This manuscript describes the establishment of a local production line for 10 cm & times; 10 cm Gas Electron Multiplier (GEM) foils at the Forschungs-und Technologiezentrum Detektorphysik (FTD) at the University of Bonn. GEM foils are widely used in modern gaseous detectors, providing high-gain signal amplification and high-rate capability. Our fabrication process utilizes a double-mask photolithographic technique on 50 & micro;m polyimide cladded on both sides with 5 & micro;m copper. The chemical etching procedure that is required to achieve uniform hole geometries with outer hole diameters of 70 & micro;m and inner hole diameters of 50 & micro;m will be described. Quality control protocols, including semi-automated optical inspection and high-voltage leakage current tests, demonstrate that foils produced at our facility achieve uniform hole size distributions and leakage currents of less than 1 nA at 600 V in air with no discharge hotspots. These results confirm that the production chain is capable of delivering high-performance foils suitable for research and development purposes.
The recent availability of a consistent electron collision cross-section set for the ultra-low GWP HFO-1234ze(E) (HFO) enables performance simulations of resistive plate chambers (RPCs) operated with HFO-based gas mixtures. We present a simulation framework that reproduces key detector observables measured in trigger-purpose RPCs, such as detection efficiency and cluster size. The simulation additionally provides new insights into streamer formation through a novel streamer inception criterion that captures the observed trends in streamer probability. For mixtures containing CO2, HFO, SF6, and isobutane, the Pareto front between avalanche-streamer separation and relative CO2 equivalent emissions is evaluated using a multi-objective Bayesian optimization approach under a low working point constraint, so the mixture can be used with already installed infrastructure. The optimization confirms that the ECO2 gas mixture (60% CO2, 35% HFO, 4% isobutane, 1% SF6), previously identified through experimental studies, is a Pareto optimal choice when the operation is constrained to a low working point. If higher working points are acceptable, mixtures with a higher HFO percentage provide larger avalanche-streamer separation while enabling a reduction of the SF6 percentage, thereby reducing the environmental impact even further.
Radiation-induced errors in high-energy physics detectors threaten data integrity and uptime, posing significant challenges for reliable operation during the future high-luminosity LHC runs. With over 150,000 ASICs to be deployed in the CMS HGCAL front-end, even a very low per-chip error probability results in a non-negligible failure rate. This work presents a firmware-based, byte-level autorecovery mechanism for the CMS HGCAL Phase-2 front-end electronics, capable of detecting transient upset-related errors and restoring chip operation in real time without requiring a full system reset, ensuring data acquisition continues uninterrupted. The system, implemented in FPGA logic and validated using front-end emulation, executes recovery actions within 4.7µs, corresponding to the measured interval from the data acquisition signal to packet arrival. Overall, the hardware approach is measured to recover approximately 73.5ms faster than software-based intervention. The results demonstrate robust, autonomous operation in radiation-prone environments while preserving continuous data acquisition.
Optical time projection chambers (OTPCs) are well suited for applications that require the highest spatial resolution for particle track reconstruction. The MIGDAL experiment uses a glass GEM-based OTPC and observes a systematic excess in both the intensity and width of particle tracks in its optical readout, when compared with charge readout simulations. One hypothesis is that scintillation light produced inside a GEM hole during the avalanche propagates through the GEM substrate and exits neighboring holes. We present lab measurements testing this hypothesized optical broadening effect in three types of GEM substrates: glass, ceramic, and FR4. Our observations quantify this optical broadening and demonstrate it to be strongest in glass GEMs. Additionally, we use Geant4 simulations to both reproduce our observations and quantify optical broadening effects in realistic charge avalanches. Applying our glass GEM effects to simulated particle tracks yields increases of track intensity and widths by up to around 26
