Neutron and gamma-ray discrimination based on pulse shape information and study of (p, n) reactions for isobaric analog states

Our group has been developing the PANDORA neutron detector. It is a one-dimensional position-sensitive neutron detector and can discriminate between neutrons and gamma rays using the difference in the decay time of their scintillation light. In order to demonstrate this discrimination and the ability to obtain clear neutron spectra, we measured isobaric analog states (IAS) via (p, n) reactions at 230 MeV for ²⁷Al, ⁹⁰Zr, ⁹³Nb, and ²⁰⁸Pb at RCNP. Neutron and gamma-ray events have been successfully separated using their decay-time difference, and clear IAS peaks have been observed. The reaction Q-values for the IAS transitions are expected to be inversely proportional to the target charge radii. Thus, the systematic study for targets with different mass numbers A has enabled us to experimentally confirm the proportionality between the nuclear radius and A^1/3. The present discrimination method uses the charge information corresponding to different decay-time components. We have been developing new Constant Fraction Time-Over-Threshold (CF-TOT) method using the timing information only. In the additional measurement using a neutron source, the data were collected by the SPADI data acquisition system (AMANEQ) and we have been trying to distinguish the different decay-time components by using the correlation between TOT and CF-TOT information. The current status of this development will be presented.