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Detekční systémy pro měření vyzařování vysokoteplotního plazmatu tokamaku COMPASS na bázi rychlých bolometrů a měkkých rentgenových detektorů
Vácha, Miroslav ; Weinzettl, Vladimír (advisor) ; Piffl, Vojtěch (referee)
Title: Detection systems for measurements of high-temperature plasma radiation on the COMPASS tokamak by fast bolometers and soft X-ray detectors Author: Miroslav Vácha Department: Institute of Particle and Nuclear Physics Supervisor: Mgr. Vladimír Weinzettl, Ph.D., Institute of Plasma Physics AS CR, v.v.i. Supervisor's e-mail address: vwei@ipp.cas.cz Abstract: Multi-channel spectroscopic diagnostics on the COMPASS tokamak com- prising AXUV-based bolometers, soft X-ray (SXR) and visible light detectors will cover a wide spectral range of the core and edge plasma emission, aiming to realize a fast tomography at microsecond time scales. This thesis reports on a development of the bolometric and SXR diagnostics. First, procedures of the detector selection and their tests are described. There the design and tests of the special complex port plug, com- bining both detection systems, taken into account a strongly limited available space, a heat protection and a shielding during a cleaning glow discharge, is also summarized. Development of new electronic amplifiers and their connection with the data acquisition system is documented. In the last chapters, basic methods for analysis of data collected using these diagnostic systems are introduced. Keywords: tokamak, plasma radiation, photodiode, tomography
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RE beam generation in MGI disruptions on COMPASS.
Ficker, Ondřej ; Mlynář, Jan ; Macúšová, Eva ; Vlainić, M. ; Weinzettl, Vladimír ; Urban, Jakub ; Čeřovský, Jaroslav ; Farník, Michal ; Markovič, Tomáš ; Papřok, Richard ; Vondráček, Petr ; Imríšek, Martin ; Tomeš, Matěj ; Havlíček, Josef ; Varju, Jozef ; Varavin, Mykyta ; Bogár, Ondrej ; Havránek, Aleš ; Gospodarczyk, M. ; Rabinski, M. ; Jakubowski, M. ; Malinovski, K. ; Zebrowski, J. ; Plyusnin, V. ; Papp, G. ; Pánek, Radomír ; Hron, Martin
In the experiments with the massive gas injection (MGI) triggered disruptions in the COMPASS tokamak, post-disruptive runaway electron (RE) beams are generated occasionally. In this contribution, a relatively large set of discharges from the recent years is analysed in order to improve our understanding of the processes behind the beam generation. It seems that despite the low toroidal field applied in the discharges (typically 1.15 T) the magnetic perturbations may be small enough to allow the acceleration and confinement of the electrons. The influence of the different components and different sections of the frequency spectrum of the magnetic perturbations on the beam generation and RE beam current is examined. Fast visible camera images are also analysed. The relevance of COMPASS runaway electron experiments for large machines is discussed. Moreover, the potential of less common diagnostic tools (Cherenkov detector, vertical ECE, ...) to clarify the role of the pre-disruption fast electron population and the influence of prompt runaway electron losses in the current quench is discussed using the recent test measurements.
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Detekční systémy pro měření vyzařování vysokoteplotního plazmatu tokamaku COMPASS na bázi rychlých bolometrů a měkkých rentgenových detektorů
Vácha, Miroslav ; Weinzettl, Vladimír (advisor) ; Piffl, Vojtěch (referee)
Title: Detection systems for measurements of high-temperature plasma radiation on the COMPASS tokamak by fast bolometers and soft X-ray detectors Author: Miroslav Vácha Department: Institute of Particle and Nuclear Physics Supervisor: Mgr. Vladimír Weinzettl, Ph.D., Institute of Plasma Physics AS CR, v.v.i. Supervisor's e-mail address: vwei@ipp.cas.cz Abstract: Multi-channel spectroscopic diagnostics on the COMPASS tokamak com- prising AXUV-based bolometers, soft X-ray (SXR) and visible light detectors will cover a wide spectral range of the core and edge plasma emission, aiming to realize a fast tomography at microsecond time scales. This thesis reports on a development of the bolometric and SXR diagnostics. First, procedures of the detector selection and their tests are described. There the design and tests of the special complex port plug, com- bining both detection systems, taken into account a strongly limited available space, a heat protection and a shielding during a cleaning glow discharge, is also summarized. Development of new electronic amplifiers and their connection with the data acquisition system is documented. In the last chapters, basic methods for analysis of data collected using these diagnostic systems are introduced. Keywords: tokamak, plasma radiation, photodiode, tomography
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Plasma Boundary Reconstruction using Fast Camera on the COMPASS Tokamak
Háček, Pavel ; Berta, Miklós ; Stöckel, Jan ; Weinzettl, Vladimír ; Budai, C. ; Szabolics, T. ; Bencze, A.
Determination of the plasma boundary is an important task for safe operation of the tokamak and diagnostic systems as well as for correct interpretation of the measured data. Magnetic reconstruction codes routinely used to determine the shape of the plasma have a number of limitations which can make the reconstruction problematic. Recently, it has been demonstrated on several devices that it is possible to provide independent measurement of the plasma boundary by observation of the visiblelight emission using fast framing cameras. In the presented work, a single fast camera on the COMPASS tokamak was used for reconstruction of the optical plasma boundary, assuming a toroidally symmetric visible-light emission profile located in the edge of plasma. As a first result, application of the method on D-shaped COMPASS shot 7145 and its comparison with magnetic reconstruction from the EFIT code is given. Both methods show good agreement with average difference 0.5 cm.
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Global Power Balance in Non-Stationary Discharge Phases in the COMPASS Tokamak
Havlíček, Josef ; Imríšek, Martin ; Kovařík, Karel ; Weinzettl, Vladimír
The global power balance between different input power and sink/loss channels is important for understanding of tokamak physics, particularly for various scaling laws. The power balance is measured easily during stationary discharge phases because the terms for both magnetic field energy and plasma thermal energy build-up can be neglected. However, many important events in tokamak plasmas occur during non-stationary phases of the discharge. This article describes, quantifies and discusses the terms of the global power balance, including time dependent parts, and exemplifies them on the typical ohmic discharge of the COMPASS tokamak.
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New Detection System for Fast Density Measurements Using the Lithium Beam on the COMPASS Tokamak
Háček, Pavel ; Berta, M. ; Stöckel, Jan ; Weinzettl, Vladimír ; Anda, G. ; Bencze, A. ; Zoletnik, S.
The lithium beam diagnostic at COMPASS is designed for measurements of the edge plasma density profile and fluctuations and edge plasma current fluctuations. The principle of the diagnostic is detection of light coming from collisionally excited Li atoms — beam emission spectroscopy (BES) - and a direct detection of the ionized part of the beam (atomic beam probe — ABP). For slow density measurements a charged coupled device (CCD) camera has been installed and is already working. For fast twodimensional density profile and density fluctuation measurements an array of avalanche photodiode detectors (APDs) will be used. The two-dimensional resolution of the measurement will be possible using fast poloidal deflection and chopping of the beam. Apart from routine density profile measurement, the diagnostic will be capable of investigating the turbulent structures in the edge plasma by cross-correlating the signals coming from poloidally deflected virtual beams.
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