Extended Data Fig. 4: Experiment details.
From: Direct observation of the Migdal effect induced by neutron bombardment
a, b, rendered view of the experiment. c, neutron spectrum. d, gamma spectrum. Several prominent peak structures are observed in the gamma spectrum: the peak at 0.5 MeV originates from electron positron annihilation, the peak at 0.8 MeV is speculated to arise from the emission line of 56Fe in the neutron generator casing, the peak at 1.4 MeV is hypothesized to result from activated 40K, and the peak at 2.2 MeV is attributed to the neutron capture process by hydrogen in polyethylene. e, f, the calibration result of the detector gain during each day of the experiments. g, h, the variations in the counting rate of the Migdal detector in two runs, as well as the neutron beam monitoring status by LSs. The neutron counts from LSs are normalized to the counting rate of the Migdal detector, with the dashed line representing the average counting rate. i, Run I detector I, j, Run II detector I, k, Run II detector II temperature (T) and pressure (P) within the chamber during the operation of the Migdal detector. P/T reflects the stability of the gaseous environment throughout the detector’s operational period.
