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First dedicated observations of runaway electrons in the COMPASS tokama

Vlainić M., Mlynář J., Weinzettl V., Papřok R., Imríšek M., Ficker O., Vondráček P., Havlíček J.

Nukleonika

2015

Vol. 60, No. 2

249--255

Runaway electrons present an important part of the present efforts in nuclear fusion research with respect to the potential damage of the in-vessel components. The COMPASS tokamak a suitable tool for the studies of runaway electrons, due to its relatively low vacuum safety constraints, high experimental flexibility and the possibility of reaching the H-mode D-shaped plasmas. In this work, results from the first experimental COMPASS campaign dedicated to runaway electrons are presented and discussed in preliminary way. In particular, the first observation of synchrotron radiation and rather interesting raw magnetic data are shown.

Estimation of ISTTOK runaway - electrons energies by means of a Cherenkov - type probe with modified AlN radiators

Jakubowski L., Plyusnin V. V., Sadowski M. J., Zebrowski J., Malinowski K., Rabiński M., Fernandes H., Silva C., Duarte P., Jakubowski M.

Nukleonika

2012

Vol. 57, No. 2

177-181

Measurements of fast electrons, as performed during recent few years in small tokamaks, demonstrated that detectors based on the Cherenkov effect are very useful tools for such studies. The modernized measuring heads, which were equipped with miniature aluminum-nitride (AlN) radiators, enabled to determine locations and instants of the fast electrons emission and to estimate their energy. A comparison of four measuring channels showed that in ISTTOK the most important role was played by electrons of energy less than 90 keV.

Generation and diagnostics of fast electrons within tokamak plasma

Sadowski M. J.

Nukleonika

2011

Vol. 56, No. 2

85-98

The first part of this invited paper is devoted to mechanisms of the production of fast electrons in plasma experiments involving magnetic traps of the tokamak type. The phenomenon of generation of the so-called runaway electrons - which may reach energies up to several dozen MeV - is considered and basic characteristics of such electrons are described. In particular, the orbits of the runaway electrons and their energy limits are presented. Problems related to the cross-field transport in tokamak plasmas and interactions of the relativistic electrons with plasma oscillations are also considered. Production of the so-called ripple-born electrons, which may be observed in the energy range from approximately 50 keV to several hundreds keV, is analyzed separately. In the second part of this paper various diagnostic methods used for investigation of the runaway and ripple-born electrons are presented. Various techniques are described, which are based on different reactions induced by the runaway electrons, e.g., the emission of X-rays or neutrons, or the synchrotron radiation. Finally, a modern technique of electron measurements is described, which was developed by the author's team at the Andrzej Sołtan Institute for Nuclear Studies (IPJ) in Świerk (Poland), and which is based on the use of Cherenkov-type detectors. Examples of applications of the discussed techniques in different tokamak experiments are described. Particular attention is paid to the Cherenkov detectors, which have already been used in experiments at the small-size CASTOR device in Prague (Czech Republic), the ISTTOK machine in Lisbon (Portugal), as well as in the larger TORE-SUPRA facility in Cadarache (France).