Neutron imaging detector based on the µPIC micro-pixel gaseous chamber

A neutron imaging detector employing the micro-pixel gaseous chamber (μPIC) and an FPGA (Field Programmable Gate Array)-based data acquisition system has been developed for applications in small-angle neutron scattering (SANS) and neutron radiography at high-intensity, pulsed neutron sources. A small amount of ³He added to the gas mixture is used as the neutron absorber, with a detection efficiency for thermal neutrons of up to 30%. Our FPGA program permits the simultaneous measurement of the track length and energy deposition for the resulting proton-triton tracks, allowing the separation of the proton and triton for improved position resolution. The detector features a spatial resolution of less than 120 μm, a time resolution of ~1 μs, and an effective gamma sensitivity of less than 10^-9. We report preliminary results from a third test experiment performed in February 2011 at the NOBORU beam line at the J-PARC spallation neutron source. We will also discuss ongoing efforts to optimize the gas mixture for improved position resolution and planned upgrades to the data acquisition system.