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Electronics for Liquid Argon Pollution Tests of the Atlas Detector Materials at IBR-2 Reactor in Dubna A. Cheplakov, V. Golikov, S. Golubyh, V. Kukhtin, E. Kulagin, 1 Universite de Montreal, Montreal
(Quebec) H3C 3J7, Canada The electronics of the liquid argon purity monitor system are described in the article. It consists of -cell, preamplifier and apparatus for measurements. High voltage of +(0-2) kV is applied to the anode of the -cell. An 241Am -source with an activity of 7.7 kBq/4 is deposited on the cathode and used for the electron production in the liquid argon gap of 0.7 mm in between the anode and cathode. The anode signal is read by a charge-sensitive preamplifier. The preamplifier box for the period of measurements is mounted on the warm flange of the cryostat and connected to the anode via a 100 Ohm cable 0.5 m long. It is linked to the measurement equipment (pulse generator, shaper, oscilloscope, ADC, HV power supply, computer) located in the counting room by coaxial cables 30 m long. The aim of the experiments is to study possible degradation of the signal caused by the irradiation of samples immersed in the liquid argon cryostat. For this purpose, the ADC spectra are recorded for various values of the high voltage in the range of 2-29 kV/cm. Then, it becomes possible to determine the -peak position and to obtain the HV dependence of the charge value measured by the purity monitor. |