Use of Cherenkov-type detectors for measurements of runaway electrons in the ISTTOK tokamak

Abstract

Gas, fluid, or solid Cherenkov-type detectors have been widely used in high-energy physics for determination of parameters of charged particles, which are moving with relativistic velocities. This paper presents experimental results on the detection of runaway electrons using Cherenkov-type detectors in the ISTTOK tokamak discharges. Such detectors have been specially designed for measurements of energetic electrons in tokamak plasma. The technique based on the use of the Cherenkov-type detectors has enabled the detection of energetic electrons (energies higher than 80 keV) and determination of their spatial and temporal parameters in the ISTTOK discharges. Obtained experimental data were found in adequate agreement to the results of numerical modeling of the runaway electron generation in ISTTOK.

Characteristics of four-channel Cherenkov-type detector for measurements of runaway electrons in the ISTTOK tokamak

“…• Detector characteristics were studied on a special test stand: moderately relativistic electron beam (6 MeV) generated by a linear electron accelerator; Energy of electrons corresponds to relativistic parameter 12<γ<13 (γ=(1-β 2 ) -1/2 , β = v e /c), which is obviously higher than detecting threshold of the AlN radiator [1]. • Radiators were separated by stainless steel plates and mounted inside a stainless steel box (See Figure);…”

“…A diagnostics capable of characterizing the runaway and super-thermal electrons has been developing on the ISTTOK tokamak. In previous paper [1] a use of single-channel Cherenkov-type detector with titanium filter for runaway electron studies in ISTTOK was reported. To measure fast electron populations with different energies a prototype of 4-channel detector with molybdenum filters was designed.…”

Correlation of Electron Beams and Hard X‐ray Emissions in ISTTOK Tokamak

“…It was earlier discussed [8] that the outward drift of the runaway electron orbit increases with an increase of the runaway energy [14,15]. The use was made of the conventional formula which determines a dependence of γ versus the initial runaway orbit radius (initial position) and plasma current…”

“…In the past a conventional theory of the runaway electrons generation was applied in order to explain the runaway regimes in the ISTTOK tokamak. The measurements by means of Cherenkov detectors within ISTTOK were initially performed with a single-channel measuring head [8,9]. The basis of a diagnostic technique, that was applied in tokamak studies by the NCBJ (National Centre for Nuclear Research) -former IPJ (Institute for Nuclear Research) -team several years ago [7], was the emission of the Cherenkov radiation by fast electrons in appropriate crystals.…”

Research on mutual influence of Cherenkov-type probes within the ISTTOK tokamak chamber

“…Sometimes mid-energy electrons (of energies amounting to hundreds of keV) can be produced during an auxiliary heating, and they become the reason for serious damages of plasma facing components and vacuum chamber walls of tokamaks [9]. Some experimental studies with the use of Cherenkov probes have already been performed in the ISTTOK tokamak facility [10][11][12][13]. Hence, it is of interest to determine how strong is an influence of the presence of a Cherenkov probe on plasma behaviour in this facility, and on responses of other probes.…”