La and La/Ce Doped BaF_2 Crystals for Future HEP Experiments at the Energy and Intensity Frontiers Part II
In addition to La-doped barium fluoride (BaF_2) crystals, La/Ce co-doped BaF_2 crystals were also investigated at the California Institute of Technology, Pasadena, CA, USA. Strong cerium-induced emissions peaked at 305 and 320 nm with a decay time of 25 ns were observed, in addition to the fast and slow scintillation at 220 and 300 nm, respectively. The La/Ce co-doping was also found effective in suppressing the slow component in BaF_2. Compared to La-doped crystals, the La/Ce co-doped crystals have a better light output in both 50- and 2500-ns gate. The fast/slow ratio of La/Ce co-doped crystal was found to be about 1/1, similar to La-doping, which is also considered not sufficient for pile-up suppression. A 20-cm-long La/Ce co-doped BaF_2 crystal shows also excellent optical quality and light response uniformity.