Contents I. Introduction
Microstrip GAS CHAMBERs (MSGCs) have been extensively developed for neutron detection with characteristics of high spatial resolution, high detection efficiency, and high count rate [1], [2]. In order to achieve optimal performance, we adopted a system with the capability of track discrimination of the secondary particles (proton and triton) created in the nuclear reaction [3]. In this detector system, the signals from each strip are amplified, pulse shaped, and individually digitized by discriminators. The number of strips with signals higher than the threshold level (suprathreshold strips) for proton is larger than that for triton, hence allowing proton and triton to be discriminated according to their numbers, and the system can measure the incident position of neutrons using the position of the suprathreshold strip by triton that is located nearest the incident position of the neutron [4], [5]. A high spatial resolution of less than 1 mm could be realized by this system regardless of the track length of the secondary particles (i.e., without requiring a large amount of a heavy gas such as ), but it is still necessary to achieve an adequate gas gain to ensure the clear discrimination of the secondary particles. A bias voltage of anode strips required to achieve an adequate gas gain increases significantly when a gas pressure of helium-3 increases, thus degrading the stability of the detector system. To address these problems, pre-gas-amplification devices (PGADs) are effective because they improve the gas gain of such detection systems and reduce a gas-gain load for the anodes.
