New Ultrafast Inorganic Scintillators With Bright Core-valence Luminescence

The design of future calorimeters for high energy physics (HEP) experiments will pose many technical challenges due to the extreme environments under which radiation detectors must operate. Avoiding pulse pileup in such high count rate applications is critical and requires detector materials with ultrafast decay times. Here we present new inorganic single crystal scintillators with potential use in fast timing applications. Compounds from the CsCl-ZnCl₂ and CsCl-MgCl₂ systems are explored due to their favorable electronic properties allowing for observation of ultrafast core-valence luminescence (CVL). So far, Cs₂ZnCl₄ has been one of the most promising candidates, with a single-component decay time of 1.7 ns and light yield around 2,000 ph/MeV (at 662 keV). Practical benefits include its non-hygroscopicity, low melting point (<600 °C), and ability to be grown in large sizes (>1 inch diameter) by the Bridgman method. Compositional engineering is also investigated to optimize the ratio of light yield to decay time. We find that doping Mg-containing crystals with Zn improves light yield by up to 60% without lengthening decay times. The combination of speed and brightness of these novel materials, along with the absence of slow decay components, makes them attractive alternatives to other scintillators being considered for fast timing applications.