09:33:53 So while Arash is setting up I'll see so rushed It is his PhD in his postdoc at UCSD, and then joined the staff at the Princeton plasma physics lab where he's a research scientist working with d3 D as well, a rash it's accomplishing both theory and experiment 09:34:10 dealing with both large and small devices, and we look forward to his talk on formation of a staircase pedestal was suppressed edge localized modes in a d3 dP pencil. 09:34:24 Can you guys hear me, I can hear you very well thank you a rash Go ahead, uh, it thank you so much. 09:34:41 Okay, thank you so much for giving me the opportunity to present my work here. And let me put this to the side if you guys are seeing this. And also thank you for a, you know, substantial talk there's lots of physics there, and very interesting stuff. 09:34:50 stuff. So today I will be talking about the formation of a staircase pedestal. 09:34:56 With suppressed edge localized modes and the 3d Tacoma, and the outside of my talk is, I'll give a little introduction. 09:35:04 Then I'll talk about the experimental observation of personal bifurcation. 09:35:09 Then I'll talk about the transport modeling with the see Jojo kinetic code, and finally I'll try to explain the cyclic bifurcation that we observed some implications of that. 09:35:19 Okay so following Luther stock we saw that the increased heating in Tokyo my results in a spontaneous transition. 09:35:28 Due to a transfer qualification from an Elmo to an edge mode. This h mode was manifest in the form of formation of a density and temperature pedestal that is the edge transport beggar. 09:35:39 And this transfer power comes with formation of er well here we see the Elmo vs ho then we see the formation of er will and suppression of turbulence and the pedestal. 09:35:50 And this formation of this pedestal elevates the pressure gradient everywhere, you know, personal is a boundary to the core. 09:36:05 Now, this does not come free edge mode is accompanied by periodic bursts of ejected plasma, that are called the edge localized modes. It turns out the confinement of H mode is too good. 09:36:19 That is the pressure increases until it hits a MHD limits, which is technically it's a peeling coupling between peeling mode and the ballooning MSG modes. 09:36:33 And, as a result of that we get when we hit that threshold, we get a collapse of density and temperature and explosion of plasma and in the form of filament or eruptions, which ends up on as a form of a large heat load to the diverse and here you can 09:37:01 this beautiful image from mast tokenization can see this film entry structure of the films that are parallel to the magnetic field lines. So this type one giant Elms, cause excessive erosion to divert and vessel walls, and are detrimental to future total. 09:37:13 So type one need to be mitigated and controlled. As a result, there, people are looking for ways to accomplish that. And one way is if you intrinsically Alfie regimes have been discovered. 09:37:31 First one, which is the most attractive one is a que quiescent the HMO and the white person choice and H more than other types of animals which are not that drastic and other types of methods is injection of pellets here by injecting players with trigger 09:37:50 more frequent and smaller alums, and finally is the using of externally applied non-active symmetric magnetic fields, cause additional transport through the pedestal, basically being the pedal stroke pressure below that MSG limit to prevent the Elms, 09:38:08 and it's been shown to successfully suppress the arms and, which is very interesting. 09:38:14 Now, This rtmp recently has been shown to provide access to a new white pedestal grass Iam regime here on the right hand side we have the bomber the alpha signal, which shows the density of the atrium. 09:38:28 Neutral tree and near the governor. And we can see why applying the equal three that's tutorial mode number of the external party magnetic field, or MP produces small grassy area here. 09:38:43 Right here we can see that the external coils are energized and we get the our MPs and these giant type one elms disappear and you're left with these wiggles which are the grassy Knolls whichever like 140 years of the amplitude of the type one else. 09:38:59 And then now looking closely at this region. 09:39:04 This window of time we observed that we have periodically enhanced density fluctuations at the pedestal top so this is a pedestal spot density fluctuations and we see these red regions are the time periods that we have the enhanced density fluctuations. 09:39:21 And keep in mind that you're externally applied the magnetic field is steady in time it's constant stuff. 09:39:29 And at the same time we have enhanced diverted flexes so here below this we have the heat flux of the murder, we see whenever we have enhanced fluctuation top fluctuation enhances the fluctuation of the personal top we have enhanced fluxes to murder. 09:39:45 And we also have Southern drop in a pedestal top temperature and density and he will be showing the pencil top temperature, and who my purpose is to show that pedestal is exhibiting a local transfer qualification, in the middle of the printer soul which 09:40:03 transforms they typically single step to a staircase structure. And why is this important, because the staircase structure has an improved ballooning stability which leads to a higher pedestal pressure, which as we talked before is very desirable. 09:40:22 Now, let's look at the time evolution that results in this periodic behavior so Penistone oscillate between a white single step structure and and wider staircase structure. 09:40:33 First let's look at the time periods where we have the single step. 09:40:36 Now, that's the time that the flux, to the river is higher, and he can see that as we said before, we have higher fluctuation levels I pedestal top, but the mid pedestal right here 0.95 is relatively quiescent, and we can see that we have a single step 09:40:54 structure, and we have. 09:40:58 We have a relatively narrow and deep radio electric field. 09:41:04 And also we have grass the items that are mitigated. 09:41:08 And during the time that we have reduced floods to the divert. 09:41:15 We have a wider pedestal, which has a flattening in the middle of it that we, that's why we call this the staircase pedestal. 09:41:24 And we also see that during these times then fluctuations that the personal top are lower, however we see fluctuations in the middle of the pedestal. 09:41:33 Now we can see that the radio electric field here is wider and shallower. 09:41:38 And we have higher level of grassy on activity. 09:41:43 Now, for why this cyclic behavior is happening. I can just shortly, say that it is caused by a pulsating Island at the pedestal talk which has a very complicated dynamics and it's beyond the scope of this talk. 09:42:02 Now, looking at one of these bursts of fluctuations, we see that it's peaked almost exactly knew where the flattening is happening, and it has a broad range of fluctuations, we can see this in the long range and low frequency and intermediate range and 09:42:21 higher frequency diagnostic for density fluctuation, and it moves in the electron demanded direction. 09:42:31 Now, the single step of. So, next we try to understand this with transport analysis, and we use CGI rojo kinetic code and new neoclassical code to calculate what the levels of transport is and compare that to the experimental levels. 09:42:53 Now, first of all, we use the linear form of the gyro to identify the modes that are exists in the middle of the single step pedestal and we find that the pressure must be pressure gradient must be constrained by the kinetic ballooning mode, which is 09:43:11 the kinetic equivalent of the MHD ballooning mode, and it's very efficient in transporting both heat and particles, and you will see by increasing the normalized pressure gradient this the alpha makes you by 10% we hit that threshold for KPMG, and that 09:43:38 is a strong indicator that the pressure is constrained by caveat. Now, looking at nonlinear Jerry can take results from the gyro and Neil we find that energy and the electron channel is predominantly driven by the electron temperature gradient bolts, 09:43:52 and these are modes that are in the electron scales and higher frequencies and are efficient in transporting heat in the electron channel, how we find the ion heat is predominantly transported by neoclassical transport and the particle transport is a 09:44:12 combination of turbulence and neoclassical and the right hand side we have the spectrum of the 80 G's, and we can see it goes all the way up to K theater west of about hundred and 50 So, but the peak is at K Federalists of 2.6 and that's about k theater 09:44:33 OE of point one to point two. 09:44:35 So it's comparable to the peak is comparable to electron students. However, in the iron scale simulation we see still see a dominant ATG with a peak in the trap electron moves which is heavily shear suppressed. 09:44:50 Now in order to understand the transition between the two regimes. 09:44:54 So, if we compare the two pedestals that are saying single step and the staircase, we see that broaden of the pedestal drastically reduces the equal species in the steep rating region here comparing the blue for the staircase and the red, we can see in 09:45:10 the middle of the pedestal the equals issue for the red is way higher than the blue and we can see there is a region for the blue one, that is the staircase, which has a purpose you very low and that's almost a place where we have this flattened information 09:45:26 in order to better understand this, we take the risk of single step pedestal and perturbed by making it wider and increasing his physical top high to come up with an intermediate pedestal, this intermediate pistol has a broad broader equal species profile 09:45:42 and shallower, so it's transitioning between the two. And doing that, we find that by increasing the width of the pedestal we, we see a drastic drop in the equal species. 09:45:59 So the width of the pistol was increased by about 10% and density and temperature and then we see a drop about 40% and equals, be sure. 09:46:10 And so here there are two dynamics that are important to us. So the first is the relaxing the gradients, especially TV because we have dominant ATG it reduces the transport of heat and particle or the other hand, reduction of equal speech year asks to 09:46:28 On the other hand, reduction of equal speech year asks to enhance the transport and these two are seem to be competing with each other. 09:46:33 Now performing. 09:46:35 Jerry Connect for the simulation for the intermediate so we see that we have enhanced transport from reduce the cost issue that leads to a negative fluctuating reaction so here we have the single step pedestal with values that I showed before. 09:46:50 And here we have the intermediate pedestal, which was that hypothetical business. So, here the gradients have been relaxed and they've been relaxed, keeping the ratio fixed, which is hypothetical it's not necessarily what's going on the experiment, but 09:47:06 this is the approach we took to analyze this and here doing that we find that as the cross species is reduced. We have a surge of trapped electro mode at longer wavelength of K through us of about point one to point to that lead to a large transport flux, 09:47:25 and this negative flux gradient so is a property of a nonlinear only nonlinear unstable solution. However, what happens in the real physical system is as the floods, is reduced, we get a southern local collapse of the gradients. 09:47:46 And the constant flux which leads to the local flattening of the pedestal and formation of the staircase structure. 09:48:10 Now in the flat part of the staircase structure so now we're looking at the other face, which has a pronounced flattening in the middle of pistol. Now we perform gigantic analysis for this one, we can see it has a broad spectrum of IR temperature gradient 09:48:11 and trap electronic turbulence with peek at a Federal Reserve point three, so it spans from long wavelength to intermediate language. 09:48:22 and here if we perform a scan of desert. 09:48:28 Perform of gradients of the system, we see a positive slope that is a non new stable. And even if we include the equal specie enhancement of that we see that it's a weekly affecting this, that is, that tells us that here, it must be the zonal flows that 09:48:46 are regulating this turbulence. 09:48:49 Now putting the two pictures together. Here we have the nonlinear honest unstable solution, close to the vicinity of the single step hustle and the denominator stable solution, close to the vicinity of the staircase and hear this dashed line is the closet 09:49:07 linear modeling which I use the mixing estimate with a correction due to equal speech year, which gives us this roll over here and put it puts everything together and what it looks like it looks like it's giving us, you know, famous S curve, structure 09:49:36 Now here we try to explain this a solitary behavior and we see the transition from staircase to the single step is driven by the enhanced flux. So on the left hand side we have the pedestal top fluctuation here, and the flux of density to the divert or 09:49:53 below, and starting from the staircase structure, we see that as the flux to the divert or is enhanced but as a result of enhanced fluctuations at the pedestal top, we see that increasing flux increases the gradients, and the pedestal as er will. 09:50:13 As a result, will narrow, and we can increase the cost issue, and add an unstable flux radial limit we have the equal species suppressing the turbulence. 09:50:25 And the pedestal transferred by advocates to the KB m demands so that we get a, you know, forward transport bifurcation from the staircase structure to the single step structure, and it's constrained by the caveat that with you. 09:50:40 And therefore we get this single step pedestal, and now on the way back as the flood of fluctuations that the personal top decrease, we get a drop in the flux of the divider. 09:50:52 And this decrease some of the flux here as the sun can follow this year relaxes the gradients from the caveat limit, as a result pistol and er will broaden n equals b shoe decreases. 09:51:04 And here again had an unstable flux gradient limit, we get shear suppression breakdown and gradients locally collapse and pedestal transport bifurcation bifurcated to the it GTM constraint turbulence, and as a result, again the staircase but also forms 09:51:23 in this a cyclic behavior explains this formation periodic formation of single step and staircase business. 09:51:32 And in conclusion, despite pedestal regime exhibits breakdown of equal species suppression of turbulence leading to steak is formation. 09:51:39 And here we see really localized turbulence leads to enhance political pressure, and it's been shown before that, when the width of the pedestal over the. 09:51:56 We have the iron scale transport becoming significant in the pedestal. And therefore, each other, the baseline is expected to have this value of 70 that means the unskilled transport could be dangerous levels. 09:52:10 However, the possible staircase formation might be beneficial to each other as it preserves and even in, it might enhance the pedestal. 09:52:22 top pressure. 09:52:23 And that's pretty much it. Thank you so much. 09:52:27 That's wonderful rash Thank you so much. 09:52:29 So we do have time for questions that people have questions either on what a rash just spoke about or earlier on motors talk, please raise your hand. 09:52:42 Zombie please. 09:52:46 I'm a question for a Russia, can you hear me. 09:52:49 Yes, interesting talk. 09:52:53 I did not understand why you didn't run simulations. In the intimidate range where the better attentional girls in the slide 16. 09:53:11 Let me go back to this and share my screen. I mean the whole story. 09:53:15 I think you mentioned that heaven slide 16. Yeah, I think that's the slide where as soon as the slide where you see exactly so so you have no no similar, it would be more convincing if you would show simulations for next year. 09:53:30 Yes, exactly. 09:53:32 Well, I mean it's a stretch week we don't have. So this perturbation that I did here, which resulted in these two simulations like two points scan here. 09:53:47 It's a very small is very small perturbation of the puzzle and we don't Okay, the good answer is we don't have well resolved pedestals. So these pedestals that I'm showing here are averaged over the whole range. 09:54:01 So let me go back to here for example. So, here in this whole range we have staircase structure and here we have a single step structure and but the transition period is very short. 09:54:15 And this. 09:54:17 These pedestals are average over tense cycles of this back and forth oscillation so this is 10 of these time periods for which we have single step, and the other one. 09:54:30 This one is still the blue one is 10 time periods for which we have, so it's averaged over the whole time bridge, and this transition time, we don't have pedestals that represent that. 09:54:42 You know, we don't really know how exactly is going from one to the other one. That's why I had this relatively crude, a perturbation to this. 09:54:55 We have a question from Patrick as well. 09:54:58 It's more of a, this is Trello thar, and it's more of a request so maybe you might want to and share your screen era. Yeah, thanks for low far it's more requests to expound on something. 09:55:12 We had an interesting talk the other day from Laura cope, which included the discussion of Barry of jet migration. 09:55:22 You alluded to, but didn't discuss the inward propagation of the pedestal with it, which is a migration problem of sorts, so I wonder if you could briefly comment on that. 09:55:37 Yes, there wasn't time because we will unfortunately I was running over. 09:55:58 But basically, there's a, there's measurements that show that there's a front that propagates in terms of how the fluctuations are surprised. So, in a normal transfer information, the deposit starts at two separate trick so at the last close flux surface 09:56:01 and then the front propagates in boards within about one millisecond was the activation successively surprised at smaller API, right and the flow formation basically going along with that, the FC in both cases better flow propagates faster than the fluctuation 09:56:22 suppression and also cases where they go hand in hand. 09:56:27 There's also been when you insert flow into the plasma so when you put momentum from the outside into the plasma via neutral beans. It often happens the other way around so because then there's a lot of momentum that is propagating out from the core that 09:56:41 creates what we call call rotation so strong. To rider, in all the Poli rotation already in the inner Shelia on the core boundary, and then the transition can happen there first and then the fluctuations on propagates out so that happens also but that 09:56:58 seems to be happening only when there's external momentum put into the plasma. So the natural formation of transport barriers when there's no external momentum applied seems to for the most part favor. 09:57:10 The last class flux of, so there's a boundary condition. 09:57:22 I'll get that. 09:57:25 All right, for now. 09:57:26 Okay, we have any other questions. 09:57:32 I think we're back back on target for keeping to time. So I'd like to thank our two speakers once again and Peter, if I can ask you to share your screen.