Monte Carlo simulation of the response of some ionization chambers

In order to understand the effects of different parameters related to source, detector, detector-circuit, shaping network, etc. on the detector response, we have carried out Monte Carlo simulation of the response of pulse-type two-electrode parallel plate ionization chambers operating under the electron sensitive mode. These simulations have been carried out incorporating the physical processes, namely, generation of electron-ion pairs by ionization in the active volume of the detector, separation and acceleration of the charge carriers, transport of the charge carriers, induction of charges on the electrodes, pulse processing by preamplifier-amplifier shaping networks, etc. The simulations show that, for an overall loss of the pulse height due to the capacitive decay of the detector-circuit less than 2%, the electrode separation should only be about 20% higher than the range of the heavy ion, the time constant of the detector-circuit should be about forty-times the maximum electron collection time and the shaping time of the main amplifier should be higher than the maximum electron collection time. Taking the time constant of the pulse-shaping network higher than the maximum electron collection time makes the ballistic deficit negligible. (authors)