Measuring the Light Yield of pure Cesium Iodide using two photomultiplier tubes at 77 Kelvin

For scintillation based detectors, improving intrinsic light yield and light collection effeciency can directly improve sensitivity used in searches for rare physics processes. In my experimentation, a light yield of ~23 PE/keV was found with an undoped cesium iodide (CsI) crystal coupled to two photomultiplier tubes (PMTs) at 77 Kelvin. This could lower the energy threshold for future dark matter and neutrino-nucleus scattering experiments that use CsI. By employing two PMTs and requiring a coincident trigger, the background dark count created by the operating PMTs can become negligible.