Electron Multiplier Detector Research Articles

NMX detector algorithms

A Gas Electron Multiplier (GEM) detector with a Gadolinium converter is being developed for the Neutron Macromolecular Diffractometer (NMX) at the European Spallation Source (ESS). Charge data from the orthogonal copper strips of the GEM detector will be collected by a number of VMM3 chips which each delivers a stream of data triplets from 64 copper strips. Each triplet consists of strip number, a charge maximum and the time when the maximum was recorded. This data has to be clustered in real time into X- and Y-cluster pairs each corresponding to a neutron event such that the entrance point location and time for the neutron event can be determined. This paper describes algorithms and their implementation for performing this task. The algorithms include an innovative streaming sorting, a novel clustering algorithm and a pairing algorithm for constructing the neutron event data. The implementation and algorithms have been tested extensively and yield a satisfactory performance without any optimization so far. The processing time is close to being constant per data triplet.

Signal and pointing accuracy of ultraviolet laser in micro-pattern gaseous detector

In the study of the gas detectors, it is an important calibration method to use the ultraviolet (UV) laser with two-photon ionization mechanism for producing ionized signal. In the last decades, micro pattern gas detector, especially gaseous electron multiplier and micromesh gaseous detector, has been widely used in high energy experiments. These kinds of gaseous detectors have the advantages of higher ion backflow suppression ability, smaller <b><i>E</i></b> × <b><i>B</i></b> effect and good radiation resistance under the relatively higher count rate environment. To obtain a higher spatial resolution with a UV laser calibration system in gaseous electron multiplier detector, two critical technical issues remain to be resolved: the measurability of the laser signal and the accuracy of the laser beam position. In this paper, the studies in simulation and experiment are conducted to discuss these two critical questions. In the simulation section, the simulation results provide an estimation of signal in the gaseous electron multiplier detector with UV laser of 266 nm wavelength in the mixture working gases of Ar/CO<sub>2</sub> (70/30), and give an evaluation of the laser pointing accuracy and the possible relative error of the electron drift velocity. In the experiment section, a UV laser calibration prototype is designed and developed. A pulsed laser of 266 nm wavelength is used as a signal source, which has a Gaussian-like cross section with a frequency of 10 Hz. The experimental results indicate that the signal of the UV laser in a triple gaseous electron multiplier detector reaches 400 mV for a readout strip width of 6 mm, a gain of detector of 5000, and a gain of amplifier of 10 mV/fC. For the calibration laser, the angle accuracy is discussed and tested. The angle uncertainty of the laser can be kept under 5′, and the accuracy of the drift velocity can reach 6.4 × 10<sup>−4</sup> with a shift of 0.33 mm in the <i>z</i> direction when the laser beam transmits a distance of 400 mm in the gas chamber. All of these results show that the laser beam specific parameters are the main reference for designing the prototype detector. According to the optimal parameters, a gaseous prototype detector will be tested in the next study.

Simulation of different options of the Inner Tracker for Novosibirsk Super Charm-Tau Factory Detector

Inner Tracker of Novosibirsk Super Charm-Tau Factory Detector has to measure momenta of soft hadrons, which do not reach the drift chamber; complement the drift chamber in measuring the momenta; detect secondary vertices of short-lived particles. Thus, proper choice of the option for the Inner Tracker is of significant interest. The simulation of charged pions propagation in the perpendicular direction to the beam axis was carried out with DD4HEP program based on GEANT4. Three options were considered: 4-layered Silicon microstrip detector, 4-layered cylindrical Gas Electron Multiplier (GEM) detector and Time Projection Chamber (TPC). The simulated Detector was located in 1.5 T magnetic field directed along beam axis. The simulation shows that pions with initial momenta less than 50 MeV/c do not pass through the beampipe and cannot be registered. Pions with momenta above 65 MeV/c leave energy depositions in all 4 layers of the Inner Tracker based on Silicon, and their trajectories can be reconstructed. Cylindrical GEM detector provides reconstruction possibility (hits in 4 layers) for pions with momenta more than 60 MeV/c. TPC with thin inner wall provides reconstruction of pions with momenta higher than 55 MeV/c. However, in this case the reconstruction procedure will be much more complicated due to a large number of background particle tracks in the sensitive volume.

Performance of the BM@N GEM/CSC tracking system at the Nuclotron beam

BM@N (Baryonic Matter at the Nuclotron) is a fixed target experiment aimed to study nuclear matter in the relativistic heavy-ion collisions at the Nuclotron accelerator in JINR. The BM@N tracking system is based on Gas Electron Multipliers (GEM) detectors mounted inside the BM@N analyzing magnet. The Cathode Strip Chamber (CSC) is installed outside the magnet. The CSC is used for improvement of particles momentum identification. The structure of the GEM detectors and the CSC prototype and the results of study of their characteristics are presented. The GEM detectors and CSC are integrated into the BM@N experimental setup and data acquisition system. The results of first tests of the GEM tracking system and CSC in last runs are shortly reviewed.

DAQ software for GEM-based imaging system

In the paper we report on the development of a dedicated data acquisition (DAQ) software being part of a full-filed X-ray fluorescence spectroscopy (XRF) imaging system based on a standard 10 cm × 10 cm 3-stage Gas Electron Multiplier (GEM) detector. Readout of a large area detector introduces additional constraints and requirements for the front-end electronics, data acquisition system and the software which are necessary for efficient system operation. The details of the front-end electronics and the data acquisition system have already been reported elsewhere. Therefore, in the paper, we focus mostly on the software part of the developed system. The software suite consists of a few independent components, each responsible for the well-defined task. A crucial part of the software, in a form of a Graphical User Interface (GUI) application written in modern C++ language with help of Qt framework and Boost libraries, is responsible for system configuration, monitoring and online data reconstruction. During data-taking periods an automated system is utilized for batch recording of the measurement data, event reconstruction and processing with results visualization. This part of the software has been split into (a) dedicated raw data recorder, (b) non-GUI event reconstruction component (C++ based) able to use most of the workstation resources (mainly CPUs time) and (c) independent, flexible offline visualization component for plots or histograms preparation (Python based). All the components of the system are completely independent of each other. Therefore, distribution of the tasks to a few workstation PCs is straightforward and significantly accelerates processing.

FPGA-based novel real-time evaluation and data quality monitoring system for tokamak high-performance GEM soft X-ray diagnostic

Based on literature review data quality monitoring topic is often being simplified in case of tokamak diagnostic systems. In previous publications Authors presented a novel model of real-time evaluation and data quality monitoring (EDQM) sub-system for use in physics experiments, mostly related to tokamak plasma measurements. The implementation of model is done in scope of monitoring raw output signals from Gas Electron Multiplier detectors used in FPGA-based soft X-ray diagnostics. System is designed to work in the real-time feedback loop for parameters control of tokamak in scope of achieving long-term plasma stability. In the paper are described results of application the DQM engine from measurements with 112-channel GEM detector and real radiation sources (isotopes, X-ray tube). The discussion provided in article covers the usefulness of applied novel EDQM techniques: technical and statistical, in scope of detection of new, corrupted output signals from the GEM detector when working under hard environment conditions. The presented in the paper results indicates the ability of the detection of subtle system defects (e.g. detector, electronics), resulting in the significant corruption of the output products of measured radiation: energy and topological spectra. This is especially important for the systems working in the real-time feedback loop. The novel approach of detection new malformed signals with ability to automatically discard those phenomena from further analysis is also described. In the summary there are described benefits of usage of the proposed novel DQM approach with indication of another unique work for further CPU extensions of the EDQM sub-system providing complex FPGA-CPU high-performance data quality monitoring unit. The EDQM system is planned to be installed in GEM SXR diagnostics on WEST tokamak.

Directionality properties of the nGEM detector of the CNESM diagnostic system for SPIDER

The ITER project requires additional heating by two neutral beam injectors, each accelerating up to 1 MV a 40 A beam of negative deuterium ions for one hour. Such requirements have never been reached, so it was decided to build in Padova a facility (PRIMA) that hosts two experimental devices: SPIDER, a 100 kV negative H/D RF beam source, and MITICA, a full-scale injector for the ITER NBI. SPIDER has begun operation in 2018, while MITICA is expected to start after 2020. In both devices the accelerated deuterium beam impinges on an actively cooled beam dump used to stop the deuterons. Detection of fusion neutrons produced between beam–deuterons and dump-embedded deuterons will be used as a means to resolve the horizontal beam intensity profile. A neutron detection system called Close-contact Neutron Emission Surface Mapping (CNESM) is installed right behind the SPIDER beam dump, with the aim to provide the neutron emission map of the beam dump surface. The core of this diagnostic system is an nGEM (neutron-Gas Electron Multiplier) detector which will be able to reconstruct the fast neutron beam profile with an efficiency of about 10−4. A crucial point in order to correctly reconstruct the profile of the deposited D− power is the directionality discrimination capability of the detector. This paper reports on the results of the characterization of the nGEM directionality capabilities, performed at the Frascati Neutron Generator (FNG) using 2.5 MeV neutrons, before installation of the detector inside the SPIDER vacuum vessel.

Operational Experience With the GEM Detector Assembly Lines for the CMS Forward Muon Upgrade

The CMS Collaboration has been developing large-area triple-gas electron multiplier (GEM) detectors to be installed in the muon Endcap regions of the CMS experiment in 2019 to maintain forward muon trigger and tracking performance at the High-Luminosity upgrade of the Large Hadron Collider (LHC); 10 preproduction detectors were built at CERN to commission the first assembly line and the quality controls (QCs). These were installed in the CMS detector in early 2017 and participated in the 2017 LHC run. The collaboration has prepared several additional assembly and QC lines for distributed mass production of 160 GEM detectors at various sites worldwide. In 2017, these additional production sites have optimized construction techniques and QC procedures and validated them against common specifications by constructing additional preproduction detectors. Using the specific experience from one production site as an example, we discuss how the QCs make use of independent hardware and trained personnel to ensure fast and reliable production. Preliminary results on the construction status of CMS GEM detectors are presented with details of the assembly sites involvement.

Development of high-speed vacuum ultraviolet spectroscopy using a modified Seya-Namioka monochromator and channel electron multiplier detector in the HL-2A tokamak.

A high-speed vacuum ultraviolet monochromator is developed for the HL-2A tokamak through the introduction of a novel channel electron multiplier in a modified Seya-Namioka spectrometer. A good signal to noise ratio of above 2000 is attained in the development phase of the system with typical operating parameters for observing routine HL-2A plasmas. The wavelength calibration is performed using characteristic line emissions from a hollow cathode light source with helium and argon discharges. The first measurement result of the monochromator at a sample rate of 60 kHz is presented in comparison with the visible Dα signals.

Characterization of the STS/MUCH-XYTER2, a 128-channel time and amplitude measurement IC for gas and silicon microstrip sensors

New physics experiments at the Facility for Antiproton and Ion Research (FAIR) in Darmstadt require application-optimized detector readout circuits. The STS/MUCH-XYTER2 (or SMX2) is a new, 128-channel prototype ASIC for silicon strip detectors and gas electron multiplier (GEM) detectors in the Compressed Baryonic Matter (CBM) experiment. It provides self-triggered amplitude and time measurement of incoming charge and serial streaming of digitized data. The 10 mm × 6.75 mm chip was fabricated employing the UMC CMOS 180 nm process. It comprises of an analog front-end with dual-path processing including a timing comparator in one path and a continuous-time 5-bit analog-to-digital converter in the other path, a digital back-end with time pre-sorting, advanced monitoring and throttling features and multiple 320 Mbps, serial links targeted for a GBT-based data acquisition structure. Specific conditions of the detector systems will be discussed prior to the structure and the features of the ASIC together with measurement results.

FPGA and Embedded Systems Based Fast Data Acquisition and Processing for GEM Detectors

Gas electron multiplier (GEM) detectors (Sauli in Nucl Instrum Methods Phys Res A 805:2–24, 2016. https://doi.org/10.1016/j.nima.2015.07.060 (special issue in memory of Glenn F. Knoll); Buzulutskov in Instrum Exp Tech 50(3):287–310, 2007. https://doi.org/10.1134/S0020441207030013) are widely used for detection of ionizing radiation. When used in the proportional mode, they provide information about time, location, and energy of a detected particle (Chernyshova et al. in Fusion Eng Design, 2017. https://doi.org/10.1016/j.fusengdes.2017.03.107; Altunbas et al. in Nucl Instrum Methods Phys Res A 490(1–2):177–203, 2002. https://doi.org/10.1016/S0168-9002(02)00910-5. http://linkinghub.elsevier.com/retrieve/pii/S0168900202009105). Modern technologies allow full utilization of detector properties, by acquiring the waveform of output current pulses and processing them using sophisticated digital signal processing (DSP) algorithms. The current pulses must be digitized at high speed (up to 125 MHz) with high resolution (up to 12-bits). Due to the high volume of the produced data, it is necessary to provide the high-performance data acquisition system (DAQ) to transmit the data to processing units. Efficient processing of the GEM data requires distributed parallel processing system to perform multiple tasks (Czarski et al. in Rev Sci Instrum 87(11), 11E336, 2016. https://doi.org/10.1063/1.4961559): (1) Filter out the background and transmit only hit related data. (2) Extract the parameters of a hit, describing the time and charge (related to energy). (3) Estimate the hit position by combining information from multiple anode pads. (4) In case of 2D GEM detectors, correlate pulses received from X and Y pads (pixels) or W, U and V pads (pixels). (5) Separate the hits overlapping in space or in time (if possible) to support detector operation at higher rates. The above functionalities may be achieved in different hardware architectures. The typical hardware platforms include FPGA chips, standard or embedded computer systems with different computation accelerators (Wojenski et al. in J Instrum 11(11):C11035, 2016. http://stacks.iop.org/1748-0221/11/i=11/a=C11035; Nowak et al. in J Phys Conf Ser 513(5):052–024, 2014. https://doi.org/10.1088/1742-6596/513/5/052024. http://stacks.iop.org/1742-6596/513/i=5/a=052024?key=crossref.c5912cfa72c30b309821e14c4384948f. The paper shows possible solutions with their feasibility for particular applications.

Analysis of Pulse Height Distributions of a Gas Electron Multiplier Detector by Using Cs-137 and Sr-90 Radioactive Sources

A double-layer gas electron multiplier (GEM) chamber was developed at the Physics Department, Changwon National University. Its performance was evaluated using Cs-137 and Sr-90 radiation sources. Using a gas mixture filling of 85% argon and 15% carbon dioxide, in the one-channel GEM chamber (5 cm × 5 cm), the pulse height distributions were detected at atmospheric pressure and room temperature. The signals from the 32-keV and the 36-keV characteristic X-rays emitted owing to internal conversion in the Cs-137 source, as were signals from the beta emissions and 662-keV gamma rays. The signals due to the 662-keV gamma rays were separated from the other signals by placing 1 mm or 1.6 mm intercepting copper plates under the source. Furthermore, regions of the GEM detector in which the photo- and Compton electrons were produced by the X-rays (32 keV and 36 keV) and gamma rays (662 keV) were analyzed.

Readout Electronics for CEPC Semidigital Hadron Calorimeter Preprototype

Circular Electron and Positron Collider (CEPC) is a large experiment facility proposed by the Chinese particle physics community. One of the running options is being the Higgs factory. The calorimeter is the main part of this experiment to measure the jet energy. Semidigital hadron calorimeter (SDHCAL) is one of the options for the hadron measurement. Gas electron multiplier (GEM) detector with its high-position resolution and flexible configuration is one of the candidates for the active layer of the SDHCAL. The main purpose of this paper is to provide a feasible readout method for the GEM-based SDHCAL. A smallscale prototype is designed and implemented, including front-end board (FEB) and data interface board (DIF). The prototype electronics has been tested. The equivalent rms noise of all channels is below 0.35 fC. The dynamic range is up to 500 fC and the gain variation is less than 1%. The readout electronics is applied on a double-layer GEM detector with 1 cm × 1 cm readout pad. The result indicates that the electronics works well with the detector. The detection efficiency of minimum ionization particle (MIP) is over 95% with a 5-fC threshold.

Collisional dampening for improved quantification in single particle inductively coupled plasma mass spectrometry

Inductively coupled plasma mass spectrometry (ICP-MS) is a powerful method for detection and quantification of nanoparticles. Unfortunately, the linear dynamic range of single particle analysis is hindered by “unruly” transient signals, momentary pulse pile-ups at the electron multiplier detector. This study seeks to extend the dynamic range of ICP-MS nanoparticle quantification via addition of a collision gas in the collision cell of the ICP-MS. The collision gas temporally broadens the nanoparticle signal resulting in decreased pulse pile-up and increased integrated intensity, up to a point where scattering losses begin to dominate. We tested collisional broadening with a dual mode simultaneous secondary electron multiplier (pulse counting switching to analog) and the same detector configured for pulse counting only operation. With no collision gas and the detector operating in its standard dual mode, the data shows a linear response for gold nanoparticles from 20 nm (smallest measured size) to 150 nm. With the addition of helium as a collision gas in the cell, the linear range extends up to 250 nm. The data collected exclusively from the pulse counting mode shows that with no collision gas there is a linear response for gold nanoparticles from 20 nm to 60 nm. While the signal slightly improves with the addition of a collision gas, the linear range fails to extend up to 80 nm, the next largest nanoparticle size in this study. The addition of a collision gas used together with the dual mode detector shows a promising path forward towards mitigating unruly transient signals, improving the dynamic range of nanoparticle quantification.

The software-defined fast post-processing for GEM soft x-ray diagnostics in the Tungsten Environment in Steady-state Tokamak thermal fusion reactor.

This article presents a novel software-defined server-based solutions that were introduced in the fast, real-time computation systems for soft X-ray diagnostics for the WEST (Tungsten Environment in Steady-state Tokamak) reactor in Cadarache, France. The objective of the research was to provide a fast processing of data at high throughput and with low latencies for investigating the interplay between the particle transport and magnetohydrodynamic activity. The long-term objective is to implement in the future a fast feedback signal in the reactor control mechanisms to sustain the fusion reaction. The implemented electronic measurement device is anticipated to be deployed in the WEST. A standalone software-defined computation engine was designed to handle data collected at high rates in the server back-end of the system. Signals are obtained from the front-end field-programmable gate array mezzanine cards that acquire and perform a selection from the gas electron multiplier detector. A fast, authorial library for plasma diagnostics was written in C++. It originated from reference offline MATLAB implementations. They were redesigned for runtime analysis during the experiment in the novel online modes of operation. The implementation allowed the benchmarking, evaluation, and optimization of plasma processing algorithms with the possibility to check the consistency with reference computations written in MATLAB. The back-end software and hardware architecture are presented with data evaluation mechanisms. The online modes of operation for the WEST are discussed. The results concerning the performance of the processing and the introduced functionality are presented.

A New Approach for Alpha Radiography by Triple THGEM using Monte Carlo Simulation and Measurement

In this research, alpha imaging in Self Quenching Streamer (SQS) mode is investigated using a triple Thick Gas Electron Multiplier (THGEM) detector by Monte Carlo method and experimental data. First, a semi-empirical equation is derived to represent the relation between the SQS voltage and the alpha energy in every hole of the triple THGEM. The accuracy of this equation is tested and confirmed by a high degree of consistency. Secondly, the images of objects that are irradiated by Am-241 alpha source (5.49 MeV) are recorded by a CMOS camera using triple THGEM detector in the SQS mode. The resolution of images in this paper is a function of the exposure time. For an alpha source with 150 kBq activity, an optimal time interval for exposure is about 30 sec. For exposure time less or more than 30 sec, the images are incomplete and ambiguous, respectively. The overall objective of this work is to facilitate the alpha radiography in nuclear imaging through a triple THGEM without any amplifier or complicated electrical equipment.

Gains, Uniformity and Signal Sharing in XY Readouts of the 10 cm × 10 cm Gas Electron Multiplier (GEM) Detector

Gains, Uniformity and Signal Sharing in XY Readouts of the 10 cm × 10 cm Gas Electron Multiplier (GEM) Detector

Study of the optimal configuration for a Gas Electron Multiplier aimed at plasma impurity radiation monitoring

For the purpose of monitoring the level of plasma impurity (especially tungsten) and its distribution reconstruction at tokamaks (ITER in particular), a Soft X-Ray (SXR) tomographic diagnostics based on Gas Electron Multiplier (GEM) detectors with energy discrimination has been extensively considered for a while. Coupled with advanced electronics, GEM detectors offer excellent time and space resolution, as well as a charge spectrum from which the SXR photon spectrum can be deconvolved. In addition, they are less subjected to a neutron damage as compared to standard semiconductor diodes. This contribution highlights the latest studies supporting the development of such diagnostics focusing on laboratory tests to examine: (a) the impact of GEM holes geometry on the properties and distribution of the electron avalanche; (b) the effect of the high rate photon flux on GEM foil performance; and (c) the optimal electric field distribution.

Triple GEM Tracking Detectors for the BM@N Experiment

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Construction of the TH-GEM detector components for metrology of low energy ionizing radiation

The Gas Electron Multiplier (GEM) detector was originally proposed as a position sensitive detector to determine trajectories of particles prevenient from high-energy collisions. In order to study the potential of TH-GEM type detectors in dosimetric applications for low energy X-rays, specifically for the mammography standard qualities, it was proposed to construct a prototype with characteristics suitable for such use. In this work the general, structural and material parameters applicable to the necessary conditions were defined, establishing the process of construction of the components of a prototype.