Nuclear Resonance Fluorescence Spectrometer Design and Detector Performance Analysis of Shanghai Laser Electron Gamma Source(SLEGS)

Nuclear resonance fluorescence(NRF) experiments can be used to study the low excitation energy levels of photonuclear reactions. Shanghai Laser Electron Gamma Source(SLEGS) designed and constructed a NRF spectrometer consisting of two large-scale coaxial high-purity germanium(HPGe, \phi 80 mm×70 mm) detectors and two CLOVER HPGe(4×\phi 50 mm×70 mm), the large-scale HPGe detectors obtained relative efficiency greater than 100% and energy resolution better than 0.3%@1 332 keV. The spectrometer adopts Mesytec MDPP-16 digital pulse processor and MVME acquisition system, which can read and record the amplitude and time information of the HPGe preamplifier output signal. The Add-back mode and Reduction mode of the CLOVER HPGe detector are studied. Results show that Add-back reconstruction can significantly improve the full-energy peak efficiency and peak-to-total ratio, the full-energy peak efficiency after Add-back reconstruction can be improved by more than 21% at 1 460 keV energy. The detector energy resolution is slightly degraded due to the coupling between multiple crystals introduced by the Add-back reconstruction. Whereas at reduction mode, it can reduce the compton peak, improve the peak-to-total ratio, and maintain the energy resolution as good as the Direct mode, however, a certain amount of full energy peak efficiency is lost.