Optical readout tracking detector concept using secondary scintillation from liquid argon generated by a thick gas electron multiplier

TL;DR

This paper demonstrates the first observation of secondary scintillation within a liquid argon environment generated by a thick gas electron multiplier, using a silicon photomultiplier for detection, which could advance particle detection technologies.

Contribution

It introduces a novel method of detecting secondary scintillation in liquid argon using a TGEM and SiPM, providing a new approach for optical readout in particle detectors.

Findings

Observed and measured secondary scintillation in liquid argon with a TGEM.

Achieved a gain of approximately 150 photoelectrons per drifted electron.

Demonstrated effective detection of VUV light with a coated SiPM.

Abstract

For the first time secondary scintillation, generated within the holes of a thick gas electron multiplier (TGEM) immersed in liquid argon, has been observed and measured using a silicon photomultiplier device (SiPM). 250 electron-ion pairs, generated in liquid argon via the interaction of a 5.9KeV Fe-55 gamma source, were drifted under the influence of a 2.5KV/cm field towards a 1.5mm thickness TGEM, the local field sufficiently high to generate secondary scintillation light within the liquid as the charge traversed the central region of the TGEM hole. The resulting VUV light was incident on an immersed SiPM device coated in the waveshifter tetraphenyl butadiene (TPB), the emission spectrum peaked at 460nm in the high quantum efficiency region of the device. For a SiPM over-voltage of 1V, a TGEM voltage of 9.91KV, and a drift field of 2.5KV/cm, a total of 62 photoelectrons were produced at the SiPM device per Fe-55 event, corresponding to an estimated gain of 150 photoelectrons per drifted electron.