Runaway electron energy measurement using hard x-ray spectroscopy in “Damavand” tokamak

Abstract

Set of experiments has been developed to study existing runaway electrons in "Damavand" tokamak plasma upon characteristics of hard x-ray emissions produced by collision of the runaway electrons with the plasma particles and limiters. As a first step, spatial distribution of hard x-ray emissions on the equatorial plane of the torus was considered. Obtained spectra of hard x-ray emissions for different alignments of shielded detector indicate isotropic emissivity in the equatorial plane. This is in agreement with wide angle cone of bremsstrahlung radiations, deduced from the mean value of energy of the runaway electrons. The mean energy was calculated from the slope of the energy spectrum of hard x-ray photons. In the second stage in order to investigate time evolution of energy of the runaway electrons, similar technique were applied to obtain hard x-ray energy in every 3 ms intervals, from the beginning to the end of plasma. The mean energy of the runaway electrons increases during the ramp up phase and reaches its maximum between 3 and 9 ms after plasma formation. Also considering the time dependence of the counted photons in each energy range shows that energetic photons are emitted during the ramp up phase of the plasma current in Damavand tokamak.

Runaway electron energy determination by angular distribution of Cherenkov radiation

“…This leads to the fact that the photon escape angle of ChR at energies less than 0.7 MeV in the case of multiple 2020 JINST 15 C08025 scattering is shifted to smaller angles θ, in comparison with the case when multiple scattering is not taken into account (see figure 6). To evaluate the reliability of ChR angular distribution determination method, we used experimental results from paper [2]. In this work, X-ray spectra in different moments of time were obtained.…”

“…Also, RE carry important information about the behaviour of ionized and neutral particles in a tokamak volume. RE can have energies from tens keV to tens MeV and knowledge of their spectrum and time evolution is important for investigating of tokamak plasma [2][3][4][5][6][7][8].…”

“…The usual RE energy indication is based on measuring the spectrum of bremsstrahlung generated in tokamak chamber walls. In "Damavand" tokamak [2], where the electron spectra do not exceed 2 MeV, such indirect method was used. Information about RE spectra was obtained from X-ray radiation generated by bremsstrahlung and electron cyclotron emission processes.…”

Lanthanum Bromide (LaBr3(Ce)) based hard X-ray spectroscopic diagnostic for the study of runaway electrons at Aditya Tokamak

“…HX emissions are commonly observed at plasma breakdown or at major disruption for high temperature/density tokamak plasma devices [5]. However, a finite RE population may exist during the current flat-top [10]. Traditionally time evolution of HX fluctuation, qualitative measurements, is employed for the correlation studies with the plasma performance [11,12].…”

Simulation of open-loop plasma vertical movement response in the Damavand tokamak using closed-loop subspace system identification

“…Damavand tokamak is a small size tokamak and like other small size tokamaks in the world is a suitable device to perform research on fusion related subjects such as plasma diagnostics [13][14][15][16], control feedback systems and power electronics [10][11][12]. In the Damavand tokamak, hydrogen plasma is sustained for 21 ms with a plasma current peak of about 35 kA [10].…”