Research and Development of Commercially Manufactured Large GEM Foils

TL;DR

This paper reports on the development and quality assurance of large, commercially manufactured GEM foils using single-mask techniques, enabling larger-area detectors for future experiments.

Contribution

It introduces a new commercial production process for large GEM foils using single-mask techniques, overcoming size limitations of previous methods.

Findings

Tech-Etch foils exhibit excellent electrical properties with leakage currents below 1 nA.

Geometrical properties of the foils meet specifications and show uniformity.

Successful establishment of quality assurance procedures for large GEM foils.

Abstract

The recently completed Forward GEM Tracker (FGT) of the STAR experiment at RHIC took advantage of commercially produced GEM foils based on double-mask chemical etching techniques. With future experiments proposing detectors that utilize very large-area GEM foils, there is a need for commercially available GEM foils. Double-mask etching techniques pose a clear limitation in the maximum size. In contrast, single-mask techniques developed at CERN would allow one to overcome those limitations. We report on results obtained using 10 $\times$ 10 cm$^2$ and 40$\times$40 cm$^2$ GEM foils produced by Tech-Etch Inc. of Plymouth, MA, USA using single-mask techniques and thus the beginning for large GEM foil production on a commercial basis. A quality assurance procedure has been established through electrical and optical analyses via leakage current measurements and an automated high-resolution CCD scanner. The Tech-Etch foils show excellent electrical properties with leakage currents typically measured below 1 nA. The geometrical properties of the Tech-Etch single-mask foils were found to be consistent with one another, and were in line with geometrical specifications from previously measured double-mask foils. The single-mask foils displayed good inner and outer hole diameter uniformities over the entire active area.