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.
تحميل البحث