Optical readout: a tool for studying gas-avalanche processes

Optical recording of avalanche-induced photons is an interesting tool for studying basic physics processes in gaseous detectors. In this work we demonstrate the potential of optical readout in avalanche-propagation investigations in Thick Gas Electron Multipliers (THGEMs) operated with Ne/CF4 (95/5). We present the results of direct measurements, with single- and cascaded-THGEM detectors irradiated with soft x-rays, of the hole-multiplicity and avalanche asymmetry within holes, as a function of detector parameters. Further study directions are discussed.