triple-GEM Detectors Research Articles

Performance of a triple-GEM detector with capacitive-sharing 3-coordinate (X–Y–U)-strip anode readout

The concept of capacitive-sharing readout, described in detail in a previous study, offers the possibility for the development of high-performance three-coordinates (X–Y–U)-strip readout for Micro Pattern Gaseous Detectors (MPGDs) using simple standard PCB fabrication techniques. Capacitive-sharing (X–Y–U)-strip readout allows simultaneous measurement of the Cartesian coordinates x and y of the position of the particles together with a third coordinate u along the diagonal axis in a single readout PCB. This provides a powerful tool to address multiple-hit ambiguity and enable pattern recognition capabilities in moderate particle flux environment of collider or fixed target experiments in high energy physics HEP) and nuclear physics (NP). We present in this paper the performance of a 10 cm × 10 cm triple-GEM detector with capacitive-sharing (X–Y–U)-strip anode readout. Spatial resolutions of the order of σxres = 71.6±0.8μm for X-strips, σyres = 56.2±0.9μm for Y-strips and σures =75.2±0.9μm for U-strips have been obtained at a beam test at Thomas Jefferson National Accelerator Facility (Jefferson Lab). Modifications of the readout design of future prototypes to improve the spatial resolution and challenges in scaling to large-area MPGDs are discussed.

Irradiation effects on GEM detectors operated at RUN1 and RUN2 at the LHCb experiment

Triple-GEM detectors with pad readout have been employed to equip the innermost region (R1) of the first station (M1) within the Muon system of the LHCb experiment. The GEM detectors have been operated with an Ar/CO2/CF4 = 45/15/40 gas mixture at a gas gain of about 4000 with an average particle flux of about 250 kHz/cm2. Throughout RUN1 and RUN2, spanning approximately 440 days of colliding beams, the GEM detectors accumulated a charge of up to 0.5 C/cm2. This paper presents a comparative analysis between a global irradiation test of GEM detectors at the Calliope facility (ENEA-Casaccia, 1.25 MeV γ ray flux from a 60Co source) and the GEMs operated at LHCb, focusing on the impacts of a CF4-based gas mixture. In both instances, the detectors were opened and the GEM foils were examined by the EN-MME-MM CERN group with a Field Emission Gun Scanning Electron Microscope (FEG-SEM) for a magnified image analysis and an X-Max Energy Dispersive X-ray Spectroscopy (EDS) for the chemical one.

Longevity study of a triple-GEM chamber for the HL-LHC upgrade

As part of the high-luminosity LHC (HL-LHC) upgrade, the CMS muon spectrometer will extend its coverage in the very forward region with triple-GEM detectors. These detectors will cope with a harsh environment with expected background fluxes up to 150 kHz/cm (Sauli, 2016) [2]. At the end of HL-LHC operation, the total accumulated charge at the hottest point is expected to reach 7.9 C/cm (Sauli, 2016) [2]. This accumulated charge is unprecedented for a GEM detector.A full-size triple-GEM chamber was built using the design planned for the most forward CMS muon station using GEM foils produced at CERN. While operated with a gas mixture of Ar/CO2 (70/30)%, the chamber was irradiated with photons from a silver-target X-ray source over 1.5 years to reach an accumulated charge of 8 C/cm2. Before and after irradiation the chamber was validated using the standard quality control procedures; gas gain and energy resolution were measured. During irradiation the gain was monitored weekly. The irradiation was interrupted only for the certification measurements. A non-irradiated sector was monitored for comparison. Temperature and pressure in the lab were continuously measured to derive correction factors to calibrate the gas gain. No degradation in gas gain was observed when reaching 8 C/cm2. Irradiated and non-irradiated chamber components were inspected for potential impacts from irradiation.

Spatial resolution improvements with finer-pitch GEMs

Gas Electron Multipliers (GEMs) are used in many particle physics experiments, employing their `standard' configuration with amplification holes of 140 μm pitch in a hexagonal pattern. However, the collection of the charge cloud from the primary ionisation electrons from the drift region of the detector into the GEM holes affects the position information from the initial interacting particle. In this paper, the results from studies with a triple-GEM detector with an X-Y-strip readout anode are presented. It is demonstrated that GEMs with a finer hole pitch of here 90 μm improve the detector's spatial resolution. Within these studies, also the impact of the front-end electronics on the spatial resolution was investigated, which is briefly discussed in the paper.

Fast timing detectors for the muon system of a muon collider experiment: requirements from simulation and prototype performance

Looking at the future path of high-energy physics, a muon collider offers incomparable potential for discovery in the multi-TeV energy range. However, its development must address some relevant technological challenges, which arise from the short muon lifetime, 2.2 μs, and from the difficulty of producing large numbers of muons in groups with small emittance. The first one in particular leads to the production of the so-called Beam-induced Background (BIB), which affects the design of the machine and detector.The purpose of this contribution is to describe the expected performance of the muon system of a multipurpose muon collider detector designed to reconstruct the products of multi-TeV collisions with extreme accuracy.We are proposing a design of the muon system fully based on Micropattern Gaseous Detectors (MPGD), which foresees the combination of tracking layers based on Triple-GEM detectors, with a timing layer based on a new generation MPGD called Picosec. Picosec was developed in the last few years by the RD51 collaboration, with the aim of obtaining a fast timing (sub ns) MPGD.A dedicated R&D is ongoing to optimize such a technology for the application in a muon collider experiment, both from the detector and the mechanics point of views.This contribution will present the results obtained during the R&D of the Picosec technology for the muon collider both from laboratory tests and test beams performed in 2023. Special attention will be given to the performance obtained with different gas mixtures. Moreover, we will discuss the plans for the R&D dedicated to the muon collider.

The upgrade of the CMS muon system for the high luminosity LHC

The muon system of the CMS experiment is expected to upgrade all of its subdetectors for the Phase-2 of the Large Hadron Collider (LHC) that will begin in 2029. The upgrade plans for drift tubes (DTs), cathode strip chambers (CSCs) and resistive place chambers (RPCs) include a new electronics for better performance in high background rate conditions and to sustain the large radiation dose delivered by the high-luminosity LHC (HL-LHC). Two new RPC stations will also be installed to complement CSCs in the forward region 1.8 < |η| < 2.4, while three stations of triple-GEM (gas electron multiplier) detectors will complement CSCs in the region 1.5 < |η| < 2.4 and extend the CMS muon system coverage to the very forward pseudorapidity region 2.4 < |η| < 2.8. We present the goals and status of the CMS muon system upgrade including the performance of the early Phase-2 upgrades demonstrated in Run 3 with proton-proton collisions, the performance validation of the new detectors in test beams and the mass production status of the new stations.

Development of a Triple-GEM detector with strip readout and GEMINI chip for X rays and neutron imaging

Thermal neutron imaging can be a useful tool in the study of the internal structure of an object. The different attenuation properties of the materials with respect to X rays give rise to different interactions and the result is a complementary non-destructive analysis, which can provide important additional information. This technique has been successfully employed in different areas of work, especially in material science and cultural heritage studies. This paper describes the development of a new detection system and its characterization performed with X ray emissions. The system features the use of a gaseous detector, based on the Gas Electron Multiplier technology, and a fully digital electronic readout, with a combination of custom-made ASICs (called GEMINI) and FPGA boards, enabling fast single photon counting. The detector can be thus used directly for X ray imaging, while the addition of a suitable converter in its active volume will allow for detection of neutrons and for reconstruction of their tracks. The readout system is based on a x-y strip structure and features the reconstruction of single events through the center of mass methodology, allowing for accurate tomography, with sub-mm spatial resolution, in combination with sub-ms time resolution and high rate capabilities (up to MHz/mm2).

PARSIFAL: A toolkit for triple-GEM parametrized simulation

PARSIFAL (PARametrized SImulation) is a fast and reliable software tool that reproduces the complete response of a triple-GEM detector to the passage of a charged particle, taking into account the main physical effects. Starting from the detector configuration and the particle information, PARSIFAL reproduces ionization, spatial and temporal diffusion, effect of magnetic field, if present, and GEM amplification to provide the dependable triple-GEM detector response. In the design and optimization stages of this kind of detectors, simulations play an important role. Accurate and robust software programs, such as GARFIELD++, can simulate the transport of electrons and ions in a gas medium and their interaction with the electric field, but they are CPU-time consuming. The necessity to reduce the processing time while maintaining the precision of a full simulation is the main driver of this work. For a given set of geometrical and electrical settings, GARFIELD++ is run once-and-for-all to provide the input parameters for PARSIFAL. Once PARSIFAL is initialized and run, it produces the detector output, including the signal induction and the output of the electronics. The results of the analysis of the simulated data obtained with PARSIFAL are compared with the results of the experimental data collected during a testbeam: some tuning factors are applied to the simulation to improve the agreement. This paper describes the structure of the code and the methodology used to match the output to the experimental data. Program summaryProgram Title: PARSIFALCPC Library link to program files:https://doi.org/10.17632/rg85kzjwwj.1Developer's repository link:https://github.com/Hilldar/PARSIFAL (branch triplegem)Licensing provisions: GPLv3Programming language: C++Nature of problem: Monte Carlo (MC) simulations are widely used in design and development of detectors for high energy physics as well as during data taking to understand how the detector geometry, acceptance, efficiency affect the experimental observations and hence infer the systematic effects. For triple-GEM detectors (one of the most used Micro Pattern Gaseous Detectors), the simulation of their response to the passage of particles is usually performed with GARFIELD++ (CERN) which provides a microscopic description of the signal creation, from the interaction of the particle with the gas to the induction of the signal on the anode. This detailed simulation is heavy and CPU-time consuming, hence it requires long computing periods to gain high statistics.Solution method: PARSIFAL software provides the MC simulation of the response of a triple-GEM detector to the passage of a charged particle by splitting the simulation into four independent steps: ionization, electron drift in gas and magnetic field, avalanche formation in the multiplication stages, signal induction on the anode and response of the electronics (APV-25 chip). For each step, PARSIFAL samples the variables of interest from distributions, obtained by using a set of input parameters. These parameters are extracted from a simulation run only once with GARFIELD++. Since the sampling is much faster than a full GARFIELD++ simulation, this reduces the CPU-time to collect a sample with high statistics. The results extracted by the PARSIFAL simulation have been tuned with experimental data collected during a testbeam at CERN and show a satisfactory compatibility.

Hybrid Garfield++ simulations of GEM detectors for tokamak plasma radiation monitoring

This work presents recent efforts in optimization of Gas Electron Multiplier (GEM) detector simulations developed so far. The mentioned triple-GEM based measurement systems were already tested at the WEST project and other devices recording soft X-ray (SXR) plasma radiation in the target range of 2-15 keV. Long term plans may envisage usage of gaseous detector based SXR diagnostics in DEMO reactor for real time plasma monitoring and control, as high neutron fluxes preclude application of semiconductor-based technologies. Conditions in fusion reactors as well as in currently operating devices necessitate simulating the interactions of high-energy photons and neutrons with the detector parts, including proper handling of primary ionization electrons paths, gas mixture fluorescence and collisions with detector materials. For this use case a full-detector simulation software was created based on the already existing interface and previous results obtained so far within the group. It combines Geant4 package for interactions with solid parts of the detector, Garfield++ for electron avalanching, Heed for X-ray interaction with gas, Gmsh and Elmer for meshing and electrostatics and introduces hybrid approach to the simulation of electron drift in different manner depending on the electron position with respect to multiplication stage. To optimize the computation time software employs precomputation algorithms in later stages of the electron cascades. The expected response profiles of the triple-GEM detector, exposed to 55Fe calibration source radiation, were simulated and verified by comparing them with experimental data.

Production and characterization of random electrode sectorization in GEM foils

In triple-GEM detectors, the segmentation of GEM foils in electrically independent sectors allows reducing the probability of discharge damage to the detector and improving the detector rate capability. However, a segmented foil presents thin dead regions in the separation between two sectors and the segmentation pattern has to be manually aligned with the GEM hole pattern during the foil manufacturing, a procedure potentially sensitive to errors. We describe the production and characterization of triple-GEM detectors obtained with an innovative GEM foil segmentation technique, the “random hole segmentation”, that allows easier manufacturing of segmented GEM foils. The electrical stability to high voltage and the gain uniformity of a random-hole segmented triple-GEM prototype are measured. The results of a test beam on a prototype assembled for the Phase-2 GEM upgrade of the CMS experiment are also presented. A high statistics efficiency measurement shows that the random hole segmentation can limit the efficiency loss of the detector in the areas between two sectors, making it a viable alternative to blank segmentation for the GEM foil manufacturing of large-area detector systems.

GEM detectors for the CMS endcap muon system: status of three new detector stations

The High-Luminosity LHC (HL-LHC, or Phase-2 LHC) will deliver proton-proton collisions at 5–7.5 times the nominal LHC luminosity, with an expected number of 140–200 pp-interactions per bunch crossing (Pile-up or PU). To maintain the performance of muon triggering and reconstruction under high background, the forward part of the Muon Spectrometer of the CMS experiment will be upgraded with Gas Electron Multipliers (GEM) and improved Resistive Plate Chambers (iRPC) detectors [1,2]. A first GEM station (GE1/1) was installed during Long Shutdown 2 (LS2, 2019–2021), a 2nd station (GE2/1) of Triple-GEM detectors will be installed in winter 2023–24 and 2024–25, while a new 6-layer station (ME0) will be installed in the third Long Shutdown (LS3, 2026–2028). GE11 is considered an early Phase-2 upgrade as it will reduce the pT threshold by combining GEM and Cathode Strip Chamber (CSC) hits in the forward muon system at twice the LHC design luminosity (ℒ = 2 · 1034 cm-2 s-1, 50 PU). After a successful start of Run-3 in 2022, with almost 40 fb-1 collected, the commissioning of the GE1/1 detector is nearly complete. Most chambers are operated stably with an efficiency in excess of 95%, next being the demonstration of the combined CSC-GEM trigger in 2023. The lessons learnt with the first large-area GEM station have lead to improvements in detector and electronics design for the Phase 2 detectors GE2/1 and ME0. This proceeding will discuss the progress made since last MPGD Conference (MPGD 2019) [3], discussing the commissioning and early performance of GE1/1; the design improvements and start of construction of GE2/1; and the R&D currently ongoing for ME0.

The novel XYU-GEM to resolve ambiguities

Removing ambiguities within a single stage becomes crucial when one can not use multiple detectors behind each other to resolve them which naturally is the case for neutral radiation. An example would be RICH detectors. Commonly, pixilated readout is choosen for this purpose. However, this causes a remarkable increase in quantity of channels. Thus, the overall costs of the detector would increase. Therefore, the XYU-GEM was proposed as a three coordinate strip-readout which is combined with a triple GEM detector. The readout complements a common XY readout with an additional projection which is tilted by 45°. The overdetermination due to three projections can be used to resovle ambiguities. Following the detector design will be explained, first measurements discussed to understand the response of the detector and a way to change the charge sharing without changing the manufacturing parameters of the readout.

Characterisation of N2-GEM: a beam monitor based on Ar-N2 gas mixture

The gas recycle is nowadays an important issue for gaseous detectors operation under study and for this reason, scientists are testing new gas systems for GEM detectors. Since some gas purifier does not allow to use oxygen, the standard Ar-CO2 (70%–30%) cannot be used; thus, new gas mixtures are under investigation. This paper presents the study of a triple GEM detector filled with new gas mixture based on Argon and Nitrogen (Ar-N2) at different concentrations: 90%–10%, 80%–20% and 70%–30%. The GEM detector characterisation has provided the High Voltage working point for the gas mixtures and a comparison between the Ar-CO2 and the Ar-N2.

Demonstration of Gd-GEM detector design for neutron macromolecular crystallography applications

The European Spallation Source (ESS) in Lund, Sweden will become the world's most powerful thermal neutron source. The Macromolecular Diffractometer (NMX) at the ESS requires three 51.2 × 51.2 cm2 detectors with reasonable detection efficiency, sub-mm spatial resolution, a narrow point-spread function (PSF), and good time resolution. This work presents measurements with the improved version of the NMX detector prototype consisting of a Triple-GEM (Gas Electron Multiplier) detector with a natural Gd converter and a low material budget readout. The detector was successfully tested at the neutron reactor of the Budapest Neutron Centre (BNC) and the D16 instrument at the Institut Laue-Langevin (ILL) in Grenoble. The measurements with Cadmium and Gadolinium masks in Budapest demonstrate that the point-spread function of the detector lacks long tails that could impede the measurement of diffraction spot intensities. On the D16 instrument at ILL, diffraction spots from Triose phosphate isomerase w/ 2-phosphoglycolate (PGA) inhibitor were measured both in the MILAND Helium-3 detector and the Gd-GEM. The comparison between the two detectors shows a similar point-spread function in both detectors, and the expected efficiency ratio compared to the Helium-3 detector. Both measurements together thus give good indications that the Gd-GEM detector fits the requirements for the NMX instrument at ESS.

Characterization and Commissioning of a Triple-GEM Detector

We present in detail the characterization and commissioning of a triple Gas Electron Multiplier (triple-GEM)detector. The response to various sources of radiation was studied, and its efficiency, gain, energy resolution,and temporal resolution were calculated. We found an energy resolution of 19.5%, a temporal resolution of40 ns., and a maximum gain of 5×106. We conclude that the detector can be confidently used in furtherstudies of medical dosimetry, since it is working in the proportional mode.

Novel GEM foil layout for high-rate particle environment in the CMS ME0 muon detector

The triple-GEM technology has been selected to extend the acceptance of the CMS muon spectrometer to the region 2 . 4 < | η | < 2 . 8 , the so called ME0 project. The ME0 stations will be formed by stacks (six-layer stations) of triple-GEM chambers, which must operate in a harsh environment with expected background particle fluxes ranging between 3 and 150 kHz/cm 2 on the chamber surface. Both the maximum background rate and the large range in particle rate set a new challenge for particle detector technologies. The rate capability of triple-GEM detectors is limited by voltage drops on the chamber electrodes due to avalanche induced currents flowing through the resistive protection circuits. Studies with large-area triple-GEM detectors with moderate fluxes, show drops up to 40% of the nominal detector gas gain. The traditional GEM foils segmentation does not allow for feasible gain compensation acting on the HV settings. To overcome this strong limitation and to cope with the large variation in background flux, a new GEM foil design with electrode segmentation in the radial direction, instead of the “traditional” transverse segmentation has been introduced.

Performance of a triple GEM detector equipped with Al-GEM foils for X-rays detection

Performance of a triple GEM detector equipped with Al-GEM foils for X-rays detection

Radiation dosimetry with a Triple-GEM detector

We studied the properties of the gaseous detector triple-GEM (triple Gas Electron Multiplier) as a dosimeter with different ionizing radiation sources used in medical applications. The detector was calibrated in energy with an Iron-55 radioactive source. We measured doses of radiation from different radioactive sources as well as from a medical portable X-ray machine, and compared them to reference values. The detector presents a linear dependence between radiation intensity and measured dose. A calibration factor of 1.13x104 was found, independently of the radiation source. These results allow us to conclude that the triple-GEM detector has the potential to be used as a dosimeter in medical applications.

Hydrodynamic simulation studies on avalanche and streamer formation in GEM detector

The dynamics of electrons and ions in gaseous ionization detectors have been studied reasonably well with particle simulation models developed using the Garfield++ numerical simulation framework. This is an important area of study since it allows prediction of the detector response in a given experimental situation. In this work, a fluid simulation model has been developed in the COMSOL Multiphysics simulation framework to simulate the avalanche and streamer formation in GEM-based detectors. Possible detector geometries in 2D, 2D axisymmetric and 3D coordinate systems have been explored to find the optimum numerical configuration. Transport of charged fluids has been simulated in the optimized model for various operating voltage ranges suitable for single, double and triple GEM detectors using Ar-CO2 (70-30) as the gas mixture. Simulated gain variations have been compared with experimental observations. Effect of space charge and its relation to streamer formation have been studied.

High rate capability studies of triple-GEM detectors for the ME0 upgrade of the CMS Muon Spectrometer

The high-luminosity LHC (HL-LHC) upgrade is presenting new challenges for particle detector technologies. In the CMS Muon System gaseous detectors, the increase in luminosity will produce a particle background ten times higher than at the LHC. To cope with the high rate environment and maintain current performance, the triple-Gas Electron Multiplier technology is a promising candidate for high-rate capable detectors for the CMS-ME0 upgrade project in the innermost region of the forward Muon Spectrometer of the CMS experiment. An intense R&D and prototyping phase is currently ongoing to prove that such technology meets the stringent performance requirements of highly efficient particle detection in the harsh background environment expected in the innermost ME0 region. Here we describe the recent rate capability studies of triple-GEM detectors operated with an Ar/CO2 (70/30) gas mixture at an effective gas gain of 2 × 104 by using a high intensity 22 keV X-ray generator. Moreover, we present a novel foils design based on double-sided segmented GEM-foils, high voltage power distribution, and filtering, which the collaboration adopted for realization of the latter projects, and their impact on the performance of the detector in the light of new rate capability studies, with a summary of the ongoing R&D activities.