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To measure the neutron spectra in a wide energy range at the China Spallation Neutron Source (CSNS), a time of flight (TOF) neutron spectrometer based on a fast ionization chamber (FIC) containing 6Li and 235U has been developed. Verification experiments have been performed at the BL09 test beam line at the CSNS, which demonstrated that the measured neutron spectra, analyzed with a spectrum-splicing technique, ranging from sub-meV to 10 keV with a limited flight path. Comparisons demonstrated that the integral thermal neutron fluence obtained by the TOF spectrometer and the cadmium difference activation measurements used were in good agreement. Moreover, the measured neutron spectra agreed well with the Monte Carlo simulations. This shows that the developed equipment and the measurement methods are reliable.

The effects of irradiation of 1-MeV electrons on p+–n GaAs/Ge solar cells have been investigated by temperature-dependent photoluminescence (PL) measurements in the temperature range of 10–290 K. The temperature dependence of the PL peak energy agrees well with the Varnish relation, and the thermal quenching of the total integrated PL intensity is well explained by the thermal quenching theory. Meanwhile, the thermal quenching of temperature-dependent PL confirmed that there are two nonradiative recombination centers in the solar cells, and the thermal activation energies of these centers are determined by Arrhenius plots of the total integrated PL intensity. Furthermore, the nonradiative recombination center, as a primary defect, is identified as the H3 hole trap located at Ev + 0.71 eV at room temperature and the H2 hole trap located at Ev + 0.41 eV in the temperature range of 100–200 K, by comparing the thermal activation and ionization energies of the defects.

Temperature-dependent photoluminescence (PL) measurements were carried out to investigate the irradiation effects of 1.0 MeV electrons on the n+- p GaInP top cell of GaInP/GaAs/Ge triple-junction solar cells in the 10–300 K temperature range. The PL intensities plotted against inverse temperature in an Arrhenius plot shows a thermal quenching behavior from 10 K to 140 K and an unusual negative thermal quenching (NTQ) behavior from 150 K to 300 K. The appearance of the PL thermal quenching with increasing temperature confirms that there is a nonradiative recombination center, i.e., the H2 hole trap located at Ev + 0.55 eV, in the cell after electron irradiation. The PL negative thermal quenching behavior may tentatively be attributed to the intermediate states at an energy level of 0.05 eV within the band gap in GaInP top cell.

Photoluminescence measurements were carried out to investigate the degradation for GaAs/Ge space solar cells which were irradiated with 1.0, 1.8, and 11.5 MeV electrons with fluences up to 3 × 1015 cm−2. The product of the defect introduction rate and the minority carrier capture cross section by electron irradiation-induced defects was determined with photoluminescence radiative efficiency related to the non-radiative recombination lifetime. Then the cross section was acquired according to the relation between the defect introduction rate and the non-ionizing energy loss. Furthermore, the non-radiative recombination could be identified among all the detected defects by comparing the cross section of the minority carrier capture.