Energy-resolution Study of Frisch-grid Ionization Chamber Using Multi-wire Proportional Chamber Readout

A Frisch-grid ionization chamber detector based on multi-wire proportional chamber readout is built. It is equipped with avalanche amplification while retaining the shielding characteristics of the Frisch-grid ionization chamber to pre-amplify the primary ionization signal inside the detector, improve the signal-to-noise ratio, and improve the energy resolution of the detector, especially for particles with low energy deposition in the detector drift region. In order to study the performance of the detector, the energy resolution and the variation of gain with anode voltage were tested in detail using a ²⁴¹Am source at different air pressures, different deposition energy, and different anode mental wire diameters. Electronical noise and detector gain and its fluctuations determine the variation of detector energy resolution. The operating voltage corresponding to the best energy resolution of the detector is related to the energy of the incident particles deposited in the detector drift region, and the lower the deposition energy, the higher the corresponding best operating voltage and the higher the gain of the detector. The energy resolution can reach 1.45% for a ²⁴¹Am source of 5.486 MeV. In practical applications, the operating voltage of the detector should be set according to the energy interval of the measured particles, so that its gain is in the appropriate range to achieve better energy resolution and meet the demand for particle detection.