PISA: Photon-induced Scintillation Amplifier with Ne-CF4 mixtures for high-radiopure gas photomultipliers

The dominant background in current noble liquid dark matter detectors arises from the radioactivity of detector components, particularly photomultiplier tubes, which contribute up to 80 % of the total. We propose the Photon Induced Scintillation Amplifier, a cost-effective and highly radiopure alternative to PMTs for ionization signal amplification in rare event searches, which enables high area coverage (>80 %). It employs secondary scintillation generated in charge avalanches within a micropattern electron multiplier - specifically a Kapton-etched MHSP for enhanced photon output and radiopurity - read out by silicon-photomultipliers. The silicon-photomultipliers allow for a flexible 2D-array fitted to specific imaging requirements and for a remote deployment of the “hot” electronics for signal readout, offering a significant advancement in detector radiopurity. • Photon Detection: PISA enables GPM signal gain with SiPMs, no FR4, no cascades. •Radiopurity & Efficiency: MHSP in Kapton boosts purity and photon sensitivity for DM. •Cost & Practicality: PISA is cheaper, purer than PMTs and suits low-radioactivity setups.