Direct Determination of Neutron Capture on the s-Process of 127I and 133Cs at the CSNS Back-n facility

The cross sections of 127I(n,gamma)128I and 133Cs(n,gamma)134Cs play a critical role in the s-process of nuclear astrophysics, the Iodine-Xenon (I–Xe) chronometer for providing the information on early meteorite evolution, and understanding the performance of CsI crystal detectors for Dark Matter Detection Experiment and Coherent Elastic Neutrino-Nucleus Scattering (CEνNS) experiments.  The neutron capture cross sections of 127I and 133Cs were measured from thermal to 1 MeV using the time-of-flight (TOF) method at China Spallation Neutron Source (CSNS) back-n facility, with gamma rays detected by C6D6 detectors. The neutron capture yield was derived via the pulse-height weighting technique (PHWT) based on the total energy detection principle. In the resolved resonance region (RRR), some new resonance peaks of 133Cs(n,gamma) were observed for the first time. Resonance parameters for 128I and 134Cs were extracted using the SAMMY code from 1 eV to 4 keV.