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The fusion energy research field presents many intricate challenges that require resolution. Many diagnostic systems employed in experiments are approaching the limits of current technology. Implementing efficient measurements requires using an appropriate set of tools to facilitate the optimal utilization of hardware. Fusion energy measurements must provide low latency processing with the capacity for future improvements and the ability to handle complex data flows efficiently. The presented work addresses these requirements and describes the implementation of a high-performance, low-latency software platform with convenient development for soft X-ray (SXR) plasma impurities emission tracing—the Asynchronous Complex Computation Platform (AC2P). This article presents the architectural design, implementation details, and performance and latency measurements based on the raw data acquired from the WEST tokamak and laboratory tests. AC2P provides the tools to develop low-latency, multi-core, multi-device complex data flow graph scale-up solutions for measuring impurities in hot plasmas. The system has been designed to operate online during experiments, calculate the energy distribution, position and occurrence time of SXR photons, monitor the data stream's quality and archive any abnormalities for subsequent offline verification and algorithm improvement. This article presents AC2P, which operates as part of the SXR measurement system on the WEST tokamak. [ABSTRACT FROM AUTHOR]

The objective of the proposed research is to develop plasma soft X-ray (SXR) radiation imaging that includes spectral information in addition to standard SXR tomography for the purpose of studying, for example, tungsten transport and its interplay with magnetohydrodynamics (MHD) in tokamak plasmas in an ITER-relevant approach. The SXR radiation provides valuable information about both aspects, particularly when measured with high spatial and temporal resolution and when tomographic reconstructions are performed. The spectral data will facilitate the tracking of both light and high-Z impurities. This approach is pertinent to both the advancement of a detailed understanding of physics and the real-time control of plasma, thereby preventing radiative collapses. The significance of this development lies in its ability to provide three-dimensional plasma tomography, a capability that extends beyond the scope of conventional tomography. The utilization of two-dimensional imaging capabilities inherent to Gas Electron Multiplier (GEM) detectors in a toroidal view, in conjunction with the conventional poloidal tomography, allows for the acquisition of three-dimensional information, which should facilitate the study of, for instance, the interplay between impurities and MHD activities. Furthermore, this provides a valuable opportunity to investigate the azimuthal asymmetry of tokamak plasmas, a topic that has rarely been researched. The insights gained from this research could prove invaluable in understanding other toroidal magnetically confined plasmas, such as stellarators, where comprehensive three-dimensional measurements are essential. To illustrate, by attempting to gain access to anisotropic radiation triggered by magnetic reconnection or massive gas injections, such diagnostics will provide the community with enhanced experimental tools to understand runaway electrons (energy distribution and spatial localization) and magnetic reconnection (spatial localization, speed...). This work forms part of the optimization studies of a detecting unit proposed for use in such a diagnostic system, based on GEM technology. The detector is currently under development with the objective of achieving the best spatial resolution feasible with this technology (down to approximately 100 µm). The diagnostic design focuses on the monitoring of photons within the 2–15 keV range. The findings of the optimization studies conducted on the amplification stage of the detector, particularly with regard to the geometrical configuration of the GEM foils, are presented herein. The impact of hole shape and spacing in the amplifying foils on the detector parameters, including the spatial size of the avalanches and the electron gain/multiplication, has been subjected to comprehensive numerical analysis through the utilization of Degrad (v. 3.13) and Garfield++ (v. bd8abc76) software. The results obtained led to the identification of two configurations as the most optimal geometrical configurations of the amplifying foil for the three-foil GEM system for the designed detector. The first configuration comprises cylindrical holes with a diameter of 70 μm, while the second configuration comprises biconical holes with diameters of 70/50/70 μm. Both configurations had a hole spacing of 120 μm. [ABSTRACT FROM AUTHOR]

The fusion energy research field presents many intricate challenges that require resolution. Many diagnostic systems employed in experiments are approaching the limits of current technology. Implementing efficient measurements requires using an appropriate set of tools to facilitate the optimal utilization of hardware. Fusion energy measurements must provide low latency processing with the capacity for future improvements and the ability to handle complex data flows efficiently. The presented work addresses these requirements and describes the implementation of a high-performance, low-latency software platform with convenient development for soft X-ray (SXR) plasma impurities emission tracing—the Asynchronous Complex Computation Platform (AC2P). This article presents the architectural design, implementation details, and performance and latency measurements based on the raw data acquired from the WEST tokamak and laboratory tests. AC2P provides the tools to develop low-latency, multi-core, multi-device complex data flow graph scale-up solutions for measuring impurities in hot plasmas. The system has been designed to operate online during experiments, calculate the energy distribution, position and occurrence time of SXR photons, monitor the data stream’s quality and archive any abnormalities for subsequent offline verification and algorithm improvement. This article presents AC2P, which operates as part of the SXR measurement system on the WEST tokamak.

The objective of the proposed research is to develop plasma soft X-ray (SXR) radiation imaging that includes spectral information in addition to standard SXR tomography for the purpose of studying, for example, tungsten transport and its interplay with magnetohydrodynamics (MHD) in tokamak plasmas in an ITER-relevant approach. The SXR radiation provides valuable information about both aspects, particularly when measured with high spatial and temporal resolution and when tomographic reconstructions are performed. The spectral data will facilitate the tracking of both light and high-Z impurities. This approach is pertinent to both the advancement of a detailed understanding of physics and the real-time control of plasma, thereby preventing radiative collapses. The significance of this development lies in its ability to provide three-dimensional plasma tomography, a capability that extends beyond the scope of conventional tomography. The utilization of two-dimensional imaging capabilities inherent to Gas Electron Multiplier (GEM) detectors in a toroidal view, in conjunction with the conventional poloidal tomography, allows for the acquisition of three-dimensional information, which should facilitate the study of, for instance, the interplay between impurities and MHD activities. Furthermore, this provides a valuable opportunity to investigate the azimuthal asymmetry of tokamak plasmas, a topic that has rarely been researched. The insights gained from this research could prove invaluable in understanding other toroidal magnetically confined plasmas, such as stellarators, where comprehensive three-dimensional measurements are essential. To illustrate, by attempting to gain access to anisotropic radiation triggered by magnetic reconnection or massive gas injections, such diagnostics will provide the community with enhanced experimental tools to understand runaway electrons (energy distribution and spatial localization) and magnetic reconnection (spatial localization, speed…). This work forms part of the optimization studies of a detecting unit proposed for use in such a diagnostic system, based on GEM technology. The detector is currently under development with the objective of achieving the best spatial resolution feasible with this technology (down to approximately 100 µm). The diagnostic design focuses on the monitoring of photons within the 2–15 keV range. The findings of the optimization studies conducted on the amplification stage of the detector, particularly with regard to the geometrical configuration of the GEM foils, are presented herein. The impact of hole shape and spacing in the amplifying foils on the detector parameters, including the spatial size of the avalanches and the electron gain/multiplication, has been subjected to comprehensive numerical analysis through the utilization of Degrad (v. 3.13) and Garfield++ (v. bd8abc76) software. The results obtained led to the identification of two configurations as the most optimal geometrical configurations of the amplifying foil for the three-foil GEM system for the designed detector. The first configuration comprises cylindrical holes with a diameter of 70 μm, while the second configuration comprises biconical holes with diameters of 70/50/70 μm. Both configurations had a hole spacing of 120 μm.

The excitation of an initially stable neoclassical tearing mode (NTM) is investigated in Experimental Advanced Superconducting Tokamak (EAST) low- β p H-mode plasmas (β p is defined as the ratio of the thermal pressure to the poloidal magnetic pressure). Using similar plasma parameters, n = 1 resonant magnetic perturbation (RMP) cannot always successfully excite the m / n = 2/1 NTM with the same RMP coil current setup (n and m are the toroidal and poloidal mode numbers, respectively). Data from a gas electron multiplier camera shows that NTM destabilization is related to RMP-induced crashes at the q = 1 resonant surface during the RMP ramp-up phase. The second RMP-induced crash amplitude decays exponentially as β p increases. There is a critical value β p ≈ 0.76 above which the crash amplitude (or seed island width) is too small (below the critical island width) to trigger an NTM. Observation and analysis indicate that the m / n = 2/1 NTM is not forcibly driven by the n = 1 RMP (such as the m / n = 2/1 component), but is probably due to electron heat transport between the q = 1 and the q = 2 resonant surfaces. This paper describes experimental observations of NTM excitation which also have implications for further investigations of NTM locking and disruptions. [ABSTRACT FROM AUTHOR]

The gas electron multiplier (GEM) detector in combination with a solid converter has been widely used in the field of neutron detection in recent decades. Typically, the submillimeter is an important indicator for neutron detectors to satisfy many applications requiring a high spatial resolution. This article proposes a novel method to improve the spatial resolution of ceramic GEM detectors by adding a stopping layer on top of the solid 10B4C neutron converter. This will restrict the emission of the secondary ion products of large angles and consequently improve the spatial resolution. The Monte Carlo program FLUKA is used to validate the method, and the verification experiments are carried out at beam line #20 (BL20) of the China Spallation Neutron Source (CSNS). The experimental results are approximately in agreement with the simulations. The measured spatial resolution is 1.87 mm for the GEM neutron detector operated at ambient pressure with a 1 $\mu \text{m}$ -thick 10B4C converter and a drift gap of 4 mm, eventually, it is improved to ~0.8 mm by coating a 3 $\mu \text{m}$ -thick titanium on top of the 10B4C converter. [ABSTRACT FROM AUTHOR]

The ion backflow (IBF) is the main limiting factor for operating time projection chambers (TPCs) at high event rates. A significant effort is invested by many experimental groups to solve this problem. This article explores a solution based on operating a passive bipolar wire grid. In the presence of the magnetic field, the grid more effectively attenuates the ion current than the electron current going through it. Transparencies of the grid to electrons and ions are measured for different gas mixtures and magnitudes of the magnetic field. The results suggest that in a sufficiently strong magnetic field, the bipolar wire grid can be used as an effective and independent device to suppress the IBF in TPCs. [ABSTRACT FROM AUTHOR]

We have developed highly interleaved zigzag-shaped electrodes for collecting charge on the readout plane of various micropattern gaseous detectors (MPGDs), including gas electron multiplier (GEM) and micromega detectors. An optimized zigzag pad (or strip) anode can greatly enhance charge sharing among neighboring pads compared to traditional straight strip or rectangular pad designs and as a result can deliver excellent position resolution with minimal channel count, while exhibiting a virtually uniform response across the detector. We have systematically studied the effects of varying the parameters that define the zigzag geometry using simulations and have measured several printed circuit boards (PCBs) comprising a range of zigzag designs. Recently, we have employed laser ablation to generate zigzag patterns with pad-to-pad gaps smaller than 1 mil (or 25 μm). Reducing the gap well below the 3-mil limit imposed by traditional chemical etching has allowed the production of zigzag electrodes with unprecedentedly small feature sizes. In turn, laser-etched zigzag PCBs were shown to exhibit markedly improved performance over earlier generation PCBs, with position resolutions below 50 $\mu \text{m}$ for a 2-mm pitch. This article will explore in detail the dependence of the position resolution on the structural parameters of a zigzag-shaped anode, specifically for the case of a quadruple GEM detector. [ABSTRACT FROM AUTHOR]

A combined time projection chamber-Cherenkov (TPCC) prototype detector has been developed as part of the detector research and development program for a future electron–ion collider (EIC). The prototype was tested at the Fermilab test beam facility (FTBF) to provide a proof of the principle to demonstrate the ability to measure particle tracks and provide particle identification (PID) information within a common detector volume. The time projection chamber (TPC) portion consists of a $10 \times 10 \times 10$ cm3 field cage, which delivers charge from tracks to a quadruple gas electron multiplier (GEM) with zigzag-shaped charge collection anodes. The Cherenkov portion consists of a photosensitive quadruple GEM detector with a CsI photocathode. As tracks pass through the drift volume of the TPC, the generated Cherenkov light is able to escape through sparsely arranged wires making up one side of the field cage, facing the CsI photocathode. The Cherenkov detector is thus operated in a windowless, proximity focused configuration for high efficiency. Pure CF4 is used as the working gas for both detector components, mainly due to its transparency into the deep UV, as well as its high N0. Results from the beam test, including the position resolution as well as the particle id capabilities of the detector, are discussed in this paper. [ABSTRACT FROM AUTHOR]

New design studies have been carried out for a readout plane for gas electron multiplier detectors using zigzag patterns that can significantly reduce the readout channel count while preserving excellent spatial resolution for tracking detectors. While zigzag patterns have been used in a number of applications, these studies were designed to investigate the fundamental limits of charge sharing between the electrodes to optimize the spatial resolution and minimize the nonuniformities across the readout plane, while exploring the limits of manufacturing capabilities for producing the readout board. Simulation studies were carried out to optimize the readout electrode structure, and readout boards were produced with similar zigzag designs that were tested in the laboratory using a scanning X-ray source. These studies were aimed at developing a readout board for the new time projection chamber for the sPHENIX experiment at relativistic heavy ion collider, but can readily be used in other applications, including various micropattern gas detectors, such as Micromegas. [ABSTRACT FROM AUTHOR]

A Time Projection Chamber (TPC) is an ideal device for the detection of charged particle tracks in a large volume covering a solid angle of almost 4 π . The high density of hits on a given particle track facilitates the task of pattern recognition in a high-occupancy environment and in addition provides particle identification by measuring the specific energy loss for each track. For these reasons, TPCs with Multiwire Proportional Chamber (MWPC) amplification have been and are widely used in experiments recording heavy-ion collisions. A significant drawback, however, is the large dead time of the order of 1 ms per event generated by the use of a gating grid, which is mandatory to prevent ions created in the amplification region from drifting back into the drift volume, where they would severely distort the drift path of subsequent tracks. For experiments with higher event rates this concept of a conventional TPC operating with a triggered gating grid can therefore not be applied without a significant loss of data. A continuous readout of the signals is the more appropriate way of operation. This, however, constitutes a change of paradigm with considerable challenges to be met concerning the amplification region, the design and bandwidth of the readout electronics, and the data handling. A mandatory prerequisite for such an operation is a sufficiently good suppression of the ion backflow from the avalanche region, which otherwise limits the tracking and particle identification capabilities of such a detector. Gas Electron Multipliers (GEM) are a promising candidate to combine excellent spatial resolution with an intrinsic suppression of ions. In this paper we describe the design, construction and the commissioning of a large TPC with GEM amplification and without gating grid (GEM-TPC). The design requirements have driven innovations in the construction of a light-weight field-cage, a supporting media flange, the GEM amplification and the readout system, which are presented in this paper. We further describe the support infrastructure such as gas, cooling and slow control. Finally, we report on the operation of the GEM-TPC in the FOPI experiment, and describe the calibration procedures which are applied to achieve the design performance of the device. [ABSTRACT FROM AUTHOR]

The bubble-assisted Liquid Hole-Multiplier (LHM) is a recently-introduced detection concept for noble-liquid time projection chambers. In this “local dual-phase” detection element, a gas bubble is supported underneath a perforated electrode (e.g., Thick Gas Electron Multiplier – THGEM, or Gas Electron Multiplier – GEM). Electrons drifting through the holes induce large electroluminescence signals as they pass into the bubble. In this work we report on recent results of THGEM and GEM electrodes coated with cesium iodide and immersed in liquid xenon, allowing – for the first time – the detection of primary VUV scintillation photons in addition to ionization electrons. [ABSTRACT FROM AUTHOR]

A Tissue-Equivalent Proportional Counter (TEPC), based on a single GEM foil of standard geometry, has been tested with pure propane gas at low pressure, in order to simulate a tissue site of about 1 µm equivalent size. In this work, the performance of GEM with propane gas at a pressure of 21 and 28 kPa will be presented. The effective gas gain was measured in various conditions using a 244 Cm alpha source. The dependence of effective gain on the electric field strength along the GEM channel and in the drift and induction region was investigated. A maximum effective gain of about 5×10 3 has been reached. Results obtained in pure propane gas are compared with gas gain measurements in gas mixtures commonly employed in microdosimetry, that is propane and methane based Tissue-Equivalent gas mixtures. [ABSTRACT FROM AUTHOR]

Positron Emission Tomography is a powerful imaging technique used for humans and animals that can also be used to study plant biology. However, since many of the structures found on plants (e.g., leaves) are very thin, a large portion of the positrons emitted from PET isotopes escape before annihilation, leading to low efficiency and quantification inaccuracies. In this study, a gas tracking detector was used to measure escaping positrons from PET radiotracer isotopes which has the ability to reconstruct three dimensional tracks that can be used to form an image of the emitting object. This device uses a triple GEM detector with a short drift region and an XY strip readout plane to measure a vector for positrons passing through a drift gap. By projecting each particle track back to the object surface, a 2-D image of the spatial distribution of the positrons that escaped from that surface can be reconstructed. In this paper, we will describe the basic principle of the GEM detector and present results on its performance using various types of phantoms and actual plant specimens. Monte Carlo simulations are also used to better understand the detector performance and compare to actual measurements. [ABSTRACT FROM PUBLISHER]

A prototype time projection chamber with 26 cm drift length was operated with a short-spaced triple gas electron multiplier (GEM) stack in a setup triggering on cosmic muon tracks. A small part of the anode plane is read out with a CMOS pixel application-specified integrated circuit (ASIC) named Timepix, which provides ultimate readout granularity. Pixel clusters of charge depositions corresponding to single primary electrons are observed and analyzed to reconstruct charged particle tracks. A dataset of several weeks of cosmic ray data is analyzed. The number of clusters per track length is well described by simulation. The obtained single point resolution approaches 50 \mum at short drift distances and is well reproduced by a simple model of single-electron diffusion . [ABSTRACT FROM AUTHOR]

Abstract: Energy-selective neutron radiography is a new method for studying the fine structure of heavy materials by using pulsed neutron sources. To perform such radiography, precise measurements of temporal information and twodimensional position are essential. Therefore, we developed a gaseous neutron detector using the gas electron multiplier (GEM). In addition, to detect neutrons, a single surface of an aluminium cathode plate and both surfaces of two GEM foils were coated with boron-10. Two normal GEM foils were stacked in a chamber for gas amplification. An anode plate with two-dimensional strips (0.8-mm pitch) was mounted in order to precisely reconstruct neutron incident positions. To allow high-speed data transfer, a compact readout system with new application-specific integrated circuit (ASIC) chips and a field programmable gate array (FPGA) was developed. Finally, several beam tests were conducted with pulsed neutron sources and two interesting applications were demonstrated. [Copyright &y& Elsevier]

Abstract: To improve material structure analysis using thermal (cold) neutrons at several pulsed neutron sources, we have developed a new gas detector for neutrons that employs a gas electron multiplier (GEM) as the detector. For neutron detection, both surfaces of a single GEM foil are coated with boron, and to increase efficiency, several GEM foils are stacked in a chamber. A prototype chamber was constructed with 10cm × 10cm GEM foils, and several beam tests were performed at a research reactor in Japan and at pulsed neutron sources (Hokkaido University and the Japan Proton Accelerator Research Complex). We achieved a detection efficiency of 30% for 0.22-nm thermal neutrons and a position resolution of ∼0.5mm. In addition, we demonstrate two applications. [Copyright &y& Elsevier]

Abstract: The delay-line readout method is suitable for the position sensitive detectors in the early stage of high energy physics experiment at low-rate environment. In this paper, we present a fast delay-line circuit (cut off frequency: 0.7GHz) equipped with a triple-GEM (Gas Electron Multiplier) detector for X-ray imaging. Using 8keV X-rays and readout strips with 0.15mm width and 0.4mm pitch, the experiment result shows that the position resolution of the detecting system is less than at a counting rate of . A full simulation model has been developed for the design of delay-line electric circuit. [Copyright &y& Elsevier]

A Gas Electron Multiplier with a Micro-Induction Gap Amplifying Structure (GEM-MIGAS) is formed when a conventional GEM is operated with a short induction gap, typically set at 50 µm. Experimental studies were carried out to investigate the single-electron response of a GEM-MIGAS, using a He/iso-C4H10 (85/15%) gas mixture operated in a flow mode at atmospheric pressure. The additional charge multiplication in the induction gap results in a gain increase up to one order of magnitude when compared to the GEM mode operation alone. A series of measurements were undertaken to examine the pulse height distributions induced by single-electrons under a wide range of bias voltages applied across the GEM holes, 100 to 550 V, and for a wide range of electric fields in the induction gap, 0.6 to 100 kV/cm. It was possible to sustain effective charge gains in excess of 3 × 105 and multiplication relative variances around 0.4 over a large range of GEM voltages, enabling us to demonstrate single-electron detection efficiencies above 98%. [ABSTRACT FROM AUTHOR]

The planned tracking upgrade of the STAR experiment at RHIC includes a large-area GEM tracker used to determine the charge sign of electrons and positrons produced from W+(-) decays. For such a large-scale project commercial availability of GEM foils is necessary. We report first results obtained with a triple GEM detector using GEM foils produced by Tech-Etch Inc. of Plymouth, MA. Measurements of gain uniformity, long-term stability as well as measurements of the energy resolution for X-Rays are compared to results obtained with an identical detector using GEM foils produced at CERN. A quality assurance procedure based on optical tests using an automated high-resolution scanner has been established, allowing a study of the correlation of the observed behavior of the detector and the geometrical properties of the GEM foils. Detectors based on Tech-Etch and CERN produced foils both show good uniformity of the gain over the active area and stable gain after an initial charge-up period, making them well suited for precision tracking applications. [ABSTRACT FROM AUTHOR]

The characterization of a scintillating GEM based gas detector for quality control of clinical radio-therapeutic beams is presented. Photons emitted by the Ar/CF4 gas mixture are detected by means of a CCD camera; in addition, the charge is measured. The detector response has been studied as a function of alpha particle energy and dose rate. The measured signal underestimation, at the Bragg peak depth, is only few percent with respect to an air filled ionization chamber. [ABSTRACT FROM AUTHOR]

Abstract: A large volume Time Projection Chamber (TPC) has been proposed as the main tracking device for one of the experiments at the International Linear Collider (ILC). Gas Electron Multipliers (GEMs) are being studied as potential replacements for the conventional wire-based gas amplification system of TPCs. In this paper, recent results are presented from R&D activities with small GEM–TPC prototypes ongoing at DESY. [Copyright &y& Elsevier]

A triple-gas electron multiplier (GEM) detector, operated with the gas mixture Ar/CO2/CF4 (45/15/40), is going to equip station M1, region R1 of the LHCb muon system. A Module-0 of this detector, with full area (20 cm × 24 cm) GEM foils, was recently built and tested. In this paper, new measurements of efficiency and pad multiplicity are presented. These new measurements were very important to select of the final pad board configuration. The sensitivity to discharges is a very important issue in this type of detector; we discuss here new measurements of the maximum number of discharges that a triple-GEM detector can stand before breakdown, and we show that detector operation in LHCb is safe from this point of view. We also discuss new measurements of the time performance of the detector in the presence of background radiation, indicating that no significant deterioration of the performances is expected in the LHCb environment. [ABSTRACT FROM AUTHOR]

Abstract: Gaseous detectors using multiple gas electron multiplier (GEM) electrodes permit to attain large amplification factors with a strong suppression of photon and ion-mediated feedback. With the first GEM in a cascade coated with a photosensitive layer, they provide efficient and fast single photon detection, with excellent position resolution. General performances of CsI-coated multi-GEM detectors are described, as well as a promising method of signal readout, the so-called hexaboard, a matrix of interconnected pads that permits to achieve ambiguity-free reconstruction of multi-photon events, a major requirement for RICH applications. [Copyright &y& Elsevier]

The microhole and strip plate (MHSP) gas electron multiplier was studied as a stand-alone device or in combination with a cascade of gas electron multipliers (GEMs), for X-ray and UV-photon detection. An MHSP operating in Ar/5%Xe yielded gains above 104 and energy resolutions of about 14% FWHM for 5.9-keY X-rays. Gains as high as 107 were reached in a 3-GEMIMHSP gaseous photomultiplier operating in an Ar/5%CH4 the ion back-flow ratio to the top of the first GEM could be reduced to ∼2%. Two-dimensional (2-D) imaging was performed using signals induced by avalanche ions on a wedge and strip (W&S) readout cathode, placed at close proximity to the anode strips; position resolution of 200-250 μm FWHM for 5.9-keV X-rays was measured. [ABSTRACT FROM AUTHOR]

Connected to the linear collider project, studies on the readout of time projection chambers (TPCs) based on the gas electron multiplier (GEM) are ongoing. Higher granularity and intrinsically suppressed ion feedback are the major advantages of this technology. After a short discussion of these tissues, we present the design of a small and very flexible TPC prototype, whose cylindrical drift volume can be equipped with endcaps of different gas detector types. An endcap with multi-GEM readout is currently set up and successfully operated with a low-noise highly integrated front-end electronics. We discuss results of measurements with this system in high intensity particle beams at CERN, where 99.3 ± 0.2 % single-pad-row efficiency could be achieved at an effective gain of 2.5 &times 10³ only, and spatial resolutions down to 63 ±3 μm could be demonstrated. Finally, these results are extrapolated to the high magnetic field in a linear collider TPC. [ABSTRACT FROM AUTHOR]

A Micro compteur a` Trous (MicroCAT) structure which is used for avalanche charge multiplication in gas filled radiation detectors has been optimised with respect to maximum electron transparency and minimum ion feedback. We report on the charge transfer behaviour and the achievable gas gain of this device. A three-dimensional electron and ion transfer simulation is compared to results derived from electric current measurements. Similarly, we present studies of the charge transfer behaviour of a Gas Electron Multiplier (GEM) by current measurements and simulations. Finally, we investigate the combination of the MicroCAT and the GEM by measurements with respect to the performance at different voltage settings, gas mixtures and gas pressures. [Copyright &y& Elsevier]

Measurements and numerical simulations on the charge transfer in Gas Electron Multiplier (GEM) foils are presented and their implications for the usage of GEM foils in Time Projection Chambers are discussed. A small test chamber has been constructed and operated with up to three GEM foils. The charge transfer parameters derived from the electrical currents monitored during the irradiation with an 55Fe source are compared with numerical simulations. The performance in magnetic fields up to 2 T is also investigated. [Copyright &y& Elsevier]

A review of methods used in the simulation of processes in gas electron multipliers (GEMs) and in the accurate calculation of detector characteristics is presented. Such detector characteristics as effective gas gain, transparency, charge collection and losses have been calculated and optimized for a number of GEM geometries and compared with experiment. A method and a new special program for calculations of detector macro-characteristics such as signal response in a real detector readout structure, and spatial and time resolution of detectors have been developed and used for detector optimization. A detailed development of signal induction on readout electrodes and electronics characteristics are included in the new program. A method for the simulation of charging-up effects in GEM detectors is described. All methods show good agreement with experiment. [Copyright &y& Elsevier]

With the advancement of the accelerator systems and the requirements of high luminosity particle beams to reach different physics goals, detectors with good position resolution and high rate handling capability have become essential for designing any High Energy Physics (HEP) experiments. The Gas Electron Multiplier (GEM) detectors are widely used in many HEP experiments as a tracking device because of their good spatial resolution and rate handling capability. The presence of the dielectric medium inside the active volume of the GEM detector changes its behaviour when exposed to external radiation. This mechanism is commonly referred as the charging-up effect. In this article, the effect of the charging-up phenomenon and the initial polarisation effect of the dielectric on the gain of the chamber are reported for a single mask triple GEM chamber with Ar/CO 2 gas mixture. [ABSTRACT FROM AUTHOR]

Abstract: The Gas Electron Multiplier (GEM), introduced several years ago, is finding numerous applications thanks to its excellent performances in detecting and localizing ionizing radiation. This note summarizes recent developments of the technology, and presents some examples of applications. [Copyright &y& Elsevier]

In this work, we report the design configuration and the performance of the hybrid Gas Electron Multiplier (GEM) detector. In order to make the detector sensitive to thermal neutrons, the forward electrode of the GEM has been coated with the enriched boron-10 material, which works as a neutron converter. A total of 5×5cm 2 configuration of GEM has been used for thermal neutron studies. The response of the detector has been estimated via using GEANT4 MC code with two different physics lists. Using the QGSP_BIC_HP physics list, the neutron detection efficiency was determined to be about 3%, while with QGSP_BERT_HP physics list the efficiency was around 2.5%, at the incident thermal neutron energies of 25meV. The higher response of the detector proves that GEM-coated with boron converter improves the efficiency for thermal neutrons detection., (Copyright © 2014 Elsevier Ltd. All rights reserved.)