The PISA concept: Photon Induced Scintillation Amplifier as an innovative high-gain photonmultiplier with Imaging capability

The current generation of noble liquid DM detectors is limited by the radioactivity from the detector materials, mostly from the specially radio-clean photomultiplier tubes (PMT), contributing to the background at ~ 80% level. We propose a simple concept, the Photon Induced Scintillation Amplifier (PISA), for ionization signal amplification. The PISA is a true photon-multiplier, where the secondary scintillation produced in the charge avalanches inside the holes of the micropattern electron multiplier is read out by suitable photosensors, such as SiPM.We have shown that a very large number of photons are produced in micropattern electron multipliers. One electron may produce about 10^5 and 10^4 photons in the THGEM avalanches in xenon and argon, respectively. A MHSP etched on Kapton for radiopurity sake, can be used instead of the GEM or THGEM cascade, since the former presents higher photon output. A large photon output in the final charge avalanche ensures the capability for single-photon sensitivity. The PISA will be cost-effective in comparison with the vacuum PMT and will allow for area coverage above 80%. The SiPM can be distributed in a 2D array with a pitch suitable for the imaging capabilities of the PISA.The PISA provides a breakthrough in radiopurity, due to reduced radioactivity levels of Kapton foils, SiPM, fused silica window, metal case and the feasibility to deploy remote "hot" electronics, since the large gains achieved in SiPMs allow for signal transmission over large distances without significant degradation.