Efficient ion blocking in gaseous detectors and its application to gas-avalanche photomultipliers sensitive in the visible-light range

TL;DR

This paper introduces a new ion blocking method for gas-avalanche detectors, achieving high gain in DC mode for gaseous photomultipliers sensitive to visible light, with potential applications in TPCs.

Contribution

The paper presents a novel ion blocking concept using cascaded micro-hole electron multipliers with patterned electrodes, enabling high gain in DC mode for visible-sensitive gaseous photomultipliers.

Findings

Ion blocking at the 10^{-4} level achieved in DC mode.

First demonstration of high gain (~10^5) in DC mode in a visible-sensitive gaseous photomultiplier.

Validated ion blocking method in a cascaded gas avalanche photomultiplier with various photocathodes.

Abstract

A novel concept for ion blocking in gas-avalanche detectors was developed, comprising cascaded micro-hole electron multipliers with patterned electrodes for ion defocusing. This leads to ion blocking at the 10^{-4} level, in DC mode, in operation conditions adequate for TPCs and for gaseous photomultipliers. The concept was validated in a cascaded visible-sensitive gas avalanche photomultiplier operating at atmospheric pressure of Ar/CH_{4} (95/5) with a bi-alkali photocathode. While in previous works high gain, in excess of 10^{5}, was reached only in a pulse-gated cascaded-GEM gaseous photomultiplier, the present device yielded, for the first time, similar gain in DC mode. We describe shortly the physical processes involved in the charge transport within gaseous photomultipliers and the ion blocking method. We present results of ion backflow fraction and of electron multiplication in cascaded patterned-electrode gaseous photomultiplier with K-Cs-Sb, Na-K-Sb and Cs-Sb visible-sensitive photocathodes, operated in DC mode.