A Compton-suppression spectrometer for γ-γ coincidence measurements: Large solid angle and excellent suppression

Abstract

For γ-γ coincidence measurements a Compton-suppression spectrometer with a large solid angle of 120 msr and excellent suppression has been designed. The dimensions of the NaI anticoincidence shield have been optimized by means of Monte Carlo calculations. The NaI shield has a length of 35 cm and a diameter of 30 cm. A 20% efficient HPGe crystal with a dead layer of 0.22 mm and a hollow core is used as central detector. For 60Co, the average suppression of the Compton background between 100 and 1100 keV amounts to 11.8 with a photopeak loss of 5.8%. The areas of the 1173 and 1332 keV peaks taken together amount to 60% of the total number of registered counts for the suppressed spectrum and to 15% for the non-suppressed spectrum. The spectrometer has been tested in a γ-γ coincidence experiment with the reaction 24Mg + (45 MeV)16O.