Observation of Neutron-Induced Signals Using Two-Dimensional Micro-Pixel Gas Chamber

A gas-based neutron detection system which reads out individual channels with a micro-pixel detector element was constructed, and preliminary neutron irradiation tests were conducted. The detection system consisted of a micro-pixel detector element, a gas chamber that had feedthroughs for lines of 541 channels, amplifier-shaper-discriminator boards, position encoders with field programmable gate arrays, and a device capable of fast data acquisition. The micro-pixel detector element pulses had a short duration, the full width at half maximum of the pulse being 160 ns. Its gas gain was about 50 with an anode-cathode voltage of 560 V and a gas pressure of 0.5 MPa (0.45 MPa for He and 0.05 MPa for CF₄). Signal pulse peaks of neutrons could be identified. The neutron detection system could easily distinguish neutron signals from other signals arising from electronic noise, gamma events, etc. The gas gain of the micro-pixel detector element did not change for 240 min in our irradiation test.