Effect of beryllium filter purity on x-ray emission measurements

Abstract

Beryllium foils of the purity grade typically specified for use as filters in soft x-ray (SXR) diagnostics may contain sufficient heavy element impurities to distort the energy transmission response of the filter. Electron microprobe analysis of the foils used in the Madison Symmetric Torus (MST) SXR tomography diagnostic revealed an impurity content of ∼0.3% fractional abundance by weight, comprised primarily of iron, zirconium, chromium, and nickel. These impurities lower the peak filter transmission in the energy range of the detector and alter the shape of the transmission curve. As a result, foil impurities introduce errors in any general measurement where radiation is being filtered. For example, neglecting the effect of impurities on filter transmission leads to large systematic errors (50%) in the electron temperature measured using the SXR double-filter technique on MST.

Soft x-ray tomography measurements in the Wendelstein 7-X stellarator

“…Another source for deviations of the camera amplitude profiles are the beryllium filters, that have thickness tolerances in the order of ∼4%. In addition the purity level is high with 99.4% however even small amounts of impurities in the filter can lead to integral differences of the total spectral response in orders of ∼10% [28].…”

Plasma electron temperature measurement by foil soft-X-Ray spectrometer installed on TUMAN-3M and Globus-M2 tokamaks

“…For example, it allows to study internal MHD-oscillations of plasma and to determine location of the surfaces with a rational value of the stability margin [1,2], to evaluate losses of electrons by using the electron-cyclotron emission ECE [3] and escaping electrons [4], ELM-events [5,6], to monitor L−H-transitions [7] and many more [8][9][10][11][12][13][14][15][16]. Such devices are widely used in the tokamaks JET [17], MAST [8], DIII-D [18], Asdex-Upgrade [19], PDX [20], NSTX [21][22][23], EAST [5], MST [24], TCV [25,26], COMPASS [27,28]. The measurement in X-ray devices is performed without interference into the process under study.…”

Измерение Электронной Температуры Плазмы Фольговым Рентгеновским Спектрометром, Установленным На Токамаках Туман-3м И Глобус-М2

“…Например, она позволяет исследовать внутренние МГД-колебания плазмы и определять расположение поверхностей с рациональным значением запаса устойчивости [1,2], оценивать потери электронов за счет электронно-циклотронной эмиссии ECE [3] и убегающих электронов [4], ELM-события [5,6], отслеживать L−Hпереходы [7] и многое другое [8][9][10][11][12][13][14][15][16]. Такие устройства широко применяются на токамаках JET [17], MAST [8], DIII-D [18], Asdex-Upgrade [19], PDX [20], NSTX [21][22][23], EAST [5], MST [24], TCV [25,26], COMPASS [27,28]. В рентгеновских устройствах измерение производится без вмешательства в ход изучаемого процесса.…”