Ph.D. degree thesis
Weizmann Insitute of Science, Israel, in 2009
Supervisor: Prof. Amos Breskin
Development of gas-avalanche photomultipliers sensitive in the visible spectral range
Avalanche-induced secondary effects
Micropattern gaseous detectors (MSGC, GEM, THGEM, RETHGEM, MICROMEGAS, InGrid, etc)
Photon detectors for UV, visible and IR photons (gas)
The aim of the present research was the development of novel gaseous-photomultiplier (GPM) concepts for the visible spectral range. The goal was to conceive novel state-of-the-art gas-avalanche electron multipliers coupled to thin-film bi-alkali photocathodes, capable of high-gain stable long-term operation in continuous-mode. The main difficulties were blocking of avalanche-ions and the stability of the highly-sensitive UV-to-visible photocathodes under gas avalanche multiplication.
During this research, the following points were thoroughly investigated: R&D on novel gaseous electron multipliers, Production and characterization of various alkali photocathodes, Ion back-flow reduction in cascaded gaseous multipliers, Photocathode ageing under the ion bombardment, Ion-induced secondary electron emission from bi-alkali photocathodes, Gaseous photon detectors assembly and operation
The most significant results obtained are: A cascaded electron-multiplier structure with unprecedentedly reduced back-flow of avalanche ions to the photocathode permitted for the first time a stable high-gain, continuous-mode operation of a gaseous photomultiplier coupled to a visible-sensitive K2CsSb photocathode.