Particle identification technique using grid ionization chamber at China Spallation Neutron Source

Back-n white neutron source at China Spallation Neutron Source facility requires a detector with charged-particle identification ability for measuring nuclear cross sections. Therefore, a grid ionization chamber (GIC) with an adjustable distance between the cathode and grid was designed and built. Moreover, a corresponding particle identification algorithm is proposed in order to use the signals of the anode (Q_A) and cathode (Q_C), or the signal (Q_A) of the anode and the time difference (Δ t) between the cathode and anode signals, based on the interactive behaviors of charged particles and the GIC's working principle. First, the GIC performance was measured using a ²⁴¹Am α  source for preliminary performance testing, which provided an energy resolution of 5.25%. Its good particle identification performance was demonstrated by identifying ³H and ⁴He from neutron reactions with ⁶Li using a 2D Q_C-Q_A plot and Δ t-Q_A plot. Furthermore, ³H and ⁴He can be completely distinguished from the updated 2D Q_C-Q_A plot and Δ t-Q_A plot, in which ³H with a small incident angle is selected. Finally, it was concluded that our GIC with the proposed particle identification algorithm could identify charged particles effectively for the future measurement of nuclear cross sections.