Development of a Charge Sensitive Preamplifier for Proportional Counter

This research work is aimed to develop a low cost preamplifier module for proportional counter. The RC-type charge sensitive preamplifier of 235 mV/Mion-pair sensitivity at the maximum operating HV bias of 3 kV was designed and constructed. An operational amplifier with 300 V/ms slew rate and low noise was employed for charge integrator at the first stage and followed by a selectable voltage gain amplifier at second stage. The 3.3 pF NPO capacitor in parallel with 30 MΩ resistor, RC feedback, was selected for 100 μs decay time. The developed preamplifier was tested for x-ray spectrometry in conjunction with the Ar gas filled proportional detector. The tested results showed the energy pulse height linearity of R2 = 0.9995 over the energy range up to 23.5 keV, the charge rate limit at 1x10-7 C/s and less than 750 μVrms noise at 0 pF input capacitance were obtained