Development of Two-dimensional Micro-pixel Gas Chamber Capable of Individual Line Readout for Neutron Measurement

An improved micro-pixel detector element that showed high voltage tolerance was fabricated, and irradiation experiments using a Cf-252 neutron source were conducted on it. A gas-based neutron detection system capable of individual line readout, consisting of the developed detector element, gas chamber, amplifier-shaper-discriminator boards, optical signal transmission device, and a fast data acquisition device, was constructed for the experiment. The neutron detection system can identify signal-pulse peaks of neutrons and easily distinguish the neutron signals from background noises. The measured gas gain was approximately 280 at the supplied anode-cathode voltage of 670 V and total pressure of 0.5 MPa (0.45 MPa of He-3 and 0.05 MPa of CF4). The gas gain did not decrease when the detection system was operated for 150 h. The average gain spread in two-dimensional imaging was 6.2%.