May 21st, 2021
The promise of a low recycling boundary, by Anurag Maan
Abstract: The Lithium Tokamak eXperiment-beta (LTX-beta) is attempting to answer key questions regarding the feasibility of operating a tokamak with a lithium boundary. Lithium coatings on high-Z plasma facing components (PFCs) in the LTX (LTX-beta predecessor) led to flat temperature profiles. The flat temperature profiles were observed along with a hot low density edge, implying a broad, collisionless Scrape-Off Layer (SOL). Additionally, in-vacuo analysis of PFCs indicated that evaporatively deposited lithium coatings appeared to be oxidized, while the ability to achieve good plasma performance was retained. Theory attributes flat temperature profiles to low recycling walls, which was assumed to be due to hydrogen binding with elemental lithium to form lithium hydride. The presence of oxidized lithium, however, raises questions regarding the exact mechanism of hydrogen retention in LTX. These questions were investigated using a new Sample Exposure Probe (SEP) for detailed in-vacuo analysis of PFC samples was designed and commissioned for LTX-beta. The SEP is equipped with a vacuum suitcase capable of transporting samples representative of LTX-beta outer mid-plane PFCs under high vacuum to a stand-alone high resolution XPS system. Surface analysis using the SEP was performed with sufficient energy resolution to identify for the first time, the compounds that grow on evaporative lithium coatings inside a tokamak. This was the first demonstration that a vacuum suitcase can afford a solution that is simpler in design and affords more flexibility than building material characterization test stands for installation on a tokamak. The results indicate that Lithium Oxide and Lithium Hydroxide are prime surface constituents of Lithium PFCs. Their presence substantiates the hypothesis that lithium oxide grows on elemental lithium before the growth transitions to lithium hydroxide for LTX-beta like vacuum conditions. It is further indicated that Lithium Oxide improves plasma performance in comparison to Lithium Hydroxide by both sequestering oxygen and increasing hydrogen retention. The talk will also outline current efforts that aim at estimating recycling in LTX-beta.
Join the talk via the Zoom link fusion.yt/as on 21/05/2021 at 15:00 (Prague). Password: E71AF0A7
April 27th, 2021 Energy balance during disruptions, by Nicola Isernia.
Abstract: In the present talk we shall study the global energy transfer for a fusion plasma undergoing a disruption, by the means of first principles and evolutionary MHD equilibrium models. The key role of the conducting structures surrounding the device will be highlighted, giving insight in the time constants which are relevant to the global energy transfer. Reference: N. Isernia et al 2020 Plasma Phys. Control. Fusion 62 095024
Join the talk via the Zoom link fusion.yt/ar on 27/04/2021 at 18:00 (Prague). Password: 05049B6A
April 21st, 2021
Sneezing tokamaks : what to do about the boogers?, by William Gracias.
Join the talk via the Zoom link fusion.yt/ar on 21/04/2021 at 16:00 (CET)
Join the talk via the Zoom link fusion.yt/as on 27/04/2021 at 18:00 (CET)
April 07th, 2021
High-Temperature Superconducting Magnets. Open an accelerated path to fusion energy, by Erica Salazar.
Abstract: High temperature superconductors (HTS) have the ability to revolutionize the fusion energy industry by enabling tokamak fusion devices, such as the SPARC fusion device, to be smaller, lower cost, and faster to build. All fusion-class devices built to date have used either low temperature superconductors (LTS) or copper to generate magnetic fields to control and drive the plasma in a fusion device. In contrast to LTS, HTS magnets can withstand and generate significantly higher magnetic fields--leading to smaller and lower cost tokamak devices. However, introducing a new HTS material will bring new scientific challenges and risks. This presentation will highlight the risk reduction strategies and test results of the VIPER cable (a HTS cable designed by MIT and Commonwealth Fusion Systems) such as fabrication feasibility testing, load cycling, strain testing, and quench testing in SPARC-relevant conditions.
Join the talk via the Zoom link fusion.yt/aq on 07/04/2021 at 19:00 (Prague). Password: 9485E377
March 31st, 2021
Why ITER after 30 years? A case study of US deciding to stay, by Emmanouil Maragkoudakis.
Abstract: Research on burning plasmas aims to deliver a carbon free, virtually unlimited and safe power source. After more than 50 years of investigation, a nuclear fusion power plant is still a future objective. For this reason, the disposal of funds and resources on the field is often subject to criticism. By studying the 2019 Final Report of the Committee on a Strategic Plan for US Burning Plasma Research, we will try to understand the motivation and the benefits of investing on nuclear fusion research.
Join the talk via the Zoom link fusion.yt/ao on 31/03/2021 at 18:00 (CET). Password: 93112F18
March 23rd, 2021
Effects of oxide layer on Tungsten, by Mykola Ialovega (FUSION-EP 2015)
Abstract: Investigations of hydrogen isotopes and helium retention in plasma facing components (PFC) that are exposed to various plasma conditions are important for future fusion devices such as ITER and DEMO. Due to its favorable physical properties, in particular its high melting point, tungsten (W) has been chosen as the plasma-facing material of the ITER divetor. In the deuterium/tritium (D/T) phase of ITER, W PFC will be subjected to intense fluxes composed of hydrogen isotopes (HI), helium, impurities and neutrons.The presence of impurities in the edge plasma may cause redeposition or codeposition of mixed layers on the surface of the PFC W, and in the presence of residual oxygen, surface oxidation is possible due to the high temperature of the ITER divertor. Such structural modifications of W PFC may modify the properties of the material, and therefore its life expectancy, as well as its hydrogen retention, which raises safety concerns as tritium is radioactive.In this work, we used laboratory experiments involving ion implantation and thermal desorption spectrometry (TDS) technique to investigate the fundamental retention properties of HI in W PFC due to the presence of an oxide layer formed on the surface of polycrystalline W (PCW) in ITER relevant conditions. The TDS measurements were coupled with microscopy observations in order to characterize the modifications occurring on the surface and in the bulk of the material at different scales: scanning electron and confocal laser scanning microscopy techniques were used for surface observations from micrometer to nanometer scale; transmission electron microscopy was used for cross-sectional observations. Raman and X-ray spectroscopy techniques were used to characterize the structure and chemical composition of the samples.
Join the talk via the Zoom link fusion.yt/an on 18/03/2021 at 16:00 (CET). Password : 269187EB
March 18th, 2021
Tritium permeation in fusion reactors. Experiments with the hypertomate setup, by Floriane Leblond
Abstract:The presentation will start with a general introduction to the challenges faced by first wall materials with a focus on tritium retention and permeation. In a second part, the need for permeation and TDS experiments will be explained, and these experimental techniques will be further explicited. Finally, the remaining challenges (e.g. interfaces modelling) will be discussed.
Join the talk via the Zoom link fusion.yt/am on 18/03/2021 at 17:00 (CET). Password : 864D7135
March 9th, 2021
A tutorial on automatic differentiation for scientific design: practical, elegant and powerful, by Nick Greivy
Abstract:Automatic differentiation (AD) is a numerical technique for computing the derivative of a function specified as a computer program. Although AD was invented decades ago, it wasnâ€™t until the recent interest in machine learning and the associated development of high-quality automatic differentiation frameworks that the benefits of AD in physics were more widely recognized. In this tutorial, I introduce AD. By the end of the tutorial, you will hopefully understand the fundamentals of how AD works in theory and how it is used in practice. For a short, 5-minute introduction to AD, feel free to read this https://twitter.com/NMcgreivy/status/1351706692317138945?s=20 and this https://twitter.com/NMcgreivy/status/1286057985987563525?s=20
Join the talk via the Zoom link fusion.yt/al on 9/03/2021 at 18:00 (CET).
March 01st, 2021
MASTER CLASS : Energy for our future: a synergetic approach between short-term nuclear fission and long-term nuclear fusion, by Jean-Marie Noterdaeme
Abstract:Ever wondered how fusion power plants could contribute to keeping our climate change in check? Will they not come too late? We need to provide sufficient energy for the increasing needs of the world population, and at the same time, limit the global temperature rise below 1.5 °C for a livable world. This requires a major effort to de-carbonize our energy supply. Time is running short. A first step would be to require that all new plants need to be carbon-free. Renewables alone (windmills and solar panels) cannot be installed in sufficient quantities on the required time scale to cover the expected additional needs. Small modular nuclear reactors could be the solution. Enough could be built and installed if they are standardized, factory build and licensed - though it will still require a major program. Acceptance for nuclear energy could be increased since these reactors can be made passively safe. The questions of fuel supply and waste management for fission reactors can also be put to rest if nuclear fission energy is seen as a transitional measure on the way to long term fusion energy.
Join the talk via the Zoom link fusion.yt/ai on 01/03/2021 at 15:00 (CET). Password 50D09934
February 22nd, 2021
Capturing collisions with neutral nets. Faster collision operators with semantic segmentation, by Andrés Miller
Abstract: Machine learning, specifically convolutional neural networks, is used to examine the possibility of accelerating the solution to a partial integro-differential equation, the Fokker-Planck-Landau collision operator. This is part of the governing equation in the particle-in-cell code, XGC, which is used to study turbulence in fusion energy devices. In particular, training has involved borrowing network architectures used for the computer vision task of semantic segmentation. The neural network emphasizes physics-inspired learning, where it is taught to respect physical conservation constraints of the collision operator by including them in the training loss. It uses a penalization method that enforces the constraints of the system and integrates error in the conservation properties into the loss function. During training, quantities representing the density, momentum, and energy for all species of the system are calculated, mirroring the procedure in XGC. This simple training has produced a median relative loss the order of 10-4, which shows promise. The run time for the current iterative solver of the operator in XGC is O(n2), where n is the number of plasma species. As the code begins to attack problems including a larger number of species, the collision operator will become expensive computationally, making the neural network solver even more important, especially since the neural network training only scales as O(n). A wide enough range of collisionality has been considered in the training data to ensure the full domain of collision physics is captured. Further work includes expansion of the network to include multiple plasma species and the use of more sophisticated optimization techniques.
Join the talk via the Zoom link fusion.yt/ai on 22/02/2021 at 15:00 (CET). Password 067A94A1
February 18th, 2021
Capturing Coulomb Collisions A Metriplectic Bracket Approach, by Riccardo Niccolo Lorio
Abstract: Since the 1980s much effort has been devoted to the study of magnetized plasmas to better comprehend the mechanisms that undergo the confinement of particles and transport phenomena inside fusion devices. The complexity of the particles trajectories in relation to the wide gap of time scales spanning from the electron cyclotron motion to the macroscopic phenomena that occur urged the development of perturbative time-scale reduction techniques to allow us to step over the computational limitations set by the gyromotion of particles. When dealing with the description of a plasma through the Vlasov-Maxwell-Landau system, both gyrokinetic and guiding-center theory are often applied to investigate solely the Vlasov-Maxwell part and the collision operator neglected or heavily approximated. In this talk it will be provided another indication of the possible existence of a metriplectic reduction theory which sheds light over the development of a collision operator for electromagnetic reduced plasma theories. An energy and momentum conserving collisional bracket is constructed for the so-called guiding-center Vlasov-Maxwell model while discussing why extensions to drift-kinetic and gyrokinetic electromagnetic theories are so difficult. Join us for an interactive discussion :-) Info: https://fusionep-talks.egyplasma.com/
Join the talk via the Zoom link fusion.yt/ai on 18/02/2021 at 18:00 (CET). Password A8B8D30F
February 12th, 2021
Isotopic effects on confinement, by Pedro Molina Cabrera (FUSION EP 2012)
Abstract: Join me for an informal discussion about turbulence and transport in tokamaks. How good a thermos is the tokamak after all? What happens if we fill the thermos with tea or coffee: which liquid remains hotter for longer? This talk will present how local temperature fluctuations change in the core of the ASDEX-Upgrade tokamak when going from hydrogen to deuterium plasmas in an effort to understand the basic physics towards deuterium-tritium operation in future fusion reactors such as ITER and SPARC. Join us for an interactive discussion :-) Info: https://fusionep-talks.egyplasma.com/
Join the talk via the Zoom link fusion.yt/ah on 12/02/2021 at 13:30 (CET). Password 2E785CD8
February 3rd, 2021
Anticipating disruptions: insights from COPASS, JET, AUG and DIII-D, by Veronika Klevarova (FUSION EP 2013)
Abstract: Disruptions present a major challenge for high-performance discharges in ITER and tokamak-based power plants. These events are accompanied by a sudden loss of magnetic confinement and, as such, pose a considerable threat to the integrity of the fusion machine. Over the course of my PhD, I collected an extensive database of disruptive discharges from COMPASS, AUG, JET and DIII-D to study the signs of a catastrophic end in fusion plasmas. In this upcoming FusionEPTalks, I will introduce an analytical model of the rotating magnetohydrodynamic modes that appear during braking and wall locking ahead of a disruption. We will look at the steps which were taken to validate this model. You will thereby understand how several factors can influence the mode duration, a key figure for disruption prevention. The corresponding scaling law, derived from this work, yields predictions for ITER from hundreds to thousands of milliseconds. This bodes well for the timely deployment of a mitigation strategy. Info: https://fusionep-talks.egyplasma.com/
Join the talk via the Zoom link fusion.yt/ag on 3/02/2021 at 14:00 (CET). Password FC9C9C21
January 20th, 2021
ICRF coupling in nonaxisymmetric fusion plasmas, by Guillermo Suarez Lopez (FUSION EP 2013)
Abstract: Ion cyclotron range of frequencies (ICRF) antennas will be installed in ITER and are also under consideration for DEMO as one of the main auxiliary heating and current-drive systems. ICRF waves are, however, evanescent in low-density plasmas, characteristic of the edge of fusion experimental reactors, but propagate beyond certain density. The coupling of these waves from the evanescent edge to the propagative core is well understood in axisymmetric plasma conditions, i.e., when the coupling region can be assumed homogeneous in poloidal and toroidal directions. However, the coupling of such waves under non-axisymmetric plasma geometries has rarely been systematically studied. Far from odd these non-axisymmetric configurations will be commonplace in fusion demonstration reactors and commercial power plants. For instance, a fusion power plant must operate in a high-confinement regime compatible with power exhaust. One candidate for the plasma scenario is the ELM-free H-mode, where toroidal symmetry is purposely broken to mitigate and even suppress edge localized modes (ELMs). To this effect, magnetic perturbation (MP) fields are applied, which induce a field-aligned plasma kink- response that breaks the usual tokamak toroidal symmetry. Likewise, Stellarators operate, by design, under non-axisymmetric geometry. In these devices, gas puff is also routinely used to improve the coupling conditions for ICRF antennas, in which a neutral cloud is non- axisymmetrically ionized at the edge, endowing the ICRF coupling region with 3D geometry. In this talk, Guillermo will present experimental and numerical results of the effect of non- axisymmetric plasma configurations on the coupling performance of ICRF waves, and prospectives for ITER. Throughout his PhD, he participated in many experiments on the ASDEX Upgrade tokamak, where the MP system was used to systematically study these effects. He compared the obtained measurements against analytical and experimental scaling. Info: https://fusionep-talks.egyplasma.com/
Join the talk via the Zoom link fusion.yt/af on 20/01/2021 at 16:00 (CET). Password 73852EAF
December 14th, 2020
How to make a plasma behave, by Yashika Ghai
Abstract: The next big step in fusion research is to create a steady-state hot plasma having temperatures an order of magnitude greater than the core of sun. One way to heat the plasma is by injecting a beam of high-energy neutral particles in the magnetically confined fusion device. As fusion reactions start, the energetic alpha particles are created as a byproduct that help keep the plasma hot for long. However, these energetic particles may also interact with various wave modes in the plasma, exchange energy with them and drive them unstable. The instabilities may lead to high heat fluxes of fast ions on the walls of the vacuum chamber, causing inefficient plasma heating as well as damage to the reactor walls. This talk will be based on explaining the physics of plasma instabilities in fusion devices that arise due to resonant interactions between energetic particles and plasma Alfven waves. Theoretical models for studying energetic particle driven instabilities and ways of mitigating them will be discussed. Info: https://fusionep-talks.egyplasma.com/
Join the talk via the Zoom link fusion.yt/ae on 14/12/2020 at 16:00 Hrs (CET).
December 9th, 2020
The TOMAS device, a good start of your fusion career, by Andrei Goriaev (FUSION-EP 2014)
Abstract: The TOMAS (TOroidal MAgnetized System) device, located in Forschungszentrum Jülich, has been significantly upgraded to enable development of various wall conditioning techniques and to complement plasma-wall interaction research in tokamaks and stellarators. The toroidal magnetic field can reach its maximum of 125 mT on axis. The EC system is operated at 2.45 GHz with up to 6 kW forward power. The IC system can couple up to 6 kW in the frequency range of 10 - 50 MHz. The direct current glow discharge system is based on a graphite anode with the maximum voltage of 1.5 kV and current of 6 A. A load-lock system with a vertical manipulator allows exposure of material samples. A number of diagnostics have been installed: single- and triple-pin Langmuir probes for radial plasma profiles, a Time-of-Flight Neutral Particle Analyzer capable of detecting neutrals in the energy range of 10 - 1000 eV, a Quadrupole Mass Spectrometer and video systems for plasma imaging. Besides the recent upgrades there are a lot of opportunities for further upgrades and improvements to the existing components. The device is suitable for tests of new concepts in plasma production systems and development of specific diagnostics for EC/IC plasma studies in toroidal magnetic field configuration. TOMAS being the "hands-on" machine has become an excellent training ground for students and young researchers to obtain necessary skills and experience in experimental physics. Info: https://fusionep-talks.egyplasma.com/
Join the talk via the Zoom link fusion.yt/ad on 9/12/2020 at 17:00 Hrs (CET).
November 30th, 2020
Kinetic models of the fusion plasma edge, by Dr. David Tskhakaya
Abstract: This masterclass will give a kinetic view on plasma edge dynamics, which significantly differs from well accepted fluid pictures. Dr. Tskhakaya will describe different numerical tools used for plasma edge study and consider examples of application of such tools - Particle-in Cell models. Plasma edge in fusion devices is a complex plasma layer, where nonlinear interaction between charged and neutral particle, and wall elements are governing plasma and heat exhaust. The optimization of the latter represents one of the main problems in design of future fusion reactors; this determines the importance of plasma edge study. Info: https://fusionep-talks.egyplasma.com/
Join the talk via the Zoom link fusion.yt/ac on 30/11/2020 at 18:00 Hrs (CET).
November 27th, 2020
Stop the runaway electron beam, by Dr. Sundaresan Sridhar (FUSION EP 2015)
Abstract: Relativistic runaway electron (RE) beams are one of the main consequences of disruptions and they carry the risk of in-vessel component damage. The prevention and control of the RE are of prime importance. The current strategy for runaway electrons is to avoid their generation by a massive material injection (MMI). If their generation cannot be avoided, a second MMI will be used to mitigate the generated RE beam. But the problem is, a background plasma of MMI impurities is formed which make the second MMI inefficient to mitigate RE beams, as observed in the JET tokamak. This talk aims to understand the physics of interaction between the RE beam and the mitigation MMI in the presence of a cold background plasma.. Info: https://fusionep-talks.egyplasma.com/
Join the talk via the Zoom link fusion.yt/ab on 27/11/2020 at 16:00 Hrs (CET).
November 18th, 2020
Abstract: Do you want to know how one of the plasma heating methods was developed? And, on the side, learn enough about its underlying physics and technology that you could use it? How about what happened at the same time in the world? Join this talk from someone who participated in this journey for the last 40 years. Info: https://fusionep-talks.egyplasma.com/
Join the talk via the Zoom link on 18/11/2020 at 15:00 Hrs (CET).
November 11th, 2020
Trap your alphas: fast particle motion in fusion plasmas, by Alena Gogoleva (FUSION EP 2012)
Abstract: One of the main difficulties to attain economically viable magnetically controlled thermonuclear fusion reactors is the confinement of alpha particles. In toroidally shaped fusion devices with a non-uniform magnetic field, alpha particles with small parallel velocity become trapped between areas of the high field, bouncing between reflection points, that might result in non-zero radial average drifts and their losses. This talk aims to highlight the link between the alpha particle transport and the confining magnetic field with an emphasis on the trapped particle characterization. Info: https://fusionep-talks.egyplasma.com/
Join the talk via the Zoom link " ://zoom.us/j/86117817013 " using the password "761C9723" (without quotes) on 11/11/2020 at 16:00 Hrs (CET).
November 5th, 2020
A practical introduction to the H-mode pedestal: ELMs and ELM-free regimes, by Andrew Nelson
Abstract: Future fusion reactors will likely be run in a high-confinement mode called H-mode in order to reach the highest plasma temperatures and densities possible. H-mode is characterized primarily by a steep gradient region near the plasma edge called the H-mode pedestal. While the pedestal helps raise fusion parameters in the core, it is also subject to intense instabilities called Edge Localized Modes (ELMs), which will be intolerable in a reactor setting. In this talk, we will cover the basics of why the H-mode pedestal forms and how it interacts with the plasma. Fundamental theoretical and experimental understandings of ELMs will be discussed, as well as advanced options to operate H-mode plasmas in regimes without ELMs, thereby attaining the benefits of H-mode while avoiding the potentially disastrous possibility of melting the reactor wall.. Info: https://fusionep-talks.egyplasma.com/
Join the talk via the Zoom link " ://zoom.us/j/86117817013 " using the password "D980ABB4" (without quotes) on 5/11/2020 at 17:00 Hrs (CET).
October 15th, 2020
Abstract: Measurement of the current distribution in tokamaks is vital for improving plasma confinement and avoiding performance limiting magneto-hydrodynamic (MHD) instabilities. However, directly measuring the current in the plasma core is challenging. Neutral beam injection systems provide external heating and current drive, and a source of neutral atoms which interact with ions and electrons in the plasma. Emission from these neutrals can be measured using spectroscopy. This opens the possibility of localised measurements of key plasma parameters, such as the toroidal current density and the safety factor (q) profile. In this talk, Sam Gibson will discuss the diagnostic techniques used to measure the current profile, how to design and develop experimental spectroscopy diagnostics for a fusion environment, and the important role spectroscopy will play in the success of ITER. Info: https://fusionep-talks.egyplasma.com/
Join the talk via the Zoom link " https:// " using the password "D7F8B3C0" (without quotes) on 15/10/2020 at 16:00 Hrs (CET).
September 14th, 2020
Abstract: As the fusion community makes pace towards commercialization, the balance in research is shifting from an academic-and-fundamental direction to a technology-and-industry-driven orientation. Internationalization, multidisciplinarity and mobility are key attributes required from leaders in the nascent fusion industry. For nearly 15 years, the FUSION-EP joint Master degree has delivered a high-level research-oriented education and a well-integrated cultural experience within an international consortium of institutions leading the interdisciplinary field of magnetic fusion. The combined and harmonized teaching and research activities coordinated among eight partner universities in Belgium, Czech Republic, France, Germany and Spain offer a variety of competences in a field of crucial importance to the problem of world energy supply. Besides the ITER International Organization, there are presently twenty-five academic and research associate partners from the EU, China, India, Lebanon, Russia, and Ukraine. Professor van Oost is one of the founders of FUSION-EP. In this talk, he will present the structure, philosophy and future perspectives of this unique graduate programme. Prospective students should note that 15 full scholarships are awarded every year to the top candidates!. Info: https://fusionep-talks.egyplasma.com/
Join the talk via the Zoom link " https:// " using the password "5463067F" (without quotes) on 14/09/2020 at 17:00 Hrs (CET).
September 3rd, 2020
Abstract: The fundamental understanding of the behavior of fusion plasmas is based on sophisticated measurements that allow non-invasive diagnosis of certain parameters. This presentation outlines the path from the need to determine a certain quantity, to a conceptual measurement principle towards an actual implementation on a fusion device, using the example of the LLAMA diagnostic. LLAMA stands for Lyman-Alpha Measurement Apparatus, a multi-channel, bandpass filter pinhole camera system and has been recently installed at DIII-D. It measures the Lyman-Alpha brightness profiles at the plasma edge, enabling the inference of edge neutral density profiles to study sourcing of plasma particles. This opens a previously hardly accessible field of studies with specific importance when scaling towards large scale future fusion devices, where the sourcing from neutrals is expected to be drastically reduced. Info: https://fusionep-talks.egyplasma.com/
Abstract: It has been known for at least two decades that, in certain regimes, magnetically confined plasmas such as those within a tokamak or stellarator, may exhibit complex, non-diffusive radial transport that is badly modelled by means of traditional, effective, eddy diffusivities or conductivities. These regimes may become very important in next-step experiments, such as the ITER tokamak currently under construction in Southern France. In this talk, we will discuss some of the reasons for the appearance of complex transport behaviour in these plasmas, their implications for plasma confinement as well as give some hints about how these kind of regimes can be more properly modelled by using fractional transport theory. Comparisons with numerical simulations and, when available, experiments, will be also discussed. Info: https://fusionep-talks.egyplasma.com/
Abstract: The talk will be about disruptions events that can arise in tokamaks producing large heat and electromagnetic loads on the structures surrounding the plasma. The dynamics of these events are complex and 3D simulations are required to understand present experiments and to assist the design and operation of future machines. Disruptions induce wall currents which in turn determine the plasma motion, therefore it is necessary to couple these currents to the plasma in a self-consistent form. In the presentation different methods for such a coupling are explained for 3D MHD codes and examples of 3D MHD simulations of Vertical Displacement Events (VDEs) are also presented. Info: https://fusionep-talks.egyplasma.com/
Abstract: Hydrogen is one of the key ingredients for fusion energy. During operations, tokamak walls are under bombardment of highly energetic hydrogen ions, which can penetrate the materials. Knowing the hydrogen content of these plasma-facing materials is crucial for several reasons. First from a safety point of view, the tritium content in the inner-vessel of the tokamak is limited to 700 g. Secondly, tritium penetrating the first wall material could reach the cooling system which must then be purified. Finally, hydrogen can brittle the materials and therefore reduce the lifetime of plasma facing components. The behaviour of hydrogen can be investigated by lab experiments but also simulated with thermokinetic models which is the topic of this talk. We’ll present the finite element code FESTIM developed by CEA and CNRS. A particular focus is made on ITER divertor and tungsten monoblocks and hydrogen retention is estimated in the whole divertor.
Abstract: Successful commercial development of fusion energy will require us to find new ways to license and regulate fusion technology that enables innovative and economically viable designs. Fusion energy will likely have unique safety challenges related to the radioactive tritium used as fuel in most proposed commercial reactors. If we want to develop safe and economically competitive fusion energy, we need to incorporate safety and possible regulatory constraints on fusion technology early in the design process. This talk will discuss the major off-site hazards related to commercial fusion technology, what regulatory tools we can use to demonstrate the safety of fusion technology, and how these regulations could affect the design of future fusion power plan.
Abstract: New diagnostics in contemporary fusion devices have minor changes but these changes are crucial, this is where diagnosticians compete. But what if all common approaches are not applicable at some place? What if you have to develop solutions which were never used and nothing similar was used? The place where things go this way is called ITER. In ITER, calibrations, adjustments and agile approach improvements are not possible to make minor changes by hand. This and ITER environment requirements make thousands of criteria to be fulfilled in order to complete the work successfully. The talk will present some features of the Thomson scattering diagnostics and focus on some uncommon and specific aspects that became the case in this Divertor Thomson Scattering diagnostic and on supplementary work that is required in such a machine.
Abstract: The interior of a fusion power plant will be an extreme radiation environment, outside the realm of humanities experience with radiation sources like fission reactors. The materials that make up these power plants must withstand heavy exposure to high energy neutrons, which damage materials, degrading their properties, and driving the components towards failure. Without the ability to accurately reproduce the expected neutron environment through experimentation or simulation, the first fusion power plants face enormous risk of radiation-induced failure of their key components. In order to improve our ability to predict material performance under fusion neutron irradiation, we need new experimental methods for high-fidelity radiation damage testing. Intermediate energy (10-30 MeV) proton irradiation is an under-utilized irradiation technique that could produce radiation damage with high fidelity to a fusion environment Recently, advances in particle accelerator technology have allowed sources of intermediate energy (10+ MeV) protons to become commercially available at a cost and size appropriate for university labs. This talk will give a high-level overview of our work to demonstrate through simulations, theoretical analysis, and experimentation, that protons could play a pivotal role in predicting fusion material performance, ultimately improving the probability of the success of fusion as a global power source.
Join the talk via the Zoom link " https://zoom.us/j/82145836365 " using the password "76E3B4CC" (without quotes) on Thursday, 18/06/2020 at 18:00 Hrs (CET).
May 28, 2020
Vignesh is a scientific machine learning engineer at the UK Atomic Energy Agency and an alumni of the European Master in Fusion Science and Engineering Physics. He uses neural networks as a surrogate for the fluid equations describing the behavior of fusion plasma in JET and MAST-U.
In his FusionEPtalk, Vignesh will introduce the neural network solvers for partial differential equations. These regression models, which provide solutions while preserving most of the underlying physics, are particularly efficient in data-starved physical scenarios. Join the webinar and learn how to use his group's state-of-the-art python package for solving PDEs with artificial neural networks.
Join the talk via the Zoom link " zoom.us/j/82145836365 " using the password "E5F5F02B" (without quotes) on Thursday, 28/05/2020 at 18:00 Hrs (CET).