Development of ultra-fast photon detection systems

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Future experiments in nuclear, hadronic and particle physics rely on the identification and complete, precise determination of the four-momentum vector of all reaction products. Imaging Cherenkov detector are an invaluable tool in providing this information. Charged particle traversing a dielectric medium with a speed greater than the speed of light inside the medium emit a come of Cherenkov radiations. The opening angle of this cone is (for a given refractive index of the radiator medium) a measure of the particles's velocity. This provides, combined with an independent moment measurement, a powerful method to infer the mass of the particle in question. Imaging Cherenkov detectors current under development can be categories in two classes, classical Ring Imaging CHerenkov (RICH) counters and counters using the Detection of Internally Reflected Cherenkov light (DIRC). The RICH principle uses the light emitted from the radiator into an expansion volume to image the Cherenkov cone, while the DIRC principle relies on the optical properties of the radiator itself to propagate the light internally towards a photon detection array. The latter technique is also studied for energy and time-of-flight measurements. The UK nuclear physics community is involved in three exciting new detector developments for precision studies of the strong interaction, the PANDA disc DIRC, the upgrade of the CLAS 12 detector with an Aerogel RICH and conceptual studies for the DIRC detector at a future electron-ion collider EIC. The nuclear physics group at the University of Glasgow is leading the development of the PANDA disc DIRC and the development and testing of the photon detection system for the CLAS 12 RICH.These detector systems rely on segmented, high rate and high granularity, single photon capable detection devices. All detector systems will have to operate within or in the vicinity of a strong magnetic field. Their photon detection systems require a large filling fraction and a compact geometry. Our current and previous tests demonstrated that none of the available commercial solutions fulfil the criteria for future Cherenkov counters in nuclear and particle physics. We propose to develop and test a new generation of photon detectors together with research and industrial partners in the UK, Kelvin Nanotechnology, Kelvin/Rutherford laboratory and Photek.The project comprised test of gain, homogeneity, rate dependence, time resolution, cathode lifetime and photon detection efficiency. These studies will be complemented by simulation studies of the detectors themselves and their properties in applications. The performance will be tested in laboratories at Photek and the University of Glasgow and by using existing Cherenkov prototypes in electron and hadron beams at the University of Strathclyde, GSI and CERN.The principal investigator of this project is leading the European Joint Research Activity "CherenkovImaging" which complements the proposed research e.g. for applications at COSY, Juelich, Germany. Furthermore we are closely collaborating with UK institutions involved in the TORCH project, a proposed upgrade of the LHCb detector based on adapting the PANDA disc DIRC design to time-of-flight measurements, and the ATLAS Forward Physics group.The properties of the photon detection system investigated are of great interest beyond the boundaries of fundamental nuclear and particle physics research. Its application in future medical imaging modalities like Time-of-Flight PET or PET/MRI fusion, is obvious. Less obvious, but potentially equally important, it could greatly enhance the current capabilities of studying time resolved fluorescence phenomena in cell research and other life-science applications. THe principle investigator and his group are currently conducting a pilot study into these applications in collaboration with the Beatson Institute for Cancer Research.