Production and validation of industrially produced large-sized GEM foils for the Phase-2 upgrade of the CMS muon spectrometer

TL;DR

This paper reports on the successful production, quality control, and validation of large-sized GEM foils by the Korean CMS collaboration, demonstrating their suitability for the HL-LHC muon spectrometer upgrade.

Contribution

It introduces a new large-area GEM foil production method and validates their performance for high-luminosity collider applications.

Findings

GEM foils meet design specifications

Detectors achieve required gain and uniformity

No aging observed after extensive charge collection

Abstract

The upgrade of the CMS detector for the high luminosity LHC (HL-LHC) will include gas electron multiplier (GEM) detectors in the end-cap muon spectrometer. Due to the limited supply of large area GEM detectors, the Korean CMS (KCMS) collaboration had formed a consortium with Mecaro Co., Ltd. to serve as a supplier of GEM foils with area of approximately $0.6\,m^{2}$. The consortium has developed a double-mask etching technique for production of these large-sized GEM foils. This article describes the production, quality control, and quality assessment (QA/QC) procedures and the mass production status for the GEM foils. Validation procedures indicate that the structure of the Korean foils are in the designed range. Detectors employing the Korean foils satisfy the requirements of the HL-LHC in terms of the effective gain, response uniformity, rate capability, discharge probability, and hardness against discharges. No aging phenomena were observed with a charge collection of $82\,mC/cm^{2}$. Mass production of KCMS GEM foils is currently in progress.