Ion-Feedback Suppression for Gaseous Photomultipliers with Micro Pattern Gas Detectors

Gaseous photomultiplier tubes (Gas-PMTs) with micro-pattern gas detectors (MPGDs) sensitive to visible light are under development. A micro-pattern gas detector of Kapton GEM is found to be incompatible with bi-alkali photocathode, while a glass capillary plate has no problem. A new production method for a hole type MPGD has been developed. In the development of Gas-PMTs the suppression of ion-feedback is crucial because the ion-feedback limits the gain of the Gas-PMT and cause aging effects of the photocathode. Studies on ion-feedback suppression using a simulation with Garfield and Maxwell 3D programs are presented.