WEBVTT 1 00:00:00.070 --> 00:00:01.510 Come back. 2 00:00:06.840 --> 00:00:26.349 Mark Kushner: Hello, everybody today. My great pleasure to introduce to you Dr. Stephanie Hanson from Sandia National Labs, Scandia. Stephanie is a senior scientist in the post Power Sciences Center may be more familiar with 3 00:00:26.840 --> 00:00:37.300 Mark Kushner: and also note that senior scientists is a very prestigious position and only a very small fraction of scientists obtain this this level during their careers at Sandia. 4 00:00:37.320 --> 00:01:01.709 Mark Kushner: Dr. Hanson specializes in atomic scale behavior of atoms and extreme environments and develops atomic spectroscopic equation, state and transport models to help predict and diagnose the behavior of high energy density plasmas. She's the author and developer of the scram, non lte spectroscopic modeling code and use a self consistent field code used for equation of state scattering and transport calculations 5 00:01:01.810 --> 00:01:08.399 Mark Kushner: in 2,015. She wanted early career work in Us. Department of energy to study materials and non-equilibrium conditions 6 00:01:08.420 --> 00:01:25.089 Mark Kushner: in 2,017 should receive the very prestigious Presidential early career award for scientists and engineers, also known as the Pkce Award In 2,019 she was elected. She was elected Fellow of the American Physical Physical Society, through the Apf. Division of plasma Physics. 7 00:01:25.200 --> 00:01:31.100 Mark Kushner: and she completed for doctoral studies at the University of Veterino, where she obtained degrees in physics and philosophy. 8 00:01:31.390 --> 00:01:57.589 Mark Kushner: Okay, also, since 2,012 she's been a visiting associate professor at Cornell University, and on a more personal note I had the great pleasure getting to work with Stephanie for nearly 8 years when I was at Sandia, and we had a lot of fun trying to solve some of the early mysteries of Sandia's fusion concept called Maglev which we'll hear a little bit about today. But certainly Stephanie's expertise and X-ray spectroscopy was very important during those times. 9 00:01:57.640 --> 00:02:07.540 Mark Kushner: So we're very fortunate to have her with here with us, and I'm looking forward to hearing a talk more on X-ray spectroscopy and HD plasmas. So with that. Let's welcome, Stephanie. 10 00:02:10.330 --> 00:02:15.060 Mark Kushner: Pretty very importantly, the famous nipsy nug. 11 00:02:18.420 --> 00:02:19.949 Mark Kushner: Thank you very much. 12 00:02:23.720 --> 00:02:39.750 Mark Kushner: Yeah, II do have to start by thanking University of Michigan. Mark Ryan, and Carolyn for inviting me and for being so hospitable. It's been a wonderful experience so far, just a delight to see all of the work that's going on here. 13 00:02:40.010 --> 00:02:44.730 Mark Kushner: I prepared this talk at a sort of like. 14 00:02:45.660 --> 00:03:04.360 Mark Kushner: Let me show you the magic of spectroscopy level, and so I hope it doesn't get very tedious. If it does, I can go into the details of density, functional theory, or atomic physics, hartree-fock equations. But I don't think that most people actually enjoy that. I think it takes a special kind of 15 00:03:04.520 --> 00:03:15.950 Mark Kushner: weirdo to enjoy that. So the title of my talk is spectroscopy. A 1,000 pictures so you've heard the phrase. A picture is worth a thousand words. 16 00:03:16.320 --> 00:03:26.620 Mark Kushner: and a spectrum is essentially many, many, many, many, many pictures in different energies. And so hopefully, by the end of this talk you will be a little bit excited about it. 17 00:03:29.080 --> 00:03:29.940 Mark Kushner: Okay. 18 00:03:31.330 --> 00:03:35.560 Mark Kushner: we are interested in matter at extreme condition. This is 19 00:03:35.950 --> 00:03:47.629 Mark Kushner: matter that has been heated up to millions of degrees kelvin matter that has been compressed to higher than solid densities. 20 00:03:47.800 --> 00:03:57.830 Mark Kushner: And this is the stuff of stars, right? This is plasma that dominates the visible universe in terms of the amount of matter that we can see. 21 00:03:58.440 --> 00:04:16.780 Mark Kushner: So understanding how that behaves is is is pretty challenging. It's exotic state of matter as far as breast real conditions are concerned. We don't run into plasmids very often in our everyday life, and if we do, it sometimes hurts real bad with lightning 22 00:04:17.540 --> 00:04:21.910 Mark Kushner: and and and so understanding, you know, how does how does plasma 23 00:04:22.270 --> 00:04:33.529 Mark Kushner: respond when you, when you push on it? How does it respond when you shine light on it? How does it respond if you put a field around it? Or if you run a current through it, that's actually really hard. 24 00:04:33.570 --> 00:04:48.890 Mark Kushner: Cause you can. You know our everyday life. We have a temperature range of maybe a hundred degrees if we're unlucky. and and a density range that goes from air to solids to maybe lead or gold. 25 00:04:50.670 --> 00:04:54.939 Mark Kushner: I guess that's an order of magnitude or 2 span. 26 00:04:55.410 --> 00:04:56.630 Mark Kushner: and the 27 00:04:56.660 --> 00:05:04.239 Mark Kushner: hard vacuum of the interstellar medium, which still has one or 2 particles per cubic centimeter to 28 00:05:04.900 --> 00:05:26.219 Mark Kushner: the interior of of neutron stars, where you know you recombined electrons, and you produce nuclei that is, is not a couple orders of magnitude that's orders of magnitude, of orders, of magnitude, so that understanding you know how material behaves that all of these crazy conditions is is important to understand the universe. 29 00:05:26.510 --> 00:05:31.130 Mark Kushner: it's also important for human plasmids. So 30 00:05:31.160 --> 00:05:58.049 Mark Kushner: this is one of the great hopes I think of of society is to find clean energy that you can get from extracting deuterium from water and fusing it together. You release energy in the form of neutrons and alpha particles. If you can trap those alpha particles and self heat a fusion plasma. If you can hold that plasma for long enough that it can self heat. You can generate energy the same way we do in sun. 31 00:05:58.230 --> 00:06:01.580 Mark Kushner: Without any carbon emissions. 32 00:06:02.810 --> 00:06:09.839 Mark Kushner: So this is actually one of the Maglev plasmas that Ryan was talking about. I'll give some more details on how it works later. 33 00:06:11.400 --> 00:06:21.169 Mark Kushner: What these both having common is an even smaller scale, right? The atomic scale, because all of these things are made with atoms. 34 00:06:21.210 --> 00:06:28.719 Mark Kushner: If we understand the behavior of atoms in these complex plasma systems. Then we can reliably predict and model them. 35 00:06:33.580 --> 00:06:34.680 Mark Kushner: So 36 00:06:34.890 --> 00:06:44.329 Mark Kushner: you're an at Dd scientist, wanna study plasmas. How do you study plasmas? You can look at them. So we can look at the 37 00:06:44.540 --> 00:06:47.829 Mark Kushner: wonderful images that modern satellites give us. 38 00:06:48.020 --> 00:07:01.449 Mark Kushner: We can look at the wonderful images that modern day diagnostics give us, and plasma diagnostics are no joke. Right? You've gotta resolve time scales and nanoseconds gotta resolve link scales of microns. 39 00:07:01.720 --> 00:07:07.819 Mark Kushner: you have to do it with high resolution. You have to do it with a proper understanding of 40 00:07:07.990 --> 00:07:13.960 Mark Kushner: You know enough range to to capture objects that maybe large in one dimension, small in another. 41 00:07:14.290 --> 00:07:17.140 Mark Kushner: It's a real challenge. And 42 00:07:17.240 --> 00:07:29.190 Mark Kushner: some of my favorite people build spectrometers and imagers. Or you, you can do active diagnostics. You can hit them with something you can send X-rays into your plasma and see how it absorbs. 43 00:07:29.400 --> 00:07:35.640 Mark Kushner: That's an example of a radiograph where we took an X-ray. I think Brian actually worked on this 44 00:07:36.120 --> 00:07:38.060 Mark Kushner: experiment. 45 00:07:39.770 --> 00:07:43.239 Mark Kushner: or you could hit them with protons or other things. So 46 00:07:43.410 --> 00:07:47.210 Mark Kushner: we've got passive and active diagnostics. But in both cases 47 00:07:47.450 --> 00:08:00.670 Mark Kushner: what you see depends on how you look, what energy you you examine. So if you look at the crowd nebula in in the optical, you see this beautiful, fuzzy thing. If you look at it in the X-ray, you see something totally different. 48 00:08:00.880 --> 00:08:06.740 Mark Kushner: So optical photons are like one Ed, energy X-ray photons are 49 00:08:06.930 --> 00:08:12.299 Mark Kushner: a Kev energy. They're a thousand times more energetic, 1,000 times smaller wavelength. 50 00:08:13.310 --> 00:08:24.230 Mark Kushner: And you can see the core of this in the same way, if if you bounce optical visible light off your hand, you see something different than if you irradiate it with X-rays. So. 51 00:08:25.460 --> 00:08:36.090 Mark Kushner: and and if you take a picture of the magnet plasma with 9 kv. X-rays, and then with a filter that lets through lower energy. X-rays you see very different images there as well. 52 00:08:38.280 --> 00:08:49.959 Mark Kushner: but the the the object of showing you that is, this spectrus spectrum is worth a thousand pictures, because you can take these pictures at 2 different energy records. 53 00:08:50.020 --> 00:09:01.629 Mark Kushner: But you can also imagine continually resolving the energy range that you see. So the light that this Maglev plasma emits can be 54 00:09:01.770 --> 00:09:06.049 Mark Kushner: separated by a crystal. You can make essentially an X-ray rainbow 55 00:09:06.320 --> 00:09:10.530 Mark Kushner: using the planes of a crystal as your diffraction plane. 56 00:09:11.460 --> 00:09:17.509 Mark Kushner: and it can give you a detailed picture of 57 00:09:17.930 --> 00:09:20.120 Mark Kushner: what kind of light is coming out of that platform. 58 00:09:20.940 --> 00:09:24.960 Mark Kushner: and this detailed picture gives you a lot of information. 59 00:09:25.190 --> 00:09:31.050 Mark Kushner: So if you look at this with a non spectroscopy, you can say, that's the 60 00:09:31.170 --> 00:09:37.020 Mark Kushner: glorious rainbow I ever saw. But if you look at it as a spectroscopist, you can say 61 00:09:37.560 --> 00:09:45.949 Mark Kushner: so. This is a hot plasma. I've got a lot of high energy X-rays that go up to 14 kb, and beyond. 62 00:09:46.680 --> 00:09:50.080 Mark Kushner: You can look at these lines and you can say. 63 00:09:50.810 --> 00:09:55.640 Mark Kushner: Wow, I've got chromium and iron and nickel in my plasma. 64 00:09:56.020 --> 00:10:02.040 Mark Kushner: Where did those come from? And actually, this was just a beryllium cylinder imploded on a deuterium fuel. 65 00:10:02.180 --> 00:10:07.350 Mark Kushner: We had no idea we'd see these things turns out beryllium has a lot of impurities in it. 66 00:10:07.380 --> 00:10:09.150 Mark Kushner: This is one way you can know that. 67 00:10:11.690 --> 00:10:13.099 Mark Kushner: But in order to 68 00:10:13.140 --> 00:10:25.169 Mark Kushner: to look at that with a spectroscopic size. You you have to understand something about the atomic scale response. And so this is my pitch for spectroscopy. 69 00:10:25.680 --> 00:10:29.710 Mark Kushner: coolest field in the world. because it couples 70 00:10:29.720 --> 00:10:35.129 Mark Kushner: really small stuff, atomic physics, quantum mechanics, electron degeneracy 71 00:10:36.280 --> 00:10:42.070 Mark Kushner: with mesoscale stuff that has lots of good societal uses and some bad 72 00:10:42.530 --> 00:10:45.189 Mark Kushner: and with astrophysics. 73 00:10:47.520 --> 00:10:55.480 Mark Kushner: And if you understand that atomic scale response, then you can control and improve. 74 00:10:55.530 --> 00:10:57.869 Mark Kushner: Mesoscale response. 75 00:10:58.040 --> 00:11:05.659 Mark Kushner: And you can interpret observational data like we get from satellites and understand universe 76 00:11:05.930 --> 00:11:08.529 Mark Kushner: to all the scales. 77 00:11:12.420 --> 00:11:17.819 Mark Kushner: So yeah, let's let's step back a little bit and talk about spectroscopy in its history. 78 00:11:18.660 --> 00:11:25.880 Mark Kushner: At bottom, it's the science of measuring and interpreting photons that are emitted and absorbed by 79 00:11:26.320 --> 00:11:28.550 Mark Kushner: system. 80 00:11:28.690 --> 00:11:29.849 Mark Kushner: And so 81 00:11:29.900 --> 00:11:47.879 Mark Kushner: maybe we stop caring about electromagnetic waves that the radio regime. But certainly we care at the infrared regime where infrared photons you can. You can see in the heat signatures and molecules. So I worked at a chemical laboratory. Once we would send an infrared beam through to measure hydrocarbon contamination in water. 82 00:11:48.580 --> 00:11:59.660 Mark Kushner: if you move from molecules to atoms, then you can probe the properties of atoms, at least the outer electrons of atoms with just white light. 83 00:11:59.940 --> 00:12:03.740 Mark Kushner: So if we had a hydrogen gas sample on the ear 84 00:12:03.790 --> 00:12:05.150 and 85 00:12:05.710 --> 00:12:13.569 Mark Kushner: ran it through a prism you would see certain energies of light. And that tells you something about the structure of matter. Right? 86 00:12:13.660 --> 00:12:25.079 Mark Kushner: X-rays sample, the deeper, highly bound electron in many electron ions. And so they give you a window into the core of atoms 87 00:12:27.120 --> 00:12:33.989 Mark Kushner: and spectroscopy is is was really in intrinsic to the development of modern physics. 88 00:12:34.190 --> 00:12:47.470 Mark Kushner: Lot of what we know about matter was learned through spectroscopy. The electronic structure of elements the development of quantum mechanics came from looking at the weirdness of spectroscopy. 89 00:12:47.590 --> 00:12:54.640 Mark Kushner: I'll show you more on that on the next slide, and trying to make sense of it as quantum mechanics is hard to make sense of. 90 00:12:55.110 --> 00:13:15.139 Mark Kushner: I don't know who said this quote originally, but Neil Degrasse Tyson has said it, and other astrophysicists have said it, but spectroscopy puts the physics and astrophysics. Otherwise you're looking at blobs of light moving around right? But spectroscopy can tell you what they're made of how fast they're moving, how they are. 91 00:13:15.750 --> 00:13:21.780 Mark Kushner: and of course we use them for asthma, physics and fusion research. 92 00:13:21.930 --> 00:13:22.630 Mark Kushner: It's good. 93 00:13:25.450 --> 00:13:30.659 Mark Kushner: So at the turn of the century. About this most recent turn of the century 94 00:13:30.680 --> 00:13:37.369 Mark Kushner: we knew that Adams were composed of nuclei and something else that was like 95 00:13:38.040 --> 00:13:41.159 Mark Kushner: from the scattering experiments of Rutherford. 96 00:13:43.030 --> 00:13:45.399 Mark Kushner: but intriguing patterns 97 00:13:45.470 --> 00:13:58.829 Mark Kushner: in the chemical behavior, that is, bonds that different atoms formed, and in the emission and absorption spectra of of pure materials had also been observed. So 98 00:13:58.890 --> 00:14:11.510 Mark Kushner: again you take white light, you shine. You try it through some hydrogen gas and and or maybe heat up the hydrogen gas, and then you disperse it with a prism. 99 00:14:11.590 --> 00:14:16.140 Mark Kushner: You get something that looks like this. You get strong. 100 00:14:16.400 --> 00:14:22.079 Mark Kushner: very localized color, and then nothing. And then a strong localized color, and then nothing. 101 00:14:22.390 --> 00:14:29.839 Mark Kushner: and then something low, and then you see that again at higher energies, and then you see it again at even higher energies. 102 00:14:30.080 --> 00:14:45.870 Mark Kushner: Nothing behaves like that in the normal world, right? Nothing is discrete like that. We're used to continuum. And and so people looked at this equation, and they figured out what this pattern was just empirically just playing around with math. 103 00:14:46.400 --> 00:14:54.670 Mark Kushner: But there was no deeper understanding, because the deeper understanding is really weird. And so it took meals. 4 104 00:14:54.810 --> 00:15:02.919 Mark Kushner: It took Schrodinger. It took direct. It took Eisenberg 105 00:15:03.060 --> 00:15:04.000 Mark Kushner: of 106 00:15:04.890 --> 00:15:12.019 Mark Kushner: a couple of decades which is actually pretty impressive to formulate a physical model based on 107 00:15:12.290 --> 00:15:13.960 Mark Kushner: an equation that 108 00:15:14.310 --> 00:15:33.710 Mark Kushner: looks actually a lot like Newton's law. If if it were written in a really weird way, right? It's got an energy kinetic and potential and total energy. But instead of just that, it also has these wave functions. And so this is the inherent weirdness of quantum mechanics. 109 00:15:34.740 --> 00:15:43.189 Mark Kushner: and it was hard to to fathom, really. But it works. It works incredibly well. 110 00:15:44.160 --> 00:15:46.600 Mark Kushner: You can make measurements 111 00:15:46.880 --> 00:15:53.309 Mark Kushner: on the atomic side of isolated atoms to precisions of a part in 112 00:15:53.590 --> 00:15:54.489 Mark Kushner: Thank you, sir. 113 00:15:54.780 --> 00:15:59.169 Mark Kushner: many millions. Our atomic clocks, our GPS are based on 114 00:15:59.400 --> 00:16:01.320 Mark Kushner: this kind of precision. 115 00:16:04.000 --> 00:16:09.360 Mark Kushner: So modern theory, we can make predictions in atomic physics 116 00:16:09.520 --> 00:16:16.280 Mark Kushner: for isolated, especially when electron ions in equilibrium. Really. 117 00:16:16.560 --> 00:16:17.400 Mark Kushner: with 118 00:16:17.730 --> 00:16:20.380 Mark Kushner: really well, we can, we know what we're doing. 119 00:16:21.390 --> 00:16:43.020 Mark Kushner: And you know, we can talk about what the different transitions mean. One of the things that I think makes spectroscopy kind of daunting, and makes people not want to do. It is that it has its own language, right? That that sort of rich history developed a sort of senseless language that people just came up with to try to describe the things that they were seeing, not knowing what they were looking at. 120 00:16:43.020 --> 00:16:56.400 Mark Kushner: So you hear terms like K. Alpha helium Beta Lyman, alpha cold K. Alpha. And if you, if you're not, if that's not a language that you speak, it's kind of unpleasant to to hear people talking spectroscopy around you. 121 00:16:56.640 --> 00:17:12.760 Mark Kushner: Because we also have like hand signals like this is Helium Beta. And if you ever go to Livermore, look up Ed Marley, and and and show him the feel your mouth and things. 122 00:17:13.089 --> 00:17:14.009 it's like that. 123 00:17:15.760 --> 00:17:41.810 Mark Kushner: So when. But we're not, we're talking about the language we've we've got like shell transitions that are denoted by the principle con quantum number. Mostly there's some angular momentum quantum numbers. There's some more quantum numbers. They're really horrible. But mostly when we do spectroscopy, practical spectroscopy, we're looking at transitions. Between N equals, one and N equals 2 or 3 or 4. 124 00:17:42.110 --> 00:17:43.040 Mark Kushner: Okay? 125 00:17:43.580 --> 00:18:05.970 Mark Kushner: And it's, you know, it's easy enough to get all this information. You can get the energy levels from the poor formula or Schrodinger equation or direct equation. You can get transition energies, and transition rates using Schrodinger and Dirac theory. You can get the width of lines using Heisenberg's uncertainty. Principle you. You know everything 126 00:18:07.250 --> 00:18:15.770 Mark Kushner: except that not all ions are hydrogenic. In fact, most ions are not. Most have more than one. Electron, that means you have to solve 127 00:18:15.950 --> 00:18:20.189 Mark Kushner: a two-body problem, a three-body problem, an end body problem. Those are hard. 128 00:18:21.830 --> 00:18:27.739 Mark Kushner: And that difficulty that complexity results in a significant 129 00:18:27.770 --> 00:18:47.389 Mark Kushner: complexity in the electronic structure, which is reflected in a complexity in the emission spectrum. So instead of seeing the the line, the line, the line, the line that was repeated 3 times. Now we see if we just look at a small area of that not one line, but but 5 or 7, or if we're looking at more complicated elements, millions of lines. 130 00:18:50.130 --> 00:19:16.280 Mark Kushner: But we can use that complexity. So when you hear the word complexity think richness, it's actually just interesting. Also hard. But there's a lot of information in complexity. And so you can use that information to say, what element am I looking at. So this cat's looking at that spectrum we saw and says, that's hydrogen. Looks like cause the energies are right, and then it looks pretty cold, cause 131 00:19:17.360 --> 00:19:21.350 Mark Kushner: it's neutral. Hydrogen and ionized is pretty fast 132 00:19:21.430 --> 00:19:27.210 Mark Kushner: with high temperatures. Or that cat could look at this spectrum and say, Whoa! 133 00:19:27.540 --> 00:19:33.729 Mark Kushner: This plasma is emitting a much higher photon energies, and I know these lines. They belong to iron. 134 00:19:33.980 --> 00:19:44.039 Mark Kushner: and I know that they belong to highly charged ions of iron, so I know that I have highly charged iron ions, and I know, therefore, that I have a high temperature. 135 00:19:45.010 --> 00:20:08.019 Mark Kushner: and that's cool. And I also said something about equilibrium. But it turns out that most plasmas are not in equilibrium. It's pretty hard to get equilibrium at high temperatures, because you need a radiation field at a high temperature, and the energy in a radiation field goes like temperature to the fourth. It's hard to get energy that goes like something to the fourth 136 00:20:08.680 --> 00:20:27.879 Mark Kushner: and each non lte plasma is is non lte in its own way, and so actually to to model that you need not only the structure of your complex ions. But you need to couple all of those States that comprise that structure with collisional radiative rate equations. 137 00:20:27.920 --> 00:20:33.219 Mark Kushner: And that's actually what this web model that II wrote does. 138 00:20:34.680 --> 00:20:46.660 Mark Kushner: And so it predicts detailed emissions, spectra that can be directly compared to experiments. Outside of this local thermodynamic equilibrium approximation. 139 00:20:46.850 --> 00:21:02.579 Mark Kushner: And it turns out these again, they're useful plasma diagnostics. Okay? But so far we've been talking about isolated atoms and high energy density environments are not just high energy, high temperature. They're high density. 140 00:21:04.550 --> 00:21:12.349 Mark Kushner: So in a low density plasma, you can think all of your ions are just happily wandering around. Sometimes they collide with each other. That's fine. 141 00:21:12.590 --> 00:21:21.190 Mark Kushner: even in a plasma. You know, they are interacting with this electron bath. Maybe it does something to the edges of the potentials. But it doesn't do a heck of a lot 142 00:21:21.890 --> 00:21:32.949 Mark Kushner: in a high density plasma when you get something that says dense as a typical solid. That's no longer true. Now, the Valence orbitals of adjacent 143 00:21:33.080 --> 00:21:36.579 Mark Kushner: ions are interacting with their neighbors. 144 00:21:36.910 --> 00:21:41.820 Mark Kushner: and that does extraordinary things to the 145 00:21:42.090 --> 00:21:45.480 Mark Kushner: electronic structure of those Valence electrons. 146 00:21:45.510 --> 00:21:50.760 Mark Kushner: So it changes the screening that each of those see. It changes the 147 00:21:50.830 --> 00:22:01.989 Mark Kushner: the potential that the electron see you start to get things like degeneracy effects, and the free electrons, because they can't occupy the same state 2 electrons and occupy the same state. 148 00:22:02.590 --> 00:22:07.260 Mark Kushner: And that's actually a super hard problem, and it's not a solved one. 149 00:22:08.670 --> 00:22:10.530 Mark Kushner: So here's our cat again. 150 00:22:11.410 --> 00:22:16.150 Mark Kushner: And looking at hydrogen now, but now sees something different 151 00:22:16.230 --> 00:22:40.529 Mark Kushner: right now, instead of these very sharp lines start to see that there are water lines. This is what we call start broadening, and it comes from the different environments that different ions that are squished close together might see. So this one might be relatively far from its neighbors in a in a plasma, and thus the line is relatively unperturbed. It's kind of at the center where the original line was. 152 00:22:40.780 --> 00:22:48.019 Mark Kushner: This guy may be squished in a lot of directions by a lot of other other ions and have 153 00:22:48.370 --> 00:22:54.189 Mark Kushner: a different energy, I mean in a different energy, and one might be relatively isolated in a minute 154 00:22:54.370 --> 00:23:00.160 Mark Kushner: at yet a different energy, but understanding the sort of typical electric field 155 00:23:00.170 --> 00:23:09.489 Mark Kushner: caused by ions in a plasma, can tell you something about what the line shape will be, and it turns out that's another very useful spectroscopic diagnostic. 156 00:23:12.770 --> 00:23:13.850 Mark Kushner: So let's 157 00:23:14.610 --> 00:23:20.030 Mark Kushner: take a break from spectroscopy. Hopefully, I haven't made hate 158 00:23:20.210 --> 00:23:31.830 Mark Kushner: and and talk about plasma high energy densities, plasmas in the laboratory, how how we create them and use them and and control them. 159 00:23:32.920 --> 00:23:43.859 Mark Kushner: So producing these extreme conditions requires compressing energy in space and time. So we can do that in a variety of ways. 160 00:23:44.070 --> 00:23:48.349 Mark Kushner: I'll talk mostly about this Mag with target fusion concept. 161 00:23:48.400 --> 00:23:49.670 Mark Kushner: where we take 162 00:23:50.070 --> 00:23:59.490 Mark Kushner: the Z machine which has tens of mega tools stored in capacitors instead of building the size of a swimming pool. It's it's really quite impressive. 163 00:24:00.680 --> 00:24:11.610 Mark Kushner: charges them up over 1 min, and if you're ever at San Diego right before Z. Is going to fire, you can hear the countdown. So somebody with a nice voice says 10 kB, 164 00:24:11.840 --> 00:24:23.040 Mark Kushner: 20 kilovolts, and it goes up to 80 kilovolts, and then it arms and fires. It's pretty cool, and then the ground shakes. There's a lot of energy in those tens of megajoules. 165 00:24:24.650 --> 00:24:28.399 Mark Kushner: and the ground shakes because it compresses that 10 mega joules 166 00:24:28.550 --> 00:24:34.550 Mark Kushner: into nanoseconds, you know, tens of 10 to the minus 9 s 167 00:24:34.930 --> 00:24:55.639 Mark Kushner: and and millimeters or microns. So it it you. It takes the capacitor banks through transmission lines. They compress that electrical energy in time and sends it all to a very small target at the center of the machine. And you can reach really extreme conditions. You can reach conditions that are similar to the 168 00:24:56.260 --> 00:25:02.559 Mark Kushner: interior of the sun. They're sufficient to perform fusion and to 169 00:25:03.410 --> 00:25:08.809 Mark Kushner: produce copious X-rays. He is one of the most powerful. In fact, I think it is. 170 00:25:09.260 --> 00:25:16.559 Mark Kushner: Well, lift me a beateness plan. But anyway, it's a very powerful X-ray source. It emits a terawatt of X rays which is 171 00:25:16.690 --> 00:25:19.900 Mark Kushner: comparable to the total power. 172 00:25:20.030 --> 00:25:24.760 Mark Kushner: On the Us. Electrical grid, or sorry the world electrical grid. 173 00:25:25.050 --> 00:25:27.289 Mark Kushner: Course it does that for a very short time. 174 00:25:28.320 --> 00:25:46.209 Mark Kushner: with, of course. Now you're taking lasers, and you're putting them into a whole realm, and that 2 mega joules of laser energy which came from 400 megajoules of capacitor energy is heating gold in this case, to the same kind of high temperatures 175 00:25:46.990 --> 00:25:50.140 Mark Kushner: the gold is re-radiating, compressing a pellet. 176 00:25:50.580 --> 00:25:55.090 Mark Kushner: heating a pellet they can get 200, gosh! 177 00:25:55.120 --> 00:26:24.769 Mark Kushner: This is outdated! Forgive me, nip that really should say, for Mega Joel, that's really impressive. That's really cool. It was a long road, and people worked really hard with diagnostics, right to understand what was going wrong. Why, they weren't getting ignition for about 10 years and it was only the exquisite diagnostics that we they were able to make and feel. You know, with help from people here to to make that progress. 178 00:26:25.260 --> 00:26:31.579 Mark Kushner: You can also do it by building miles and miles of undulators and sending electron bunches through them 179 00:26:31.740 --> 00:26:58.569 Mark Kushner: and and getting now only 2 milligules. So not no longer mega tools, but 2 milliguls, but putting in a very, very, very small space in time. So something like 10 to seconds. I think that's right and and micron scales. And then you can create high energy density plasma conditions. And those are actually super interesting from an atomic physics point of view, because when you heat something up with X-rays you knock out the inner shell electrons first. 180 00:26:58.630 --> 00:27:01.780 Mark Kushner: That's very different than if you heat something up thermally. 181 00:27:04.170 --> 00:27:14.469 Mark Kushner: So let's talk about Magliff on on Magliff. We start with just a plain old beryllium cylinder. If you have a mechanical pencil, it looks very much like the end that your eraser protector. 182 00:27:16.470 --> 00:27:21.280 Mark Kushner: I don't know if you could actually put it on anything. Probably Brian. 183 00:27:22.190 --> 00:27:32.210 Mark Kushner: the razor protector. Could you put it on Z as a target. Why not? Okay? Sure. 184 00:27:33.070 --> 00:27:43.629 Mark Kushner: Then you put big coils around it and you put a magnetic field in the center, and that's an axial magnetic field that inhibits thermal conduction losses, which is important and stabilizes 185 00:27:43.960 --> 00:27:51.420 Mark Kushner: the pinch there. I just saw an experiment this morning where Pinch was stabilized by a magnetic field. It was really exciting. 186 00:27:51.840 --> 00:28:20.750 Mark Kushner: Then you hit it with a laser at the top that preheats your fuel to about a hundred electron holes. And this this gives you some initial energy, so you don't have to implode super fast. And it gives you an initial temperature. So you don't have to implode super far to reach fusion temperatures, which are several Kev. And then you use the full might, and Z. To compress this with the J. Cross B. Force at a current. You've got a magnetic field that was interact and send you in give you an implosion. 187 00:28:21.390 --> 00:28:25.520 Mark Kushner: And that heats the fuel to fusion temperatures kill electron volts. 188 00:28:25.570 --> 00:28:28.820 Mark Kushner: It compresses the trapped 189 00:28:28.840 --> 00:28:41.629 Mark Kushner: axial, magnetic field. So you go from about a Tesla to about 20 kilo Tesla magnetic fields, cool, high magnetic field and it and it traps your charge fusion products. 190 00:28:41.880 --> 00:28:55.299 Mark Kushner: So the magnetic field. It's kind of an amalgam of inertial fusion and magnetic fusion. But here the the magnetic field is trapping the particles. So let's look at this with the I have a spectroscopist. 191 00:28:56.370 --> 00:29:03.329 Mark Kushner: This is a spectrum that made me really happy. Eric Harding made the spectrometer, and he 192 00:29:03.450 --> 00:29:08.739 Mark Kushner: built it with exquisite calibration, precision, resolution. 193 00:29:09.810 --> 00:29:12.319 Mark Kushner: man, this is, I love this instrument. 194 00:29:12.410 --> 00:29:35.660 Mark Kushner: so we shoot a Mac with target. We take an image that's cool. I showed you a blown up version of of something like this image earlier in the talk. Here it's hard to see. But there's structure, and it's interesting structure. And then you spread it out into your 1,000 pictures. And you see, this is a narrow or spectral range than we were looking at before. It only goes from 6 to maybe 8 Kev. And photon energies. 195 00:29:35.890 --> 00:29:47.309 Mark Kushner: And you see this rich, rich, rich information. So you see colds. Well, you see hot iron lines, and you and your cat know that that means you have a hot plasma. 196 00:29:47.570 --> 00:29:50.179 Mark Kushner: It also tells you that something 197 00:29:50.380 --> 00:30:07.669 Mark Kushner: some iron impurity in the beryllium mixed in with the hot fuel that's not good for a fusion target. But it's okay. It's tolerable. This is a way to measure it. You better know about it. And, in fact, one of I think the roadblocks for Nif was they went from Germanium doped capsules where the X-rays would escape 198 00:30:07.680 --> 00:30:19.429 Mark Kushner: to silicon dope capsules where the silicon X-rays, if they got into the center, couldn't escape the rest of the target. They? They were blind to mix because they changed the target design. 199 00:30:19.730 --> 00:30:25.849 Mark Kushner: Here we see very clearly that we've got a a fair bit of mix because we have hot iron lines. 200 00:30:26.180 --> 00:30:28.100 Mark Kushner: We also, however, see 201 00:30:28.130 --> 00:30:33.620 Mark Kushner: what we call cold. K alpha. This is some of the jargon of the spectroscopist and cold K Beta. 202 00:30:34.000 --> 00:30:43.049 Mark Kushner: Those are the 2 to one and 3 to one transitions in a near neutral iron atom, where you've knocked out one of the inner shell electrons. 203 00:30:43.210 --> 00:30:50.410 Mark Kushner: and here. The hot continuum emission from this fusion core gives you that bright 204 00:30:50.500 --> 00:31:00.240 Mark Kushner: continuum X-ray emission that knocks out some of the inner shell electrons in the compressive liner and gives you the signature of cold. Kl. One. 205 00:31:00.610 --> 00:31:08.630 Mark Kushner: So now you know something. About a mixy region of your hot fuel. You know something about your liner 206 00:31:10.630 --> 00:31:14.760 Mark Kushner: and you know that you have greetings, and you know we need that. 207 00:31:15.090 --> 00:31:17.870 Mark Kushner: But but this is confirmation. 208 00:31:18.060 --> 00:31:30.039 Mark Kushner: and you know I say, hot plasma whatever. But you can really know it's like 2.2 Kev. And and the density is 2 times 10 to the 23. And for plasma physics that's pretty good. 209 00:31:32.020 --> 00:31:38.539 Mark Kushner: So we know we have gradients. Are there gradients that we weren't seeing when we just looked at the iron 210 00:31:39.330 --> 00:31:55.489 Mark Kushner: and one way to find out, is to introduce some other elements in some other place, and so Adam Harvey Thompson put a very thin layer and nanometer of cobalt on the laser and console window that hold in the fuel. 211 00:31:56.180 --> 00:32:06.979 Mark Kushner: and then they shot it with a laser, and we saw that depending on the laser protocol, you got more or less of this cobalt pushed into your asthma, and cobalt is 212 00:32:07.450 --> 00:32:09.030 Mark Kushner: again, 2 213 00:32:09.580 --> 00:32:13.920 Mark Kushner: above iron. I think it's 28. 214 00:32:14.010 --> 00:32:29.149 Mark Kushner: It rates 27 so it's right. Next to iron in the periodic table. It emits right next to iron. In its case shell emission, and we see hot cobalt. We don't see Cobalt K. Alpha, because it's not present in the liner. 215 00:32:30.080 --> 00:32:43.139 Mark Kushner: and we can diagnose that temperature of the cobalt and see if it's different from the temperature of the iron that we know is mixed in from the liner, and it is, and it's substantially different. So it's about twice as hot 216 00:32:43.230 --> 00:32:45.110 Mark Kushner: and about half as dense 217 00:32:45.320 --> 00:32:50.720 Mark Kushner: as the iron that is mixed in from liner. That's kind of cool 218 00:32:50.750 --> 00:32:54.400 Mark Kushner: cause that tells us we we have a hot core. 219 00:32:54.940 --> 00:32:56.600 a mixed layer 220 00:32:56.690 --> 00:33:00.069 Mark Kushner: and a cold, dense, confining beryllium liner. 221 00:33:00.350 --> 00:33:11.599 Mark Kushner: and that the mix layer and the hot core kind of isobaric. They have about the same pressure, because the offset and density, and the offset and temperature are equal and opposite vectors. 222 00:33:16.030 --> 00:33:20.780 Mark Kushner: This gets a little wonky, but this is one of my favorite spectra ever 223 00:33:21.490 --> 00:33:25.909 Mark Kushner: so I told you I love that spectrometer, and the reason is because 224 00:33:26.020 --> 00:33:40.960 Mark Kushner: when we measure this Macleod plasma on this spectrometer, we get the blue lines. and when we take a Manson source, which is like, I've got a block of iron, and I'm going to hit it with an electron beam. And we use the same spectrometer. We get the black lines. 225 00:33:42.990 --> 00:33:44.400 Mark Kushner: and they're different. 226 00:33:45.530 --> 00:33:50.710 Mark Kushner: There's a little blue shift, a shift to lower energy in the cold. K. Alpha. 227 00:33:51.360 --> 00:33:52.120 Mark Kushner: That's 228 00:33:52.340 --> 00:34:06.329 Mark Kushner: not surprising, actually atomic physicists. Oh, back in like 1954 published papers on how? That if you ionize iron just a couple of times the differential splitting gives you a little bit of a blue shift. Okay, that's fine 229 00:34:07.110 --> 00:34:18.489 Mark Kushner: in K Beta, which is the 3 P. To one S. Transition from those ones electrons that you knocked out with that fusion emission we see a much larger shift 230 00:34:18.659 --> 00:34:22.900 Mark Kushner: again to the red. and that's weird. 231 00:34:23.810 --> 00:34:35.190 Mark Kushner: Had it never been seen before. So, K Beta, you've seen all the time hot electrons. Right? You hit something with a femtosecond laser, a Petawatt laser. You get hot electrons, you see. Calcul k Beta all over the place. 232 00:34:35.449 --> 00:34:38.869 Mark Kushner: Those electrons are knocking out those inner shells 233 00:34:39.340 --> 00:34:46.159 Mark Kushner: and you will see as you maybe heat and ionize your plasma, that the K. Beta will move to higher energies. 234 00:34:46.449 --> 00:34:56.339 Mark Kushner: It never moves to lower energies. Never. I mean it just doesn't. You can do all the quantum mechanic calculations in the world, and it will not move to lower energies. 235 00:34:56.440 --> 00:35:01.540 Mark Kushner: And so, seeing this 12 ev. Shift, which is, you know, much larger than the like 3 v. Shift here 236 00:35:02.580 --> 00:35:09.650 Mark Kushner: was super exciting. because this is not an instrument that's going to make a mistake. This is a real effect. 237 00:35:11.200 --> 00:35:19.360 Mark Kushner: And so we were able to do some density functional theory calculations with the average atom code that we use to generate transport coefficients 238 00:35:20.270 --> 00:35:28.460 Mark Kushner: and show that. you know, if when you ionize, you're removing electrons and changing the screening of the 3 P State. 239 00:35:29.130 --> 00:35:39.369 Mark Kushner: If you compress, you're smooshing a bunch of electrons into that ion sphere, and it's doing the opposite thing. It's changing the electronic structure in in the other way. 240 00:35:39.420 --> 00:35:41.430 Mark Kushner: And so this is. 241 00:35:41.670 --> 00:36:06.290 Mark Kushner: oh, a way to diagnose how dense this plasma got. So we know that mass conserved. We could estimate that density, and then we could confirm it through its effect on the electronic structure of this K data line. And and we found it was compressed to about 8 times solid density. So beryllium and solid density is about 2 grams per c. This was 16 grams per c. 242 00:36:07.050 --> 00:36:10.840 Mark Kushner: that's that's almost as dense as as tungsten. 243 00:36:11.160 --> 00:36:15.680 Mark Kushner: So this is a a pretty cool experiment. 244 00:36:17.820 --> 00:36:23.549 Mark Kushner: We can even measure magnetic fields. And and this slide, too, is is a little bit out of date. 245 00:36:24.520 --> 00:36:32.099 Mark Kushner: But we can look at the differential splitting in a certain pair of lines to tell us something about 246 00:36:33.840 --> 00:36:50.499 Mark Kushner: how Adams respond to strong magnetic fields. And remember, I told you we had about 20 kilo Tesla in the flux compressed version of this plasma, although we expect it to be maybe a little bit less around the edge because of something called the Nernst defect in Mhc. 247 00:36:50.710 --> 00:37:20.000 Mark Kushner: and this is terrible data. You should look at this and say, Stephanie, nobody's got that doesn't make sense. But what I'm trying. I'm what I'm I'm claiming here is that this line is gonna split a little bit more than this line. And so if you overlay those 2 top of each other, normalize them, and you know what ratio they need to be. You could infer something about a very high magnet. We've since taken data that is better than this data. I'm showing here 248 00:37:20.150 --> 00:37:24.540 Mark Kushner: that will, I think, give us a real opportunity to do this kind of measurement. 249 00:37:30.190 --> 00:37:31.220 Mark Kushner: So 250 00:37:31.880 --> 00:37:50.480 Mark Kushner: oh, and I guess I should say, you know, in order to do that kind of analysis, you need to know. Every other source of broadening the claim that sambalchick and others have made is that those other sources of broadening are identical for these 2 lines. It's only the magnetic field that leads to different behavior. 251 00:37:52.140 --> 00:37:53.520 Mark Kushner: Okay? So 252 00:37:54.670 --> 00:38:01.020 Mark Kushner: now, you've built up a detailed picture of your fusion plasma. You know it's got a hot core 253 00:38:01.390 --> 00:38:15.859 Mark Kushner: with a high magnetic field. If you trust that. And I'm yes, I mean I wouldn't. But I think it does have a high magnetic field. You have a more mixed layer with a lower temperature, a higher density, and you have a cool, compressed minor with 254 00:38:15.990 --> 00:38:26.689 Mark Kushner: a temperature that we know is 10 to 20 ev. And we actually measure that from the degeneracy broadening of the edge. And we know the electron density because we saw that shift. 255 00:38:26.960 --> 00:38:30.380 Mark Kushner: So, looking at all these details of spectroscopy gives us 256 00:38:30.420 --> 00:38:36.960 Mark Kushner: information that we can use to rigorously validate red Hydro, Mhd. Simulations 257 00:38:37.100 --> 00:38:48.829 Mark Kushner: and understand how, when we change one thing in the target, maybe we heat it with a different laser protocol. Maybe we put a different density of gas in we get different neutron yields 258 00:38:49.130 --> 00:38:55.999 Mark Kushner: and that's cool. But a lot of fusion research is actually just yield right. My yield went up, my yield went down 259 00:38:56.480 --> 00:39:06.510 Mark Kushner: super that tells you a little bit. Pictures. My yield went up, and I was more symmetric. That tells you something. 260 00:39:06.640 --> 00:39:13.100 Mark Kushner: Spectroscopy just adds a new dimension. A yield went up. my temperature went up. 261 00:39:13.320 --> 00:39:19.010 Mark Kushner: my symmetry went up. My, you know you can really get my mix went down. 262 00:39:19.120 --> 00:39:22.019 Mark Kushner: You can understand why design changes. 263 00:39:22.220 --> 00:39:25.969 Mark Kushner: Have affected your your target performance. 264 00:39:27.290 --> 00:39:28.490 Mark Kushner: Oh, gosh. 265 00:39:28.610 --> 00:39:31.959 Mark Kushner: II really puddled on there. 266 00:39:33.360 --> 00:39:48.470 Mark Kushner: okay, so hopefully. Now everybody's like, yes, that trust is cool, and I can understand it if I work a little, and I can talk to Stephanie about it. But you have to know that your models are reliable. And this actually is, is the pitch that I want to leave you with. 267 00:39:48.550 --> 00:39:54.839 Mark Kushner: To test them. You need to do benchmark experiments and benchmark experiments are hard 268 00:39:55.060 --> 00:39:56.480 Mark Kushner: because it's not just 269 00:39:56.540 --> 00:40:09.370 Mark Kushner: I'm gonna build a bigger, bigger laser or or try a different target or it's not a tweak. You you have to do a very deliberate, careful, experimental campaign 270 00:40:09.400 --> 00:40:18.440 Mark Kushner: where you've designed a bit of material to be relatively uniform. You characterized its conditions, its temperature and density, some independent way. 271 00:40:18.870 --> 00:40:30.380 Mark Kushner: and you've done your measurement with a good assessment of error bars so one such benchmark measurement is 272 00:40:31.810 --> 00:40:44.950 Mark Kushner: just a gas discharge measurement of hydrogen, and would not believe how many times this paper has been cited. And it's because one. It's one of a handful, a literal handful of really high quality benchmark data sets. 273 00:40:45.400 --> 00:40:51.460 Mark Kushner: they're difficult. They're harder than just saying what happens when I hit this thing with this thing. 274 00:40:51.830 --> 00:41:02.109 Mark Kushner: but they're enduring. Because if you do this kind of careful measurement, you've made a contribution to knowledge that's valid here in a fusion plasma on on the side. 275 00:41:02.900 --> 00:41:05.960 Mark Kushner: So the closer you get to, you know. 276 00:41:06.030 --> 00:41:20.449 Mark Kushner: Denmark, experiment where you can really take your time and measure everything carefully the better these kind of experiments are. And you don't actually need a lot of energy to get into an interesting regime. Warm dance matter 277 00:41:20.570 --> 00:41:27.669 Mark Kushner: doesn't take a lot of energy to reach. And it's very hard computationally. So, a benchmark measurement there can have a huge impact. 278 00:41:29.370 --> 00:41:41.599 Mark Kushner: And this is kind of what we try to do on Z. In addition to fusion, we have what's called the Zap astrophysical properties collaboration. And we've tried a benchmark astrophysically relevant plasmas. 279 00:41:41.820 --> 00:41:51.549 Mark Kushner: So we start with a wire right? We imploded it gives us this stagnation column that's about as hot as nag live, but much more massive, more 280 00:41:51.700 --> 00:42:00.240 Mark Kushner: more material and high Z material that then radiates these terawatts of X-rays. We put a target at the top. 281 00:42:00.680 --> 00:42:06.490 Mark Kushner: and then we use the true stagnation photons to backlight that and 282 00:42:06.500 --> 00:42:18.350 Mark Kushner: magnesium tracers in the foil to diagnose it. So we use spectroscopy to diagnose the conditions. At this target. We also put iron in it. And that's what we want to measure. We want to measure the iron opacity. 283 00:42:18.420 --> 00:42:36.560 Mark Kushner: We also put things around the deep pinch, and so we can look at line formation in micro or photospheres time dependent ionization in beyond gas. That's with Roberta Mansini and we're working with some of of Carolyn's folks to to 284 00:42:37.020 --> 00:42:37.940 Mark Kushner: a 285 00:42:38.490 --> 00:42:44.610 Mark Kushner: do experiments that are are relevant to systems of interest, Michigan 286 00:42:44.670 --> 00:42:46.079 Mark Kushner: and other places. 287 00:42:49.810 --> 00:42:50.960 Mark Kushner: So 288 00:42:52.210 --> 00:43:03.080 Mark Kushner: briefly, you know, we take these X-rays. We sign half of them through plastic. half of them through our iron magnesium, and then you can divide those 2 roughly to get transmission. 289 00:43:03.240 --> 00:43:07.170 Mark Kushner: and you can compare that transmission to models. 290 00:43:07.320 --> 00:43:14.799 Mark Kushner: and and in 2,007 Jim Bailey published the results of about 5 years of experiments 291 00:43:14.850 --> 00:43:23.030 Mark Kushner: kind of at a temperature and density slightly lower than that that you find in the solar convection boundary, and found really good agreement with models. 292 00:43:23.070 --> 00:43:41.530 Mark Kushner: And then he did 5 more years of work, and got to higher temperatures and densities after the refurbishment of the Z machine, did the same kind of experiment, and got really poor agreement with models, and that was shocking actually to the atomic physics community. We did not expect that, and we still haven't explained it. 293 00:43:42.200 --> 00:43:46.719 Mark Kushner: And yet, because he had done all of this careful work. 294 00:43:46.930 --> 00:43:51.769 Mark Kushner: People trusted him. People took this result very seriously, and still do 295 00:43:54.290 --> 00:44:07.300 Mark Kushner: I think we we get surprised a lot when we do new stuff in high energy, density, science, we'll certainly be surprised again. This kind of careful experiment is really stimulating the development of atomic physics theory 296 00:44:07.310 --> 00:44:14.560 Mark Kushner: embedded in dense plasma systems. And that's. I think, a pretty interesting frontier. 297 00:44:16.140 --> 00:44:18.060 Mark Kushner: And it's inspired other measurements. 298 00:44:18.230 --> 00:44:27.970 Mark Kushner: Now, they're doing similar experiments on the national ignition facility, where they use the whole round to heat the plasma instead of X-rays from a pinch. 299 00:44:28.130 --> 00:44:33.330 Mark Kushner: and they use a laser driven backlighter to to give them their their backlight. 300 00:44:33.740 --> 00:44:40.809 Mark Kushner: And these are really nice complementary experiments. This is being led by Bob, Peter and Ted, Perry and Heather John 301 00:44:41.250 --> 00:44:57.110 Mark Kushner: And there intriguingly finding within the limits of their error bars now, which are fairly large similar results. So if you look at the anchor one, what we call it the lower density. Lower temperature you see pretty good agreement with the models. 302 00:44:57.200 --> 00:45:08.750 Mark Kushner: and if you look at a slightly higher density and slightly higher temperature, you see disagreement. And again, this disagreement is not something anybody understands. 303 00:45:10.300 --> 00:45:13.540 Mark Kushner: So yeah, spectroscopy is magic. 304 00:45:13.810 --> 00:45:17.739 Thank you for listening. 305 00:45:23.430 --> 00:45:26.529 Mark Kushner: hey? It's hot questions for Stephanie. 306 00:45:29.550 --> 00:45:30.220 Mark Kushner: And 307 00:45:30.320 --> 00:45:41.320 Mark Kushner: so when with the comparison. But do they disagree with the model same way? Or 308 00:45:41.710 --> 00:45:43.949 Mark Kushner: that's a good question. 309 00:45:43.970 --> 00:45:46.610 Mark Kushner: so far, in a similar way. 310 00:45:46.780 --> 00:46:01.199 Mark Kushner: It looks like the the really distressing part of this disagreement of the iron opacity measurements is the the strength of the continuum. And and it's distressing, because if you just took cold iron. 311 00:46:01.490 --> 00:46:08.910 Mark Kushner: which has all of its L shell electrons. And that's what's being probed at this energy range. You get this dash blue line. 312 00:46:09.090 --> 00:46:16.869 Mark Kushner: So to get something higher than the dash blue line means. You need more than 8 l. Shell electrons. That doesn't happen 313 00:46:17.040 --> 00:46:23.329 Mark Kushner: or you're there's a physical effect that you're missing in your models. And that's what we worry about. 314 00:46:23.420 --> 00:46:32.709 Mark Kushner: So the Nif data is here at those same conditions, and it, too, appears to be higher. I will point out that there is some 315 00:46:33.430 --> 00:46:58.539 Mark Kushner: a residual error indicated by these red error bars, which are kind of hard to see. So this is not a a solid result, yet it needs more announcements. And, in fact, Tynagana has done some extraordinary work. Re analyzing some of the DZ. Data. W. We selected this one just because it was the closest match, the conditions. But we have other cases where we've done 5 or 10 shots. 316 00:46:58.820 --> 00:47:12.770 Mark Kushner: and those have been analyzed so that the error bars here are comparable to the error bars here, and you actually find that it moves down a little bit under ties. Free analysis. So it's not as distressing, but it's still 317 00:47:13.090 --> 00:47:16.859 Mark Kushner: departing from the theory at at like the 3 Sigma level 318 00:47:22.070 --> 00:47:22.750 Mark Kushner: sounds. 319 00:47:22.980 --> 00:47:31.360 Mark Kushner: What was your journey into spectroscopy. Was it starting an undergrad and our spectrum? 320 00:47:31.720 --> 00:47:46.129 Mark Kushner: Yeah, yeah. So II ran into all the saffronova at the time, and she taught 321 00:47:46.280 --> 00:47:50.490 Mark Kushner: a couple of classes at U. Nr. And was willing to take me on as a student. 322 00:47:50.560 --> 00:48:01.460 Mark Kushner: And she worked with some experimentalists who collected laser and pinch spectra. And so, yeah, II just started looking at that and thinking about 323 00:48:01.690 --> 00:48:02.740 Mark Kushner: you know. 324 00:48:03.190 --> 00:48:08.580 Mark Kushner: I have to tell you the story the first time I got paid to sit in a chair and solve an equation, I thought. 325 00:48:09.620 --> 00:48:22.349 Mark Kushner: and this even be real. So I I'm a computationalist at heart, for sure. Ii knew I wanted to do something theoretical that that combination of quantum mechanics and and plasma physics 326 00:48:22.360 --> 00:48:24.909 Mark Kushner: was really intriguing. 327 00:48:28.930 --> 00:48:38.650 Mark Kushner: Yeah, would you care to comment on what maybe the leading ideas are for what might be the cause of the discrepancy. 328 00:48:38.900 --> 00:48:40.370 Mark Kushner: Yeah, Hi. 329 00:48:40.600 --> 00:48:45.949 Mark Kushner: we've as a community looked at a couple of things people have looked at 330 00:48:46.050 --> 00:48:48.859 Mark Kushner: 2 photon excitation which isn't 331 00:48:48.970 --> 00:48:53.840 Mark Kushner: included in in the models. And that would be where you know you. This 332 00:48:53.900 --> 00:48:57.349 Mark Kushner: plasma is in local thermodynamic equilibrium. So you have this. 333 00:48:57.430 --> 00:49:03.530 Mark Kushner: I energy radiation field that is giving you a lot of photons around your your iron ions. 334 00:49:03.620 --> 00:49:06.400 Mark Kushner: And it could be that when your back lighter comes in. 335 00:49:06.450 --> 00:49:23.019 Mark Kushner: it interacts with part of the plasma that's already interacted with one of those environmental photons, and both of those together act to destroy that incoming photon. So it doesn't show up at your detector and and is interpreted. It has an opacity. 336 00:49:23.180 --> 00:49:28.729 Mark Kushner: These calculations are hard. 337 00:49:28.840 --> 00:49:42.100 Mark Kushner: I put a lot of work. This is, my model scram, and I put a lot of work into making it fast and efficient by making it use hybrid structure. Other models like 338 00:49:42.270 --> 00:49:48.830 Mark Kushner: this is a Los Alamos model developed by Chris Mons. And Joe Abdullah. Opal is 339 00:49:49.000 --> 00:49:52.089 Mark Kushner: a model from Ca, and 340 00:49:52.430 --> 00:50:09.160 Mark Kushner: no, that's Carl Carlos Glaze model from Livermore and prism. Is from the Us. But all the models in the world right are based on the same kind of physics, but they have different levels of completeness, different approximations for things line broadening. 341 00:50:09.160 --> 00:50:23.680 Mark Kushner: And some of them take weeks to run. Maybe not for this case, maybe for more complex time. But they're they're expensive models. And that's just with the one electron transition. The 2 electron transitions. Is 342 00:50:24.610 --> 00:50:34.950 Mark Kushner: orders of magnitude more difficult, because now you have to include not only all of the coupling between all of the energy levels that you have 343 00:50:35.570 --> 00:50:38.609 Mark Kushner: the direct coupling. But all of the 344 00:50:38.850 --> 00:51:00.239 Mark Kushner: 4 different kinds of RAM on 2 electron processes that can happen, the quantum mechanics for that is miserable, and to do it for a complete model that would be adequate to test the hypothesis. Here is, nobody has done it. I'm not sure. If there's hope to do it. So it's it's an open question. People have also suggested that the 345 00:51:00.440 --> 00:51:13.250 Mark Kushner: the the plasma environment changes the electronic structure in some way like it did for the K Beta that we're not capturing in our models. And that's probably true, too, because all of these are built on isolated atom physics. 346 00:51:13.350 --> 00:51:27.249 Mark Kushner: That we can test and we can test. We've tested it pretty exhaustively. It doesn't look like that's the case. and you can kind of I don't know. Guess that that's probably not the plasma effects. And yet 347 00:51:27.460 --> 00:51:37.780 Mark Kushner: and yet we see it when we go to higher densities, almost invariably. And we're seeing it not only in iron, but in oxygen, which is interesting. 348 00:51:39.280 --> 00:51:48.719 Mark Kushner: And the crazy thing the thing that really makes us that is that we don't see it in chromium. And we don't see it in nickel. And it's nobody folks. 349 00:51:54.640 --> 00:52:20.009 Mark Kushner: Can you explain why? X-ray midst the air electron like a check center? Electron, rather. Oh, so oh, that's that's a really good question. It's due to the shape of the photo Organization Cross section. So if you ever go to. If if you're working with filters and you want a filter transmission, you go to Cxro when you look up the Hanky data tables and you'll see? That a typical opacity. 350 00:52:20.010 --> 00:52:34.299 Mark Kushner: It starts kinda high. And that's actually related to conductivity. It's really interesting. It's a whole different talk. And then it falls. And then you hit a shell like you hit hit the L. Shell and it rises, and then it falls, and then you hit the K shell and it rises and it falls in those edges. 351 00:52:34.330 --> 00:52:36.799 Mark Kushner: It has just has to do with the 352 00:52:37.190 --> 00:52:44.969 Mark Kushner: coupling of the energy of your incoming photon to the energy of your bound electron. 353 00:52:45.080 --> 00:52:58.579 Mark Kushner: It likes to. You see that shell structure in an absorption spectrum. whereas electrons you know, even if they're high energy, they will interact with the Valence preferentially. 354 00:53:02.590 --> 00:53:18.009 Mark Kushner: I know a lot of work has been put into making time resolved spectral measurements, wondering if you have, like any conclusions on how? That is. 355 00:53:18.010 --> 00:53:32.769 Mark Kushner: No, that is a great question. That's a really interesting question. So we designed the experiment. Actually, it was serendipity. I just heard this story from Jim Bailey a couple of days ago, actually said 356 00:53:32.770 --> 00:53:47.870 Mark Kushner: they just had some titanium that was close enough to the pinch. But when they took us a spectrum of the pinch. They saw some absorption lines. Jim identified them as titanium and said, That's one of the nicest absorption spectrum I have ever seen. And then he developed this platform. 357 00:53:48.300 --> 00:53:56.279 Mark Kushner: But it was done like serendipity, and and there was some kind of like empirical development of this platform. Well, if I put more 358 00:53:56.550 --> 00:54:02.189 Mark Kushner: plastic tamper on my target, I get higher density and temperature. Okay, 359 00:54:03.890 --> 00:54:16.519 Mark Kushner: we didn't model it. We didn't do the Rad hydro modeling. Until more recently, when we do the Rad hydro modeling, we predict that it is expanding and cooling. The time resolve measurements show us that it is getting hotter. 360 00:54:16.630 --> 00:54:19.460 Mark Kushner: and and let's dance 361 00:54:19.470 --> 00:54:21.609 Mark Kushner: no, and dancer. 362 00:54:23.080 --> 00:54:26.459 Mark Kushner: So hikers not working for us here. 363 00:54:27.660 --> 00:54:31.920 Mark Kushner: What are the consequences to the disagreement? Right? 364 00:54:33.850 --> 00:54:44.479 Mark Kushner: well, Ty again, and others have done some really careful analysis to say, well, I'm gonna take the time, resolve, temperature, and density measurements. Do the calculations 365 00:54:44.690 --> 00:54:50.840 Mark Kushner: fold them together with a backlighter intensity curve and see if it changes the results. And 366 00:54:51.040 --> 00:54:54.879 Mark Kushner: to like a 10% level, it does a little bit. 367 00:54:54.970 --> 00:54:59.069 Mark Kushner: not anything like what is needed to resolve that discrepancy. 368 00:54:59.900 --> 00:55:06.989 Mark Kushner: And again, part of that is because that discrepancy. It's so profoundly weird. You need more than 8 electrons. 369 00:55:08.600 --> 00:55:12.210 Mark Kushner: So gradients are gonna change that 370 00:55:16.810 --> 00:55:18.210 Mark Kushner: other questions 371 00:55:19.350 --> 00:55:23.670 Mark Kushner: very short question. Could you maybe comment on 372 00:55:24.340 --> 00:55:31.900 Mark Kushner: the implications for the opacity measurement in the in a broader sense. So why does it matter what 373 00:55:31.940 --> 00:55:36.870 Mark Kushner: it? It? It is called the 374 00:55:38.310 --> 00:55:57.889 Mark Kushner: It's related to the solar abundance problem. Okay? So here's another story. Helmologists look at vibrations in the sun, and they can detect when the radiation pressure gives way to material pressure. And that boundary the I think it's called the convection boundary. But don't quote me. Is 375 00:55:57.990 --> 00:56:05.010 Mark Kushner: an important part of the structure, and and they can see it in the vibrations. They know where it should be relative to the center of the sun. 376 00:56:05.180 --> 00:56:15.019 Mark Kushner: And it's controlled largely by opacity, because that is the thing that controls, how radiation is transported, and when it starts to be free streaming 377 00:56:15.990 --> 00:56:19.070 Mark Kushner: for a long time 378 00:56:19.220 --> 00:56:38.589 Mark Kushner: models of stellar evolution. And these helio seismological measurements were in agreement. And then, I think, in 1998 a group of astrophysicists came along and re-evaluated the abundances of heavy metals in the sun, and that's anything above helium for solar businesses. 379 00:56:38.740 --> 00:56:40.630 Mark Kushner: But it includes iron. 380 00:56:40.860 --> 00:56:50.309 Mark Kushner: And they said, with this new reevaluation of these abundances, our models are now 6 sigma away from the Helo seismological measurements. 381 00:56:50.530 --> 00:56:54.219 Mark Kushner: now increasing the opacity 382 00:56:54.250 --> 00:56:55.820 Mark Kushner: might help that 383 00:56:59.940 --> 00:57:03.339 Mark Kushner: just online. 384 00:57:05.940 --> 00:57:07.140 Mark Kushner: Any other questions 385 00:57:07.570 --> 00:57:08.240 spring 386 00:57:08.500 --> 00:57:13.249 Mark Kushner: good question in a model. Do you need to consider? 387 00:57:13.490 --> 00:57:26.599 Mark Kushner: That explain? You know 388 00:57:26.870 --> 00:57:28.829 Mark Kushner: the discrepancy between. 389 00:57:30.740 --> 00:57:45.729 Mark Kushner: Not here. I don't think, just because this is enough. Above the pinch, that it's magnetic. Fields are fringe fields at that point, so I don't think you have super high fields there. 390 00:57:46.850 --> 00:57:56.630 Mark Kushner: certainly magnetized atomic physics is another frontier, right? What happens to atoms when you give them very high fields, they actually turn into like needles. 391 00:57:56.780 --> 00:57:58.710 Mark Kushner: They're no longer skiers. 392 00:58:04.470 --> 00:58:08.510 Mark Kushner: Yeah. Nice talk, Stephanie. So 393 00:58:08.850 --> 00:58:16.830 Mark Kushner: I've been trying to think about how to raise this question short way. But you mentioned that benchmarking experiments 394 00:58:17.000 --> 00:58:27.690 Mark Kushner: would be, you know, very useful that folks haven't really taken in you also kind of mentioned that the 395 00:58:27.820 --> 00:58:37.700 Mark Kushner: high energy surprises us sometimes with things that we don't expect from modeling and things like that. So is there. 396 00:58:38.100 --> 00:58:53.269 Mark Kushner: I guess if if you ask experiment. Let's say it'd be great. We could do this thing. Where do you think the interesting problems lie in in creating nice spectrum? 397 00:58:53.660 --> 00:58:57.120 Mark Kushner: yeah. So 398 00:58:58.590 --> 00:59:08.819 Mark Kushner: theoretically, the most challenging region of the space we work in is this is warm dance matter, regime. So where you have the thermal and the density effects that are competing. 399 00:59:08.830 --> 00:59:16.350 Mark Kushner: But stuff doesn't emit there. So you have to do transmission measurements. and those are inherently hard. 400 00:59:16.540 --> 00:59:24.879 Mark Kushner: and I mean, ask, when you a lot of complexity in in, in the data that is 401 00:59:25.120 --> 00:59:32.649 Mark Kushner: not as straightforward to interpret as something like this, this emissions pack so if if 402 00:59:34.450 --> 00:59:42.780 Mark Kushner: that's one area where I think measurements that are carefully prepared and characterized. And then 403 00:59:43.310 --> 00:59:57.559 Mark Kushner: a measurement, an absorption measurement was made. That that's interesting again. Now you're in this regime of of like super multi electron ions where you need really sophisticated atom. 404 00:59:58.240 --> 01:00:14.500 Mark Kushner: That also incorporates the effects of events. Plasma. If you, if you're in a dense plasma. So if it but that's what makes it interesting. The other area that I think is interesting is this non lte email. So non, lte models 405 01:00:14.660 --> 01:00:24.379 Mark Kushner: don't have just the States. They have the rates. And we have a community, a wonderful community of atomic modelers that do like code comparisons. 406 01:00:24.450 --> 01:00:25.829 Mark Kushner: We're all over the place. 407 01:00:26.220 --> 01:00:29.729 Mark Kushner: I mean, we're not as bad as we used to be, but still pretty good. 408 01:00:32.500 --> 01:00:39.439 Mark Kushner: Right, speaker. Go and let's thank our speaker again. 409 01:00:42.800 --> 01:00:46.189 Mark Kushner: See you next time 410 01:00:48.330 --> 01:00:49.969 Mark Kushner: put one of those.