Optimizing the Sensitivity of a GAGG:Ce-Based Thermal Neutron Detector

The neutron sensitivity of the cerium-doped gadolinium aluminum gallium garnet (GAGG:Ce) has been determined for five different scintillator volumes. The good y ray detection performance of GAGG:Ce potentially results in a background signal that hides the low-lying neutron-capture y rays from de-excitation of
¹⁵⁶
Gd and
¹⁵⁸
Gd when the detector volume, and therefore the total y ray absorption, is large. We have investigated the competition between the detection of the neutron signature and discrimination of the background y rays. A significant improvement in the neutron response has been demonstrated with a reduction in the scintillator volume. The peak-to-background ratio of the key neutron signature increased with decreasing scintillator thickness to a maximum value of 14 ± 3 for 50 μm. The limit of this correlation was not determined since the thinnest scintillator available (50 μm) is greater than the mean free path of a neutron in
¹⁵⁷
Gd (15.54 ± 0.09 μm).