THGEM-based detectors for sampling elements in DHCAL: laboratory and beam evaluation

TL;DR

This paper evaluates Thick-Gas Electron Multiplier (THGEM) detectors for use in Digital Hadron Calorimetry, demonstrating high efficiency, low discharge probability, and promising performance in laboratory and beam tests.

Contribution

It introduces new THGEM-based detector configurations with resistive anodes, achieving high efficiency and low discharge rates suitable for DHCAL applications.

Findings

Detection efficiency above 95% for ~6 mm thick single-THGEM

Pad multiplicity of 1.1-1.2 per event

Discharge probabilities of 1e-6 to 2e-6 depending on structure

Abstract

We report on the results of an extensive R&D program aimed at the evaluation of Thick-Gas Electron Multipliers (THGEM) as potential active elements for Digital Hadron Calorimetry (DHCAL). Results are presented on efficiency, pad multiplicity and discharge probability of a 10x10 cm2 prototype detector with 1 cm2 readout pads. The detector is comprised of single- or double-THGEM multipliers coupled to the pad electrode either directly or via a resistive anode. Investigations employing standard discrete electronics and the KPiX readout system have been carried out both under laboratory conditions and with muons and pions at the CERN RD51 test beam. For detectors having a charge-induction gap, it has been shown that even a ~6 mm thick single-THGEM detector reached detection efficiencies above 95%, with pad-hit multiplicity of 1.1-1.2 per event; discharge probabilities were of the order of 1e-6 - 1e-5 sparks/trigger, depending on the detector structure and gain. Preliminary beam tests with a WELL hole-structure, closed by a resistive anode, yielded discharge probabilities of <2e-6 for an efficiency of ~95%. Methods are presented to reduce charge-spread and pad multiplicity with resistive anodes. The new method showed good prospects for further evaluation of very thin THGEM-based detectors as potential active elements for DHCAL, with competitive performances, simplicity and robustness. Further developments are in course.