A gamma-ray detector system of large NaI(Tl) crystals has been constructed to investigated heavy ion reaction mechanisms and highly excited nuclear structure with heavy ion beams. The NaI(Tl) crystals have as a whole a cross section of hexagonal shape of 30 cm between the parallel sides and a length of 20 cm, and are composed of seven substructures based on a honeycomb shape. This is designed for detection of high energy gamma rays with high resolution, and also for use as an anti-Compton spectrometer for a Germanium detector. A good energy resolution of 2.7 (3.2)% fwhm was obtained for 22.3 MeV gamma rays with 18 (39)% detection effeciency of the full-energy-loss peak with anti-Compton mode (sum mode) operation of the trapezoidal NaI(Tl) crystals. Compton scattering background in a spectrum by a Ge detector was successfully reduced by about 60% in applying the trapezoidal NaI(Tl) crystals for Compton suppression. The performance of the spectrometer is discussed.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics