La and La/Ce Doped BaF_2 Crystals for Future HEP Experiments at the Energy and Intensity Frontiers Part I

Because of its fast scintillation component with subnanosecond decay time, BaF_2 crystals are considered as a candidate for ultrafast crystal calorimeters for future high energy physics experiments at the energy and intensity frontiers. Undoped BaF_2 , however, has a slow scintillation component with 600 ns decay time, which causes pile-up. In the part I of this paper, we report investigations on La doping in BaF_2 crystals to suppress the slow component. While typical fast/slow (F/S) ratio observed in undoped BaF_2 is 1/5, La-doped BaF_2 crystals were found to improve this ratio to about 1/1. The overall F/S ratio, however, is considered not sufficient for pile-up suppression