J. Havlíček
A5039316559- Magnetic confinement fusion research
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Particle accelerators and beam dynamics
- Fusion materials and technologies
- Laser-Plasma Interactions and Diagnostics
- Plasma Diagnostics and Applications
- Nuclear reactor physics and engineering
- GNSS positioning and interference
- Vacuum and Plasma Arcs
- Solar and Space Plasma Dynamics
- Nuclear Engineering Thermal-Hydraulics
- Magnetic Field Sensors Techniques
- Spacecraft and Cryogenic Technologies
- Advanced Data Storage Technologies
- Health and Medical Studies
- Seismology and Earthquake Studies
- Seismic Waves and Analysis
- Particle Accelerators and Free-Electron Lasers
- Atomic and Subatomic Physics Research
- Health Promotion and Cardiovascular Prevention
- Particle Detector Development and Performance
- Laser-induced spectroscopy and plasma
- Advanced Fiber Laser Technologies
- Meteorological Phenomena and Simulations
Czech Academy of Sciences, Institute of Plasma Physics
2015-2024
Czech Academy of Sciences
2014-2021
Charles University
2008-2016
Ghent University
2015
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 The amplitude of locked instabilities, likely magnetic islands, seen as precursors to disruptions has been studied using data from the JET, ASDEX Upgrade and COMPASS tokamaks. It was found that thermal quench, often initiates disruption, is triggered when reached a distinct level. This information can be used determine thresholds for simple disruption prediction schemes. measured in part depends on distance perturbation measurement coils. Hence threshold mode location (i.e. rational...
As in many of today's tokamaks, plasma start-up ITER will be performed limiter configuration on either the inner or outer midplane first wall (FW). The massive, beryllium armored FW panels are toroidally shaped to protect panel-to-panel misalignments, increasing deposited power flux density compared with a purely cylindrical surface. chosen shaping should thus optimized for given radial profile parallel heat flux, scrape-off layer (SOL) ensure optimal spreading. For plasmas limited this is...
Asymmetrical disruptions may occur during ITER operation and they be accompanied by large sideways forces rotation of the asymmetry. This is particular concern because resonance rotating asymmetry with natural frequencies vacuum vessel (and other in-vessel components) could lead to dynamic amplification forces. A significant fraction non-mitigated JET have toroidally asymmetric currents that flow partially inside plasma surrounding ('wall'). The toroidal asymmetries (otherwise known as...
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...
Partial detachment is the desired regime for baseline burning plasma scenario in ITER and next-step devices, as it allows to dissipate majority of energy carried by charged particles through scrape-off-layer (SOL) thus avoids localised heat flux deposition divertor region.The COMPASS tokamak equipped with an open has a relatively short connection length, both factors being unfavourable access detachment.As such, only approach naturally detached operation at very high lineaveraged densities...
Abstract This paper reports on probe measurements of the electron energy distribution function and plasma potential in divertor region COMPASS tokamak during D‐shaped plasmas. The data have been processed using novel first‐derivative technique. A comparison with results obtained by processing same classical technique, which assumes Maxwellian functions is presented discussed. In vicinity inner outer strike points can be approximated a bi‐Maxwellian, dominating low‐energy population (4‐7 eV)...
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...
Abstract The understanding of the halo current properties during disruptions is key to design and operate large scale tokamaks in view thermal electromagnetic loads that they entail. For first time, we present a fully self-consistent model for simulations including neutral particles sheath boundary conditions. used simulate vertical displacement events (VDEs) occurring COMPASS tokamak. Recent experiments have shown parallel density at plasma-wall interface limited by ion saturation...
The contribution focuses on plasma tomography via the minimum Fisher regularisation (MFR) algorithm applied data from recently commissioned tomographic diagnostics COMPASS tokamak. MFR expertise is based previous applications at Joint European Torus (JET), as exemplified in a new case study of position analyses JET soft x-ray (SXR) reconstruction. Subsequent application cameras with absolute extreme ultraviolet (AXUV) photodiodes disclosed peaked radiating region near limiter. Moreover, its...
The core Thomson scattering diagnostic (TS) on the COMPASS tokamak was put in operation and reported earlier. Implementation of edge TS, with spatial resolution along laser beam up to ∼1/100 minor radius, is presented now. procedure for calibration alignment both systems described. Several further upgrades TS system, like a triggering unit piezo motor driven vacuum window shutter, are introduced as well. together now routine provides electron temperature density profiles.
Abstract The reduction of the incident heat flux onto divertor will be a necessity for future thermonuclear reactors. Impurity seeding is recognized as an efficient way to achieve partial detachment regime, which allows dissipate large fraction power by radiation. This paper presents real-time feedback system (RTFS) based on impurity controlled combined ball-pen and Langmuir probe array in COMPASS tokamak. A number features have been studied, such type impurity, location, constants used...
Abstract This work presents the first analysis of disruptive locked mode (LM) triggered by dynamics a confinement change. It shows that, under certain conditions, LM threshold during transient is significantly lower than expected from steady states. We investigate sensitivity to controlled n = 1 error field (EF) activated prior L-H transition in COMPASS tokamak, at q 95 ∼ 3, β N 1, and using EF coils on high-field side vessel. A for penetration subsequent identified, which no significant...
This paper presents a survey of the experiments on runaway electrons (RE) carried out recently in frames EUROFusion Consortium different tokamaks: COMPASS, ASDEX-Upgrade, TCV and JET. Massive gas injection (MGI) has been used scenarios for RE generation small medium-sized tokamaks to elaborate most efficient reliable ones future experiments. New data generated at disruptions COMPASS ASDEX-Upgrade was collected added JET database. Different accessible parameters disruptions, such as current...