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John Edison Foster: Okay So here we go so gives me great pleasure to introduce Dr cydia check out.

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John Edison Foster: Our speaker today so Dana is a research scientist of CNS are at the largest fundamental science agency.

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John Edison Foster: and your she works in the I care unit which focuses on combustion reactive flows that misfiring environment also space propulsion.

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John Edison Foster: So Dana received a bs from Massachusetts Institute of Technology and her PhD from ECO Polytechnic a postdoc was with the French Space Agency.

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John Edison Foster: Her talking it's going to be on some of our ongoing research and that's an area of low temperature plasmas she's been focusing as of late on instabilities and self organization and crossfield devices.

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John Edison Foster: And she's been she's well well known world renowned I should say for laser based plasma diagnostics to measure electron dynamics in fact she's been hosted by researchers all over the.

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John Edison Foster: planet to learn more about a diagnostic and students have been sent to your lab to learn more as well i'm one of those people that are interested in doing this as well, learning more about the diagnostic.

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John Edison Foster: or my plasma applications she's also received numerous awards for her work, including the French physics society award the CSR metal.

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John Edison Foster: and, more recently, the International electric propulsion conference best paper award and if you're if you're asking what is she star wars are tricky thing she's she's a trekkie.

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John Edison Foster: Then she would probably like to have a trekkie background the bridge of the enterprise up, but this is a formal sort of talk so so Dana i'ma turn it over to you we're glad to have you and I will mute my MIC and let you get started.

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Mark Kushner: Okay, just one one short.

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Mark Kushner: delay before silliness starts, this is a mitzi seminar that is jointly sponsored by the online ldp seminar series, and I think you have Jenny would like to say a few words.

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Yevgeny Raitses: Well, actually, I, for me, I will be happy to say something about it, you know I noticed it in a long time, and she is a.

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Yevgeny Raitses: Frontier researcher or scientist in electric propulsion community and did excellent work on understanding of transport costs to transport him off rosters and, more recently, she expanded work to.

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Yevgeny Raitses: monitor on some, we are very happy to have a joint seminar with missy seminar and it's a record for attending faulty piece of it says more than 66 people so it's great to see you know welcome.

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Mark Kushner: And unfortunately will not have our mitzi mug ceremony.

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Mark Kushner: Today they mitzi mug assembler caught in the French mail system so that it will override soon and we have we will photoshop a mug into a picture of it's a Dino drina for the website.

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Sedina Tsikata: Okay um yeah so thank you for the tip to the people attending and thank you so much.

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Sedina Tsikata: For Krishna if Danny.

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Sedina Tsikata: Professor kinda for the invitation to present in very grateful for the chance and.

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Sedina Tsikata: i'd like to acknowledge also I have been able to learn a lot from you from you guys and your research, so thank you for the end this invitation.

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Sedina Tsikata: So I think i'll start sharing my screen.

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Sedina Tsikata: Alright, so I hope every everyone can see it, so this talk is to give some insight into the physics of local media plasmas and i'll select specifically magnet con clean amanda Collins.

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Sedina Tsikata: and

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Sedina Tsikata: As john mentioned on this, I worked with the cnrs so the French national research Center and my dad visiting or the oh so with this research was conducted at this lab, but I would like to acknowledge.

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Sedina Tsikata: My colleagues in other that who've contributed enormously to my research over the years, and some of the research present.

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Sedina Tsikata: So this is really been a joint effort, and I feel fortunate that i've been able to work with a lot of people in France were great researchers in many, many areas, so these are some of the colleagues and I mentioned for study.

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Sedina Tsikata: So I think it's clear that there are a lot of in order to temperature plasmas there, so a lot to do and a lot of interesting physics.

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Sedina Tsikata: And so, these are just a list of some of the topics that are emerging recent decades, micro plasmas metamaterials with crystals there's an affinity of new fields that young researchers can can consider going into so i'd like to encourage Grad students.

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Sedina Tsikata: and other people looking for new topics to check out some of the work done in these areas as well.

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Sedina Tsikata: But we can't get away from the fact that there are a lot of long standing questions that we still have to answer.

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Sedina Tsikata: In plasma specifically a lot of mega magnetized plasmas so one of the things that I find so fascinating and motivating for for research.

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Sedina Tsikata: In this area, is the fact there are a lot of phenomena which are common to plasmas across many different skills we have astrophysical plasmas we have fusion plasmas.

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Sedina Tsikata: And we have, for example, a hall thrusters plasma thrusters where we can find some types of, for example, instabilities which are excited in in these devices which are similar.

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Sedina Tsikata: or created under similar conditions, so this is really fascinating it's to to to observe and to try to understand what role, some of these phenomena play in these different contexts in this space context in the fusion context and also in in the low temperature plasma community.

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Sedina Tsikata: So thankfully.

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Sedina Tsikata: Despite the fact that these problems of our logs any problems we have a chance, I think today to try to get a bit further in our understanding of these phenomena and that's thanks to a lot of.

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Sedina Tsikata: New experimental methods and also a lot of numerical methods which have been developed over over decades, so now we have a chance to address some of these problems.

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Sedina Tsikata: So please talk i'll focus on just 1000 device and I don't want to disappoint the hall thruster people, but this devices night for proportion and i'm going to focus on the plane and megatron I specifically and.

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Sedina Tsikata: This device is an equal to the device on so this image here shows the.

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Sedina Tsikata: The nicer plasma and it was, which is formed and we have typically a structure simplified structure which is shown on the left, which has a cathode.

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Sedina Tsikata: And Axial lichfield to direct it towards the cathode and the radio and medic field, so this sets up the crossfield geometry that I mentioned earlier.

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Sedina Tsikata: On typically the principles is different from that of a plasma thrusters so in halter search for example we're developing this equals B drift in the hopes of confining electrons and then flying an Axial.

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Sedina Tsikata: Electric field direct it outwards, which is meant to accelerate ions outside of the device.

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Sedina Tsikata: Now, in the case of magnitudes we're using this equals be drift to confined the plasma, so that we can accelerate ions in the working gas against our cathode which we can sputter from which we can sputter metal particles and this could be Adams and also is.

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Sedina Tsikata: Now playing a minute rounds have been known for several decades, however, the novelty relative novelty of this.

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Sedina Tsikata: This device is in the operating regime which is known as happens, and this is a very high current operating regime which has been used for in recent decades, so one notable early work was from kuznetsov published in 1999 exploring this regime.

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Sedina Tsikata: Why is this review important simply because in this regime this high current policy regime, we can generate a very dense plasmas we can sputter.

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Sedina Tsikata: metal ions as well, and all of these different these modified characteristics compared to the DC operation allow us to generate thin films which can, in many cases have superior qualities compared to the typical DC magnet contradictory, so this is the value of this regime and this image.

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Sedina Tsikata: showed here is from the work of failure, and our colleagues from 2017.

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Sedina Tsikata: Where the top image is showing the grade structure for tantalum attentive and film deposited using DC sputtering and the lower image is showing what you get when you use the hype the hype intrusion and you can see clearly the density of the film is improved.

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Sedina Tsikata: One other aspect which is interesting for hyperemesis you can also sometimes to in property, so you can obtain aspect is hydrophobic city, you can attain better adhesion to the substrate.

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Sedina Tsikata: On and many other other properties, depending on the type of film and the conditions in which it's produced.

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Sedina Tsikata: So this is the interest of the high beams regime, it should be noted that all of these characters inside that I mentioned.

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Sedina Tsikata: are generated from a plasma, which is difficult to study and if we're talking about dense cosmos with can reach 10 to the 20 per cubic meter in density.

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Sedina Tsikata: And we're dealing with a highly transgender regime, so the current is very rapidly, we have currents typically rising to several 10s of vampires.

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Sedina Tsikata: and recent work is shown on the importance of considering 3D physics, for this device.

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Sedina Tsikata: So all of these aspects, mean that although we have a promising technological plasma, which is currently on being more and more used to generate them films, we do have a proportional difficulty in in modeling this regime, so this is the challenge we have today with hypes.

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Sedina Tsikata: Now i'm in order to overcome this challenge we have to consider the possibility of.

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Sedina Tsikata: New tools numerical and.

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Sedina Tsikata: diagnostic tools and typically we want to do is use techniques which are non invasive which was of experimental techniques non invasive.

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Sedina Tsikata: which will not perturb the plasma during its post operation and typically offer us some spatial and temporal resolution and typically the diagnostic switch unite all these characteristics are optical diagnostics.

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Sedina Tsikata: So this talk will focus specifically on Thompson scattering and will, this is the diagnostic that we've been.

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Sedina Tsikata: Using in recent years in order to answer some of these questions that we have around amanda con hyphens operation.

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Sedina Tsikata: So I think many people are familiar with dumping scattering now on I just like to remind you that this is a diagnostic which is.

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Sedina Tsikata: A pretty standard infusion studies so it's only in recent decades that it again more prominent in the low temperature plasma community by the principal principal is is quite simple, where we're sending in into the plasma.

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Sedina Tsikata: Some electromagnetic radiation typically furnished by a laser and we're looking at the scattering on these three charged particles in the case in our case in electrons.

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Sedina Tsikata: And this setup here this image here is showing this incident field and observation at this position, which sets up the characteristics of our observation way factor so depending on opposition to positioning of our detection direction or detector.

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Sedina Tsikata: We have a certain observation with Victor certain.

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Sedina Tsikata: Kate which is determined from the scattering refactored ks and the incident with a Turkey I so as we will see in later slides it's possible to tune observation.

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Sedina Tsikata: to observe different aspects of different dynamics in the plasma and also different direction so observation in order to obtain different for for information.

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Sedina Tsikata: So the first thing to note is that, although in the literature, if you do a quick scan of the literature it's it's quite common for to see references to laser Thompson scattering.

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Sedina Tsikata: In many cases this refers to the incoherent regime, but it should be.

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Sedina Tsikata: I guess emphasized, there are two agents that are actually covered by the term laser Thompson scattering they go ahead regime and the current regime.

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Sedina Tsikata: Now, in the incoherent regime we're going to be focusing on our observation i'd like skills which are inferior to the divided.

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Sedina Tsikata: And what this means is that a decent skills were sensitive to observation of individual fluctuations of the electrons so this term here is showing the scattered power.

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Sedina Tsikata: And as you can see the scattered power contains a term which is the one dimensional velocity distribution function in the direction of observation with vector K now, this is an interesting this term sums up a lot of interesting features and the idea here is that if we have.

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Sedina Tsikata: are scattered spectrum are scattered scattered power we can deduce directly the velocity additional solution function without making any particular assumptions on its shape now if we have.

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Sedina Tsikata: Maxwell boltzmann lossy distribution function, then we can have this term fk, which is a compact Lee written as shown here.

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Sedina Tsikata: Where we have terms with the density electron density and the the current temperature to eat, so what this means is that.

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Sedina Tsikata: From a fit of are scattered spectrum, we can attain directly with the proper calibration the density of the plasma and the region that we're looking at, and also the temperature of.

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Sedina Tsikata: Our electronics, so this is only, of course, a valid for the other Maxwell boltzmann Rossi distribution function, however, we can just we can abandon the notion of temperature.

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Sedina Tsikata: And still look at distribution functions which are not Maxwell boltzmann type.

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Sedina Tsikata: Now, in the Korean regime in this case we're not fixing our observation skills to scale much larger than the Dubai length.

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Sedina Tsikata: And in this case the scattered powerhouses form, as you can see here, so in this term, now we have the the tremor of interest is this is K Omega, which is a scattering form factor.

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Sedina Tsikata: And it's got a form factors portion to the free transform an electron density and what this means is that if we have the skills of observation, we have some organization in the plasma or some some spatial organization set up and reset our observation skills, the skills of this.

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Sedina Tsikata: plasma organization, the European large scattered signal, and we can use this to reduce the the the presence or not correlated motion of the electrons.

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Sedina Tsikata: So what this means is that we can use the observation of the the term rather than scattered signal intensity in this coherent regime.

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Sedina Tsikata: As a way to deduce whether or not certain waves are present in at what skills these waves of present so this makes coherent Thompson scattering and incoherent tom's got it in both.

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Sedina Tsikata: Powerful techniques complimentary techniques in terms of understanding what the electrons are doing in a low temperature plasma.

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Sedina Tsikata: Now the implementation, I will present all the details of the diagnostic but just the general principles of these diagnostics on.

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Sedina Tsikata: that are mentioned in the talk, but they go here in terms of scattering diagnostic as many I think people know.

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Sedina Tsikata: it's quite challenging to to deploy in low temperature plasmas and the main issue here which the terms on the previous slide show.

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Sedina Tsikata: For both incoherent and clear in terms of scattered, we have to deal with plasmas low temperature plasmas where the density is extremely low.

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Sedina Tsikata: And this means proportionately scattered power is lower compared to fusion plasmas, and this is a significant challenge it means we're trying to detect a very few photons.

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Sedina Tsikata: And this is what makes incoherent scattered a challenge to apply in in looted plasmas.

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Sedina Tsikata: Now, the task is completed further by the presence of Australia and spirit signals what's Various signals but additional signals which make it extremely difficult to.

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Sedina Tsikata: Access the Thompson scattered signal alone.

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Sedina Tsikata: So this diagram here is showing the setup the basic setup for thompson's.

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Sedina Tsikata: observation, or we have the laser line sent in and observation or detection direction channel the top is perpendicular.

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Sedina Tsikata: And we're measuring this observation with vector K align the destruction formed by the position of our leisure line and our detection direction.

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Sedina Tsikata: Now.

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Sedina Tsikata: Sorry, the the this these these little sketches are meant to just show the procedures for obtaining the signal which is related just Thompson scattered.

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Sedina Tsikata: information.

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Sedina Tsikata: And in the first case, we see the raw signal is composed with Thompson scattered signal, but additional the streetlight, which is the laser frequency.

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Sedina Tsikata: And then some additional thousand emission peaks which, of course, depend on the type of gas use to generate the plasma.

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Sedina Tsikata: So it's necessary to acquire a number of spectrum, which will allow you to subscribe subtract the noise contributions in order to get the pure signal.

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Sedina Tsikata: shown here, and from this it's necessary to do a calibration using, for example, Robin are really scattering and from this, we can reduce an absolute.

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Sedina Tsikata: value for the electron density, as it just by.

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Sedina Tsikata: From the measurement of this area, we know exactly to what it corresponds in terms of the number of electrons in the volume that we're measuring and then the load the width of the spectrum.

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Sedina Tsikata: is also related to the the current temperature if we're dealing with a gaussian shape.

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Sedina Tsikata: Now what is, I think it's a sign of some progress is that we've been able to lower the detection threshold.

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Sedina Tsikata: For this diagnostic tool as little as 10 to 16 per cubic meter sorry I missed, you know, a three at the end, and what this means.

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Sedina Tsikata: Is that there are new there's a new range of diagnostics that we earn diagnostic studies that we can perform for many different sources how he done this is by determining.

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Sedina Tsikata: A new configuration for the are optical diagnostic which allows us to collect the maximum number of photons and avoid some of the losses that are associated with conventional setups so I can provide additional details on that later on in the talk, but the idea is to.

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Sedina Tsikata: maximize our rather rather minimize the number of elements in the system which prevent the transmission of the photons that we're trying to collect from our R squared value it's got involved so.

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Sedina Tsikata: This typically involves the use of a volume brag rating instead of a triple grading spectrometer.

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Sedina Tsikata: And this preserves.

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Sedina Tsikata: Significantly significantly preserves the photons that are that are scattered, which are already trying to as a reminder.

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Sedina Tsikata: they're already we already have few photons we're collecting from this low density plasma and so, our priority should be maximizing who we actually get at the end of our detection branch.

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Sedina Tsikata: So during w scattering.

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Sedina Tsikata: Is all is a another.

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Sedina Tsikata: presents other challenges, we still have the same challenge of the low density plasma, which means we have lower scattered power which we can collect, but the setup is also, I would say a lot more complex than the incoherent of the scattering setup.

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Sedina Tsikata: You have just shown a very simple diagram of the setup of us.

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Sedina Tsikata: And I can provide additional details on that later, but here we have a setup of laser beams to laser beams which enter the plasma volume which intersect and define our scattering volume shown in Gray.

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Sedina Tsikata: And what's interesting year with the setup it's the same thing, for, in fact, the incoherent i'm just getting set up.

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Sedina Tsikata: Is the control, we have over not only the main skills that were examining, but also the orientation of our observation with actor key shown here, so how we take advantage of this is a buy.

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Sedina Tsikata: from, for example, if we have we're trying to look at a wave propagating in a particular direction.

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Sedina Tsikata: Is agnostic gives us control over which direction we are looking in.

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Sedina Tsikata: And from this, we can try to understand how the wave is propagating, what are the characteristics of the wave in according to certain direction.

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Sedina Tsikata: And this has been a very valuable tool.

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Sedina Tsikata: For us in our in terms of identifying certain instabilities so we'll see this later in the talk.

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Sedina Tsikata: So in this case the signal analysis is completely different we obtain the time very complex signal.

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Sedina Tsikata: Once that new technique is to point fft of the signal and look at which frequencies are present in the spectrum.

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Sedina Tsikata: From this we can use a different type of calibration in order to obtain the dynamic form factor, which is the absolute expression of the intensity of the density fluctuations over a range of frequency, so this the spectrum that i've gone here.

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Sedina Tsikata: And we can integrate this dynamic form factor to obtain a static form factor which is just a damages number.

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Sedina Tsikata: which you can use to express the intensity of these dentists fluctuations relative to one said the plasma is completely.

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Sedina Tsikata: has no correlated movements know correlate emotionally that counts as an educator working at.

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Sedina Tsikata: Then about this one factor would be one, however, if we have strong correlations, then we can have this factor to be significant so in our measurements, we have been able to measure, a form factors extremely.

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Sedina Tsikata: at a very high levels for example 10 to the five or 10 to the six Even so, this is a sign that we have strong correlations of these electron.

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Sedina Tsikata: fluctuations strong fluctuations of the the cons at certain skills that you've been able to measure.

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Sedina Tsikata: Now one thing we can do so and reason why things you've been looking at is how to not just content ourselves with measurement of the.

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Sedina Tsikata: Most frequency, but to also try to look at the temporal character of this instability, how the instabilities So if you measure, a particular signal associated with a present of particular wave.

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Sedina Tsikata: Is there a way we can study how this wave is evolving and time in terms of frequency and in terms of amplitude and it turns out, this is actually This can be done, we, in many cases for the magnet on I don't think i'll show.

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Sedina Tsikata: These aspects during this talk, but it's possible to do very sophisticated analysis of some of these situations and still and preserve some information of of how, for example, micro turbulence develops during a short pulses of platinum sources so there's something we're looking at.

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Sedina Tsikata: Now to return to the features of the magnet on um, as I mentioned this a challenging plasma city.

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Sedina Tsikata: And typically we have this this regime is characterized by a current profile, which varies quite quite rapidly, so we have typically.

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Sedina Tsikata: pulses partner bosses, which are some 10s of microseconds wide and this image here, taken from the textbook recently published textbook of.

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Sedina Tsikata: These colleagues.

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Sedina Tsikata: shows a ramp up during the pulse time of the current between zero to 12 on Paris typically in the hype hymns operation, we can have several 10s of on Paris in terms of the current ramp.

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Sedina Tsikata: But this is just an image to show you what the pulse the profile for the credit looks like now what's fascinating about this hyperion and when the reasons why.

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Sedina Tsikata: Even aside from the technological application, it would be, it would merit.

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Sedina Tsikata: examination in just as a physical a physical system, which is very intriguing is the fact that it along with this variation in current we of course have a very behavior of the species present in the puzzle.

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Sedina Tsikata: And in this image from the work of bull mock until 2006 he was very.

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Sedina Tsikata: Quick very he determined right early though the variation, for example in if we look at the two species which are present in this plasma that he considered so it's Oregon singly charged.

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Sedina Tsikata: Oregon ions and sputtered titanium ions the bottom, and we have different colors different colors for the different times within a pulse, which is.

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Sedina Tsikata: Up to 160 microseconds and what we see here, though this for each species, the intensity, so the end the energy is is changing, according to the moments in the poster we're looking at.

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Sedina Tsikata: And this is a typical of the heightens regime we don't have any possibility to to consider a steady state behavior or steady state properties for for the particles, so this is one of the reasons why it's challenging reading to analyze.

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Sedina Tsikata: Now, in this.

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Sedina Tsikata: slide I wanted to just make mention of some of the codes that have been that are emerging in the Community, and there were many.

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Sedina Tsikata: Many, many models which were developed early on and are still in use today, which have been very helpful to understanding the physics.

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Sedina Tsikata: And some of them are listed here.

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Sedina Tsikata: Increasingly there's an interest in the use of PIC Monte Carlo codes and some of the the colleagues that I work with have developed software just includes encodes in two dimensions for very short short pulses.

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Sedina Tsikata: And once again it's worth emphasizing the difficulty of studying this high this dense pattern region.

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Sedina Tsikata: The policies that have been studied in this work are very short but we see for a nine second I microsecond pulse, it takes three weeks for building time.

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Sedina Tsikata: Like what was interesting in this work, for example, was that it was able to to capture this the the profiles of current which are typical of this this region.

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Sedina Tsikata: Now.

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Sedina Tsikata: There are there are huge number of models to have Bob has models zero dimensional models.

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Sedina Tsikata: all the way up to these these 2d pick simulations for short pulses yet, not a single model.

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Sedina Tsikata: and capture.

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Sedina Tsikata: All the features of the discharge, so the temporal physics related to the electron dynamics the spatial physics so typically, we have to.

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Sedina Tsikata: limit the spatial region that were examining and we also have to limit ourselves typically to two dimensions at best.

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Sedina Tsikata: So this is the challenge of the hyper diversion.

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Sedina Tsikata: And so now.

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Sedina Tsikata: we're going to have to be looking at other methods to to gain insight into the behavior with this, the hype in sports now yeah i've just shown a couple examples from the codes just to illustrate some of the information we can get out so in this.

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Sedina Tsikata: This this code, here we have profiles.

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Sedina Tsikata: Realistic profiles.

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Sedina Tsikata: Of the electrode temperature what happened to the temperature during a pulsing and the electronic identity and in this recent recently published article by of our.

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Sedina Tsikata: Colleagues, this image here on the left is meant to show what happens what's happening with the electron density and this image here shows what's happening happening with the potential.

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Sedina Tsikata: But again, as I mentioned, this is for short short pulses, and the idea here is that we want to get information on typical pauses used during the position which are several 10s of a micro seconds wide.

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Sedina Tsikata: So, given these the existing limitations of these codes is worth checking if we can give additional information by using diagnostics, or we can eliminate.

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Sedina Tsikata: Some some we can validate some of these codes using experimental tools, unfortunately, a nightmare probes are not very well suited for for this type of plasma.

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Sedina Tsikata: very hostile environment, but also in the near Catholic region, which is a strong be magnetized line reports and not ideal.

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Sedina Tsikata: Of the commission's philosophy is, which is why we used to retain information, but there are some some limitations of this technique.

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Sedina Tsikata: Including line integration and also the mission models are needed, and I think one a very promising on diagnostic is.

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Sedina Tsikata: The terahertz a base diagnostics, which are emerged recently and Meyer in 2018 was able to show density density measurements.

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Sedina Tsikata: For the high beams regime using this technique, so this is a promising tool and I think we'll be seeing more more publications using using this terahertz technique to measure density and others.

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Sedina Tsikata: So, in our case we're going to look at more on, as I mentioned equal here, Dr scattering for London property that determination and in this image here, I just want to illustrate when I mentioned that we have access to highly spatially resolved.

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Sedina Tsikata: Information the idea here is that.

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Sedina Tsikata: We send in our laser and we're focusing, in fact, that we're collecting information, so the scattered signal from a very small volume that's which we can determine we can set up.

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Sedina Tsikata: In the limitation that we used it was typically on the order of a cubic millimeter in turn in volume and decisions we have very good access to.

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Sedina Tsikata: The new terms of spatial spatial resolution Additionally, we have high temporal resolution.

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Sedina Tsikata: And what I mean by this is basically we're taking advantage of the fact that we're we have several reproducible near identical pulses.

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Sedina Tsikata: And instead of collecting information from one POPs alone, what we do is collect information from the same instant in time from a chain of boxes, so you typically have a 6000 laser shots.

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Sedina Tsikata: from each shot, we have time, each shot, so that we can collect information from.

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Sedina Tsikata: A particular incident false and repeat this.

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Louise Willingale: me yeah.

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Louise Willingale: How are you.

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Sedina Tsikata: Okay.

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Sedina Tsikata: And the collection of information.

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Louise Willingale: From tending to work because i'm listening to the mix the seminar at the same time.

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Sedina Tsikata: Oh.

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Louise Willingale: Yes, low temperature.

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John Edison Foster: Luis Luis.

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Yevgeny Raitses: We don't get a meal.

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Louise Willingale: yeah Louis you know when we're allowed out yeah a year in line for you yeah well done.

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Louise Willingale: i'm just like i'm like literally the last person on the list.

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Sedina Tsikata: Okay.

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John Edison Foster: Okay it's okay she's muted.

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Sedina Tsikata: Okay, thank you.

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Sedina Tsikata: So what we do is collect are scattered information from the same point in in several policies and we use this to attain what I call this when I mentioned time resolution, this is how we we obtain it.

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Sedina Tsikata: So, based on this, we can get very detailed information about these pulses, and what I mean by that is.

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Sedina Tsikata: This this image here as Meta summarize are the electron properties and measured determined from.

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Sedina Tsikata: The spectra collected a different instance in a single pulse, and this policy is typically so in this case 60 microseconds with.

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Sedina Tsikata: And the in green is the current the current profile for this type of regime and what we find here, so these points in blue are the values.

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Sedina Tsikata: For for the electron density shown you and you can see here, for example, in this case we have electron densities, which are following our our current boss a profile quite closely, and then we have.

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Sedina Tsikata: This drop off in the afterglow or region by the point here that I want to make is that we're able to measure the electron density from very low levels throughout the current ramp and even into the post discharge, which is.

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Sedina Tsikata: very useful of capability, in addition to that we're also able to measure the temperature from the discharge initiation and even after to throughout the pulse into the end.

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Sedina Tsikata: So this information is on this is pretty valuable and we hope to use it in further characterizations for the codes now what aspect in which.

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Sedina Tsikata: We can attain information about some of the processes going on in the hype and spokes is when we're looking at this second example here.

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Sedina Tsikata: And this example again shows another case where we have a wrap up of the current and we're able to measure the electron density senior and blue and electron temperature from the initiation of the discharge and into the shut off of the pulse.

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Sedina Tsikata: what's interesting here, and the reason i've circled this peek at the end is that this is not an artifact from the experiments it's a real physical effect and evidence of a pending ionization so.

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Sedina Tsikata: it's it's we can obtain information not only intellectual properties, but also certain fundamental processes which are characterized the hype is regime and this sudden jump in in electron density has been suggested.

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Sedina Tsikata: In the codes and it's something we can validate directly with our diagnostic.

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Sedina Tsikata: So I now The last point I wanted to make about incoherent Thompson scattering version of the measurements, we can get out is the fact that, again, we can take advantage of this dirt dirt activity of our observation with vector and in the example shown here.

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Sedina Tsikata: We are interested in looking at the drift velocity specifically so on the first measurement we did in this course, we were not we were just looking at.

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Sedina Tsikata: A in a direction which basically mixed, which would you give us information about both the the the as mutual and the radio direction to the same time.

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Sedina Tsikata: But in this particular setup shown here, you can see from the orientation of this observation way vector that we should be able to obtain information in the azimuth of direction shown with this this orientation for observation with vector.

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Sedina Tsikata: Now, how do we gain information regarding this direction is it's from this orientation, we can obtain information about electron properties.

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Sedina Tsikata: localized in the musical direction, and also the electronic drift and the electron drift in the azimuth of direction would be a global shift of the scattered spectrum so here sorry about this figure it's it's not updated but.

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Sedina Tsikata: It should be 505.30 times 10 to.

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Louise Willingale: The minus.

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Sedina Tsikata: seven.

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Sedina Tsikata: But.

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Sedina Tsikata: This image here is meant to show that.

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Sedina Tsikata: We have a shift a very small shift of our spectrum, from the main laser line which is 532 nanometers and what this means is that we can determine a global movement of the electrons, and this is the typical middle drift that we can actually directly measure.

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Sedina Tsikata: Now, always surprising to us, we need to experiment which is really is, which is a relatively recent decided sexually last year was, although we were expecting a strong.

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Sedina Tsikata: equals B drift and we're able to measure it, this is shown here in blue have some several 10s of kilometers per second.

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Sedina Tsikata: What was more surprising was the presence of a radio drift and this radio graph that we measured resume and superior to the the the azimuth or electronic drift, so we basically What this means is that we have we are able to detect an electron flow.

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Which is directed.

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Sedina Tsikata: In the radio direction, and this is quite surprising so we're still trying to understand this, but it's a relatively robust robust result.

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Sedina Tsikata: So the point I want to make from these recent implementations on the plane and megatron we can get any information on some of the processes involved and some of the electron.

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Sedina Tsikata: properties as well, now we can go further and look at other behavior instabilities using go here in Tampa scattering and see what that gives us.

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Sedina Tsikata: Now.

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Sedina Tsikata: Before going into those emails like to step back and and I think, where people will know magnet cons, but this is.

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Louise Willingale: A pretty evident but.

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Sedina Tsikata: In high premiums, the hyphens regime of cranium and neutrons there's a they've been have been several studies which are focused on fluctuations large scale fluctuations, known as books and this type of self Organization has been baptized using cameras.

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Louise Willingale: Sometimes probes.

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Sedina Tsikata: and has been extensively described by others, such as adders and symbol which so many very interesting studies studying and looking at how a spokes arise under different conditions of operation different.

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Louise Willingale: currents.

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Sedina Tsikata: Different gases different target materials, etc.

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Sedina Tsikata: What is a very interesting in this device and again.

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Sedina Tsikata: we're returning to this this common theme.

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Sedina Tsikata: of equals B devices in general.

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Sedina Tsikata: Is the fact that.

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Sedina Tsikata: We observe an enormous.

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Sedina Tsikata: enormously large.

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Sedina Tsikata: electron current in in plano megaphones and especially in the high conversion effect.

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Sedina Tsikata: So what has been.

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Sedina Tsikata: Typically, what we would expect is that the hall current gh relative to the discharge current GD would be on the order of say 16 to 4060 to 40, but what is actually observed, is a ratio, which is only.

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Sedina Tsikata: twice as it's with the hawkwind is twice as large typically in the high beams regime as the the discharge current.

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Sedina Tsikata: This is surprising, I suggest we have extremely high.

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Sedina Tsikata: On the concord and the question is why.

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Sedina Tsikata: So, as for many of these devices, as you move on instabilities have been invoked to describe this to tell for this.

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Sedina Tsikata: And there are many interesting studies.

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Sedina Tsikata: performed in I would say in recent years.

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Sedina Tsikata: The most important study was first performed by London.

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Sedina Tsikata: and colleagues, where the.

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Sedina Tsikata: I think we have some problem.

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Sedina Tsikata: Okay, I think there's something going on with the presentation.

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Sedina Tsikata: someone's drawing on the presentation okay well.

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Sedina Tsikata: Measurements performed by Julian and colleagues identified megahertz of situations with probes is sorry to interrupt, but it is.

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Sedina Tsikata: Does anyone see some.

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Sedina Tsikata: Something on the presentations and yellow.

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yeah.

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Steven Shannon: Remove the waste from the call she's.

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Sedina Tsikata: yeah yes please.

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John Edison Foster: yeah let me.

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John Edison Foster: Okay.

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John Edison Foster: it's been removed, you can get it.

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Sedina Tsikata: No problem.

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Sedina Tsikata: Yes.

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Sedina Tsikata: So one of the important studies was from London and colleagues and he actually he measured megahertz of situations using probes and.

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Sedina Tsikata: suggested that this could be modified to stream instability.

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Sedina Tsikata: Now other recent studies have linked spokes instead to anomalous transport, and I think this particular study was inspired in part by the work that it can you righteous did in how thrusters showing a link between these large scale retained structures and an electron.

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Sedina Tsikata: Transport.

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Sedina Tsikata: So what's important something that should be noted, is that these studies didn't am big unambiguously link.

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Sedina Tsikata: These instabilities to to electron transport at there for now it's still something to be said on the Community and there many good ideas.

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Sedina Tsikata: that emerged from these these works in our recent studies we're trying to focus on the transaction or Defense ability and one of the reasons why is because in holders, the Community.

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Sedina Tsikata: This instability was linked in simulations and ambiguously with electron drift across the magnetic field minds.

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Sedina Tsikata: So he did experiments are trying to identify or this instability in the magnet on geometry, and it turns out that yes, it is present on a very high levels in the high beams regime.

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Sedina Tsikata: And to do this we perform we orient our riveter observation with vector.

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Sedina Tsikata: In the direction as the same direction as the module eight these modulation of density in the medical director so here the sketch is meant to show.

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Sedina Tsikata: These this modulation this modulation of density in the asthma for direction which we observe.

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Sedina Tsikata: Now we have on the Left under left these two peaks which are associated with observation, the summer thing is observation of.

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Sedina Tsikata: The two sides of the plasma plasma region on the Left and the Right, and this is why we have these symmetric peaks now what I want to stress is that, even though we've been able to add another instability, to the zoo of the potential I guess the corporate for animals transport.

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Sedina Tsikata: This is not the only instability that we we likely have to consider, so we have to keep.

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Sedina Tsikata: The open to the possibility of other modes contributing, and this is something that will see.

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Sedina Tsikata: In the next slide.

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Sedina Tsikata: So the other modes that we've identified able to identify using we're discovering include the iodine to stream instability and this actually propagating wave.

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Sedina Tsikata: We found initially just by chance of looking at the plasma thrusters and for this observation, it involves looking at an observation with vector which is oriented actually.

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Sedina Tsikata: In the in the plasma, so it can pick up modulation of the density electron density, which are in this actual direction.

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Sedina Tsikata: Now what we find in the case of the planet megatron is again so in this case i've shown a pretty low level signal, but this is a small peak positive frequency showed here which corresponds in that particular setup they used to fluctuations propagating outside away from the cathode.

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Sedina Tsikata: Now what's interesting about the idea side is that it's it's basically ignored to understand what it was or tweet to at first identified in the context we had just we just had information from.

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Sedina Tsikata: experiments and.

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Sedina Tsikata: Information or experiments, combined with the linear kinetic theory which showed that the only possibility for exciting a mode at these times skills.

307
00:45:48.600 --> 00:46:04.470
Sedina Tsikata: and add these frequencies that we measured the megahertz frequencies was the consideration of additional iron species in the in the plasma now the regulation for this iteration instability is quite simple it's pretty much the same as.

308
00:46:05.520 --> 00:46:15.960
Sedina Tsikata: Our standard electrostatic dispersion relation it only contains the addition of this w charged contribution so a certain fraction of the we charged ions.

309
00:46:16.710 --> 00:46:30.750
Sedina Tsikata: Combined with the Cindy charged ions in the plasma and the magnetized electrons are the condition for us to find this iodine to experiments ability now if we take a look at the what this means for our plasma.

310
00:46:32.520 --> 00:46:41.370
Sedina Tsikata: what's interesting here is that in this this image here i'm showing the result from the simulation and this simulation shows clearly the development of.

311
00:46:41.850 --> 00:46:57.000
Sedina Tsikata: The so the standard electron Cyclotron Defense ability which is propagating the, as we have a direction, so this we have these moderations here of this field, showing up in the middle direction along why.

312
00:46:58.050 --> 00:46:58.980
Sedina Tsikata: When we consider.

313
00:47:00.630 --> 00:47:08.790
Sedina Tsikata: A simulation which takes into account the presence of additional is species, so instead of in this case, for example, xena w charged a singlet.

314
00:47:10.530 --> 00:47:19.020
Sedina Tsikata: Instead of zero percent, as you know, w charge and and just to simply charged or Zealand present.

315
00:47:20.250 --> 00:47:34.530
Sedina Tsikata: In the second case we're considering now a certain percentage of xena the recharge combined with his uncle charged ions what happens here is we develop in addition to the the azimuth modulation of the electric field, we also develop an axiom modulation.

316
00:47:35.550 --> 00:47:38.700
Sedina Tsikata: And this is a very interesting result which basically confirmed.

317
00:47:39.720 --> 00:47:49.140
Sedina Tsikata: Our admission regarding the the iodine to students ability, once we have these two iron populations streaming a different velocities due to the presence of the electric field.

318
00:47:49.770 --> 00:48:02.220
Sedina Tsikata: And in addition we have these magnetized electrons we can set up this type of visibility, which coexists with the other consecutive disability, so this these images here are showing.

319
00:48:03.480 --> 00:48:14.070
Sedina Tsikata: Two types of modes, which are present in this battle one propagating actually died on to students ability and one propagating primarily azimuth will be.

320
00:48:14.550 --> 00:48:24.630
Sedina Tsikata: Seen in the electronically hundred disability and the reason why this is particular interesting for magnet cons and for the Highlands review it because the hyphens regime is naturally.

321
00:48:25.650 --> 00:48:33.450
Sedina Tsikata: meant to generate these metallic species, in addition to the gas, the gas ions so we have working gas, for example, Oregon.

322
00:48:34.470 --> 00:48:38.520
Sedina Tsikata: And we create Oregon ions which are used to bombard in sputter.

323
00:48:39.570 --> 00:49:02.130
Sedina Tsikata: Our our our cafeteria now this cathode we generate typically in DC sputtering regenerate majority of Adams from the from particles from the sub from the cathode which are not Ionized However, in the hype interview were generating a large fraction of metal ions in addition to.

324
00:49:03.720 --> 00:49:10.320
Sedina Tsikata: submit up to middle items, and so we have a huge number of species with different degrees of ionization different.

325
00:49:10.980 --> 00:49:21.060
Sedina Tsikata: Atomic masses present in this plasma and would expect to be able to drive a range of of instabilities including different types of i&i to stream instabilities.

326
00:49:21.570 --> 00:49:26.820
Sedina Tsikata: So this is the relevance of this mode to the to the magnet on case.

327
00:49:27.630 --> 00:49:36.360
Sedina Tsikata: Now I simulations have been extremely valuable in studying this sensibility in giving us insight that you weren't able to get from our initial experiments.

328
00:49:36.750 --> 00:49:40.770
Sedina Tsikata: And from the use of linear kinetic theory to study the mode and what I mean by that is.

329
00:49:41.280 --> 00:49:57.240
Sedina Tsikata: There are several nominee or effects, notably the effects on on transport, which were only shown by the simulations done last year, and what we can find so in the case of this is a plot of the actual electron velocity as a function of the Axial position.

330
00:49:58.320 --> 00:50:05.730
Sedina Tsikata: And for a thruster, for example, here we have the the electron segment on Defense ability overlapping with the iodine to submit stability.

331
00:50:06.270 --> 00:50:18.270
Sedina Tsikata: But what is this work showed was that we have typically for know xenon w charge is present, so a plasma constituted only have a xenon plus.

332
00:50:18.780 --> 00:50:27.690
Sedina Tsikata: We end up having is this level of actually travelocity However, when we take into account the presence or the potential presence of.

333
00:50:28.650 --> 00:50:39.450
Sedina Tsikata: w charged ions or any ions of higher higher charge date we actually increase the extra electron velocity, and this is what gives us this this we see this enhanced.

334
00:50:39.870 --> 00:50:48.360
Sedina Tsikata: A transport arising from different percentages of Lions, have w who shines present, so this is interesting result, contrary to what.

335
00:50:49.350 --> 00:51:05.640
Sedina Tsikata: might have been envisaged the transport is not dictated uniquely by the CDI but it's the date dictated by a coupling between the iits treatments ability and the consecutive on Defense ability to the image is much more complex than what we originally envisaged.

336
00:51:06.810 --> 00:51:17.700
Sedina Tsikata: This image here shows what the streamlines look like in the presence of the vdi alone and and the CDI and the CSI, and you see here that the street lines are also modified we have.

337
00:51:18.900 --> 00:51:36.330
Sedina Tsikata: In the top image, here we have this modulation in the y direction, which is a cgi but in this the bottom image we have the motivation of the CDI and the idea sigh Axial modulation and the combination of these modifies electron streamlined, so it is possible to.

338
00:51:37.350 --> 00:51:45.390
Sedina Tsikata: just see directly a visual representation of how the electron streamlines become directed more actually the presence of these two instabilities not one single.

339
00:51:45.870 --> 00:51:56.760
Sedina Tsikata: Instability dictating transport but two combined have an additional effect, so this is something to take into account for cleaner magnets, and this makes the problem more challenging.

340
00:51:58.170 --> 00:52:07.830
Sedina Tsikata: Now, one aspect that we also found recently actually verizon from experiments is the nature of propagation of the the ideas I.

341
00:52:08.520 --> 00:52:18.330
Sedina Tsikata: Is where someone unexpected so these two peaks it's quite difficult to see the second peak them showing here, but this peak is they actually two.

342
00:52:19.260 --> 00:52:35.040
Sedina Tsikata: peaks when when it tends to speak, which corresponds to propagation away from the cathode and one lower peak which propagates corresponds to publications toward the cathode, and this is actually a surprising surprising when you consider.

343
00:52:37.230 --> 00:52:44.700
Sedina Tsikata: Typically, it means we have a combination of propagation directions for this this primarily Axial instability.

344
00:52:46.860 --> 00:52:56.580
Sedina Tsikata: What happens so if we if we plot, in fact, the the fluctuation amplitude for these different modes and apologize for only having three points for this this this peak.

345
00:52:57.240 --> 00:53:06.180
Sedina Tsikata: We have a different rate of decrease for these two modes and clearly, it seems that way if we if we extend if we.

346
00:53:07.170 --> 00:53:18.390
Sedina Tsikata: extrapolate these two lines, we end up with a position further far from the cathode where we have a know privilege direction of the publications, we have publications which are.

347
00:53:19.680 --> 00:53:28.350
Sedina Tsikata: Flying away from the the cathode in which are moving upstream towards the katha, it is a curious curious behavior and the question that we recently asked was.

348
00:53:28.770 --> 00:53:37.620
Sedina Tsikata: Do we have any simulation results which see something which could explain why the i&i to students abilities can propagate in both directions.

349
00:53:39.270 --> 00:53:43.350
Sedina Tsikata: And the answer is actually yes, if we go back to.

350
00:53:44.460 --> 00:53:53.820
Sedina Tsikata: Some of the models that have been constructed by reading and colleagues in this is very important work no many results, but one of the interesting results.

351
00:53:54.300 --> 00:54:01.620
Sedina Tsikata: Is a feeler Russell which was described in the Highlands regime it doesn't exist in DC reading but it's found in the items regime.

352
00:54:02.340 --> 00:54:10.290
Sedina Tsikata: So in this model they weren't able they didn't model exactly what happens at the cathode and the other region, but in the Capital Region i've.

353
00:54:10.860 --> 00:54:18.030
Sedina Tsikata: i've drawn this arrow additional the typically expect the electric field to be directed towards the cathode that's where we're we're accelerating.

354
00:54:18.870 --> 00:54:29.610
Sedina Tsikata: The ions of the working gas, however, this model did show that there's a point in the plasma, where we have a reversal of the electric field to is no longer directed.

355
00:54:30.120 --> 00:54:43.170
Sedina Tsikata: towards the cathode but it flips indirection due to the pressure electron pressure exceeding the discharge current and what this means is that we have in this plasma we have.

356
00:54:44.400 --> 00:54:59.730
Sedina Tsikata: Where we're access to to a region where the electric field in one case is directing the ions outwards and we have another region where the electric field is directing the ions towards the cathode.

357
00:55:00.810 --> 00:55:08.730
Sedina Tsikata: So what this means is we're setting up different directions of propagation for the iron species and this seems to account for why we can observe.

358
00:55:09.150 --> 00:55:13.830
Sedina Tsikata: electron density fluctuations propagating towards the cathode and also we're from the Catherine.

359
00:55:14.310 --> 00:55:27.450
Sedina Tsikata: So the challenge here would be to try to look at this model in our conditions, the conditions which are reserved for an experiment and determine if this field reversal does appear as a clear effect.

360
00:55:28.620 --> 00:55:43.140
Sedina Tsikata: via our observations of the industry of its ability, but so far, I would say, it seems promising and it was it's a very it's a unique feature this type of filter Russell to the this particular hype machine we don't see it in DC and.

361
00:55:44.400 --> 00:55:58.200
Sedina Tsikata: it's worth also noting that the only time you've seen this double directly these two directions were propagation of the i&i distributes ability is when we do look in the hype intrusion it's absent in in DC, so this is something we we can investigate further.

362
00:55:59.310 --> 00:56:07.680
Sedina Tsikata: We have access to to these insights from experiments and now we can see if the models are up to the task of of capturing for you observed.

363
00:56:08.970 --> 00:56:10.140
Sedina Tsikata: So in conclusion.

364
00:56:11.400 --> 00:56:11.880
Sedina Tsikata: Experimental.

365
00:56:12.900 --> 00:56:25.680
Sedina Tsikata: limitations have a lot to offer I think in terms of just not only looking at the particle properties so electron properties which have long been inaccessible in regimes just items.

366
00:56:26.430 --> 00:56:32.700
Sedina Tsikata: but also in terms of looking at the transport, environment fluctuations, so we can focus on.

367
00:56:33.660 --> 00:56:47.040
Sedina Tsikata: trying to figure out which modes are responsible for the transport and in for this were greatly aided by the existence of numerical simulations which are trying to figure out which modes are present and what their features are.

368
00:56:48.300 --> 00:56:55.500
Sedina Tsikata: We can also determine whether there are particular features, for example in terms of the transport of particles.

369
00:56:56.760 --> 00:57:04.650
Sedina Tsikata: In the magnet on plasma, which we can capture in our measurements and whether the codes that have been developed are up to the task.

370
00:57:05.010 --> 00:57:13.860
Sedina Tsikata: Of also describing some of these features, so the point I want to make is that we have to advance the hand in hand with the simulations and that's what we're trying to do.

371
00:57:15.450 --> 00:57:24.720
Sedina Tsikata: So the hype rooms regime and the mapping and megatron source is important, I know i've had this question why do you care about the physics of.

372
00:57:25.650 --> 00:57:33.540
Sedina Tsikata: Easy crosby sources, and I think it's it's safe to say that the reason why we care for the hyphens regime is because it's just been shown.

373
00:57:33.900 --> 00:57:42.840
Sedina Tsikata: To be extremely interesting for the production of thin films of various types in recent years, and whoever you want to do is to clarify the physics of this.

374
00:57:43.950 --> 00:57:55.170
Sedina Tsikata: This regime, and we can hopefully do so with experiments and valleys and with the models, possibly refined some of the models that have come out in recent years.

375
00:57:57.150 --> 00:58:04.050
Sedina Tsikata: What is quite daunting is the fact that the physics, the more you look at it is the more complex, it becomes so I think.

376
00:58:05.430 --> 00:58:11.190
Sedina Tsikata: The introduction of the SDI and the it side to this this megatron community.

377
00:58:12.600 --> 00:58:17.700
Sedina Tsikata: is something that has yet to be taken into account fully in simulations.

378
00:58:18.690 --> 00:58:33.300
Sedina Tsikata: But it's an interesting problem to try to put all these ingredients of physics together, and I think our understanding is progressing it's it's it's harder than than expected, but are they understand is progressing and so the future looks looks bright, I would say.

379
00:58:34.590 --> 00:58:43.320
Sedina Tsikata: So, thank you very much for your attention, I think I should end my talk here, so if you have questions, please let me know.

380
00:58:45.030 --> 00:58:46.980
John Edison Foster: Thank you so data for such a great talk.

381
00:58:48.720 --> 00:58:56.400
John Edison Foster: Around the applause it's it's a zoom but we're going to now take questions from the audience.

382
00:58:56.790 --> 00:59:09.810
John Edison Foster: And so I don't see any questions in the chat so you can place questions in the chat as well, and then i'll ask you to unmute but while we're waiting for that if you have a question right away, you can unmute yourself and ask the question.

383
00:59:13.500 --> 00:59:19.980
John Edison Foster: And so, while while they're doing oh look like you've Guinea as a question.

384
00:59:20.460 --> 00:59:22.950
Sedina Tsikata: Okay, should I continue sharing which I stop sharing.

385
00:59:23.040 --> 00:59:25.650
John Edison Foster: Oh yeah you could continue you continue to share.

386
00:59:25.860 --> 00:59:38.520
John Edison Foster: Okay Okay, so we have people are raising their hand telling me i'm me take a look to see who we have here and we'll take them it's a long list and trying to okay so Scott.

387
00:59:40.620 --> 00:59:44.490
John Edison Foster: Scott, you can you can go ahead and unmute and ask your question.

388
00:59:45.690 --> 00:59:46.920
Scott David Baalrud: thanks for the Nice talk.

389
00:59:49.110 --> 00:59:54.810
Scott David Baalrud: So Mike my question is about what we were talking about toward the end with iron iron to stream instabilities.

390
00:59:54.900 --> 00:59:55.320
Sedina Tsikata: mm hmm.

391
00:59:55.950 --> 00:59:56.460
and

392
00:59:57.570 --> 01:00:06.360
Scott David Baalrud: In in chiefs we've observed something where the electric field and appreciate can cause the separation of ions of a different mass in.

393
01:00:07.680 --> 01:00:08.130
John Edison Foster: Yes.

394
01:00:08.220 --> 01:00:17.370
Scott David Baalrud: And that, when the instabilities turn on it limits the speeds of each species from significantly becoming more than instability threshold.

395
01:00:17.760 --> 01:00:18.180
Sedina Tsikata: Yes.

396
01:00:18.240 --> 01:00:21.420
Scott David Baalrud: And I was curious if you see that sort of effect in your studies.

397
01:00:21.930 --> 01:00:26.160
Sedina Tsikata: Yes, we don't see this, I think yeah i'm, as I mentioned this morning.

398
01:00:26.370 --> 01:00:27.450
Scott David Baalrud: i'm familiar with your.

399
01:00:27.540 --> 01:00:28.230
Sedina Tsikata: Your grade work.

400
01:00:28.650 --> 01:00:30.780
Sedina Tsikata: On the sheets, I think.

401
01:00:31.800 --> 01:00:35.640
Sedina Tsikata: Unfortunately, we don't have the possibility to look at the the sheath.

402
01:00:37.140 --> 01:00:46.740
Sedina Tsikata: Typically, the sheet would be, I would say, a fraction a fraction of a millimeter and the condition is that we're looking at and we're looking at.

403
01:00:47.250 --> 01:00:56.700
Sedina Tsikata: A region, which is a few millimeters at best from the from the cathode surface, so I don't think we have the capability to.

404
01:00:57.390 --> 01:01:08.820
Sedina Tsikata: To see exactly what you've what you've been able to show, but I think it would there's there's no reason why it wouldn't wouldn't actually apply, I think, in your case you considered on islands of.

405
01:01:08.910 --> 01:01:12.660
Sedina Tsikata: Different masses so not different ionization degrees.

406
01:01:14.670 --> 01:01:20.250
Sedina Tsikata: But it would be, it would be valid, yes, it would be would be valid for practice that's my my intuition.

407
01:01:21.300 --> 01:01:22.350
Scott David Baalrud: So can I follow up quickly.

408
01:01:23.430 --> 01:01:29.520
Scott David Baalrud: So not even necessarily in the sheets, but like in the hall thruster case where you have the two on ionization states.

409
01:01:29.970 --> 01:01:35.610
Scott David Baalrud: uh huh is, is there any observation of the speed of each of the ionization states and weather.

410
01:01:36.120 --> 01:01:36.540
Sedina Tsikata: Ah.

411
01:01:36.690 --> 01:01:42.150
Scott David Baalrud: The difference between the speeds of the annotation states of each one would correspond to an instability threshold.

412
01:01:42.510 --> 01:01:58.350
Sedina Tsikata: OK, I see um let's see so the measurements, we have, I would say um let's see in the hall crestor no I don't have I don't have measurements of the only for the for the xenon I would say.

413
01:01:59.610 --> 01:02:02.760
Sedina Tsikata: Is universities from a similar chart Zealand from.

414
01:02:05.340 --> 01:02:05.670
Sedina Tsikata: yeah.

415
01:02:07.320 --> 01:02:08.610
Sedina Tsikata: yeah from infinite familiar.

416
01:02:09.630 --> 01:02:11.550
Sedina Tsikata: But not for the w charged.

417
01:02:12.870 --> 01:02:13.500
Sedina Tsikata: species.

418
01:02:16.050 --> 01:02:20.910
John Edison Foster: Okay, so you give me, you can go ahead and unmute yourself actually question.

419
01:02:21.750 --> 01:02:32.100
Yevgeny Raitses: I see, I see no, thank you very much, excellent job thanks I have two quick questions first I would like to clarify point about Roger written magnet wrong.

420
01:02:32.490 --> 01:02:32.940
Okay.

421
01:02:34.740 --> 01:02:44.370
Yevgeny Raitses: So if you come back to the so basically you supposed to hear, I do believe, because my native few licenses in the right direction, yes, what is also present.

422
01:02:44.550 --> 01:02:48.930
Sedina Tsikata: Okay sell me yes let's see, let me go back to the.

423
01:02:49.980 --> 01:02:51.720
Sedina Tsikata: figure yeah so.

424
01:02:53.070 --> 01:03:03.900
Sedina Tsikata: Yes, there, there is electron motion along the medical industry sure, but when my what it seems a bit perplexing is with the diagnostic.

425
01:03:06.120 --> 01:03:15.660
Sedina Tsikata: quarter basically what we're showing by this large radio drift is that there's a net it's a net drift, so what I would expect would be electron motion.

426
01:03:16.740 --> 01:03:34.140
Sedina Tsikata: back and forth long the field lines, so, in the end of the spectrum, that we will look like the average motion of the the electrons taken at a particular position would just be wouldn't wouldn't show this this net motion in a particular direction along the lines if it's raining.

427
01:03:35.460 --> 01:03:44.010
Yevgeny Raitses: So basically but you haven't been case magnetic metering and our case you have candidates, so it means you may have some of the seemingly right.

428
01:03:44.550 --> 01:03:45.720
Sedina Tsikata: Exactly so so.

429
01:03:46.560 --> 01:03:52.620
Yevgeny Raitses: Technical computational studies of magnitudes didn't use a symmetric situation.

430
01:03:52.980 --> 01:04:05.460
Sedina Tsikata: No, in fact, I have not seen Maybe someone someone else in the Community can jump in, but I have not seen a single study, which suggests that, globally, we should expect a global or radio radio.

431
01:04:06.330 --> 01:04:24.210
Sedina Tsikata: Drift on the order, for we are we measured so between you know almost 100 kilometers per second, which is again, not just the simple back and forth of the electrons are running back and forth on the in the mirror, but a real net net effect of electrons flowing out from the.

432
01:04:25.890 --> 01:04:26.700
Sedina Tsikata: Individual direction.

433
01:04:27.030 --> 01:04:27.450
Yevgeny Raitses: and be.

434
01:04:29.940 --> 01:04:30.300
Sedina Tsikata: glad.

435
01:04:32.190 --> 01:04:34.560
Yevgeny Raitses: So if I mean let's question so very quickly.

436
01:04:35.580 --> 01:04:42.600
Yevgeny Raitses: You mentioned with in magnesium you don't observe close to current fuselage structures Is that correct.

437
01:04:43.800 --> 01:04:44.400
Sedina Tsikata: I.

438
01:04:44.940 --> 01:04:46.860
Sedina Tsikata: misinterpreted, no, no.

439
01:04:47.910 --> 01:04:51.810
Sedina Tsikata: No, in fact, yes I the reason the work of.

440
01:04:53.130 --> 01:04:58.290
Sedina Tsikata: some of which are suggest that we do have transport like what you were able to show.

441
01:04:59.340 --> 01:05:15.450
Sedina Tsikata: With ellison so that's I think in fact that his His work was partly inspired by what you did in terms of tracking I correlate data on the kind of situations with with touch points in spokes So yes, we do.

442
01:05:16.770 --> 01:05:19.260
Yevgeny Raitses: Okay, so I probably wasn't good, thank you very much.

443
01:05:21.660 --> 01:05:24.240
John Edison Foster: ego or you can unmute and ask your question.

444
01:05:27.510 --> 01:05:31.080
Igor Kaganovich: yeah Thank you john Thank you see uniform talk.

445
01:05:32.790 --> 01:05:51.780
Igor Kaganovich: yeah and kind of fun a follow on Scott borrowed line of questioning um so when Ken was what can ppl gives us when we looked at I instability, we looked at instability between very fast and beam and background plasma.

446
01:05:52.980 --> 01:05:54.150
Igor Kaganovich: And so, in that case.

447
01:05:54.720 --> 01:06:05.550
Igor Kaganovich: Because being velocity is comparable to electron the last two, you can have a coupling between first time being, which couples to wave as possible ways which couples to electrons.

448
01:06:05.850 --> 01:06:21.960
Igor Kaganovich: Yes, now, if you have a slow and being for examples case which is well studied experimentally, he killed boys Scott bold and Greg severson right, you have cufflink which try to move on the last is to the same velocity but.

449
01:06:22.320 --> 01:06:23.460
Igor Kaganovich: That uncoupling doesn't.

450
01:06:24.030 --> 01:06:28.260
Igor Kaganovich: affect electrons whatsoever, and this is extremely clear.

451
01:06:30.090 --> 01:06:47.070
Igor Kaganovich: And so you have relatively slow beams right it's really slow ions so i'm still don't quite understand how the slaw ions and and b boys excited between slow ions can affect electrons.

452
01:06:47.760 --> 01:06:49.200
Igor Kaganovich: which are much faster.

453
01:06:49.710 --> 01:06:57.390
Igor Kaganovich: So that's something which, again, maybe i'm missing very complicated nonlinear interaction that could be good to clarify at some point.

454
01:06:58.260 --> 01:07:10.110
Sedina Tsikata: yeah you're right it's it's it's quite difficult, I guess, probably intuitively to to grasp, but one thing that's clear is that the situation we find is only if the electron.

455
01:07:10.980 --> 01:07:19.260
Sedina Tsikata: electron motion is restricted by by the magnetic field, so we have to have the electrons magnetized, which is the case number.

456
01:07:19.890 --> 01:07:32.340
Sedina Tsikata: Our device, and also in the plasma thruster and once we have the combination of this in these magnetite electrons and the these two, even if the either I am drifts seem slow.

457
01:07:34.170 --> 01:07:42.900
Sedina Tsikata: compared to what you're you're familiar with this, this is enough, in fact, to the combination of magnetized electrons and and these uh.

458
01:07:44.160 --> 01:07:48.600
Sedina Tsikata: These streaming ions these i'm streaming the different velocities if we had, for example.

459
01:07:49.980 --> 01:07:53.220
Sedina Tsikata: These beams me, so I names and.

460
01:07:54.570 --> 01:07:58.320
Sedina Tsikata: On magnetized electrons you will not excite this this MOD this disability.

461
01:07:58.590 --> 01:08:08.550
Igor Kaganovich: But not rejected that all the time, but you know it should be for way or fee way process which you can probably control right how.

462
01:08:08.580 --> 01:08:11.100
Sedina Tsikata: Basically, one way or three way.

463
01:08:11.250 --> 01:08:18.240
Igor Kaganovich: yeah nonlinear process which will capture all these waves and to kind of look at it, at some point.

464
01:08:18.600 --> 01:08:19.260
Igor Kaganovich: And just to.

465
01:08:19.650 --> 01:08:29.160
Igor Kaganovich: quickly finish if that's the case may be, experimental you can look at minute on reputation in hydrogen hydrogen and helium.

466
01:08:29.490 --> 01:08:31.230
Igor Kaganovich: And she's a difference right so.

467
01:08:31.440 --> 01:08:33.420
Igor Kaganovich: Would you like to do this.

468
01:08:33.810 --> 01:08:34.710
Sedina Tsikata: Yes, exactly.

469
01:08:36.630 --> 01:08:42.480
Sedina Tsikata: So I what I can say is so that we can we can discuss this afterwards, if you like, you go.

470
01:08:46.050 --> 01:08:50.100
John Edison Foster: Okay, so Andre you can unmute and ask your question.

471
01:08:51.660 --> 01:09:02.220
Andrei Smolyakov: Thank you john yeah I think it's enough for a nice talk, I have two questions actually both been already touched upon a one about again about this nine.

472
01:09:03.510 --> 01:09:14.820
Andrei Smolyakov: To stream instability and the question is in this conditions there is another instability or actual instability, which is same duration, which is irresistible.

473
01:09:15.000 --> 01:09:21.780
Andrei Smolyakov: And extra visibility can be played by anomalous transport and.

474
01:09:22.920 --> 01:09:32.940
Andrei Smolyakov: instability is rather easy to change the direction of propagation and my question is, have you take a title look and listen if that can be.

475
01:09:35.280 --> 01:09:38.190
Andrei Smolyakov: culprit or source of what you're observing.

476
01:09:38.220 --> 01:09:39.900
Sedina Tsikata: Okay okay.

477
01:09:40.650 --> 01:09:47.550
Sedina Tsikata: that's interesting, so the instability or metric you're you're mentioning so that would be a lot larger skills, I believe.

478
01:09:49.500 --> 01:09:59.760
Andrei Smolyakov: will not necessarily it's actually a static it's it occurs in fact almost inertial scale, so I I can is parameters.

479
01:10:01.890 --> 01:10:02.250
Andrei Smolyakov: To.

480
01:10:03.060 --> 01:10:03.480
Okay.

481
01:10:04.650 --> 01:10:05.010
Andrei Smolyakov: Is.

482
01:10:05.340 --> 01:10:10.650
Andrei Smolyakov: It has a similar similar frequencies, so all the order of like a transit time.

483
01:10:10.680 --> 01:10:18.930
Andrei Smolyakov: Again, and scale slagle yeah we have some some can estimate or not, but they can be small tool.

484
01:10:19.380 --> 01:10:34.080
Sedina Tsikata: Okay, small, will you tell me what only because I from what i've seen, I think, maybe I might be the wrong, but I think the skills are were larger what would be larger, I think, maybe centimeter scale.

485
01:10:35.250 --> 01:10:36.180
Andrei Smolyakov: Okay well yeah.

486
01:10:38.040 --> 01:10:47.790
Andrei Smolyakov: Those are kind of iron type so they would know linear with surgery, and like not so sure elixir they collapse into various really sharp peaks.

487
01:10:48.180 --> 01:10:51.510
Andrei Smolyakov: Yes, yes, long island sound shock waves and.

488
01:10:51.630 --> 01:10:54.570
Andrei Smolyakov: Okay, that point, it will they will be very small but.

489
01:10:55.050 --> 01:11:01.050
Sedina Tsikata: it's Okay, when the more changes, then it will be a smaller scale okay Now I will look into that um.

490
01:11:02.130 --> 01:11:02.820
Sedina Tsikata: yeah and.

491
01:11:03.660 --> 01:11:14.700
Andrei Smolyakov: yeah just the common to the same point I think critics of the science is again it's very similar towards quote was looking at his work, so one would expect similar effect.

492
01:11:15.060 --> 01:11:17.700
Andrei Smolyakov: But my second question again.

493
01:11:18.870 --> 01:11:30.840
Andrei Smolyakov: Again, you touched upon in this situation, about the radio transmitter which is it like a situation or would you fight to to to stay on stability when you're when you're on the money, if you want.

494
01:11:31.080 --> 01:11:32.490
Sedina Tsikata: I can you repeat the last.

495
01:11:33.870 --> 01:11:34.950
Sedina Tsikata: Is it is it what.

496
01:11:35.190 --> 01:11:39.870
Andrei Smolyakov: Is it the situation where you can expect modified to steam instability, where there is.

497
01:11:39.870 --> 01:11:42.060
Andrei Smolyakov: A little emotional on the magnetic.

498
01:11:42.060 --> 01:11:42.810
Andrei Smolyakov: field, yes.

499
01:11:43.290 --> 01:11:55.260
Sedina Tsikata: Yes, so so Okay, this is, I didn't want to go into this aspect, because I think it's relatively recent so you actually showed this modified to cms about the conditions in the case of.

500
01:11:58.290 --> 01:12:13.830
Sedina Tsikata: The hall thruster and that was very interesting, so if again if we can we can show we would have to have a more proof that this Axial this radio drift is produced by instability, I consider this but for now I don't have the.

501
01:12:15.150 --> 01:12:21.900
Sedina Tsikata: The solid proof, because I don't have measurements along the in the in the radio direction, but I think an experiment that that could show this categorically.

502
01:12:22.290 --> 01:12:34.200
Sedina Tsikata: would be in addition to the coherent discarding measurement of this drift, the stronger your drift would be to measure the fluctuations in the same direction and show that there is there is this mdi.

503
01:12:37.200 --> 01:12:39.720
Andrei Smolyakov: geometry understand yeah I think you just.

504
01:12:39.750 --> 01:12:39.960
that's.

505
01:12:41.610 --> 01:12:54.780
John Edison Foster: Okay, so we're going to take two more questions getting late for Dana here so so we'll take Alex and then married and then we'll close it out oh Alex you can unmute.

506
01:12:55.860 --> 01:12:58.770
Alex Vazsonyi: and ask your question okay thanks.

507
01:13:00.180 --> 01:13:03.630
Alex Vazsonyi: Dr Tucker thanks a lot for your talk, I really enjoyed it and learned a lot.

508
01:13:05.220 --> 01:13:10.140
Alex Vazsonyi: I was also curious about the die and instruments ability that you talked about.

509
01:13:11.610 --> 01:13:17.610
Alex Vazsonyi: And, regarding your in your in cars paper from 2020 I believe it was a.

510
01:13:18.720 --> 01:13:23.250
Alex Vazsonyi: more of a just DC discharge if them if i'm not mistaken.

511
01:13:24.870 --> 01:13:37.890
Alex Vazsonyi: So, and with this this field reversal region that you were talking about in the hype is configuration, yes I would you how would you expect that would actually affect instabilities and, for example, the i&i instruments ability.

512
01:13:38.550 --> 01:13:49.590
Sedina Tsikata: yeah that's it that's a great question, so the the article, the 2020 article like you mentioned is just a DC situation because that's what so far.

513
01:13:50.460 --> 01:14:02.730
Sedina Tsikata: The PIC simulations can model, so my intuition is effectively if we do have a big simulation which can model, the hype is regime, and we can show this field reversal.

514
01:14:03.750 --> 01:14:09.840
Sedina Tsikata: which has been suggested as something appears, I mean the hydrogen then it's right clear to me that.

515
01:14:10.650 --> 01:14:19.740
Sedina Tsikata: The presence of these once we have this reversal of the field, the ions are the that we've generated in the plasma volume are going to respond to the to this field.

516
01:14:20.250 --> 01:14:30.480
Sedina Tsikata: direction so we'll have it, contrary to what to the DC case that we we've been able to study, we would have, in this case a combination, so I am not only.

517
01:14:32.220 --> 01:14:42.870
Sedina Tsikata: For example, if we take just a single charged, we have, I am simply charged ions streaming away from the cathode and towards the cathode we have the same thing happening for the w charged.

518
01:14:44.010 --> 01:14:58.920
Sedina Tsikata: w charged or higher higher charge states also subjected to depending on where they are generated so addicted to electric field which might be pointing away from the cathode or towards the cathode and what's interesting there is that on.

519
01:14:59.970 --> 01:15:14.100
Sedina Tsikata: The financial statements ability will come necessarily more complex, because we can have is the same charge date so assembly charged ions but counter streaming streaming in opposite directions, and this can also set up.

520
01:15:15.510 --> 01:15:36.870
Sedina Tsikata: Some some fluctuations, so do something that has been seen, for example in space space so plasmas on, so I think how that how that would modify our results, basically, the simulation would pick up a lot more modulation, so instead of I would suggest that, instead of a single.

521
01:15:37.890 --> 01:15:43.920
Sedina Tsikata: characteristic limescale for the for the actual moderation, we would instead have a multiplicity of.

522
01:15:45.120 --> 01:15:47.160
Sedina Tsikata: of modulation depending on.

523
01:15:48.210 --> 01:15:55.950
Sedina Tsikata: Where how the ions which species are present, but also which directions, they are being are forced to move in due to this field reversal so don't be.

524
01:15:57.210 --> 01:16:03.180
Sedina Tsikata: um I think instead of instead of the Nice, the Nice friends, so if I go back to the image.

525
01:16:09.090 --> 01:16:10.260
Sedina Tsikata: Instead of these are.

526
01:16:11.310 --> 01:16:12.330
Sedina Tsikata: These these Nice.

527
01:16:13.740 --> 01:16:24.870
Sedina Tsikata: friendly friends that you are there, you can see here, instead, we would have something which is just mixed up with the number of modes that we are present, so we would look pretty pretty chaotic, because you have all these different.

528
01:16:26.040 --> 01:16:34.590
Sedina Tsikata: directions of iron acceleration different species present but that's that's my intuition has to be seen in the simulation for for now there's no simulation that can capture this.

529
01:16:36.360 --> 01:16:41.910
Sedina Tsikata: High beams regime that we've that that would would match our conditions exactly.

530
01:16:42.960 --> 01:16:47.550
Alex Vazsonyi: Okay okay well fingers crossed that it's coming sometime in the near future, thank you.

531
01:16:48.540 --> 01:16:48.840
Sedina Tsikata: Thank you.

532
01:16:50.130 --> 01:16:53.040
John Edison Foster: Very until your last question.

533
01:16:54.210 --> 01:16:54.990
Marien Simeni Simeni: I said, you know.

534
01:16:55.560 --> 01:16:58.830
Marien Simeni Simeni: Thank you, thank you for the Nice talk, I really enjoyed.

535
01:16:59.850 --> 01:17:12.420
Marien Simeni Simeni: Actually, I have a slide on this side and decide before it, which is related to the I think the The reversal, so I don't know much about minute on plasma and that was also a reason to be very interested in this talk.

536
01:17:12.930 --> 01:17:21.570
Marien Simeni Simeni: But the client to say that if they say diagnostics on metal to measure the electrical distribution temporarily is especially.

537
01:17:22.020 --> 01:17:29.850
Marien Simeni Simeni: In addition, then it will help you disentangle some of the public world is integrity, a nice looking at this high pimps.

538
01:17:30.960 --> 01:17:31.410
Marien Simeni Simeni: mode.

539
01:17:32.100 --> 01:17:34.740
Sedina Tsikata: Exactly that's exactly right yes.

540
01:17:35.220 --> 01:17:44.910
Marien Simeni Simeni: Yes, so Kenya, can you help me then expand on the condition so it's running in xenon what is the density.

541
01:17:45.060 --> 01:17:59.430
Sedina Tsikata: So, so in this case the the simulation guess i'm not showing the case for xenon but, in this, for example, this hype Williams situation typically background gas will be they are good, for example, you can use different gases, but.

542
01:17:59.880 --> 01:18:00.900
Marien Simeni Simeni: I reach pressure.

543
01:18:01.710 --> 01:18:03.870
Sedina Tsikata: Typically, all depends, but.

544
01:18:05.310 --> 01:18:06.480
Sedina Tsikata: Say maybe a bicycle.

545
01:18:07.350 --> 01:18:09.420
Marien Simeni Simeni: Okay that's I think that's feasible.

546
01:18:10.650 --> 01:18:16.860
Marien Simeni Simeni: Okay, and the field strength, I saw a point to about Point two kilowatt per centimeter is correct.

547
01:18:17.880 --> 01:18:21.000
Sedina Tsikata: I yeah yeah yeah that.

548
01:18:22.020 --> 01:18:25.860
Sedina Tsikata: depends on what you're looking at depends on so in this particular figure from this work.

549
01:18:27.090 --> 01:18:35.220
Sedina Tsikata: I have to check but it's not it's because it's not the same exactly the same condition is as we're looking in and typically the field.

550
01:18:36.360 --> 01:18:37.950
Sedina Tsikata: is very high, close to the cathode.

551
01:18:38.370 --> 01:18:38.910
So.

552
01:18:40.320 --> 01:18:48.540
Sedina Tsikata: It changes rapidly so you'd have to look at the magnitude corresponding to where we're measuring, but I can get to that the yeah.

553
01:18:51.450 --> 01:18:56.100
Marien Simeni Simeni: Yes, I think I think it is possible to move it could be possible to measure.

554
01:18:56.580 --> 01:18:57.660
Sedina Tsikata: Yes, yes.

555
01:18:59.100 --> 01:18:59.400
Thanks.

556
01:19:00.420 --> 01:19:00.930
Sedina Tsikata: yeah Thank you.

557
01:19:02.220 --> 01:19:02.430
Sedina Tsikata: yeah.

558
01:19:02.460 --> 01:19:17.820
John Edison Foster: thanks for all the great questions and thanks for great talks Dana I mean if you if everyone can they can unmute and give so Dana around the applause, we really, thank you for interesting talk to Danny a lot of interesting and very detailed questions, so thank you.

559
01:19:19.410 --> 01:19:21.570
Sedina Tsikata: guys, I appreciate it, thank you.

560
01:19:25.650 --> 01:19:26.130
Sedina Tsikata: Thanks.

561
01:19:36.750 --> 01:19:40.170
On that note, we will end the.

562
01:19:41.250 --> 01:19:42.000
symposium.