Development of high-gain gaseous photomultipliers for the visible spectral range

TL;DR

This paper reports the development of high-gain, visible-sensitive gaseous photomultipliers combining novel photocathodes with advanced electron multipliers, achieving stable operation and high quantum efficiency for potential large-area imaging applications.

Contribution

Introduction of a new gaseous photomultiplier system with high gain, stability, and sensitivity in the visible spectrum, utilizing innovative photocathodes and electron multiplication techniques.

Findings

K$_2$CsSb photocathodes achieved QE above 30% at 360-400 nm.

Stable operation at gains of 10^5 in continuous mode at 700 Torr.

Demonstrated single-photon sensitivity in the visible range.

Abstract

We summarize the development of visible-sensitive gaseous photomultipliers, combining a semitransparent bi-alkali photocathode with a state-of-the-art cascaded electron multiplier. The latter has high photoelectron collection efficiency and a record ion blocking capability. We describe in details the system and methods of photocathode production and characterization, their coupling with the electron multiplier and the gaseous-photomultiplier operation and characterization in a continuous mode. We present results on the properties of laboratory-produced K$_2$CsSb, Cs$_3$Sb and Na$_2$KSb photocathodes and report on their stability and QE in gas; K$_2$CsSb photocathodes yielded QE values in Ar/CH$_4$(95/5) above 30% at wavelengths of 360-400 nm. The novel gaseous photomultiplier yielded stable operation at gains of 10$^5$, in continuous operation mode, in 700 Torr of this gas; its sensitivity to single photons was demonstrated. Other properties are described. The successful detection of visible light with this gas-photomultiplier pave ways towards further development of large-area sealed imaging detectors, of flat geometry, insensitive to magnetic fields, which might have significant impact on light detection in numerous fields.