Development of very-thick transparent GEMs with wavelength-shifting capability for noble element TPCs

M Kuźniak,S Leardini,T Łȩcki,M Kuźwa,T R Pollmann,T Sworobowicz,D González-Díaz,D J Fernández-Posada,L Manzanillas,C D R Azevedo,P Amedo,D Muenstermann,A Saá Hernández,S Williams,C Türkoğlu,G Nieradka,A Leonhardt,R De Oliveira

doi:10.1140/epjc/s10052-021-09316-0

Abstract

A new concept for the simultaneous detection of primary and secondary scintillation in time projection chambers is proposed. Its core element is a type of very-thick GEM structure supplied with transparent electrodes and machined from a polyethylene naphthalate plate, a natural wavelength shifter. Such a device has good prospects for scalability and, by virtue of its genuine optical properties, it can improve on the light collection efficiency, energy threshold and resolution of conventional micropattern gas detectors. This, together with the intrinsic radiopurity of its constituting elements, offers advantages for noble gas and liquid based time projection chambers, used for dark matter searches and neutrino experiments. Production, optical and electrical characterization, and first measurements performed with the new device are reported.

Highlights

Dual-phase or gaseous time projection chambers (TPCs) based on noble elements, mainly argon and xenon, are being used for a wide range of fundamental physics experiments, including direct dark matter detection [1–4], long baseline neutrino oscillation experiments [5,6], searches for neutrinoless double beta decay [7], and even applications outside fundamental physics, e.g. in medical or biological imaging [8,9].Energy deposits in such detectors result in primary scintillation (S1) and ionization
By means of a mild electric field, electrons from ionization are collected into a high field region where they induce secondary scintillation (S2) through electroluminescence (EL) or avalanche generation
Since high light yield and light collection are crucial for achieving the low energy threshold necessary for direct dark matter searches, UV-sensitive CsI photocathode coatings were used to make THGEMs S2 and S1-sensitive [19], with a a few percent photon detection efficiency (PDE) demonstrated in LXe

Summary

Introduction

Dual-phase or gaseous time projection chambers (TPCs) based on noble elements, mainly argon and xenon, are being used for a wide range of fundamental physics experiments, including direct dark matter detection [1–4], long baseline neutrino oscillation experiments [5,6], searches for neutrinoless double beta decay [7], and even applications outside fundamental physics, e.g. in medical or biological imaging [8,9] Energy deposits in such detectors result in primary scintillation (S1) and ionization. Since high light yield and light collection are crucial for achieving the low energy threshold necessary for direct dark matter searches, UV-sensitive (below 400 nm) CsI photocathode coatings were used to make THGEMs S2 and S1-sensitive [19], with a a few percent photon detection efficiency (PDE) demonstrated in LXe (for a recent review see [20]). The new concept and its possible configurations, fabrication process, a simulation of the main optical properties (yields and point spread function) and first functionality tests of the prototype devices will be introduced

Concept and possible configurations

Production

Expected light collection performance

Findings

High voltage tests and validation in xenon gas