Yttrium-doped barium fluoride crystals for future HEP experiments (Conference Presentation)

In high energy physics (HEP) and nuclear physics experiments, total absorption electromagnetic calorimeters (ECAL) made of inorganic crystals are known for their superb energy resolution and detection efficiency for photon and electron measurements. A crystal ECAL is thus the choice for those experiments where precision measurements of photons and electrons are crucial for their physics missions. Because of its ultrafast scintillation component with sub nanosecond decay time, BaF2 crystals are considered as a candidate for an ultrafast crystal calorimeter for future high energy physics experiments, where unprecedented event rate and radiation environment are expected. Undoped BaF2, however, has also a slow scintillation component with 600 ns decay time, which causes pile-up. Rare earth doping with La, La/Ce and Y was found effective to suppress the slow component. While typical fast/slow (F/S) ratio observed in undoped BaF2 is 1/5, La doping and La/Ce co-doping were found to improve this ratio to about 1/1, which is considered not sufficient for pile-up suppression. It was found recently that yttrium doping is more effective in improving the F/S ratio, while maintaining the intensity of its ultrafast light not changed. This novel ultrafast scintillator with excellent radiation hardness will find wide applications for future HEP experiments, ranged from ultrafast timing detector at the HL-LHC to ultrafast calorimeter for the proposed Mu2e-II experiment at Fermilab. Applications of this ultrafast crystal scintillator for Gigahertz hard X-ray imaging for the proposed Marie project at LANL will also be discussed