Further progress in ion back-flow reduction with patterned gaseous hole-multipliers

TL;DR

This paper introduces a novel electrode design, the F-R-MHSP, which significantly reduces ion back-flow in gaseous hole-multiplier detectors, enhancing performance for applications requiring minimal ion contamination.

Contribution

The paper presents the F-R-MHSP as a new electrode configuration that improves ion back-flow suppression compared to existing designs, demonstrated through experimental comparisons.

Findings

F-R-MHSP effectively deviates and captures back-drifting ions.

Achieved ion back-flow fractions as low as 1.5×10^{-4}.

Enhanced ion-blocking performance in cascaded multipliers.

Abstract

A new idea on electrostatic deviation and capture of back-drifting avalanche-ions in cascaded gaseous hole-multipliers is presented. It involves a flipped reversed-bias Micro-Hole & Strip Plate (F-R-MHSP) element, the strips of which are facing the drift region of the multiplier. The ions, originating from successive multiplication stages, are efficiently deviated and captured by such electrode. Experimental results are provided comparing the ion-blocking capability of the F-R-MHSP to that of the reversed-bias Micro-Hole & Strip Plate (R-MHSP) and the Gas Electron Multiplier (GEM). Best ion-blocking results in cascaded hole-multipliers were reached with a detector having the F-R-MHSP as the first multiplication element. A three-element F-R-MHSP/GEM/MHSP cascaded multiplier operated in atmospheric-pressure Ar/CH4 (95/5), at total gain of ~10^{5}, yielded ion back-flow fractions of 3*10^{-4} and 1.5*10^{-4}, at drift fields of 0.5 and 0.2 kV/cm, respectively. We describe the F-R-MHSP concept and the relevance of the obtained ion back-flow fractions to various applications; further ideas are also discussed.