TESTING AND DEVELOPMENT OF A NOVEL PHOSWICH SCINTILLATOR DETECTOR FOR PARIS

LaBr(3)(Ce) is a novel scintillator that holds a lot of potential in gamma-ray spectroscopy due to its high energy resolution and timing properties, despite exhibiting self-activity due to the (138)La isotope in the crystal (0.09% abundance). However, due to the high cost of these scintillators, a phoswich detector was acquired as a more cost effective approach to constructing the new Photon Array for the study of Radioactive Ion and Stable beams (PARIS), intended for the SPIRAL2 beam-line at GANIL. Tests on the timing and energy response of a 1 '' x 1 '' x 2 '' LaBr(3)(Ce) and 1 '' x 1 '' x 6 '' CsI(Na) phoswich detector is presented. Little is known about what happens to these crystals during neutron activation, and this was also investigated, where the study of the pulse shapes from neutron and gamma sources were used to show that (n, gamma) discrimination was not possible. An activated spectrum from a (241)Am/(9)Be source was acquired where neutron activation due to excited states of lanthanum and bromine ((140)La, (80)Br and (82)Br) were found. The timing of the phoswich was also investigated, and found to be similar to 650 Ps when used in a start-stop set-up with BaF(2). A marginal improvement of around 40 Ps was achieved despite the set-up being poorly time matched.