A5000955962- Magnetic confinement fusion research
- Fusion materials and technologies
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Superconducting Materials and Applications
- Nuclear Physics and Applications
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Nuclear reactor physics and engineering
- Atomic and Subatomic Physics Research
- Particle Accelerators and Free-Electron Lasers
- Solar and Space Plasma Dynamics
- Electron and X-Ray Spectroscopy Techniques
- Particle Detector Development and Performance
- Semiconductor materials and devices
- Seismic Imaging and Inversion Techniques
- Advanced Data Storage Technologies
- Medical Imaging Techniques and Applications
- Nuclear Materials and Properties
- Radiation Detection and Scintillator Technologies
- Pulsed Power Technology Applications
- Physics of Superconductivity and Magnetism
- Catalytic Processes in Materials Science
- High-pressure geophysics and materials
- Emergency and Acute Care Studies
Czech Academy of Sciences, Institute of Plasma Physics
2015-2025
Czech Technical University in Prague
2014-2024
Max Planck Institute for Plasma Physics
2016-2024
Culham Science Centre
2024
Culham Centre for Fusion Energy
2024
CEA Cadarache
2021
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2021
Charles University
2021
National Centre for Nuclear Research
2021
Czech Academy of Sciences
2020
For the first time it is experimentally demonstrated on JET tokamak that a combination of low impurity concentration bulk plasma and large magnetohydrodynamic instabilities able to suppress relativistic electron beams without measurable heat loads onto facing components. Magnetohydrodynamic simulations instability modeling postinstability confirm prompt loss runaways absence regeneration during final current collapse. These surprising findings motivate new approach dissipate runaway...
Abstract The tokamak à configuration variable (TCV) continues to leverage its unique shaping capabilities, flexible heating systems and modern control system address critical issues in preparation for ITER a fusion power plant. For the 2019–20 campaign configurational flexibility has been enhanced with installation of removable divertor gas baffles, diagnostic capabilities an extensive set upgrades new dual frequency gyrotrons. baffles reduce coupling between main chamber allow detailed...
Abstract The JET hybrid scenario has been developed from low plasma current carbon wall discharges to the record-breaking Deuterium-Tritium plasmas obtained in 2021 with ITER-like Be/W wall. development started pure Deuterium refinement of current, and toroidal magnetic field choices succeeded solving heat load challenges arising 37 MW injected power ITER like environment, keeping radiation edge core controlled, avoiding MHD instabilities reaching high neutron rates. have re-run Tritium...
Abstract This paper discusses the development of a benign termination scenario for runaway electron (RE) beams on ASDEX Upgrade and TCV. A systematic study revealed that low density ( n e ) companion plasma was required to achieve large MHD instability, which expelled confined REs over wetted area allowed conversion magnetic energy radiation. Control achieved via neutral pressure regulation agnostic material injection method. The recombination found be dependent impurity species, quantity RE...
The evolution of the JET high performance hybrid scenario, including central accumulation tungsten (W) impurity, is reproduced with predictive multi-channel integrated modelling over multiple confinement times using first-principle based core transport models.8 channels ( , ) are modelled predictively, self-consistent sources, radiation and magnetic equilibrium, yielding a system non-linearities: This can reproduce observed radiative temperature collapse after several times.W transported...
COMPASS Upgrade is a new medium size, high magnetic field tokamak (R = 0.9 m, Bt 5 T, Ip 2 MA) currently under design in the Czech Republic. It will provide unique capabilities for addressing some of key challenges plasma exhaust physics, advanced confinement modes and configurations as well testing facing materials liquid metal divertor concepts. This paper contains an overview preliminary engineering main systems (vacuum vessel, central solenoid poloidal coils, toroidal support structure,...
Abstract A series of experiments have been executed at JET to assess the efficacy newly installed shattered pellet injection (SPI) system in mitigating effects disruptions. Issues, important for ITER disruption mitigation system, such as thermal load mitigation, avoidance runaway electron (RE) formation, radiation asymmetries during quench electromagnetic control and RE energy dissipation addressed over a large parameter range. The efficiency has examined various SPI strategies. paper...
The TCV tokamak is augmenting its unique historical capabilities (strong shaping, strong electron heating) with ion heating, additional heating compatible high densities, and variable divertor geometry, in a multifaceted upgrade program designed to broaden operational range without sacrificing fundamental flexibility. rooted three-pronged approach aimed at ITER support, explorations towards DEMO, research. A 1 MW, tangential neutral beam injector (NBI) was recently installed promptly...
Abstract The research program of the TCV tokamak ranges from conventional to advanced-tokamak scenarios and alternative divertor configurations, exploratory plasmas driven by theoretical insight, exploiting device’s unique shaping capabilities. Disruption avoidance real-time locked mode prevention or unlocking with electron-cyclotron resonance heating (ECRH) was thoroughly documented, using magnetic radiation triggers. Runaway generation high- Z noble-gas injection runaway dissipation...
Relativistic electron (RE) beams at high current density (low safety factor, qa) yet very low free-electron accessed with D2 secondary injection in the DIII-D and JET tokamak are found to exhibit large-scale MHD instabilities that benignly terminate RE beam. In JET, this technique has enabled termination of MA-level currents without measurable first-wall heating. This scenario thus offers an unexpected alternate pathway achieve mitigation collisional dissipation. Benign is explained by two...
Abstract Experiments on ASDEX Upgrade (AUG) in 2021 and 2022 have addressed a number of critical issues for ITER EU DEMO. A major objective the AUG programme is to shed light underlying physics confinement, stability, plasma exhaust order allow reliable extrapolation results obtained present day machines these reactor-grade devices. Concerning pedestal physics, mitigation edge localised modes (ELMs) using resonant magnetic perturbations (RMPs) was found be consistent with reduction linear...
Abstract Plasma disruptions present a significant challenge to the viability of fusion energy production in tokamak reactors. Among disruption mitigation techniques, shattered pellet injection (SPI) has emerged as promising approach. The results presented this paper show novel findings impact nitrogen and neon seeding on sequence following SPI Joint European Torus (JET). This study exposes an order magnitude reduction pre-thermal quench duration for highly seeded plasmas pure deuterium SPI,...
Abstract We present a model for the particle balance in post-disruption runaway electron plateau phase of tokamak discharge. The is constructed with help of, and applied to, experimental data from TCV discharges investigating so-called ``low-Z benign termination'' mitigation scheme. In termination scheme, free density first reduced order subsequently induced MHD instability to grow rapidly spread electrons widely across wall. show that observed non-monotonic dependence measured neutral...
Retrieving spatial distribution of plasma emissivity from line integrated measurements on tokamaks presents a challenging task due to ill-posedness the tomography problem and limited number lines sight. Modern methods therefore implement a-priori information as well constraints, in particular some form penalisation complexity. In this contribution, current under development (Tikhonov regularisation, Bayesian neural networks) are briefly explained taking into account their potential for...
The role of the COMPASS tokamak in research generation, confinement and losses runaway electron (RE) population is presented. Recently, two major groups experiments aimed at improved understanding control REs have been pursued. First, effects massive gas injection ( Ar/Ne particles) impurity seeding were studied systematically. observed phenomena include generation post-disruption RE beam current conversion from plasma to RE. Zero loop voltage was implemented order study decay simplified...
Abstract A runaway electron (RE) fluid model is used to perform non-linear magnetohydrodynamic simulations of a relativistic beam termination event in JET. The case considered that post-disruption low density cold plasma the plateau phase, wherein high-Z impurities have been largely flushed out via deuterium second injection (Shot:95135). Details experiment are found separate publications. Our studies reveal combination and hollow current profile which confirmed by experimental causes fast...
Abstract Runaway electrons (REs) created during tokamak disruptions pose a threat to the reliable operation of future larger machines. Experiments using shattered pellet injection (SPI) have been carried out at JET investigate ways prevent their generation or suppress them if avoidance is not sufficient. Avoidance possible SPI contains sufficiently low fraction high-Z material, it fired early in advance disruption prone runaway generation. These results are consistent with previous similar...
Abstract An overview of recent results obtained at the tokamak ASDEX Upgrade (AUG) is given. A work flow for predictive profile modelling AUG discharges was established which able to reproduce experimental H-mode plasma profiles based on engineering parameters only. In center, theoretical predictions current redistribution by a dynamo effect were confirmed experimentally. For core transport, stabilizing fast ion distributions turbulent transport shown be important explain isotope and...
Abstract The paper presents an overview of the design status Radial Neutron Camera (RNC), that, together with Vertical Camera, will provide, through reconstruction techniques applied to measured line-integrated neutron fluxes, time resolved measurement ITER and α-source profile (i.e. emissivity, neutrons emitted per unit volume). RNC is composed two subsystems, In-Port Ex-Port located, respectively, inside outside Plug Equatorial Port #01. subsystem in a more advanced stage since it has...
Abstract Runaway electron gamma-ray detection system, a novel hard x-ray (HXR) spectrometer optimized for bremsstrahlung radiation measurement from runaway electrons in fusion plasmas, has been developed. The detector is based on 1‘×1’ LaBr 3 :Ce scintillator crystal coupled with photomultiplier tube. system an energy dynamic range exceeding 20 MeV resolution of 3% at 661.7 keV. gain stable even under severe loads, shift that stays below HXR counting rates excess 1 MCps. performance the...
Post-disruption runaway electron (RE) beams in tokamaks with large current can cause deep melting of the vessel and are one major concerns for ITER operations. Consequently, a considerable effort is provided by scientific community order to test RE mitigation strategies. We present an overview results obtained at FTU TCV controlling position improve safety repeatability studies such as massive gas (MGI) shattered pellet injections (SPI). show that proposed beam controller (REB-C) implemented...
The significant role of magnetic perturbations in mitigation and losses runaway electrons (REs) was documented dedicated experimental studies RE at the COMPASS tokamak. REs are produced both low density quiescent discharges disruptions triggered by massive gas injection (MGI). seed beginning discharge on subsequent population proved significant. Modulation MHD instabilities observed several characteristic frequencies, as well field oscillations related to power supplies. Magnetic islands...
This paper presents two scenarios used for generation of a runaway electron (RE) beam in the COMPASS tokamak with focus on decay phase and control beam. The first scenario consists massive gas injection argon into current ramp-up phase, leading to disruption accompanied by plateau generation. In second scenario, smaller amount is order isolate RE from high-temperature plasma. performances radial vertical position feedback were experimentally studied analysed. role energy stability seems be...