Development of Tracking Detectors with industrially produced GEM Foils

TL;DR

This paper evaluates the performance of industrially produced GEM foils for large-scale tracking detectors, demonstrating their suitability through uniformity, stability, and resolution tests compared to CERN-produced foils.

Contribution

It presents the first performance comparison of Tech-Etch and CERN GEM foils, establishing quality assurance procedures for industrial GEM foil production.

Findings

Both foil types show good gain uniformity.

Detectors exhibit stable gain after initial charge-up.

Tech-Etch foils are suitable for precision tracking.

Abstract

The planned tracking upgrade of the STAR experiment at RHIC includes a large-area GEM tracker used to determine the charge sign of electrons and positrons produced from W+(-) decays. For such a large-scale project commercial availability of GEM foils is necessary. We report first results obtained with a triple GEM detector using GEM foils produced by Tech-Etch Inc. of Plymouth, MA, USA. Measurements of gain uniformity, long-term stability as well as measurements of the energy resolution for X-Rays are compared to results obtained with an identical detector using GEM foils produced at CERN. A quality assurance procedure based on optical tests using an automated high-resolution scanner has been established, allowing a study of the correlation of the observed behavior of the detector and the geometrical properties of the GEM foils. Detectors based on Tech-Etch and CERN produced foils both show good uniformity of the gain over the active area and stable gain after an initial charge-up period, making them well suited for precision tracking applications.