The flow of avalanche ions towards the radiation-conversion volume of a Time Projection Chamber (TPC) or the photocathode of a gaseous photomultiplier (GPM) may seriously affect the TPC’s drift field, damage the GPM’s photocathode or severely limit the GPM gain due to ion-induced secondary avalanches. Some applications require the suppression of ion flow by at least a factor of 103-104. We demonstrated that a unique combination of GEM, MHSP and R-MHSP multipliers in cascade suppress the ions’ back-flow (IBF) down to the 10-4 level, while maintaining the full electron detection efficiency. In another new principle, with Coimbra and Aveiro colleagues, we demontrated the "optical gate" concept. in UV-emitting counting gases, a first multiplier operating in avalanche mode transmits avalanche-induced UV photons to the following amplification stage coated with CsI. The phoelectrons are multiplied to form the final signal while ions cannot flow back to the first stage.
Department of Particle Physics and Astrophysics
Department of Particle Physics and Astrophysics
Radiation Detection Physics
