D. Dunai

33067488800

Publications - 9

Plasma edge current fluctuation measurements during the ELM cycle with the atomic beam probe at COMPASS

M. Berta G. Anda D. Dunai P. Hacek D. Réfy M. Aradi J. Krbec S. Zoletnik A. Bencze

Publication Name: 46th Eps Conference on Plasma Physics Eps 2019

Publication Date: 2019-01-01

Volume: Unknown

Issue: Unknown

Page Range: Unknown

Description:

No description provided

Open Access: Yes

DOI: DOI not available

Development of an ion beam detector for the atomic beam probe diagnostic

M. Berta G. Anda D. Dunai P. Hacek D. Réfy M. Aradi J. Krbec R. Pánek S. Zoletnik A. Bencze V. Weinzettl J. Stockel

Publication Name: Review of Scientific Instruments

Publication Date: 2018-11-01

Volume: 89

Issue: 11

Page Range: Unknown

Description:

The atomic beam probe diagnostic concept aims at measuring the edge magnetic field and through that edge current distribution in fusion plasmas by observing trajectories of an ion beam stemming from a diagnostic neutral beam. The diagnostic potentially has microsecond scale time resolution and can thus prove to be a powerful option to study fast changes in the edge plasma. A test detector has been installed on the COMPASS tokamak as an extension of the existing lithium beam diagnostic system. It employs a relatively simple concept of an array of conductive detection plates measuring the incident ion current, which is then amplified and converted to a voltage signal. The aim of the test detector is to experimentally examine the idea of the diagnostic and provide background data for design and installation of a final detector. Also, a numerical code based on the CUDA parallel computing platform has been developed for modeling lithium ion trajectories in the given COMPASS plasma discharges. We present the developments of the detector design and test measurements of the diagnostic performed both in a laboratory beam system and on the COMPASS tokamak.

Open Access: Yes

DOI: 10.1063/1.5044529

Advanced neutral alkali beam diagnostics for applications in fusion research (invited)

D. Réfy B. Tál G. Petravich G. I. Pokol M. Vécsei G. Anda D. Dunai M. Aradi O. Asztalos S. Bató G. Demeter S. Hegedus P. Hacek M. Berta A. Bencze T. Krizsanóczi M. Lampert G. H. Hu D. Nagy J. Németh M. Otte S. Zoletnik

Publication Name: Review of Scientific Instruments

Publication Date: 2018-10-01

Volume: 89

Issue: 10

Page Range: Unknown

Description:

Diagnosing the density profile at the edge of high temperature fusion plasmas by an accelerated lithium beam is a known technique since decades. By knowledge of the relevant atomic physics rate coefficients, the plasma electron density profile can be calculated from the relatively calibrated light profile along the beam. Several additional possibilities have already been demonstrated: Charge Exchange Resonance Spectroscopy (CXRS) for ion temperature/flow and Zeeman polarimetry for edge plasma current; therefore the Li-beam diagnostic offers a wealth of information at the plasma edge. The weaknesses of the method are the relatively faint light signal, background light, and technical difficulties of the beam injector which usually seriously limit the applicability. In this talk, we present systematic developments in alkali-beam diagnostics (Li, Na) for the injector and the observation system and detectors which resulted in strongly increased capabilities. Advanced systems have been built, and microsecond scale density profile, turbulence, and zonal flow measurement have been demonstrated. A novel edge current measurement technique has also been designed, and components have been tested with potential microsecond-scale time resolution. Additional possibilities of these advanced systems for spectral measurements (CXRS and various Zeeman schemes) are also discussed.

Open Access: Yes

DOI: 10.1063/1.5039309

Atomic Beam Probe diagnostic for plasma edge current measurements at COMPASS

M. Berta G. Anda D. Dunai P. Hacek D. Réfy M. Aradi M. Lampert J. Krbec M. Palánkai S. Hegedus B. Leskó J. Kádi D. Nagy R. Pánek S. Zoletnik A. Bencze V. Weinzettl

Publication Name: 45th Eps Conference on Plasma Physics Eps 2018

Publication Date: 2018-01-01

Volume: 2018-July

Issue: Unknown

Page Range: 1028-1031

Description:

No description provided

Open Access: Yes

DOI: DOI not available

Progress in diagnostics of the COMPASS tokamak

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

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

Lithium beam diagnostic system on the COMPASS tokamak

M. Berta G. Anda S. Bató D. Dunai T. Krizsanóczi T. Ilkei P. Hacek D. Réfy J. Krbec I. G. Kiss G. Veres S. Zoletnik A. Bencze

Publication Name: Fusion Engineering and Design

Publication Date: 2016-10-01

Volume: 108

Issue: Unknown

Page Range: 1-6

Description:

An improved lithium beam based beam emission spectroscopy system - installed on COMPASS tokamak - is described. The beam energy enhanced up to 120 keV for Atomic Beam Probe measurement. The size of the ion source is doubled, using a newly developed thermionic heater instead of the conventionally used heating (tungsten or molybdenum) filament. The neutralizer is also improved. It produces the same sodium vapor in a cell but minimize the loss condensing the vapor on a cold surface which is led back (in fluid state) into the sodium oven. This way we call it recirculating neutralizer. The observation system consists of a CCD camera and an avalanche photodiode array.

Open Access: Yes

DOI: 10.1016/j.fusengdes.2016.04.022

Li-BES detection system for plasma turbulence measurements on the COMPASS tokamak

M. Berta G. Anda D. Dunai P. Hacek D. Réfy A. Kovácsik J. Krbec M. Hron G. Veres R. Pánek S. Zoletnik A. Bencze V. Weinzettl

Publication Name: Fusion Engineering and Design

Publication Date: 2015-10-01

Volume: 96-97

Issue: Unknown

Page Range: 795-798

Description:

A new Li beam emission spectroscopy (Li-BES) diagnostic system with a ∼ cm spatial resolution, and with beam energy ranging from 10 keV up to 120 keV and a 18 channel Avalanche photo diode (APD) detector system sampled at 2 MHz has been recently installed and tested on the COMPASS tokamak. This diagnostic allows to reconstruct density profile based on directly measured light profiles, and to follow turbulent behaviour of the edge plasma. The paper reports technical capabilities of this new system designed for fine spatio-temporal measurements of plasma electron density. Focusing on turbulence-induced fluctuation measurements, we demonstrate how physically relevant information can be extracted using the COMPASS Li-BES system.

Open Access: Yes

DOI: 10.1016/j.fusengdes.2015.06.030

Concept of an atomic beam probe diagnostic on COMPASS tokamak

M. Berta G. Anda D. Dunai M. Aradi G. Veres S. Zoletnik A. Bencze

Publication Name: 36th Eps Conference on Plasma Physics 2009 Eps 2009 Europhysics Conference Abstracts

Publication Date: 2009-12-01

Volume: 33 E2

Issue: Unknown

Page Range: 1399-1402

Description:

No description provided

Open Access: Yes

DOI: DOI not available

Results of Joint Experiments and other IAEA activities on research using small tokamaks

N. Kirneva V. Vershkov M. Sokolov C. Silva D. Valcrcel R. Gonzales A. Fonseca B. Kuteev L. Petrov M. Kolokoltsov J. Herrera M. Nieto-Perez A. Czarnecka A. Talebitaher A. Melnikov P. Khorshid V. Soldatov C. R. Gutierrez Tapia R. Dejarnac P. Balan M. Hron H. Fernandes I. Ďuran D. Dunai J. Stockel J. Brotankova L. A. Berni E. Del Bosco J. Sentkerestiova M. Gryaznevich G. Van Oost E. Dufkova P. Peleman A. Sharnin V. Pavlov J. Ferreira R. Gomes M. Berta V. Weinzettl A. Malaquias B. Tl J. Zajac G. Mank F. J.R. Simes I. El Chama Neto H. Figueiredo N. Dreval D. Nurov A. W. Kraemer-Flecken B. Brotas P. Carvalho S. Zoletnik Y. Kuznetsov L. Ruchko H. Hegazy A. Ovsyannikov R. Coelho A. Duarte J. Santos H. Hegazy G. M. Vorobjev E. Sukhov A. Singh G. Kirnev V. Budaev J. Figueiredo G. Ramos L. I. Krupnik I. Nedzelski A. Neto

Publication Name: Nuclear Fusion

Publication Date: 2009-09-21

Volume: 49

Issue: 10

Page Range: Unknown

Description:

This paper presents an overview of the results obtained during the Joint Experiments organized in the framework of the IAEA Coordinated Research Project on 'Joint Research Using Small Tokamaks' that have been carried out on the tokamaks CASTOR at IPP Prague, Czech Republic (2005), T-10 at RRC 'Kurchatov Institute', Moscow, Russia (2006), and the most recent one at ISTTOK at IST, Lisbon, Portugal, in 2007. Experimental programmes were aimed at diagnosing and characterizing the core and the edge plasma turbulence in a tokamak in order to investigate correlations between the occurrence of transport barriers, improved confinement, electric fields and electrostatic turbulence using advanced diagnostics with high spatial and temporal resolution. On CASTOR and ISTTOK, electric fields were generated by biasing an electrode inserted into the edge plasma and an improvement of the global particle confinement induced by the electrode positive biasing has been observed. Geodesic acoustic modes were studied using heavy ion beam diagnostics on T-10 and ISTTOK and correlation reflectometry on T-10. ISTTOK is equipped with a gallium jet injector and the technical feasibility of gallium jets interacting with plasmas has been investigated in pulsed and ac operation. The first Joint Experiments have clearly demonstrated that small tokamaks are suitable for broad international cooperation to conduct dedicated joint research programmes. Other activities within the IAEA Coordinated Research Project on Joint Research Using Small Tokamaks are also overviewed. © 2009 IAEA, Vienna.

Open Access: Yes

DOI: 10.1088/0029-5515/49/10/104026