Radiation distributions in TCV

Abstract

Tomographically reconstructed total radiative powers from bolometer and AXUV camera systems are compared to SOLPS5 simulations in low and high density deuterium and helium diverted discharges on the TCV tokamak. For low density the match between simulation and measurements is satisfactory, but at high density strongly radiating regions outside the SOLPS5 simulation grid are seen in measurements and maybe due to enhanced convective particle transport in the low field side midplane region. The chord coverage of the foil bolometer system does not, however, allow detailed resolution in this region. The comparison of foil and AXUV data also demonstrates that ageing of the AXUV diodes under plasma irradiation combined with the unevenness of the diode spectral response, strongly limits their application for total radiative power measurements.

Application of AXUV diode detectors at ASDEX Upgrade

“…To achieve a time resolution of a few microseconds, semiconductor based wide spectral range radiation meaa) Electronic mail: matthias.bernert@ipp.mpg.de surements are used in other tokamak experiments such as Alcator C-Mod 4,5 , DIII-D 6 and TCV 7 . An extensive set of these AXUV diodes was recently installed at the ASDEX Upgrade tokamak (AUG) 8 .…”

Determination of electron thermal diffusivity at the WEGA stellarator

“…It is noteworthy that only the Au-resistive bolometer could be used for measuring the radiative power loss. Because of aging effects [10], the sensitivity of the diode array did not correspond to the calibration in the relevant wavelength range. The ECRH-modulation experiments are carried out when the OXB-heated plasma reaches a stationary state.…”

“…"Particles" representing in our case a certain amount of energy are started from the power deposition zone and weighted by . They are traced in Cartesian coordinates as (9) , (10) where [x t ,,y t ] is the location of a Monte Carlo "particle" at the time t and [x t+ ,y t+ ] is the termination after a small time step . and are two independent random numbers taking the value of 1 with equal probability of 50%.…”

Fast radiation dynamics during ELMs on TCV

“…Multiple camera systems consisting of several photodiode arrays and allowing for radiation detection along several lines of sight, enable tomographic inversion of the measured signal and the computation of the 2D radiation distribution. Just such an array of pinhole cameras has recently been installed on TCV [4] providing high spatial resolution across the whole poloidal cross-section.…”

“…Put another way, this means that the derived 2D radiation distributions are objective and quantitative. A new array of fast radiation detectors based on AXUV diodes (manufacturer: International Radiation Detectors [2]) has recently come into operation on the TCV tokamak [3,4]. It comprises 7 individual cameras providing 140 lines of sight encompassing the entire poloidal cross-section and is equipped with amplification and acquisition electronics permitting time resolution up to 5 µs.…”