> 00:25:03.490 align:middle line:84% AUDIENCE: Bolometers were measuring 00:25:03.490 --> 00:25:08.890 align:middle line:84% radiation fluxes, mostly heat loads, and it's fast bolometers. 00:25:08.890 --> 00:25:10.288 align:middle line:90% So they're AXUVs. 00:25:10.288 --> 00:25:11.080 align:middle line:90% JACK HARE: Awesome. 00:25:11.080 --> 00:25:12.010 align:middle line:90% Thank you. 00:25:12.010 --> 00:25:13.890 align:middle line:90% Anyone in the room? 00:25:13.890 --> 00:25:14.390 align:middle line:90% Come on. 00:25:14.390 --> 00:25:15.307 align:middle line:90% One of the NIF people. 00:25:15.307 --> 00:25:15.860 align:middle line:90% Come on. 00:25:15.860 --> 00:25:17.820 align:middle line:84% We need to push up into this corner. 00:25:17.820 --> 00:25:18.845 align:middle line:90% Ok. 00:25:18.845 --> 00:25:21.500 align:middle line:90% 00:25:21.500 --> 00:25:33.080 align:middle line:90% AUDIENCE: [INAUDIBLE] 00:25:33.080 --> 00:25:34.040 align:middle line:90% Hi, I'm Chris. 00:25:34.040 --> 00:25:36.630 align:middle line:90% 00:25:36.630 --> 00:25:43.420 align:middle line:84% So I'm NSC HGDP [INAUDIBLE] confinement fusion. 00:25:43.420 --> 00:25:45.300 align:middle line:84% And our temperatures are over here, 00:25:45.300 --> 00:25:49.320 align:middle line:90% 3 to 10 keV, I'm going to say. 00:25:49.320 --> 00:26:00.560 align:middle line:84% And then I work in units of rho r, so 300 to 600. 00:26:00.560 --> 00:26:01.790 align:middle line:90% JACK HARE: [INAUDIBLE] 00:26:01.790 --> 00:26:03.260 align:middle line:84% AUDIENCE: And that's where I don't know if they 00:26:03.260 --> 00:26:04.385 align:middle line:90% operate in magnetic fields. 00:26:04.385 --> 00:26:06.110 align:middle line:84% But I'm going to say Skyler does. 00:26:06.110 --> 00:26:10.917 align:middle line:90% 10, 100 tesla. 00:26:10.917 --> 00:26:11.750 align:middle line:90% JACK HARE: Yeah, no. 00:26:11.750 --> 00:26:12.170 align:middle line:90% I know it is. 00:26:12.170 --> 00:26:13.253 align:middle line:90% You don't start with that. 00:26:13.253 --> 00:26:15.780 align:middle line:90% 00:26:15.780 --> 00:26:19.540 align:middle line:84% Have you been doing the [INAUDIBLE]?? 00:26:19.540 --> 00:26:20.100 align:middle line:90% Go for it. 00:26:20.100 --> 00:26:20.670 align:middle line:90% Yeah, yeah, yeah. 00:26:20.670 --> 00:26:21.270 align:middle line:90% AUDIENCE: I'm going to go with-- 00:26:21.270 --> 00:26:21.720 align:middle line:84% JACK HARE: [INAUDIBLE] the yellow one. 00:26:21.720 --> 00:26:22.220 align:middle line:90% There we go. 00:26:22.220 --> 00:26:24.800 align:middle line:90% 00:26:24.800 --> 00:26:27.590 align:middle line:84% AUDIENCE: NIF extreme, and then what are we up to? 00:26:27.590 --> 00:26:28.370 align:middle line:90% Four? 00:26:28.370 --> 00:26:34.830 align:middle line:84% So for mine, I'll put neutron spectrometry-- 00:26:34.830 --> 00:26:35.330 align:middle line:90% neutron. 00:26:35.330 --> 00:26:39.970 align:middle line:90% 00:26:39.970 --> 00:26:40.990 align:middle line:90% What about you guys? 00:26:40.990 --> 00:26:43.982 align:middle line:90% 00:26:43.982 --> 00:26:45.232 align:middle line:90% AUDIENCE: Prolon cardiography. 00:26:45.232 --> 00:26:58.070 align:middle line:90% 00:26:58.070 --> 00:26:59.320 align:middle line:90% JACK HARE: Thomson scattering. 00:26:59.320 --> 00:27:02.010 align:middle line:90% Good, good. go on, then. 00:27:02.010 --> 00:27:04.830 align:middle line:90% We've got four there. 00:27:04.830 --> 00:27:08.000 align:middle line:90% Where's the mic? 00:27:08.000 --> 00:27:08.702 align:middle line:90% Cool. 00:27:08.702 --> 00:27:10.660 align:middle line:84% All right, do we have anyone else from Columbia 00:27:10.660 --> 00:27:13.070 align:middle line:90% willing to volunteer? 00:27:13.070 --> 00:27:14.330 align:middle line:90% AUDIENCE: Yeah. 00:27:14.330 --> 00:27:16.010 align:middle line:90% AUDIENCE: I also do-- 00:27:16.010 --> 00:27:17.050 align:middle line:90% I hope you can hear me. 00:27:17.050 --> 00:27:19.420 align:middle line:84% I also do DIII-D experiments, particularly 00:27:19.420 --> 00:27:20.740 align:middle line:90% runaway electron experiments. 00:27:20.740 --> 00:27:23.320 align:middle line:84% And we use a gamma ray imager and also 00:27:23.320 --> 00:27:25.970 align:middle line:90% some hard X-ray detectors. 00:27:25.970 --> 00:27:31.440 align:middle line:84% So they're scintillators, which register heart X-ray instagram 00:27:31.440 --> 00:27:32.343 align:middle line:90% HXR. 00:27:32.343 --> 00:27:33.010 align:middle line:90% JACK HARE: Cool. 00:27:33.010 --> 00:27:35.302 align:middle line:84% I'm going to put that on as gamma rays and hard X-rays. 00:27:35.302 --> 00:27:37.310 align:middle line:90% That's good stuff. 00:27:37.310 --> 00:27:38.240 align:middle line:90% Anyone in the room? 00:27:38.240 --> 00:27:39.170 align:middle line:90% Yeah, go for it. 00:27:39.170 --> 00:27:44.900 align:middle line:90% 00:27:44.900 --> 00:27:45.860 align:middle line:90% AUDIENCE: I'm Stan. 00:27:45.860 --> 00:27:46.660 align:middle line:90% I'm in NSCI. 00:27:46.660 --> 00:27:48.200 align:middle line:90% I also work on Spark. 00:27:48.200 --> 00:27:49.880 align:middle line:90% And I do soft X-ray. 00:27:49.880 --> 00:27:53.870 align:middle line:90% 00:27:53.870 --> 00:27:56.640 align:middle line:84% JACK HARE: What you are working on? 00:27:56.640 --> 00:27:58.430 align:middle line:84% AUDIENCE: So the ones I'm working on 00:27:58.430 --> 00:28:03.230 align:middle line:84% are diamond based, because specifically for Spark, 00:28:03.230 --> 00:28:06.630 align:middle line:84% traditional silicone diode would die from the neutrons. 00:28:06.630 --> 00:28:09.770 align:middle line:84% So we're using a diamond-based detector instead. 00:28:09.770 --> 00:28:13.040 align:middle line:84% And they're in very early stage development. 00:28:13.040 --> 00:28:15.440 align:middle line:84% Although, our collaborators in Rome have 00:28:15.440 --> 00:28:17.906 align:middle line:84% had some promising results so far. 00:28:17.906 --> 00:28:18.698 align:middle line:90% JACK HARE: Awesome. 00:28:18.698 --> 00:28:21.340 align:middle line:90% 00:28:21.340 --> 00:28:21.840 align:middle line:90% Yeah. 00:28:21.840 --> 00:28:26.828 align:middle line:90% 00:28:26.828 --> 00:28:27.370 align:middle line:90% AUDIENCE: Hi. 00:28:27.370 --> 00:28:28.690 align:middle line:90% I'm Nikola. 00:28:28.690 --> 00:28:31.000 align:middle line:84% I'm working on arc stuff right now, 00:28:31.000 --> 00:28:33.010 align:middle line:84% but I wanted to mention what I was working 00:28:33.010 --> 00:28:34.960 align:middle line:90% for my master's back in Serbia. 00:28:34.960 --> 00:28:37.600 align:middle line:84% I was working with pseudospark discharges, 00:28:37.600 --> 00:28:41.800 align:middle line:84% which were like ionized gases more than actual plasmas. 00:28:41.800 --> 00:28:47.790 align:middle line:84% They were somewhere in like this region-ish here. 00:28:47.790 --> 00:28:49.110 align:middle line:90% What number is it? 00:28:49.110 --> 00:28:49.950 align:middle line:90% JACK HARE: 5. 00:28:49.950 --> 00:28:51.670 align:middle line:90% AUDIENCE: 5. 00:28:51.670 --> 00:28:56.560 align:middle line:84% And what I was doing with those was vacuum ultraviolet 00:28:56.560 --> 00:28:57.550 align:middle line:90% spectroscopy. 00:28:57.550 --> 00:29:13.230 align:middle line:90% 00:29:13.230 --> 00:29:16.290 align:middle line:84% And those were like not magnetized. 00:29:16.290 --> 00:29:17.635 align:middle line:90% JACK HARE: All right, thank you. 00:29:17.635 --> 00:29:18.510 align:middle line:90% Anyone from Columbia? 00:29:18.510 --> 00:29:21.570 align:middle line:90% 00:29:21.570 --> 00:29:23.030 align:middle line:90% AUDIENCE: I can say one. 00:29:23.030 --> 00:29:26.000 align:middle line:90% So CNT is no longer operational. 00:29:26.000 --> 00:29:28.430 align:middle line:90% But I'm working on upgrading it. 00:29:28.430 --> 00:29:34.760 align:middle line:84% And the operational density was of the order of 10 to the 16th. 00:29:34.760 --> 00:29:37.580 align:middle line:90% And magnetic field 0.06 tesla. 00:29:37.580 --> 00:29:43.050 align:middle line:84% I think temperature, order of an eV. 00:29:43.050 --> 00:29:44.297 align:middle line:90% I'm not too sure. 00:29:44.297 --> 00:29:44.880 align:middle line:90% JACK HARE: OK. 00:29:44.880 --> 00:29:46.260 align:middle line:90% So kind of like here? 00:29:46.260 --> 00:29:47.850 align:middle line:84% AUDIENCE: Yeah, probably low, yeah. 00:29:47.850 --> 00:29:49.080 align:middle line:90% JACK HARE: And you said 0.06. 00:29:49.080 --> 00:29:50.205 align:middle line:90% I'm going to call that 0.1. 00:29:50.205 --> 00:29:51.453 align:middle line:90% We'll round up. 00:29:51.453 --> 00:29:52.620 align:middle line:90% AUDIENCE: Yeah, sounds good. 00:29:52.620 --> 00:29:53.160 align:middle line:90% Sounds good. 00:29:53.160 --> 00:29:53.827 align:middle line:90% JACK HARE: Cool. 00:29:53.827 --> 00:29:57.780 align:middle line:84% So this is CNT plus plus, or whatever the new name will be. 00:29:57.780 --> 00:29:59.010 align:middle line:90% AUDIENCE: Exactly, exactly. 00:29:59.010 --> 00:29:59.677 align:middle line:90% JACK HARE: Cool. 00:29:59.677 --> 00:30:01.800 align:middle line:84% And what are you going to be diagnosing it with? 00:30:01.800 --> 00:30:04.560 align:middle line:84% AUDIENCE: So they had an electron beam 00:30:04.560 --> 00:30:09.060 align:middle line:84% that also was paired with a fluorescent rod 00:30:09.060 --> 00:30:12.870 align:middle line:84% to map the magnetic field surfaces. 00:30:12.870 --> 00:30:14.935 align:middle line:90% JACK HARE: Nice. 00:30:14.935 --> 00:30:17.480 align:middle line:84% Yeah, I saw them doing that technique on W7-X as well. 00:30:17.480 --> 00:30:18.460 align:middle line:90% It's really cool. 00:30:18.460 --> 00:30:20.075 align:middle line:90% AUDIENCE: Nice. 00:30:20.075 --> 00:30:20.950 align:middle line:90% JACK HARE: All right. 00:30:20.950 --> 00:30:26.088 align:middle line:90% 00:30:26.088 --> 00:30:26.630 align:middle line:90% AUDIENCE: Hi. 00:30:26.630 --> 00:30:28.100 align:middle line:90% I'm Lainey. 00:30:28.100 --> 00:30:30.740 align:middle line:84% So I actually work in the aerospace department. 00:30:30.740 --> 00:30:33.750 align:middle line:84% And I work with non-equilibrium plasmas. 00:30:33.750 --> 00:30:36.950 align:middle line:90% So I actually am in-- 00:30:36.950 --> 00:30:39.230 align:middle line:84% we go from-- we work from low pressure 00:30:39.230 --> 00:30:43.910 align:middle line:84% to atmospheric pressure in this general area. 00:30:43.910 --> 00:30:47.570 align:middle line:84% But in a nonthermal plasma, our electrons 00:30:47.570 --> 00:30:51.530 align:middle line:84% are closer to the 10 eV, anywhere from 1 to 10 eV. 00:30:51.530 --> 00:30:58.040 align:middle line:84% And our gas temperature is much lower, so kind of in that region 00:30:58.040 --> 00:31:00.010 align:middle line:90% right there. 00:31:00.010 --> 00:31:11.040 align:middle line:84% And then we typically use OES, Optical Emission Spectroscopy, 00:31:11.040 --> 00:31:20.195 align:middle line:84% or FTIR, Fourier Transform Infrared Resonance. 00:31:20.195 --> 00:31:21.070 align:middle line:90% JACK HARE: Thank you. 00:31:21.070 --> 00:31:23.170 align:middle line:84% Yeah, so I remember doing this class 2 years ago, 00:31:23.170 --> 00:31:24.740 align:middle line:84% and there were some folks from [INAUDIBLE] as well, 00:31:24.740 --> 00:31:26.657 align:middle line:84% who came and talked about those plasmas, which 00:31:26.657 --> 00:31:29.080 align:middle line:84% is why this scale now goes down to what I consider 00:31:29.080 --> 00:31:30.760 align:middle line:90% to be quite a low density. 00:31:30.760 --> 00:31:31.580 align:middle line:90% But there we go. 00:31:31.580 --> 00:31:34.540 align:middle line:84% And that's why it's kind of fun that we can go all the way up, 00:31:34.540 --> 00:31:36.550 align:middle line:90% much higher densities as well. 00:31:36.550 --> 00:31:40.827 align:middle line:84% Any more volunteers in the room or from Columbia? 00:31:40.827 --> 00:31:41.660 align:middle line:90% Lansing, come on up. 00:31:41.660 --> 00:31:46.610 align:middle line:90% 00:31:46.610 --> 00:31:47.940 align:middle line:90% AUDIENCE: Hello, everybody. 00:31:47.940 --> 00:31:48.440 align:middle line:90% I'm Lansing. 00:31:48.440 --> 00:31:50.090 align:middle line:90% I work with Jack. 00:31:50.090 --> 00:31:52.580 align:middle line:84% My project is magnetic reconnection on Z. 00:31:52.580 --> 00:31:54.890 align:middle line:84% It's in collaboration with Sandia National Labs. 00:31:54.890 --> 00:31:58.310 align:middle line:84% So on the Z machine, the largest pulsed power machine, 00:31:58.310 --> 00:32:00.980 align:middle line:84% I think we're achieving densities around 10 00:32:00.980 --> 00:32:05.940 align:middle line:84% to the 24 to 10 to the 25 electrons per cubic meter 00:32:05.940 --> 00:32:07.520 align:middle line:90% in the reconnection layer. 00:32:07.520 --> 00:32:10.070 align:middle line:84% And I believe our temperature is-- 00:32:10.070 --> 00:32:12.530 align:middle line:84% for the bulk of the plasma, I think are 10's of eV, 00:32:12.530 --> 00:32:16.130 align:middle line:84% but for plasmoids can get up to a little bit above 100 eV. 00:32:16.130 --> 00:32:21.660 align:middle line:84% So maybe somewhere like in this region-ish. 00:32:21.660 --> 00:32:24.140 align:middle line:84% And then I believe the magnetic fields we're achieving 00:32:24.140 --> 00:32:26.060 align:middle line:90% are 10's of tesla, typically. 00:32:26.060 --> 00:32:29.030 align:middle line:84% So the work I've been focusing on-- 00:32:29.030 --> 00:32:32.967 align:middle line:84% I'll give this a number, number eight. 00:32:32.967 --> 00:32:35.050 align:middle line:84% Lately, the diagnostics that I've been working on, 00:32:35.050 --> 00:32:36.800 align:middle line:84% it's all been synthetic, so just modeling. 00:32:36.800 --> 00:32:38.680 align:middle line:84% But it's preparation for an upcoming shot. 00:32:38.680 --> 00:32:41.440 align:middle line:84% It's on shadowgraphy, so using a probing laser beam 00:32:41.440 --> 00:32:44.890 align:middle line:84% to try to indirectly constrain the electron density. 00:32:44.890 --> 00:32:54.190 align:middle line:90% 00:32:54.190 --> 00:32:55.565 align:middle line:90% Thank you. 00:32:55.565 --> 00:32:56.440 align:middle line:90% JACK HARE: All right. 00:32:56.440 --> 00:32:59.402 align:middle line:90% Anyone else? 00:32:59.402 --> 00:33:00.110 align:middle line:90% Yeah, come on up. 00:33:00.110 --> 00:33:05.720 align:middle line:90% 00:33:05.720 --> 00:33:09.210 align:middle line:84% AUDIENCE: So I work with inertial electrostatic 00:33:09.210 --> 00:33:12.150 align:middle line:84% confinement fusion, which is a bit different from this. 00:33:12.150 --> 00:33:16.500 align:middle line:84% I would assume way up here somewhere, maybe in here. 00:33:16.500 --> 00:33:19.050 align:middle line:84% And the range is 40 to 100 keV, but the pressure 00:33:19.050 --> 00:33:21.973 align:middle line:90% is incredibly low, very low. 00:33:21.973 --> 00:33:23.890 align:middle line:84% JACK HARE: And try and keep the microphone up. 00:33:23.890 --> 00:33:25.360 align:middle line:90% AUDIENCE: Oh, sorry. 00:33:25.360 --> 00:33:29.800 align:middle line:84% So I guess very similar to NIF, we're 00:33:29.800 --> 00:33:35.870 align:middle line:84% only using neutron detectors, kind of like Hc3. 00:33:35.870 --> 00:33:39.165 align:middle line:90% 00:33:39.165 --> 00:33:41.270 align:middle line:84% We're looking to upgrade that soon. 00:33:41.270 --> 00:33:42.980 align:middle line:90% JACK HARE: Right, thank you. 00:33:42.980 --> 00:33:43.855 align:middle line:90% Anyone from Columbia? 00:33:43.855 --> 00:33:49.067 align:middle line:90% 00:33:49.067 --> 00:33:50.150 align:middle line:90% AUDIENCE: Hey, I'm Daniel. 00:33:50.150 --> 00:33:52.160 align:middle line:84% I'm also working on Spark, specifically 00:33:52.160 --> 00:33:53.782 align:middle line:90% on equilibrium dynamics. 00:33:53.782 --> 00:33:55.490 align:middle line:84% And for that, most of what I'm looking at 00:33:55.490 --> 00:34:00.260 align:middle line:84% are flux loops, so finding where the plasma boundary actually 00:34:00.260 --> 00:34:02.570 align:middle line:90% is inside the vacuum vessel. 00:34:02.570 --> 00:34:03.270 align:middle line:90% JACK HARE: Nice. 00:34:03.270 --> 00:34:03.770 align:middle line:90% Good stuff. 00:34:03.770 --> 00:34:05.250 align:middle line:90% Thank you. 00:34:05.250 --> 00:34:07.410 align:middle line:90% Anyone in the room? 00:34:07.410 --> 00:34:07.910 align:middle line:90% Yeah. 00:34:07.910 --> 00:34:08.410 align:middle line:90% Come on up. 00:34:08.410 --> 00:34:13.088 align:middle line:90% 00:34:13.088 --> 00:34:13.630 align:middle line:90% AUDIENCE: Hi. 00:34:13.630 --> 00:34:15.130 align:middle line:90% I'm Jacob. 00:34:15.130 --> 00:34:19.520 align:middle line:84% Similar to Amelia, I'm doing ASDEX Upgrade in pedestal. 00:34:19.520 --> 00:34:23.719 align:middle line:84% So I'll put that in her same bubble. 00:34:23.719 --> 00:34:30.530 align:middle line:84% And I work on correlation ECE to look 00:34:30.530 --> 00:34:32.210 align:middle line:90% at temperature fluctuations. 00:34:32.210 --> 00:34:33.491 align:middle line:90% JACK HARE: What's ECE? 00:34:33.491 --> 00:34:35.074 align:middle line:84% AUDIENCE: Electron Cyclotron Emission. 00:34:35.074 --> 00:34:37.338 align:middle line:90% 00:34:37.338 --> 00:34:39.880 align:middle line:84% JACK HARE: We like our acronyms, but we should spell them out 00:34:39.880 --> 00:34:41.150 align:middle line:90% at least once. 00:34:41.150 --> 00:34:41.650 align:middle line:90% Cool. 00:34:41.650 --> 00:34:43.250 align:middle line:90% Anyone else? 00:34:43.250 --> 00:34:43.750 align:middle line:90% Yeah. 00:34:43.750 --> 00:34:44.250 align:middle line:90% Come on up. 00:34:44.250 --> 00:34:47.518 align:middle line:90% 00:34:47.518 --> 00:34:48.060 align:middle line:90% AUDIENCE: Hi. 00:34:48.060 --> 00:34:49.150 align:middle line:90% I'm Leo. 00:34:49.150 --> 00:34:50.429 align:middle line:90% I'm working on Spark. 00:34:50.429 --> 00:34:52.960 align:middle line:84% I'm looking at the SOL in the virtual areas. 00:34:52.960 --> 00:34:59.010 align:middle line:84% So depending on how detached it is, somewhere right here. 00:34:59.010 --> 00:35:00.470 align:middle line:90% And Langmuir-- 00:35:00.470 --> 00:35:01.470 align:middle line:90% JACK HARE: All Langmuir? 00:35:01.470 --> 00:35:01.800 align:middle line:90% Cool. 00:35:01.800 --> 00:35:03.217 align:middle line:84% AUDIENCE: Well, I mean synthetics. 00:35:03.217 --> 00:35:04.360 align:middle line:90% Probably doesn't exist yet. 00:35:04.360 --> 00:35:05.280 align:middle line:90% [LAUGHTER] 00:35:05.280 --> 00:35:06.125 align:middle line:90% JACK HARE: Good. 00:35:06.125 --> 00:35:08.250 align:middle line:84% At least they're planning to have some diagnostics. 00:35:08.250 --> 00:35:08.940 align:middle line:90% Nice. 00:35:08.940 --> 00:35:12.220 align:middle line:90% All right, anyone else? 00:35:12.220 --> 00:35:12.730 align:middle line:90% Yeah. 00:35:12.730 --> 00:35:13.230 align:middle line:90% Come on up. 00:35:13.230 --> 00:35:18.620 align:middle line:90% 00:35:18.620 --> 00:35:20.870 align:middle line:84% AUDIENCE: So I work with plasma, but it was actually 00:35:20.870 --> 00:35:22.880 align:middle line:90% simulation for accelerators. 00:35:22.880 --> 00:35:26.983 align:middle line:84% So the magnetic field for some simulation for plasma 00:35:26.983 --> 00:35:27.900 align:middle line:90% wakefield accelerator. 00:35:27.900 --> 00:35:30.230 align:middle line:84% It went up for some cases, because we 00:35:30.230 --> 00:35:33.710 align:middle line:84% were trying to scale up to 15 TeV scaled up to a few thousand 00:35:33.710 --> 00:35:34.700 align:middle line:90% tesla. 00:35:34.700 --> 00:35:37.455 align:middle line:84% So it's a simulation, so I would put it-- 00:35:37.455 --> 00:35:38.700 align:middle line:90% JACK HARE: Another color? 00:35:38.700 --> 00:35:45.638 align:middle line:90% 00:35:45.638 --> 00:35:46.180 align:middle line:90% There you go. 00:35:46.180 --> 00:35:47.040 align:middle line:90% That's yours. 00:35:47.040 --> 00:35:48.930 align:middle line:90% [LAUGHTER] 00:35:48.930 --> 00:35:51.910 align:middle line:84% AUDIENCE: But the diagnostic is all from simulation. 00:35:51.910 --> 00:35:57.498 align:middle line:84% So it's like a particle histogram and photon energy. 00:35:57.498 --> 00:36:00.190 align:middle line:90% JACK HARE: [INAUDIBLE] 00:36:00.190 --> 00:36:03.235 align:middle line:84% AUDIENCE: Well, it depends on what collision you want to do. 00:36:03.235 --> 00:36:04.860 align:middle line:84% You could make them really ultra tight, 00:36:04.860 --> 00:36:06.858 align:middle line:84% and that would put them somewhere like here. 00:36:06.858 --> 00:36:08.400 align:middle line:84% For the temperature, I'm not so sure. 00:36:08.400 --> 00:36:12.280 align:middle line:84% But the ultimate goal is to scale it up to 15 TeV. 00:36:12.280 --> 00:36:14.850 align:middle line:90% JACK HARE: [INAUDIBLE] 00:36:14.850 --> 00:36:17.760 align:middle line:84% AUDIENCE: It would be good if we had a log scale. 00:36:17.760 --> 00:36:19.260 align:middle line:90% JACK HARE: All right, thank you. 00:36:19.260 --> 00:36:20.700 align:middle line:90% Good stuff. 00:36:20.700 --> 00:36:21.860 align:middle line:90% Anyone else from Columbia? 00:36:21.860 --> 00:36:23.400 align:middle line:84% I know there's-- I think there's like nine of you, 00:36:23.400 --> 00:36:24.250 align:middle line:90% and there's 30 of us. 00:36:24.250 --> 00:36:25.590 align:middle line:84% So I've been trying to balance it a little bit. 00:36:25.590 --> 00:36:27.270 align:middle line:84% So I may have got through you all now. 00:36:27.270 --> 00:36:29.430 align:middle line:90% Hey, I see your hand. 00:36:29.430 --> 00:36:30.630 align:middle line:90% AUDIENCE: Hey, yeah. 00:36:30.630 --> 00:36:33.750 align:middle line:84% So I've done work on C2W, which sits 00:36:33.750 --> 00:36:39.900 align:middle line:84% kind of in between numbers 2 and 3 blobs, so 10 to the 19. 00:36:39.900 --> 00:36:42.840 align:middle line:90% And yeah, just under 1 keV. 00:36:42.840 --> 00:36:47.535 align:middle line:84% And then the magnetic field is just under 1 tesla. 00:36:47.535 --> 00:36:52.530 align:middle line:84% JACK HARE: 1 Tesla, so I can put it in like this. 00:36:52.530 --> 00:36:54.515 align:middle line:90% So what are you using on C2W? 00:36:54.515 --> 00:36:55.140 align:middle line:90% AUDIENCE: Yeah. 00:36:55.140 --> 00:36:56.880 align:middle line:84% So a lot of them have been mentioned, 00:36:56.880 --> 00:37:00.750 align:middle line:84% but I don't think interferometry has been mentioned, 00:37:00.750 --> 00:37:07.133 align:middle line:84% or a bias bolometer, so like energy analyzers. 00:37:07.133 --> 00:37:07.800 align:middle line:90% JACK HARE: Cool. 00:37:07.800 --> 00:37:09.710 align:middle line:84% I'll put both of those in, bias bolometer. 00:37:09.710 --> 00:37:10.210 align:middle line:90% Nice. 00:37:10.210 --> 00:37:18.650 align:middle line:90% 00:37:18.650 --> 00:37:20.165 align:middle line:90% All right, anyone else? 00:37:20.165 --> 00:37:32.100 align:middle line:90% 00:37:32.100 --> 00:37:33.080 align:middle line:90% Anyone from Columbia? 00:37:33.080 --> 00:37:39.233 align:middle line:90% 00:37:39.233 --> 00:37:40.900 align:middle line:84% All right, it looks like we're all good. 00:37:40.900 --> 00:37:43.290 align:middle line:84% So I feel like the purpose of this exercise 00:37:43.290 --> 00:37:45.810 align:middle line:84% is just to get a feel for some of the different things 00:37:45.810 --> 00:37:48.450 align:middle line:84% that we might end up talking about. 00:37:48.450 --> 00:37:51.510 align:middle line:84% I've got a few other things on here to add. 00:37:51.510 --> 00:37:53.913 align:middle line:84% So we've already had Spark and NIF. 00:37:53.913 --> 00:37:55.830 align:middle line:84% There's a very cool technique for doing fusion 00:37:55.830 --> 00:37:57.060 align:middle line:90% using pulse power. 00:37:57.060 --> 00:37:58.860 align:middle line:84% It is dear to my heart, which is magnetized 00:37:58.860 --> 00:38:01.170 align:middle line:90% liner inertial fusion. 00:38:01.170 --> 00:38:04.380 align:middle line:84% This is an interesting one because it works using 00:38:04.380 --> 00:38:05.580 align:middle line:90% magnetic field compression. 00:38:05.580 --> 00:38:09.780 align:middle line:84% So we start out with fields of about 10 tesla or so. 00:38:09.780 --> 00:38:11.610 align:middle line:84% And we start out at densities of about 10 00:38:11.610 --> 00:38:14.940 align:middle line:84% to the 26, which is about here, and temperatures 00:38:14.940 --> 00:38:17.640 align:middle line:90% of about 300 eV. 00:38:17.640 --> 00:38:20.058 align:middle line:84% But then as we compress, we obviously 00:38:20.058 --> 00:38:22.350 align:middle line:84% get to much higher densities, much higher temperatures, 00:38:22.350 --> 00:38:24.100 align:middle line:84% and we're also compressing the magnetic field. 00:38:24.100 --> 00:38:25.830 align:middle line:84% So in fact, the number I've got written on here 00:38:25.830 --> 00:38:28.060 align:middle line:84% means I'm allowed to use the green chalk as well. 00:38:28.060 --> 00:38:34.320 align:middle line:84% And we're going to go up to 10 to 29 in density and 8 keV here. 00:38:34.320 --> 00:38:36.535 align:middle line:90% So this is magLIF. 00:38:36.535 --> 00:38:39.070 align:middle line:90% 00:38:39.070 --> 00:38:40.570 align:middle line:84% And there's lots of cool diagnostics 00:38:40.570 --> 00:38:42.910 align:middle line:90% that they use on magLIF. 00:38:42.910 --> 00:38:46.810 align:middle line:84% But one of the ones which I think is rather neat 00:38:46.810 --> 00:38:50.970 align:middle line:84% is that they have some neutron spectrometers 00:38:50.970 --> 00:38:52.650 align:middle line:84% that they can actually use to measure 00:38:52.650 --> 00:38:55.830 align:middle line:84% the magnetic fields because they fill this with deuterium. 00:38:55.830 --> 00:38:58.500 align:middle line:84% And you get deuterium reactions that make tritium. 00:38:58.500 --> 00:39:00.570 align:middle line:84% And then when the tritium reacts, 00:39:00.570 --> 00:39:03.250 align:middle line:84% it's already moved some distance along the magnetic field. 00:39:03.250 --> 00:39:06.060 align:middle line:84% And so you actually get an anisotropic neutron spectrum 00:39:06.060 --> 00:39:08.620 align:middle line:84% from these secondary ET reactions. 00:39:08.620 --> 00:39:13.023 align:middle line:84% So you're able to use neutron spectroscopy 00:39:13.023 --> 00:39:14.940 align:middle line:84% to get the B-field out, which is not something 00:39:14.940 --> 00:39:20.110 align:middle line:84% that you would necessarily expect to be able to do. 00:39:20.110 --> 00:39:22.330 align:middle line:84% Another one I've got on here is a Hall thruster. 00:39:22.330 --> 00:39:24.400 align:middle line:84% Does anyone work on Hall thrusters here? 00:39:24.400 --> 00:39:27.470 align:middle line:84% This is a type of plasma thruster for satellites. 00:39:27.470 --> 00:39:32.330 align:middle line:84% These are working with relatively low magnetic fields. 00:39:32.330 --> 00:39:34.910 align:middle line:90% I got 0.01 tesla written here. 00:39:34.910 --> 00:39:36.950 align:middle line:90% 10 to the 18 kind of densities. 00:39:36.950 --> 00:39:40.970 align:middle line:84% And they're also working at about 30 eV, so somewhere 00:39:40.970 --> 00:39:45.060 align:middle line:90% here, so Hall thruster. 00:39:45.060 --> 00:39:48.240 align:middle line:84% I don't a huge amount about the diagnostics used on these. 00:39:48.240 --> 00:39:50.490 align:middle line:84% But the sorts of diagnostics people would probably use 00:39:50.490 --> 00:39:51.900 align:middle line:84% are things like Langmuir probes, again, 00:39:51.900 --> 00:39:54.420 align:middle line:84% because these are relatively low temperature, low density 00:39:54.420 --> 00:39:55.120 align:middle line:90% plasmas. 00:39:55.120 --> 00:39:57.090 align:middle line:84% So you can get away with sticking stuff inside. 00:39:57.090 --> 00:40:03.890 align:middle line:90% 00:40:03.890 --> 00:40:07.460 align:middle line:84% Just down the road from here, in fact, not very far from here 00:40:07.460 --> 00:40:08.000 align:middle line:90% at all-- 00:40:08.000 --> 00:40:09.740 align:middle line:84% I'm not sure I can point directly at it right now-- 00:40:09.740 --> 00:40:12.380 align:middle line:84% is a machine called [INAUDIBLE],, which is a helicon plasma. 00:40:12.380 --> 00:40:14.540 align:middle line:84% That's used for plasma material interactions. 00:40:14.540 --> 00:40:18.380 align:middle line:84% That's got magnetic fields of about 0.1 tesla, densities 00:40:18.380 --> 00:40:22.520 align:middle line:84% around about 10 to 17, and relatively low temperatures, 00:40:22.520 --> 00:40:23.360 align:middle line:90% about 5 eV. 00:40:23.360 --> 00:40:26.400 align:middle line:90% It also sits around about here. 00:40:26.400 --> 00:40:31.110 align:middle line:84% So this is a helicon, which is a sort of RF-driven plasma. 00:40:31.110 --> 00:40:33.720 align:middle line:84% And again, the diagnostics that tend to be used in that 00:40:33.720 --> 00:40:35.870 align:middle line:90% are things like Langmuir probes. 00:40:35.870 --> 00:40:39.595 align:middle line:84% And then the work that I do, both before I came here 00:40:39.595 --> 00:40:41.970 align:middle line:84% and now the machine we're building is using pulsed power. 00:40:41.970 --> 00:40:44.360 align:middle line:84% So this is similar to the stuff that Lansing was talking 00:40:44.360 --> 00:40:48.860 align:middle line:84% about on Z. And what we were talking about with magLIF, 00:40:48.860 --> 00:40:51.680 align:middle line:84% but on a more modest scale, because we're only a university. 00:40:51.680 --> 00:40:54.110 align:middle line:84% And so we tend to be in a regime where 00:40:54.110 --> 00:40:58.580 align:middle line:84% we're dealing with fields of up to about a 10 tesla or so. 00:40:58.580 --> 00:41:01.130 align:middle line:90% We've got densities of around-- 00:41:01.130 --> 00:41:02.510 align:middle line:90% I haven't done this in CC. 00:41:02.510 --> 00:41:06.710 align:middle line:84% So it's 10 to the 23 or so, and temperatures up to about 100 eV. 00:41:06.710 --> 00:41:11.495 align:middle line:84% So quite similar to magLIF and the Mars shot. 00:41:11.495 --> 00:41:14.730 align:middle line:90% 00:41:14.730 --> 00:41:16.920 align:middle line:84% And we use diagnostics, some of which 00:41:16.920 --> 00:41:22.600 align:middle line:84% have already been mentioned, so interferometry, 00:41:22.600 --> 00:41:25.750 align:middle line:84% Faraday rotation imaging, which is this technique for measuring 00:41:25.750 --> 00:41:30.290 align:middle line:84% magnetic fields using the polarization of light, 00:41:30.290 --> 00:41:32.050 align:middle line:84% and my favorite diagnostic, which 00:41:32.050 --> 00:41:35.080 align:middle line:84% is why we spend so long talking about it, Thomson scattering. 00:41:35.080 --> 00:41:37.742 align:middle line:90% 00:41:37.742 --> 00:41:39.950 align:middle line:84% But that's kind of where I'm coming from, just so you 00:41:39.950 --> 00:41:41.330 align:middle line:90% know what my background is. 00:41:41.330 --> 00:41:44.510 align:middle line:84% That obviously feeds into my biases about what exactly 00:41:44.510 --> 00:41:46.520 align:middle line:84% I spend more or less time teaching. 00:41:46.520 --> 00:41:49.160 align:middle line:84% But I will try and cover as much as I can 00:41:49.160 --> 00:41:51.440 align:middle line:84% this parameter space and some of the diagnostics 00:41:51.440 --> 00:41:52.550 align:middle line:90% that you've mentioned. 00:41:52.550 --> 00:41:55.640 align:middle line:84% But the thing about teaching a class like this that I always 00:41:55.640 --> 00:41:58.918 align:middle line:84% find is whenever I teach on some specific diagnostic, 00:41:58.918 --> 00:42:01.460 align:middle line:84% there'll be someone in the class who's doing their PhD on it, 00:42:01.460 --> 00:42:03.260 align:middle line:84% and they know much more about it than me. 00:42:03.260 --> 00:42:04.760 align:middle line:84% And I know much, much less about it. 00:42:04.760 --> 00:42:05.643 align:middle line:90% And that's great. 00:42:05.643 --> 00:42:07.310 align:middle line:84% This is what makes this class enjoyable. 00:42:07.310 --> 00:42:09.377 align:middle line:84% So please, if I say something that's wrong, 00:42:09.377 --> 00:42:11.210 align:middle line:84% or if you think you've got something to add, 00:42:11.210 --> 00:42:13.040 align:middle line:84% or "These days, we do it like that. 00:42:13.040 --> 00:42:14.960 align:middle line:84% That was 20 years ago," just shout out, 00:42:14.960 --> 00:42:16.670 align:middle line:84% and please add to the conversation, 00:42:16.670 --> 00:42:18.830 align:middle line:84% because I know I'm not the expert on this stuff. 00:42:18.830 --> 00:42:21.380 align:middle line:84% Most of the time, I'm using a textbook to try and learn 00:42:21.380 --> 00:42:22.550 align:middle line:90% about it myself. 00:42:22.550 --> 00:42:24.930 align:middle line:84% There are often not very many good review papers either. 00:42:24.930 --> 00:42:27.230 align:middle line:84% So if you a good review paper for a diagnostic, 00:42:27.230 --> 00:42:31.520 align:middle line:84% I've never found a good one for an electron cyclotron emission 00:42:31.520 --> 00:42:33.632 align:middle line:84% diagnostics, for example, then let me know, 00:42:33.632 --> 00:42:35.090 align:middle line:84% and I can read that, and then I can 00:42:35.090 --> 00:42:36.440 align:middle line:84% regurgitate it to the rest of the class 00:42:36.440 --> 00:42:37.523 align:middle line:90% and look very intelligent. 00:42:37.523 --> 00:42:39.760 align:middle line:84% So that would help me a great deal. 00:42:39.760 --> 00:42:42.180 align:middle line:90% But I'll pause here. 00:42:42.180 --> 00:42:44.375 align:middle line:84% If anyone has any questions, and then 00:42:44.375 --> 00:42:46.000 align:middle line:84% we'll probably just leave it for today. 00:42:46.000 --> 00:42:46.940 align:middle line:84% I know it's a little bit early, but I 00:42:46.940 --> 00:42:48.080 align:middle line:84% think we can all do with a little bit 00:42:48.080 --> 00:42:49.955 align:middle line:84% of a break in our first week of the semester. 00:42:49.955 --> 00:42:50.775 align:middle line:90% So any questions? 00:42:50.775 --> 00:42:51.275 align:middle line:90% Yes. 00:42:51.275 --> 00:43:02.700 align:middle line:90% 00:43:02.700 --> 00:43:03.360 align:middle line:90% Yes. 00:43:03.360 --> 00:43:05.170 align:middle line:84% I mean, I rushed through this a little bit. 00:43:05.170 --> 00:43:07.620 align:middle line:84% So the subtlety is that they were using-- 00:43:07.620 --> 00:43:10.480 align:middle line:84% they weren't looking-- they're not looking at the DD neutrons. 00:43:10.480 --> 00:43:12.210 align:middle line:90% Those are isotropic. 00:43:12.210 --> 00:43:14.313 align:middle line:84% So they fill it with deuterium gas only. 00:43:14.313 --> 00:43:15.480 align:middle line:90% There's no tritium in there. 00:43:15.480 --> 00:43:17.230 align:middle line:84% And they look at the DD neutrons. 00:43:17.230 --> 00:43:18.540 align:middle line:90% That's isotropic on magLIF. 00:43:18.540 --> 00:43:19.530 align:middle line:90% It wasn't on ZETA. 00:43:19.530 --> 00:43:21.000 align:middle line:90% So on magLIF, it is thermal. 00:43:21.000 --> 00:43:24.900 align:middle line:84% What's cool is that DD reaction can produce a tritium ion. 00:43:24.900 --> 00:43:27.750 align:middle line:84% That tritium ion is energetic, but these magnetic fields 00:43:27.750 --> 00:43:28.500 align:middle line:90% are huge. 00:43:28.500 --> 00:43:29.670 align:middle line:90% So it is magnetized. 00:43:29.670 --> 00:43:33.360 align:middle line:84% So in fact, the tritium moves preferentially in one direction 00:43:33.360 --> 00:43:35.230 align:middle line:84% or in two directions along the field lines. 00:43:35.230 --> 00:43:37.170 align:middle line:84% So when it collides with the deuterium 00:43:37.170 --> 00:43:42.050 align:middle line:84% and produces a distinctive neutron at 14 MeV, 00:43:42.050 --> 00:43:44.870 align:middle line:84% those neutrons are now coming out anisotropically. 00:43:44.870 --> 00:43:47.480 align:middle line:84% And the strength of that anisotropy 00:43:47.480 --> 00:43:49.760 align:middle line:84% can be used to measure the magnetic field, 00:43:49.760 --> 00:43:52.400 align:middle line:84% because it tells you how confined the tritiums are 00:43:52.400 --> 00:43:55.430 align:middle line:84% in a certain direction, which is pretty neat. 00:43:55.430 --> 00:43:56.900 align:middle line:84% So it's not a problem for magLIF, 00:43:56.900 --> 00:44:01.010 align:middle line:84% because the neutrons are isotropic. 00:44:01.010 --> 00:44:03.080 align:middle line:84% And in a real magLIF, if you wanted 00:44:03.080 --> 00:44:05.180 align:middle line:84% to do magLIF as a power plant, then you 00:44:05.180 --> 00:44:07.970 align:middle line:84% just do [INAUDIBLE] fusion, and you wouldn't see this anisotropy 00:44:07.970 --> 00:44:09.762 align:middle line:84% at all because all the fusion would happen. 00:44:09.762 --> 00:44:12.250 align:middle line:90% 00:44:12.250 --> 00:44:13.548 align:middle line:90% Any other questions? 00:44:13.548 --> 00:44:18.130 align:middle line:90% 00:44:18.130 --> 00:44:19.510 align:middle line:90% All right, thank you very much. 00:44:19.510 --> 00:44:21.630 align:middle line:90% And I'll see you on Tuesday. 00:44:21.630 --> 00:44:26.000 align:middle line:90%