J. Mlynar

6603814421

Publications - 4

Overview of the COMPASS results

S. Brezinsek M. Gobbin W. Bin K. Bogár I. Borodkina P. Buratti J. Seidl M. Peterka A. Kallenbach N. Patel O. Kovanda A. Podolnik I. Ďuran M. Dimitrova P. Bilková R. Roccella A. Casolari C. Castaldo M. Hron J. Čaloud J. Gerardin M. Berta T. Markovic A. Devitre M. Komm O. Grover E. Macúšová V. Yanovskiy F. J. Artola S. Atikukke P. Hacek None Fuková E. Gauthier M. Jirsa P. Junek E. Matveeva D. Cipciar J. Mlynar D. Naydenkova J. Matějíček K. Kovarik I. Mysiura F. Napoli J. K. Park M. Poradzinski J. Preinhaelter P. Kulhánek M. Lehnen N. Lemoine G. Mazzitelli D. Šesták M. Rabinski A. Marin Roldan X. Litaudon Y. Q. Liu J. Adamek J. Horacek D. Tskhakaya A. Prishvitsin R. Pánek P. Barton P. Mácha R. Dejarnac F. Brochard J. Havlicek A. Havranek J. Čečrdle J. Čeřovský C. Hidalgo P. Lourenco K. Hromasová O. Hronova M. Iafrati N. Isernia R. Pitts S. Entler M. Farník H. Fernandes G. Grenfell Y. Gribov M. Grof L. Kripner T. Loarer A. Loarte N. C. Logan L. Krlín P. Böhm J. Cavalier O. Ficker M. Imrišek F. Jaulmes M. Jeřáb D. Réfy J. Krbec O. Bogár S. Lukes P. Pavlo A. Bencze J. P. Gunn D. Fridrich

Publication Name: Nuclear Fusion

Publication Date: 2022-04-01

Volume: 62

Issue: 4

Page Range: Unknown

Description:

COMPASS addressed several physical processes that may explain the behaviour of important phenomena. This paper presents results related to the main fields of COMPASS research obtained in the recent two years, including studies of turbulence, L-H transition, plasma material interaction, runaway electron, and disruption physics: Tomographic reconstruction of the edge/SOL turbulence observed by a fast visible camera allowed to visualize turbulent structures without perturbing the plasma. Dependence of the power threshold on the X-point height was studied and related role of radial electric field in the edge/SOL plasma was identified. The effect of high-field-side error fields on the L-H transition was investigated in order to assess the influence of the central solenoid misalignment and the possibility to compensate these error fields by low-field-side coils. Results of fast measurements of electron temperature during ELMs show the ELM peak values at the divertor are around 80% of the initial temperature at the pedestal. Liquid metals were used for the first time as plasma facing material in ELMy H-mode in the tokamak divertor. Good power handling capability was observed for heat fluxes up to 12 MW m-2 and no direct droplet ejection was observed. Partial detachment regime was achieved by impurity seeding in the divertor. The evolution of the heat flux footprint at the outer target was studied. Runaway electrons were studied using new unique systems - impact calorimetry, carbon pellet injection technique, wide variety of magnetic perturbations. Radial feedback control was imposed on the beam. Forces during plasma disruptions were monitored by a number of new diagnostics for vacuum vessel (VV) motion in order to contribute to the scaling laws of sideways disruption forces for ITER. Current flows towards the divertor tiles, incl. possible short-circuiting through PFCs, were investigated during the VDE experiments. The results support ATEC model and improve understanding of disruption loads.

Open Access: Yes

DOI: 10.1088/1741-4326/ac301f

Progress in diagnostics of the COMPASS tokamak

V. Weinzettl J. Seidl M. Peterka R. Paprok A. Podolnik P. Vondráček T. Krizsanóczi M. Stano M. Dimitrova P. Bilková N. Vianello M. Sos J. Varju M. Tomes M. Varavin M. Hron J. Zajac F. Zacek M. Berta T. Markovic A. Devitre M. Komm O. Grover P. Hacek E. Gauthier E. Matveeva J. Mlynar D. Naydenkova K. Kovarik M. Rabinski J. Adamek J. Stöckel J. Horacek R. Pánek R. Dejarnac J. Havlicek A. Havranek R. Gomes M. Vlainic A. Silva S. Zoletnik P. Böhm J. Cavalier O. Ficker G. Anda M. Imrišek D. Dunai D. Réfy T. Pereira Tsv Popov D. Sarychev G. P. Ermak J. Zebrowski M. Jakubowski J. Krbec S. Nanobashvili M. Spolaore O. Bogár K. Mitošinková K. Malinowski J. P. Gunn D. Fridrich

Publication Name: Journal of Instrumentation

Publication Date: 2017-12-07

Volume: 12

Issue: 12

Page Range: Unknown

Description:

The COMPASS tokamak at IPP Prague is a small-size device with an ITER-relevant plasma geometry and operating in both the Ohmic as well as neutral beam assisted H-modes since 2012. A basic set of diagnostics installed at the beginning of the COMPASS operation has been gradually broadened in type of diagnostics, extended in number of detectors and collected channels and improved by an increased data acquisition speed. In recent years, a significant progress in diagnostic development has been motivated by the improved COMPASS plasma performance and broadening of its scientific programme (L-H transition and pedestal scaling studies, magnetic perturbations, runaway electron control and mitigation, plasma-surface interaction and corresponding heat fluxes, Alfvenic and edge localized mode observations, disruptions, etc.). In this contribution, we describe major upgrades of a broad spectrum of the COMPASS diagnostics and discuss their potential for physical studies. In particular, scrape-off layer plasma diagnostics will be represented by a new concept for microsecond electron temperature and heat flux measurements - we introduce a new set of divertor Langmuir and ball-pen probe arrays, newly constructed probe heads for reciprocating manipulators as well as several types of standalone probes. Among optical tools, an upgraded high-resolution edge Thomson scattering diagnostic for pedestal studies and a set of new visible light and infrared (plasma-surface interaction investigations) cameras will be described. Particle and beam diagnostics will be covered by a neutral particle analyzer, diagnostics on a lithium beam, Cherenkov detectors (for a direct detection of runaway electrons) and neutron detectors. We also present new modifications of the microwave reflectometer for fast edge density profile measurements.

Open Access: Yes

DOI: 10.1088/1748-0221/12/12/C12015

Plasma tomographic reconstruction from tangentially viewing camera with background subtraction

M. Berta G. Verdoolaege P. Hacek T. Odstrčil M. Odstrčil T. Szabolics J. Mlynar A. Bencze V. Weinzettl

Publication Name: Review of Scientific Instruments

Publication Date: 2014-01-01

Volume: 85

Issue: 1

Page Range: Unknown

Description:

Light reflections are one of the main and often underestimated issues of plasma emissivity reconstruction in visible light spectral range. Metallic and other specular components of tokamak generate systematic errors in the optical measurements that could lead to wrong interpretation of data. Our analysis is performed at data from the tokamak COMPASS. It is a D-shaped tokamak with specular metallic vessel and possibility of the H-mode plasma. Data from fast visible light camera were used for tomographic reconstruction with background reflections subtraction to study plasma boundary. In this article, we show that despite highly specular tokamak wall, it is possible to obtain a realistic reconstruction. The developed algorithm shows robust results despite of systematic errors in the optical measurements and calibration. The motivation is to obtain an independent estimate of the plasma boundary shape. © 2014 AIP Publishing LLC.

Open Access: Yes

DOI: 10.1063/1.4862652

Overview of the COMPASS diagnostics

M. Aftanas V. Weinzettl I. Ďuran P. Bilková G. Veres M. Hron J. Zajac F. Zacek M. Berta P. Hacek J. Mlynar D. Naydenkova R. Melich D. Šesták J. Adamek F. Janky J. Brotankova J. Stöckel J. Horacek R. Pánek R. Dejarnac J. Havlicek R. Gomes M. Manso D. Jares J. Ghosh A. Szappanos V. F. Shevchenko R. Scannell V. K. Kiselov M. Walsh H. W. Müller V. Igochine A. Silva S. Zoletnik P. Böhm G. Anda Tsv Popov D. Sarychev S. Nanobashvili

Publication Name: Fusion Engineering and Design

Publication Date: 2011-10-01

Volume: 86

Issue: 6-8

Page Range: 1227-1231

Description:

The COMPASS tokamak, a divertor device with clear H-mode and ITER-relevant geometry, has been re-installed in IPP Prague after its transport from CCFE in UK. The first plasma was achieved in December 2008. Many new diagnostic tools with both high temporal and spatial resolutions have been developed to address the scientific programme of COMPASS focused on H-mode physics and pedestal investigations. In the paper, an overview of existing and in near future planned diagnostics (magnetic, spectroscopy, microwave, probe and beam/particle) on COMPASS is given including their basic technical specifications and achievements. © 2011 EURATOM. Published by Elsevier B.V. All rights reserved.

Open Access: Yes

DOI: 10.1016/j.fusengdes.2010.12.024