A low noise highly integrated bolometer array for absolute measurement of VUV and soft x radiation

Abstract

A new low noise miniaturized multichannel bolometer module for absolute measurements in the VUV and soft x spectral ranges is described. Highly integrated four-channel modules (2×3.3×1.5 cm3) each comprising four independent ac-excited (50 kHz) metal resistor bolometer bridges were successfully tested on a large tokamak (Tore Supra in Cadarache) and on an electron synchrotron (BESSY in Berlin). The bolometer system features a linear response to the absorbed radiation power, a low detection limit (≤1.0×10−6 W cm−2 on Tore Supra with an integration time of τint=10×10−3 s) and a low NEP (≤10×10−9 W on BESSY). The thermal cross-talk between adjacent detectors is negligible (<0.003) and a low thermal drift ΔUBr/ΔT < 10−4 V °C−1 is achieved. It can be operated at a maximum temperature of 150 °C, at high magnetic fields (tested up to B=4.5 T in the laboratory) and survives high nuclear radiation doses. The system offers the possibility of detecting low-power VUV and soft x-radiation with sampling rates of up to 10 kHz on plasma machines and of absolutely calibrating VUV and soft x instruments. Effective suppression of electric, thermal and nuclear radiation interferences is characteristic of the bolometer system.Strain gauge effects, which could affect the behavior of the bolometers at high magnetic fields, are suppressed by the ac-excitation technique.

Data acquisition and real-time signal processing of plasma diagnostics on ASDEX Upgrade using LabVIEW RT

“…The digitized signals of up to 128 channels are transferred serially to a single PXI 7813R FPGA card with 4 x 40 DIO connectors from four modules. The raw signal from four bolometer channels during a discharge is shown in Fig 1. In comparison with the AC system previously described [18], the offset compensation is greatly simplified. The AD7730 has several features including the ability to correct the DC bridge offset due to a mismatch of the meander resistances, ratiometric measurement of the bridge voltage and square wave excitation which avoids complications arising from cable capacitance when using AC excitation.…”

“…The temperature increase of the bolometer foil, resulting from heating of the four micron thick platinum absorber by radiated power from the plasma, is measured as a voltage difference on a Wheatstone bridge [18] using the AD7730 (Analog Devices) bridge amplifier. A 5 V square wave at 2 kHz is applied to the Wheatstone bridge arrangement of a bolometer foil [19].…”

Development of an automated method for in situ measurement of the geometrical properties of the ITER bolometer diagnostic

“…A bolometer measures the plasma radiation over a wide spectral range (from soft-X to the infrared) by monitoring the temperature rise induced by deposition of photon energy in the absorber layer of the bolometer. The reference detector type chosen for ITER is the metal resistor bolometer [1,2]. In order to derive the spatially resolved radiation emission profile from the line integrated measurements tomographic reconstruction methods are applied to the measurements of many lines-of-sight (e.g.…”

Investigation of the Neutral Gas Pressure Effect on the Metal Resistive Bolometer

“…The bolometer system planned for W7-X consists mainly of metal (Au) resistive detector arrays [1] already widely used for other devices [2][3][4]. In addition to measuring the total radiated power, the bolometer system is capable of performing tomographic reconstruction of spatial radiation distribution.…”