Novel Process for Realization of High-QE Bialkali Photocathodes

Nuclear detection and spectroscopy is used to detect and characterize global nuclear security threats and prevent spread of materials, technology, and expertise related to weapons of mass destruction. High performance scintillation detectors are the backbone of such tools. Recent advances in scintillators have demonstrated superior spectroscopic qualities, rivaling those of the semiconductor detectors. However, their performance is significantly hampered by other elements of the detection chain. The most prominent among these is current state-of-the-art photocathodes. Development of photocathodes with higher quantum efficiency and a more uniform response over large areas will effectively address this issue, and enable such very low cost workhorse materials as the NaI:Tl to be used in applications where only advanced and costly material can now be considered. RMD proposes to manufacture advanced photocathodes by thermal evaporation using the low-cost, proprietary, pre-synthesized compounds, a transformational technology that has never been imaginable before. The evaporated cathodes will be evaluated over large areas, for UV-visible sensitivity, fast response, high-QE, and response uniformity. Research will focus on bulk preparation of compounds using impurity-free raw elements and the subsequent thermal vapor deposition of the stoichiometric photocathode thin films in a PMT envelope. The goal of the proposed Phase I is to demonstrate feasibility of our technique. During Phase I, we will conduct (1) chemical synthesis of bulk photocathode compounds, (2) build a glass phototube apparatus for thermal evaporation, and (3) synthesize photocathodes and characterize their performance to demonstrate feasibility. We will work closely with a PMT manufacturer for the translation of this transformative technology into commercial photodetectors.