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Good.

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Carolyn Christine Kuranz: Alright, let's get started. We've got people still coming in but Hi, everyone. Good afternoon, and welcome to the Mitzi seminar.

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Carolyn Christine Kuranz: I'm very excited to be hosting their Schaefer who I've known for some time. I Derek is an associate research scholar in the astrophysical sciences at Princeton University. He received his bachelor's degree in from Cornell University and his PhD from physics.

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Carolyn Christine Kuranz: In physics, from UCLA, and I should mention that Derek is the first of our early career lecturer that we would are incorporating into part of our Mitzi lecture series.

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Carolyn Christine Kuranz: And Derek has done some really interesting work that he'll tell us about

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Carolyn Christine Kuranz: In both in high energy density physics, but in some lower density plasmas to

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Carolyn Christine Kuranz: And Derek has been sent our exclusive Mitzi mug. So if you just if you prove that we sent it to. Yes.

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Carolyn Christine Kuranz: And maybe someday we'll get to share a cup of coffee together. And again, I should say.

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Carolyn Christine Kuranz: And then a lot of the Mitzi membership has heard me talk about the fee SEC community planning process. Derek was a part of that and helped a lot.

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Carolyn Christine Kuranz: With organizing a lot of that endeavor and those workshops that we had. And so I'll a couple reminders. If people have any technical issues, please put that in the chat. And we have two students will be monitoring the chat. And then once we're all done. We will

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Carolyn Christine Kuranz: Go through moderate questions through the chat or if people have questions or comments. So with that, Derek. Please take it away.

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Derek Schaeffer (he/him): All right. Thank you very much. Carolyn.

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Derek Schaeffer (he/him): And everything is still working. Okay. Well, good afternoon everyone. So yeah, I'm sorry I couldn't be there in person, but I've had a very nice visit today, so I'm looking forward to

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Derek Schaeffer (he/him): Giving this seminar. So today I'll be talking about bringing cosmic shock waves down to earth and specifically how and why we study astrophysics Lee related relevant collision. The shots in the lab.

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Derek Schaeffer (he/him): And I do want to first thank Mitzi for the honor of inviting me to give this first inaugural early career seminar. So let me, let me start by thanking my collaborators who helped carry out this work as well as the Department of Energy Office of Science and NSA and NASA for funding it

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Derek Schaeffer (he/him): So, in the spirit of this lecture series. Let me just give a little brief history on myself.

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Derek Schaeffer (he/him): So as Kelly mentioned, I went to grad school at UCLA primarily working on the lack large plasma device on low Mach number shots. So here's me crawling around on the inside of

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Derek Schaeffer (he/him): The machine during when the few times. He was actually open to air and we would do these low Mark number shocks. This is an image of one of those. And that would sort of take up pretty much the whole diameter this not too far from where I'm sitting inside this machine.

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Derek Schaeffer (he/him): And when I wasn't doing those kinds of experiments I did quite a bit of programming work making a Star Trek theme control system for the whole laser lab.

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Derek Schaeffer (he/him): To get everything running. So after I graduated came to Princeton to be a postdoc in the HDD plasma group. So this is our core group.

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Derek Schaeffer (he/him): See me here will Fox on the type of battery charging and then again it fixes who's right there at the University of Michigan.

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Derek Schaeffer (he/him): You can see they've got us wearing hard hats in this picture. But of course, if you've ever been in, if you know they don't let you anywhere near anything that would fall on you. So this is mostly aspirational, I suppose. But it does sort of

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Derek Schaeffer (he/him): indicates that the largest shift that I've had is I've gotten from grad school into into the postdoc, and now research scientists from. So this sort of more hands on.

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Derek Schaeffer (he/him): Aspect and really getting into these machines to larger, more hands off machines like the NIF that we're at here. And here's an example from one of my experiments or a mega which is the facility that are mostly be talking about experiments today.

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Derek Schaeffer (he/him): So for the last couple years I've been a research scientist at Princeton, and what is our group do

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Derek Schaeffer (he/him): So we study higher energy density or add magnetized plasmas primarily in laser driven systems. And what's nice about HDD plasmas is they can often be mapped to vastly different parameters teams including astrophysics really relevant plasmas of the time, I'll be talking about

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Derek Schaeffer (he/him): Just by matching important dimension is parameters and I'll come back to that shortly.

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Derek Schaeffer (he/him): So, are our various experiments include things like collision list shocks magnetic be connection and scale magnetosphere is biermann battery magnetic field generation.

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Derek Schaeffer (he/him): And anomalous transporting magnetized plasmas but for the purpose of today, I'll just focus on pleasingly shocks and in particular magnetized occasionally shocks.

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Derek Schaeffer (he/him): So here's the punch line. We've developed a platform for studying laser driven. Hi, Mark number collision, the shocks using the advanced diagnostics and he was a highlight reel of some of the results of the going through today.

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Derek Schaeffer (he/him): And this has resulted in the first observation of a high Mark number magnetite shark in the laboratory.

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Derek Schaeffer (he/him): And that's important because it opens a new class of experiments for studying shark physics and being able to compare it to.

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Derek Schaeffer (he/him): Space and space observations and simulations. We've also been able to do the first measurements of the iron and electron velocity distributions in developing shark and that's

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Derek Schaeffer (he/him): Really demonstrates the advanced capabilities diagnostic capabilities we can bring to bear on the shack physic problems.

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Derek Schaeffer (he/him): At the same time, we've been carrying out particle and sell simulations that model. These are driven shocks and experimental the relevant conditions.

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Derek Schaeffer (he/him): And these have helped reveal signatures of shock formation on kinetic scales. And that's important for any experiment really were classical theory is challenging to apply, which in our case is pretty much all of the experiments.

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Derek Schaeffer (he/him): So here's a brief outline of what I'll be going through today, I'll start with an introduction to monetize collision. The sharks.

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Derek Schaeffer (he/him): I find simulations to be a very helpful view of where the big picture. So I'll go into some particle and sell simulations we have the piston driven shack formation.

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Derek Schaeffer (he/him): Then I'll discuss to have our experiments. The first looks at particle velocity distributions inertia precursor. And then the second at the actual observation of high mocking the shot in the lab and it's finally some concluding remarks. Alright, so let's go ahead and jump in.

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Derek Schaeffer (he/him): So what is a magnetite shock. I will tell flow. I guess to start first with what a normal shock is or a collision will shock. So you've probably seen an image like this before. This is a jet going supersonic creating this Shockwave as it does that.

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Derek Schaeffer (he/him): And the purpose of this feature the shark itself is basically to take this incoming flow and slow it down to sub sonic speeds by increasing the temperature and pressure. So if you look at this track down here.

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Derek Schaeffer (he/him): We have an upstream region ahead of the sharp a downstream region behind the shot. And what it does is it takes the pressure and temperature ahead compresses, and he and heats it into the downstream and in that process. It slows down this flow.

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Derek Schaeffer (he/him): Across the shock, so we can characterize these by Mark number. So the speed over sound speed and this region here is quite thin

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Derek Schaeffer (he/him): So that the shock with in these collisions shocks is on the order of the particle collision domain free path. So basically, the smallest length scale.

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Derek Schaeffer (he/him): That the shock can be set up in a system like this. This is an irreversible process. So there's some sort of dissipation mechanism that happens as you go through the shock and in this case that's provided by the collisions themselves and then

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Derek Schaeffer (he/him): You can relate these upstream parameters of things like pressure and temperature to their downstream values using energy and momentum conservation and these are called junk conditions which I'll come back to

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Derek Schaeffer (he/him): So that's a terrestrial shock. Something we were familiar with here on Earth. But if you look out in space. You also see shucks. In fact, we see them in quite a few different systems.

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Derek Schaeffer (he/him): We see a bunch of planetary Bell shocks. So things like the bow shock around Earth Jupiter or Saturn mercury.

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Derek Schaeffer (he/him): interplanetary shots, things that are launched, for example by coronal mass ejections and stellar Bell shocks and so for example as the solar system itself travels through the interstellar medium. There's a termination shock.

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Derek Schaeffer (he/him): That is created and in fact that termination sharpest sort of famous recently because the Voyager spacecraft just pass through it.

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Derek Schaeffer (he/him): And finally, more exotic systems like supernova remnants where you get all the injecting material traveling out into the interstellar medium can drive shots as well.

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Derek Schaeffer (he/him): So we know they're sharks. They behave the same way as is what I described earlier, there's these compressions and heating and the general slowing down to these supersonic flows, but we know there's no collisions. And to illustrate that. Just think about the

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Derek Schaeffer (he/him): System in our own solar system. A typical Krypton that's wants from the sun here will travel this entire distance one of you before encountering a typical collision.

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Derek Schaeffer (he/him): And yet the features we're seeing are much, much smaller orders of magnitude smaller at the same time, we know these sharks are the source of very high particle acceleration, including cosmic rays, we see that with both spacecraft and telescope observations.

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Derek Schaeffer (he/him): So the question is, you know, if we have these sharks. We know they exist, they know when they play an important role and astrophysical systems, but there's no collisions.

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Derek Schaeffer (he/him): How are they for me right without collisions. What, what is mediating the sharks. Well, as you might expect for something that takes place in a plasma, the answer through collective the

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Derek Schaeffer (he/him): Collective electromagnetic effects. And because of that, we can categorize these in three broad regimes magnetized electrostatic in turbulent

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Derek Schaeffer (he/him): I'm only going to focus on magnetized which are shocks that form in a pre existing magnetic field and we focus on that because these are the most common types of sharks that we see out in space. And they also tend to be the easiest to to create

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Derek Schaeffer (he/him): So within magnetite sharks. There are different ways of dissipating that energy Semyon occasional shock we talked about collisions during the dissipation

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Derek Schaeffer (he/him): Or a magnetized shot that is patient depends on the criticality or basically the Mach number

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Derek Schaeffer (he/him): So for low Mark number sharks. It's up critical sharks, there's some sort of anomalous resistive at that provides that this patient that mediates the shock and this is actually an open question is exactly what for mistakes.

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Derek Schaeffer (he/him): But as you go faster and faster. You need get into high Mark number sharks are super critical sharks. This is no longer sufficient

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Derek Schaeffer (he/him): Even with this anomalous resist diversity. And so another process comes into play. And that's iron reflection and we'll talk a lot about iron reflection later on.

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Derek Schaeffer (he/him): Also because this takes place in the background magnetic field, you can classify these sharks by the magnetic geometry. So, you've got a quasi perpendicular or quasi parallel that's

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Derek Schaeffer (he/him): The angle that you're shocked normal makes with the background field and this can play a role in what kind of physics goes into both creating the shark and

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Derek Schaeffer (he/him): Mediating it later on. And also, and things like shock acceleration and for our purposes, will be focusing on supercritical quasi perpendicular sharks.

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Derek Schaeffer (he/him): So this class, the shock with instead of being on conditional skills are now on plasma kinetic scale. So things like the iron and electron inertial length.

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Derek Schaeffer (he/him): And finally, we can characterize these by a Magneto Sonic Mach number. So this is the Magneto Sonic speed of combination of the pain speed plus the sound speed in the plasma.

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Derek Schaeffer (he/him): And another way of saying this is that the shock ultimately grows out of the nonlinear deepening of the main meter sonic wave in the plasma.

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Derek Schaeffer (he/him): And on the right here I have a schematic of what a supercritical perpendicular magnetized pollution, the shock looks like.

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Derek Schaeffer (he/him): And you can see it's pretty complicated. A lot of different parts here and I like to show this, because this is the simplest type of

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Derek Schaeffer (he/him): Collision this shot. This is the one we know the most about and understand the best and it's still quite complicated and they still several open questions, even for this type of system, let alone the more complex systems that you might get into in other machines.

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Derek Schaeffer (he/him): So if you are trying to understand a system like this, the obvious place to look is straight up.

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Derek Schaeffer (he/him): Earth has a bow shock that's easily accessible, relatively speaking, food satellites and this is in fact how you've gained most of our information about shocked by sending satellites up and collecting the data.

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Derek Schaeffer (he/him): The issue is that that satellites are limited in some ways, so they're primarily confined to one, the trajectories, or maybe just small constellations.

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Derek Schaeffer (he/him): As they travel to the shock, were these areas here.

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Derek Schaeffer (he/him): This is a natural system. So there you're forced to encounter variable and uncontrolled plasma parameters.

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Derek Schaeffer (he/him): And because they're so small relative to all the skills here. They're also hyper focused on on small scale structure.

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Derek Schaeffer (he/him): On the opposite end. You have telescope observations, similar to the picture of the supernova remnant I showed earlier.

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Derek Schaeffer (he/him): So these give you very large field structure and they're primarily static. And so between these two regimes.

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Derek Schaeffer (he/him): You have some some gaps there. And so as a result, there's still quite a few questions fundamental physics questions on open shots that remain unanswered.

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Derek Schaeffer (he/him): So, for example, how is energy partition between the electrons and ions across the sharp. So I mentioned the gym conditions earlier.

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Derek Schaeffer (he/him): That relate the bulk quantities like pressure, temperature as you go across, but it doesn't tell you anything about the micro physics as you go through that shock or how different species are energizes to go through

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Derek Schaeffer (he/him): Another big open question at the moment is our particles injected into shock acceleration mechanisms.

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Derek Schaeffer (he/him): As I mentioned that sharks are known to be the source of very high energy particles we know they're accelerating them.

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Derek Schaeffer (he/him): We have a decent idea of how they're being accelerated. The question is, how does that acceleration process start

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Derek Schaeffer (he/him): In order to to get that going. You have to get some particles out of the thermal population into a non thermal energies before they can be accelerated and this is known as the injection problem is currently a hot topic now and understanding and shock physics.

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Derek Schaeffer (he/him): Some other some other questions include what are the characteristics skills, a shark formation and information.

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Derek Schaeffer (he/him): So simulations have shown for a long time that the sharks can compare actually jump the shark layer can can jump around. Though it's unclear if this happens in reality.

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Derek Schaeffer (he/him): And then as you go to higher and higher mock numbers. What is the role of turbulence and reconnection so I meant I mentioned I and reflection is a form of dissipation

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Derek Schaeffer (he/him): But even that may not be enough as you go to hiring hiring mock numbers and so other physical process is may come in at least according the simulations and so it's it's a question of whether or not that's actually the case.

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Derek Schaeffer (he/him): So because of all this lab experiments can can help complement spacecraft and telescope observations.

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Derek Schaeffer (he/him): Basically, by providing controlled and reproducible conditions, a wide range of mock numbers multi dimensional data sets.

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Derek Schaeffer (he/him): And because we're primarily going to be concerned with laser driven systems. You also have a fairly flexible magnetic geometry. So switching between quasi parallel and quality perpendicular is is not as difficult

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Derek Schaeffer (he/him): And more recently, we can also do things like philosophy distribution measurements and that's important because that is will allow eventually some direct comparisons between space and laboratory data since those kinds of measurements are exactly what spacecraft are are making

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Derek Schaeffer (he/him): So a lot of experiments. I'll discuss are shown on the right here, this is sort of a schematic outline. And the idea is we drive a supersonic piston plasma through a magnetized Ambien plasma to create the Shabbat

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Derek Schaeffer (he/him): And so if you're looking down here. We take a high powered laser you shoot it at a target that creates this piston plasma that expands out

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Derek Schaeffer (he/him): expands into a magnetized background. And as it does that it sweeps up Ambien plasma and magnetic flux, kind of like a snowplow and compresses that all out on the frontier.

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Derek Schaeffer (he/him): And as as ambient ions get accelerated to supersonic speeds, they start to overrun the upstream ions and eventually drive a shock and we'll go into more detail on that in a moment.

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Derek Schaeffer (he/him): Before I do, let me just briefly return to the

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Derek Schaeffer (he/him): Topic of scaling. So he was just a table of various plasma parameters and dimension is parameters for three different systems here. It's foul shot a laboratory

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Derek Schaeffer (he/him): Low Mark number experiment like you might find on the lapd at UCLA or a high Mach number experiment, like the ones. I'll talk about. And as you can see the physical parameters are all over the place right they span orders of magnitude but the dimensional is parameters are quite similar.

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Derek Schaeffer (he/him): Now that being said, just matching the dimension is parameters mass how difficult it can be to actually create these sharks in the lab. And that's because it's hard to fit them into the spatial and temporal skills that we have access to. In most laboratories

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Derek Schaeffer (he/him): What's not so hard as making the ions collision list, which is important because in most sharks. The ions dominate the shark physics. So if you can make the ions collision with you can get most of the shock physics out of it.

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Derek Schaeffer (he/him): On the other hand, if you want to get deeper and deeper into the questions I raised before the electron physics becomes more important.

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Derek Schaeffer (he/him): And for that you want a collision list electrons, at least if you're trying to compare it to space and that does become more difficult in the lab and something that's sort of

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Derek Schaeffer (he/him): An object of future study. So for these purposes. The electrons are sort of moderately collision or but the islands are collision. This

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Derek Schaeffer (he/him): Alright so that is our introduction

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Derek Schaeffer (he/him): So we'll go ahead and jump into the simulations here. So these are all done with the particle and so code PSC, could we have it. Princeton. It's PSC itself is a an explicit 3D

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Derek Schaeffer (he/him): Fully relativistic electromagnetic code, but I'm only going to be focusing on 2D and really causing one, the type simulations for for this talk.

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Derek Schaeffer (he/him): The simulations do have a cool on collision operators. So we are able to

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Derek Schaeffer (he/him): Simulate the effect of collisions and try and match those two experiments. So for example, we can get

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Derek Schaeffer (he/him): Effectively collision list ions and moderately collision electronics, like I was just talking about.

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Derek Schaeffer (he/him): We don't directly model. The laser target interaction and that would require too high, the spatial resolution and too much computational time. So instead, we have this heating operator that mimics please

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Derek Schaeffer (he/him): Ablation basically creates the supersonic distance. So we heat the quote unquote target it creates this plasma that

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Derek Schaeffer (he/him): Expands off supersonic Lee through through our background. So in these new simulations that is an example in these movies on the right here or piston.

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Derek Schaeffer (he/him): Is expanding into just a uniform magnetized Ambien plasma. Here's the magnetic field in the middle here and the density on the right.

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Derek Schaeffer (he/him): And as you can see, as it expands out it's sweeping out this magnetic flux and Ambien plasma creating these cavities compressing it on the edge and towards the end, you see the shark form and begin to separate

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Derek Schaeffer (he/him): I'll note that we can simulate multi species plasmids, which is important because in experiments you typically using targets like plastic that have carbon and hydrogen.

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Derek Schaeffer (he/him): And so you can look at the effect of those. I won't have time to get into that today, but we can include that effect as well.

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Derek Schaeffer (he/him): Alright so digging into into this in more detail. So here is a street plot from one of these quality Wendy run says this is the magnetic field versus time and space.

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Derek Schaeffer (he/him): This is one of our simple runs just with hydrogen ions and a perpendicular magnetic geometry dream. So, which is strictly perpendicular here because it's the easiest sharks.

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Derek Schaeffer (he/him): To create, like I mentioned before, in the sense that it takes the least amount of space and time to form. So if you're trying to create a shack in the lab. This is the type you want to create it's easiest to do

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Derek Schaeffer (he/him): So you can see the different regions that I'll be going into later on, we have this stream region ahead of everything that's happening.

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Derek Schaeffer (he/him): This magnetic cavity that's created as the piston expands out and then this sort of yellowish line here representing the piston in shock. So originally. It's all piston.

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Derek Schaeffer (he/him): And eventually, these bifurcated into two pieces, you know, the slower piston and the faster shock and behind the shock is the downstream region.

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Derek Schaeffer (he/him): So let's focus in on this early time. This is sort of the time in which this piston and ambient or clean to to first create this shop.

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Derek Schaeffer (he/him): So what I have here is faith based plots and so the ambient ions on the top and the piston ions in the middle and the electrons on the bottom at four different times easier in units of the upstream gyro period, and I'll take each of these in turn.

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Derek Schaeffer (he/him): So initially at at very early times what we see is just a direct coupling of the piston to the ambient plasma primarily through

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Derek Schaeffer (he/him): Something like MB polar electric fields and now the piston is just directly sweeping up these ambient ions. As you can see here, so they've been accelerated up the piston, in turn,

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Derek Schaeffer (he/him): Has this sort of classic ablation profile to the fastest the elements out out in front of them progressively slower. As you go back to the target and the electrons are just sort of smoothly transitioning from the cold upstream to the hotter have piston dominated plasma.

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Derek Schaeffer (he/him): Now we go a bit later in times half a Jerry, Jerry. Jerry period we see

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Derek Schaeffer (he/him): The beginning of of this sort of

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Derek Schaeffer (he/him): Shocked formation. So what you're seeing here is this deformation in these flows as you this sort of gray highlighted region here.

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Derek Schaeffer (he/him): And this is important because this is the beginning of when the ambient is that we're accelerated by the piston begin to interact with the upstream ambience, so the first Ambien Ambien coupling.

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Derek Schaeffer (he/him): And that is important because it's not the piston. That actually drives the shock and the systems, the piston is just a means of coupling laser energy into our Ambien plasma.

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Derek Schaeffer (he/him): It's the ambient plasma that wanted to accelerate it to supersonic speeds that then drives the shark as it as it streams through upstream ions.

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Derek Schaeffer (he/him): We go a bit later in time. Now we're at about one Jerry period. And now we see the the onset of shock formation. So this is a critical time in this process.

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Derek Schaeffer (he/him): And we know this because we start to see the presence of reflected ions.

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Derek Schaeffer (he/him): So that is this population here. So in the shock frame. This would be ions that stream in don't have enough energy to pass through the potential barrier and get reflected out and in the lab frame. These are items that are accelerated to speed faster than, than the shock.

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Derek Schaeffer (he/him): And so this presence is is a key hallmark of the supercritical shocks. So as I mentioned before, the main dissipation mechanism for these sharks is this iron reflection and that's what you start to see here

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Derek Schaeffer (he/him): At the same time, the, the originally piston accelerated ions that that we're out here now generated and so ended up in the downstream and don't play much more of a role.

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Derek Schaeffer (he/him): We also see that the piston ions start to get trapped behind here. So as as magnetic fields gets compressed, as this is expanding out that provides a barrier for these business lines, they start to get trapped and it's going to be the beginning of the separation between these two pieces.

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Derek Schaeffer (he/him): Finally, just a little bit later at 1.25 Jared periods, we do see this separation of these two features. So the shark is moving faster than the piston. So eventually they're going to separate and you see that fully here. So again, you can see that reflected ions.

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Derek Schaeffer (he/him): Says, be the upstream reflected ions and Shockley are right here. And then the piston that's stuck in this behind region here. So these are all of the originally accelerated I entered have now been swept downstream and this is the piston that's trapped back here and what you

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Derek Schaeffer (he/him): key signature that you get out of this. Is this double bump structure in the density of magnetic field profiles. Right. So you've got one density compression associated with the shock.

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Derek Schaeffer (he/him): And another density compression associated with the piston that's going to be a key observable that will be looking for in experiments.

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Derek Schaeffer (he/him): So looking out further in time, we find that these piston driven shocks form in three stages. And so this first one is not really a stage. This is just our initial setup that I talked about before, we've got the Ambien is being swept up by the piston to get this process going.

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Derek Schaeffer (he/him): Then around one giant time we see this onset of shock formation. So this is presence of reflective ions. So that's our first major stage. And we also call this a shot. Precursor

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Derek Schaeffer (he/him): As we go later this separates we saw that a little bit earlier, but as as it fully separates and becomes independent of the piston.

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Derek Schaeffer (he/him): We, we say that this shop is now fully formed on iron scales. So the shock itself is is a kinetic scale structure. So, these, these ramps are on the order of

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Derek Schaeffer (he/him): The island inertial link. And so these can form and kinetic skills before they fully satisfy all the image de conditions.

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Derek Schaeffer (he/him): And that happens at a later stage. Once this is separated enough for the downstream region to actually become developed and satisfy the junk conditions where these sharks and so around this time, not only do we have the same features here.

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Derek Schaeffer (he/him): That we saw before, but now there's this downstream region. And if you were to look at the compression ratios across here and the density ratios or press here, they would begin to satisfy the

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Derek Schaeffer (he/him): Junk conditions. So this is important because that at these earliest stages which tend to be accessible to experiments, more so than than these later ones.

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Derek Schaeffer (he/him): You can generally apply this junk conditions because there's no downstream region. These are not developed on the MACD scales that are implied

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Derek Schaeffer (he/him): When deriving this junk conditions. And so you really need some other set of deliverables. When looking at a system like this to determine whether or not your shock is for you.

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Derek Schaeffer (he/him): And then lastly, I'll just note that this final stage is classically what is thought of as a shock.

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Derek Schaeffer (he/him): So overall, then

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Derek Schaeffer (he/him): I think you can see the piston driven shock formation is a complex process here is just another snapshot at about one direct time showing all these different elements that are interacting with each other.

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Derek Schaeffer (he/him): But what's important here is that simulations allow us to extract key observable that we can use to interpret the experiments. And so we've talked about these different

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Derek Schaeffer (he/him): Shark formation times and each of these has their own key signatures, things like deformation of these flows strong compressions. This

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Derek Schaeffer (he/him): Presence of these reflected ions and as you go later this double bumped structure or even later is development of a downstream that's consistent with the junk conditions.

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Derek Schaeffer (he/him): One thing that's important to note is that distinguishing between piston dominated and shock driven processes can be can be tricky.

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Derek Schaeffer (he/him): So you can see, for example, magnetic and density compressions that would show up, just from a piston driven flow without necessarily being a shot. So it's important to distinguish these two and we'll get into what that might look like in the experiments in a moment.

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Derek Schaeffer (he/him): But first, let me just briefly discuss the experiment or the diagnostics. We're going to use

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Derek Schaeffer (he/him): For these experiments. I find it easier to just do this at once. Then introducing them piecemeal

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Derek Schaeffer (he/him): So let's start with proton radiography

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Derek Schaeffer (he/him): So this is a diagnostic that measures a 2D image of the path integrated magnetic field. As you can see a schematic on the top here, we have some source of protons that we shoot through our plasma the protons are deflected by electromagnetic fields in the plasma.

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Derek Schaeffer (he/him): And then collected on a detector and because this deflection is primarily related to the magnetic field. And here I'm ignoring electric fields because they tend not to play a role in these in these particular experiments.

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Derek Schaeffer (he/him): So because he's related to the magnetic field, you can use the position of the protons on the detector relative to where they'd be without any deflections

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Derek Schaeffer (he/him): To back out what the megalithic structures in this plasma look like. So here's an example in the bottom here is a what might

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Derek Schaeffer (he/him): Magnetic cavity might look like with a compression on the edge and sort of know field in the middle.

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Derek Schaeffer (he/him): When you send protons through that you can get a fluence profile that looks kind of like this. So you have this caustic feature. For example, and you can invert this to then get what the path integrated field looks like. You can see the compression the upstream and the cavity here.

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Derek Schaeffer (he/him): This is a fairly simple setup that you can directly invert, but you can for more complicated systems. There are their algorithms for doing 2D reconstructions or conversions that we have access to

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Derek Schaeffer (he/him): So that's proton radiography for for magnetic fields.

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Derek Schaeffer (he/him): Next is optical Thompson scattering. So this is a very powerful diagnostic for for measuring local parameter

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Derek Schaeffer (he/him): Plasma parameters and, more generally, for velocity distributions. So the idea in terms of scattering is you shoot a laser to your plasma that scatters of coherence structures that in our case, basically electron plasma ways and I and acoustic waves.

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Derek Schaeffer (he/him): And importantly he scattered signals is proportional to the structure factor as

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Derek Schaeffer (he/him): Which is just a linear combination of an electron term and an eye on term, each of which depends on the velocity of distribution for either the electrons, where the ions.

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Derek Schaeffer (he/him): The result of this, then as you can extract a lot of information from the spectrum. So things like temperatures densities flows and more

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Derek Schaeffer (he/him): And in practice. You do this by either deeply fitting and analytic distribution to your fingers spectral data. So here's an example on the rate

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Derek Schaeffer (he/him): For assuming Maximilian distribution, just to give you an idea of what the spectrum might look like and how the different features are related to different plasma parameters. So this is the electron feature, which is the broader feature than the iron feature which is much narrower.

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Derek Schaeffer (he/him): One. One thing I'll point out, are these two wings that you see in each. These are actually just the reverse and forward propagating waves that you're scattering off of for each of these populations.

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Derek Schaeffer (he/him): So for each population, whether its electrons are ions are multiplying species will have a set of wings like this in your in your spectrum.

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Derek Schaeffer (he/him): Now for sharks generally the ion distributions are non next willing as you could see in the simulations, they're definitely not next willing, as you go through the shock.

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Derek Schaeffer (he/him): But for our purposes, because the electrons are more occasionally they do tend to be pretty Maxwell and and this is a good approximation.

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Derek Schaeffer (he/him): So what I'll be showing is basically quantitative information extracted from these electron features, where we can assume x value distributions and then mostly qualitative discussion of the eye and features and deriving what those distributions are for the ions is an open area of research.

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Derek Schaeffer (he/him): Lastly, we have angular filter refract symmetry. So this measures the path integrated density gradient contours. So the idea here is, again, we have a pro beam.

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Derek Schaeffer (he/him): That we send to our plasma gets refracted passes through this special Angular filter and then image and the result looks kind of like this you get these bands.

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Derek Schaeffer (he/him): Where the edges of these bands correspond to spit and specific refraction angles, which in turn are related to some density gradient some known density gradient

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Derek Schaeffer (he/him): Now for our purposes, the main takeaway here is that narrow bands correspond to large changes in density gradient, whereas broad bands correspond, the small changes in density gradient

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Derek Schaeffer (he/him): Okay, so with that in hand, we can go ahead and look at our experiments. So I'll start with some experiments on the mega 60 leisure facility.

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Derek Schaeffer (he/him): Which is part of the laboratory for leisure energetics at the University of Rochester. So here's our setup. It's relatively straightforward. We've got some coils.

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Derek Schaeffer (he/him): That we pulse to generate the magnetic field. So the magnetic field here is basically vertical or parallel to this great target parallel to that service.

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Derek Schaeffer (he/him): Then we've got these two plastic targets. This one for generating our Ambien plasma in this one for generating piston plasma. And so the idea is you fire up this coil create the magnetic field, then you hit this

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Derek Schaeffer (he/him): Ambient target to create that plasma that streams in and fills this area. And once that has mixed in with the field you then hit this piston target to drive your piston plasma through that magnetized ambient plasma and here's a top down view of what that looks like.

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Derek Schaeffer (he/him): So for these experiments, the primary diagnostics will return radiography. So for that we implode this capsule here and it generates protons as fusion vibe byproducts that then stream through

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Derek Schaeffer (he/him): along this axis which is the z axis in this coordinate system that generates an image in the xy plane. So sort of cross image in in this view.

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Derek Schaeffer (he/him): And then we have Thompson scattering here. The setup is the Thompson being comes in along this factor here and gets collected here.

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Derek Schaeffer (he/him): And what's important is that means it probes exactly along this x axis or parallel to the propagation of the of the piston plasma and perpendicular to the field.

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Derek Schaeffer (he/him): So it means that the distribution functions. We're going to be probing in this experiment are perpendicular distribution functions.

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Derek Schaeffer (he/him): So I'll start with the proton radiography. So here's an image from a 15 MTV.

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Derek Schaeffer (he/him): Protons, this is on CR 39 is the raw image you can see the outline of the Ambien target this and targets over here. My Feds targets that generate the

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Derek Schaeffer (he/him): The magnetic fields are out of you and then you see this large bubble feature. And this is the magnetic cavaney that's generated by the piston as it expands out and all that flux is swept up into these narrow light regions and the corresponding dark regions out here.

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Derek Schaeffer (he/him): So I mentioned we can invert this to get the magnetic field profiles. So this red or these red dots you see here the raw data just taken from from the image.

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Derek Schaeffer (he/him): From that, we convert it to get this path integrated magnetic field. That's the black line here. As you can see, there's a lot of flux that has been swept up here.

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Derek Schaeffer (he/him): Then if you make an assumption about how that path integration works. And in this case, we basically are assuming spiritual expansion here and integrating through that you get this blue curve here.

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Derek Schaeffer (he/him): So this would be the unfolded total magnetic field along this red line and you can see this quite a bit of compression that's happening.

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Derek Schaeffer (he/him): And this green line is we take this blue line and then synthetically send protons through to create a synthetic radio graph and look at what the fluids looks like. And we get this green line so it matches up quite well.

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Derek Schaeffer (he/him): So you've had strong magnetic compressions. We've seen and I'll come back to this profile in a bit.

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Derek Schaeffer (he/him): Moving on to the Thompson scattering the main takeaway here is that, especially for the ions. You see these 1D philosophy distributions right right in the spectrum.

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Derek Schaeffer (he/him): So here I'm showing the iron feature on top. The electron feature on the bottom. These are streaks, so it's time along the horizontal and the wavelength on the vertical

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Derek Schaeffer (he/him): And this is a no show this is a piston plasma just going through a magnetic field in vacuum.

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Derek Schaeffer (he/him): And what you see is just a single feature here and it's broken into these two lines. These are the forwarded reverse propagating waves. I mentioned. So it's just one population of violence.

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Derek Schaeffer (he/him): It has this sort of classic completion profiles, the fastest first so

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Derek Schaeffer (he/him): For this kind of measurement. We're sitting in one spot. Basically, and watching as this goes by so you see the fastest stuff first and then and then the slower stuff.

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Derek Schaeffer (he/him): And then the electrons, you get something similar here, the distance from from the center line is related to the density and the width of these related to the temperature as you seem to the less dense polish the first and then it gets into colder dense your stuff as you go further back.

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Derek Schaeffer (he/him): I'll note that we are using plastic targets. So, in principle, there are both carbon and hydrogen ions, but for these kinds of experiments, the hydrogen tends not to show up in the Thompson, because it's heavily landale damp.

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Derek Schaeffer (he/him): When scattering. And so we're primarily just seeing the carbon hydrogen can have an effect on on the spectrum.

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Derek Schaeffer (he/him): So now we add back in our Ambien plasma take away the magnetic field. So it's a piston plasma going through an ambient plasma know magnetic field.

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Derek Schaeffer (he/him): And we see two features now. So this one is the similar to before. It's a little bit brighter.

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Derek Schaeffer (he/him): So a little bit more intense scattering, you can't really see the two lines, but they're in there and then another feature down here that's related to the Ambien plasma. And we know this is the ambient

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Derek Schaeffer (he/him): Because it starts basically at zero Doppler shift. So zero velocity stationary upstream

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Derek Schaeffer (he/him): At least perpendicular to the field and then it gets slowly accelerated over time. So there's some interaction between these two that you can see, you know, eventually, you could imagine the emerging but not much happening and in the electrons. You can see there's some additional heating

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Derek Schaeffer (he/him): As you're going back years sort of getting broader, but again, not much, not much happening.

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Derek Schaeffer (he/him): Finally, we add in our magnetic fields. This is our fooling

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Derek Schaeffer (he/him): Pistol going into magnetized mean plasma and we get very different behavior, right. You can see these strongly formations in the aliens and and electrons happening all at the same time.

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Derek Schaeffer (he/him): And what we're seeing is we'll break this down different pieces out here. If you're a call from the simulations, or this population of violence is just sort of get ahead of everything and don't do much. And that's these guys. So the free streaming

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Derek Schaeffer (he/him): Primarily piston lines that have gone ahead, then you get this dramatic deceleration happening very quickly in this region, and at the same time and acceleration

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Derek Schaeffer (he/him): In the ambient ions and at the same time there's blip in the in the electrons indicating and very strong density in temperature gradients happening here. And then later in time you start to see them marriage together.

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Derek Schaeffer (he/him): So this is just a couple of profiles, taken from this

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Derek Schaeffer (he/him): Electron feature. So the green one earlier in time the Redwood as we go through this blip. And you can see that they are getting changed quite dramatically, and we can

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Derek Schaeffer (he/him): Fit these to get quantitative information, which I'll show in a moment.

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Derek Schaeffer (he/him): First, I just want to point out again the comparison with the one day velocity distributions, as this is from our pic simulation similar to what I showed earlier, this is a multi species.

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Derek Schaeffer (he/him): Simulations as carbon plus hydrogen and this is the one the phase space.

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Derek Schaeffer (he/him): A strict in time and you can see the the strong similarity here as you as you would expect to you've got this population of stuff that streamed out ahead.

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Derek Schaeffer (he/him): You've got this deformation that's happening here and corresponding acceleration here that you received in the data as well. And then this sort of general merging that happens later as the stragglers get swept up at lead time

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Derek Schaeffer (he/him): Now, one thing that's very important here is that what we're not seeing is a basically a connection in phase space all the way around as you as you look at this

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Derek Schaeffer (he/him): So if you recall from our earlier simulations. When we drive a shock. These ambient is get accelerated.

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Derek Schaeffer (he/him): All the way up past the shock speed which becomes this population and reflected ions. But that's not what we're seeing here, right, there's still a whole here in phase, phase, meaning that we've started this process.

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Derek Schaeffer (he/him): Of shark formation, but we haven't completed it right so we we are observing the interaction directly between the piston and been ions in a shock precursor. But importantly, not, not the fully formed shock.

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Derek Schaeffer (he/him): Now you may notice that there's this little, little blue future here in the simulation. That does look like it connects and indeed this is

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Derek Schaeffer (he/him): A shock, but this is a shark in the hydrogen ions.

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Derek Schaeffer (he/him): So he didn't get much of a chance to talk about it, but both the hydrogen and carbon ions can can create shots at the same time, and the hydrogen will form one first because it's lighter element.

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Derek Schaeffer (he/him): So it forms on fantasy type skills in the carbon. And that's what we're seeing here. So a shock is formed in the hydrogen that actually does go all the way around and contributes to this feature.

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Derek Schaeffer (he/him): But not yet in the carbon

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Derek Schaeffer (he/him): But like I said before, the hydrogen is heavily Lando damped when it comes to the tungsten scattering. So you don't really see it in here, though it can have an effect on how you interpret the rest of this spectrum which again makes it complicated to do

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Derek Schaeffer (he/him): So we can be more quantitative. So here are three plots. I'm fluid speed, the electron density and the electron temperature extracted from

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Derek Schaeffer (he/him): The spectrum and I'm comparing magnetized and and magnetized just to emphasize these points.

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Derek Schaeffer (he/him): So for example, in the eye and flow speed, you're getting this strong deformation. So you've got a strong deceleration, and at the same time acceleration of the ambient is happening.

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Derek Schaeffer (he/him): You don't see anything like that in the UNM magnetized case this very clear, strong density gradient and then very strong electron heating also happening again. You don't see that in the magnetized case.

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Derek Schaeffer (he/him): So clear difference between these two and we can pull all this information together, including the magnetic field. I showed with the

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Derek Schaeffer (he/him): Proton radiography and we get a very nice self consistent demonstration directly observed this piston Ambien Kathleen in this shock precursor stage. So, for example, you've got this magnetic compression and behind that we get the pilot of artists in ions.

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Derek Schaeffer (he/him): This results in a data Keating of the electrons that we see here from these magnetic pressure gradients and magnetic field gradient

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Derek Schaeffer (he/him): Electric fields and pressure gradient electric fields point. This way we get an acceleration in the MDI answer. That's this feature here and these are also modify the flow of the the pistons, which results in that deceleration. And so we see all that happening at the same time.

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Derek Schaeffer (he/him): And so I think you know this point that the velocity distribution measurements are critical to understanding the shark formation as well represented here.

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Derek Schaeffer (he/him): Alright so lastly I'll talk about our observations of high Mark number sharks.

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Derek Schaeffer (he/him): And so these took place on the mega EP leisure facility, it's right next door to the mega leisure facility that we were just talking about.

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Derek Schaeffer (he/him): And they set up is very similar. As you can see here though you'll note that there's a second set of coils.

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Derek Schaeffer (he/him): So the idea is the same. This was originally an experiment set up to study reconnection. So, the idea being you. You take your to plumes you inject all that field to the center and reconnect them right in the middle.

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Derek Schaeffer (he/him): But in hindsight, it's not too surprising. These could also drive sharks. It's basically the same setup. We've got an Ambien plasma magnetic field in the nice pistons driving through it. We just need to look at times before they actually collide.

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Derek Schaeffer (he/him): So here the were probing again with proton radiography. This is a little bit different. This is TSA pretend radiography but same idea. So these are streaming on this direction, creating x y image.

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Derek Schaeffer (he/him): Then we've got the angular filter reflect telemetry and should atrophy. These are both density measurements. These are probing along z. So, they create this x, y.

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Derek Schaeffer (he/him): Image that will see and I already went to this process. But again, you know, the idea is we fire. These coils to create a magnetic field fill this volume with the ambient plasma and then drag these pistons through

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Derek Schaeffer (he/him): And in this case, instead of having them Clyde, we're going to look at them before they collide, for the purposes of the sharks.

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Derek Schaeffer (he/him): Now, there's no Thompson scattering on the mega EP system, but we wanted to get the ambient plasma characteristics like density in temperature that's important for calculating things like the

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Derek Schaeffer (he/him): Compressions or how much is being heated. So we basically ported the entire experiment over to a mega all the same parameters and took these measurements.

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Derek Schaeffer (he/him): Which we get here. So these will come up in a moment.

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Derek Schaeffer (he/him): And with the AFR, we can then look at the the density structure. So here's an example from an inertia. This is just a piston plasma expanding into vacuum and when we see it basically just two blocks right these are not

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Derek Schaeffer (he/him): Very interesting structures, and you can see the two edges that correspond try to density gradient, but they're quite broad. And here's the reference image of what we're looking at.

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Derek Schaeffer (he/him): So now much going on their

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Derek Schaeffer (he/him): Reality in our magnetized Ambien now we're getting very different behavior. So this is three different snapshots.

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Derek Schaeffer (he/him): This first one just had the one target instead of both, which is why there's only one set of features here. The other two had both targets.

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Derek Schaeffer (he/him): But you can see principally, you also have these big blobs, but mainly this very thin band the talent front and it travels towards the center until late time bifurcated into these two bands.

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Derek Schaeffer (he/him): You can also see that at the top here, they've they've collided. That would be the sort of reconnection part of the experiment.

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Derek Schaeffer (he/him): And we can track these bands to get a time of flight speed and estimate the market numbers is about 700 kilometers per second to market number 15

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Derek Schaeffer (he/him): We can also look at these features more closely. So the AFR tells you what the density gradients are at these two edges, the leading edge and the following message but doesn't tell you anything that's happening.

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Derek Schaeffer (he/him): In between, so if you wanted to know what the spatial structure is as you're going across this you can use should atrophy for them.

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Derek Schaeffer (he/him): So Sheila graffiti is just related to the second derivative of the density and you get a profile that looks like this. So it gets you the total jump in density and just as importantly,

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Derek Schaeffer (he/him): The spatial skills, over which that jump is happening in this case, it's about half an inertial length. So these are definitely on kinetic scales.

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Derek Schaeffer (he/him): Then we can reconstruct the density profiles, which I'll show a little bit later on, but to see what the density compressions are at this late time. And those are larger than a factor for so strong density compressions.

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Derek Schaeffer (he/him): And finally, we look at the magnetic field. So here's a proton radio graph looks a little bit different. These are TNS a proton since his film instead of car 39 but

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Derek Schaeffer (he/him): Same idea, I've got this large magnetic cavity. This is zero field. It's been swept out by the piston and compressed all into this sort of thin white ribbon here and again this is a reference what we're looking at.

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Derek Schaeffer (he/him): And we can analyze this like we did before to back out with the magnetic field looks like. So we find an average background field of about for Tesla, which we can use for the mark number and then a magnetic impression of about three. So these are strongly compressed in the magnetic field.

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Derek Schaeffer (he/him): So we've got a high Mark number. We've got the strong density in the neck field compressions.

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Derek Schaeffer (he/him): On kinetic skills.

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Derek Schaeffer (he/him): In order to to wrap this up. We need to figure out what's going on with this bifurcation. So here I'm showing

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Derek Schaeffer (he/him): Three times on the top is the reconstructed density profiles in black and gray and then a pic simulation in red. And on the bottom, or just the iron profiles, I am density profiles from that simulation. So the total than the ambient interesting contributions in red and green.

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Derek Schaeffer (he/him): And really times, we find that this is these narrow bands that we're seeing in the AFR

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Derek Schaeffer (he/him): Is associated just with that pilot, but the piston so stuff that we also saw in the simulations. I showed earlier, and this continues for a little bit of time we see it again at this time.

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Derek Schaeffer (he/him): But then at lead time where this splits into this double bump structure. This is represents the separation of the shark from the piston, just like we saw

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Derek Schaeffer (he/him): In the simulations. I showed earlier. Um, so now we've got a separate feature that is separating away. Has it turned into the compression and that's that's our shot features. So this combined with with everything else gave us our high Macklin magnetized shock.

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Derek Schaeffer (he/him): So summarize once more. So we've we've developed this platform for studying laser view in high market and with sharks using these advanced diagnostics. And again, here's our highlight reel of these different

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Derek Schaeffer (he/him): Results. So under this platform. We've been able to observe a high Mach number magnetite shock for the first time in the laboratory. So for example, this guy here and also make measurements of birth, I an intellectual gloss you distributions and developing shock.

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Derek Schaeffer (he/him): These guys here.

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Derek Schaeffer (he/him): And then at the same time, carrying out quite a few particle and sell simulations to model these laser driven sharks and back out with signatures of connect scale shocked formation.

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Derek Schaeffer (he/him): And so going forward. The development of this platform can allow several key questions and magnetized shock physics to be addressed.

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Derek Schaeffer (he/him): And I mentioned this earlier. So, for example, our particles, he did and how his energy partition as you go through the shark. How is our particles injected and accelerated in the shocks.

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Derek Schaeffer (he/him): Again, how can spatial and temporal scales, a shock formation and Reformation, what do they look like. And then as you get into higher and higher mock numbers. What is the interplay between the sharks reconnection turbulence. And so, more recently, we've been doing some simulations.

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Derek Schaeffer (he/him): With quasi perpendicular sharks that show under the conditions, similar to the experiments. I just, should we can see non thermal electron population. So, this

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Derek Schaeffer (he/him): relates back to this particle injection problem that it may be possible in the lab to study how particles are specifically electrons are injected in a quality perpendicular or yeah

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Derek Schaeffer (he/him): Literally shocked. And then we've got some experiments underway exploring quasi parallel collision shots, which have a whole other set of interesting physics questions. Alright. With that, thank you. I'll take any questions.

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Carolyn Christine Kuranz: Everyone's clapping just unmute

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Carolyn Christine Kuranz: Oh, thank you so much, Eric. That was really excellent. Oh, yes. Take a drink from your, your map so much

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Yeah.

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Carolyn Christine Kuranz: Yeah, so while people are formulating their questions. They can either put them in the chat or if they just want to put like q i will call on them. And while people are doing that, I will take the opportunity as host to ask the first question.

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Carolyn Christine Kuranz: Um, so I might have missed the geometry, but in the AFR images. So in the proton radiography

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Carolyn Christine Kuranz: It looks like you've got these two plumes, essentially, and then something in between them. But, and they AFR a look. Yeah, right there. But in the previous slide or two in the air far it looks doesn't look in symmetric. Do you have any

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Carolyn Christine Kuranz: Thoughts on why that is, or is it just an effective the jam.

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Derek Schaeffer (he/him): A symmetric

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Carolyn Christine Kuranz: You mean I mean

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Derek Schaeffer (he/him): I wouldn't realize

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Carolyn Christine Kuranz: There was, like, so you see two features coming towards each other, but then it looks like maybe you've got then it looks kind of like they're off centered maybe late at the later.

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Carolyn Christine Kuranz: Oh, please.

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Um,

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Derek Schaeffer (he/him): So yeah, there's a couple of things going on. One, some of this is is just going to be target non uniform. These are the way that you know this thing is actually constructed

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Derek Schaeffer (he/him): Here and I think you can tell from here that this sort of top part tends to be interacting first and the bottom parts are still expanding out, which is why we can see them at later times when we can't see the exact same features appear

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Derek Schaeffer (he/him): You know exactly what what causes it. You know, I think it's primarily comes down to the target fabrication, more than anything else, because there's nothing that's in this that should inherently biased towards one one spot or the other.

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Carolyn Christine Kuranz: Okay. Okay, interesting. Um, let's see, in the chat. We've got a question about since the power density of the laser producing the plasma, but maybe it's just the power. Yeah.

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Derek Schaeffer (he/him): So let me see if I can remember that top my head.

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Derek Schaeffer (he/him): The ambient plasmas. We tend to hit pretty softly, relatively speaking with about 100 Joules of energy and about a nanosecond.

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Derek Schaeffer (he/him): So what is that that's like 10 to the 11

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Derek Schaeffer (he/him): Watts of power and for the piston plumes those we hit harder. Those are probably an order of magnitude more energy and power.

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Derek Schaeffer (he/him): Roughly the same poll shape. So these are all you know long post. I guess I would say compared to, say, a short pause generally on the order of a nanosecond and something between 100 and 1000 truths.

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Carolyn Christine Kuranz: And then do you want like a really big spot size because you're just trying to get a bunch of plasma moving or

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Derek Schaeffer (he/him): Yeah, for these

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Brilliant.

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Derek Schaeffer (he/him): So we tend to hit this with pretty oblique lasers. So you can actually see comes in it quite a steep angle.

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Derek Schaeffer (he/him): And that is exactly to to create this sort of longer ellipses little spot size. So it's fairly planar in this direction.

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Derek Schaeffer (he/him): So that you know we sort of take out that dimension as a as a factor.

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Derek Schaeffer (he/him): And just sort of help sort of smooth things out.

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Carolyn Christine Kuranz: Okay, great.

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Carolyn Christine Kuranz: Let's see, and then the chat. Oh, we have a question. I'm kind of the overall motivation for the work. So why is this important to understand and study these shocks.

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Derek Schaeffer (he/him): Read three, you know, again,

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Derek Schaeffer (he/him): That comes back to some of the key questions that that astronomers have. So, you know, there's always a fundamental sort of interesting physics question about about sharks and can we understand them more fully, but in

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Derek Schaeffer (he/him): I suppose a slightly more applied sense, you know, and when astronomers. Look out, they see these very strong

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Derek Schaeffer (he/him): Particle acceleration sources that are associated with sharks. We also see that in the heliosphere with some of those strong rebel shocks.

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Derek Schaeffer (he/him): And the, you know, you have these contributions to your energized particles. They don't really understand yet.

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Derek Schaeffer (he/him): How that is happening. So this, again, this injection problem you, how do you get particles into this process so that they then get accelerated.

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Derek Schaeffer (he/him): And so a lot of this motivation comes from Ash physicists and astronomers who want to know what are you, how are the sources of these things coming about.

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Derek Schaeffer (he/him): You know, partly I suppose to to better diagnose what they're looking at in that cluster.

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Carolyn Christine Kuranz: Great, thank you. Another question from the chat. Did you find any relation between your lab sharks with observational astronomy.

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Derek Schaeffer (he/him): So that is a work in progress.

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Derek Schaeffer (he/him): You know, we, I think we're, we're at the stage where we can now start to do this and the next stage would be to to begin exploring these questions, like the ones I laid out.

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Derek Schaeffer (he/him): The hope is. Yeah. And we have projects where we're working with collaborators in NASA to compare the results to spacecraft data. So that's very much a work in progress.

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Derek Schaeffer (he/him): And hopefully maybe within the next couple years will start to make those kind of comparisons with observational astronomy, at least within the heliosphere

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Derek Schaeffer (he/him): It's harder to compare to astrophysical objects because there's not a whole lot of detail that's available. So for those you'd probably want to do you acceleration type experiments. And those are a little bit further off.

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In the next few years.

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Carolyn Christine Kuranz: Great, thank you. Are there. Oh, and then regarding your pic Sims. Did you use an open source code.

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Derek Schaeffer (he/him): technically, technically I don't think it's open source,

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Derek Schaeffer (he/him): It's, it's not proprietary, it's sort of in this in between stage. I think if someone went through the effort to, you know,

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Derek Schaeffer (he/him): Put it on yet or something. It could be open source is nothing particularly proprietary about it. It's just not in that state at the moment I forget, I forget exactly which code is based off of. But I believe that the original code is is open source.

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Derek Schaeffer (he/him): This is your sort of modification

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Mark Kushner: Hey, Carolina. This is Mark. I have a short question now. I think it's your next slide.

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Mark Kushner: Where you have the just as the two sharks are intersecting the radiography

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Okay.

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Mark Kushner: Yeah, that yes, that that one.

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Mark Kushner: Those shopfronts look amazingly smooth.

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Mark Kushner: Yeah, I would have expected that as they come together, you know, there's just enough statistical variation and the launching of the two pistons that

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Mark Kushner: You would have some sort of density variation at the surfaces and almost sort of a really tailor type of structure occurring as the chalks collide. You don't see that it's there. If there's something that's intrinsically stabilizing that prevents that

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Derek Schaeffer (he/him): Yeah, we were pretty strictly perpendicular geometries. So sort of coming back to Kevin's question. Yeah, we, we set these up to be pretty uniform in

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Derek Schaeffer (he/him): Along so

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Derek Schaeffer (he/him): I guess both this direction and into the plane when doing it this way so that it's a it's a fairly planar expansion and when you've got this sort of strictly perpendicular

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Derek Schaeffer (he/him): Expansion, there isn't.

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Derek Schaeffer (he/him): There isn't a mode. That's going to grow that will go unstable.

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Derek Schaeffer (he/him): In this geometry. So you really just sweeping up the magnetic field and compressing it and

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Derek Schaeffer (he/him): And there's not really anything else that it does so we we have seen systems where you do get sort of these flutes or or instabilities develop and those tend to happen at other angles relative to the background field.

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Derek Schaeffer (he/him): So I think in this case that is primarily suppressed just by being so perpendicular relative to the field.

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Mark Kushner: Okay, thank you.

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Carolyn Christine Kuranz: Any further questions. Also, feel free to unmute if you'd like to ask her question, or you can put it in the chat.

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Carolyn Christine Kuranz: I'm very jealous of your mug, Derek. I don't have. I don't have one, as I lament all the speakers. So it's very special.

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Felipe Veloso: During something

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Felipe Veloso: Sure, please. Yeah. Hi.

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Felipe Veloso: My question would be experiment scalable for lower density power density laces.

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Derek Schaeffer (he/him): Well,

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Derek Schaeffer (he/him): You know, the difficulty, you're going to run into

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Derek Schaeffer (he/him): Is is getting the ions to be collision list. So it would depend on on what your coupling that too. So when I was in grad school. We did experiments on the LAPD, which is a very different machine, much lower density is much lower and magnetic fields.

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Derek Schaeffer (he/him): But our laser that we were using to drive it was was comparable. It was it was again in the tend to be 11 to 12 range.

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Derek Schaeffer (he/him): Because you just need a lot of energy to go into that piston both to make it fast so that you are super authentic.

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Derek Schaeffer (he/him): To make sure it's fast enough.

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Derek Schaeffer (he/him): That the islands are clueless on your skills and that you have enough energy to actually couple into the background.

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Derek Schaeffer (he/him): So depending on, you know, I think it would be hard for example to do with like a one Julie's here.

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Derek Schaeffer (he/him): Yeah, we'd really depend on what else you're coupling it with

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Carolyn Christine Kuranz: Okay, I think that might be all of our questions.

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Carolyn Christine Kuranz: Going once, going twice. Alright, well let's thank Derek again thank

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Derek Schaeffer (he/him): You all

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Carolyn Christine Kuranz: Take care, and it was great to see you.

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Carolyn Christine Kuranz: Mark you have any closing words.

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Mark Kushner: To a congratulation to Derek for being our first early career lecture you have set a very high standard. And I hope that I will be able to see you in person very soon. Thank you for participating and what I think has been a long day for you.

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Derek Schaeffer (he/him): I really enjoyed it. Thank you so much for for inviting me, even if it was all remote had a good time.

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Carolyn Christine Kuranz: Yeah, thanks for being a good sport there. All right, take care, we'll talk soon.