Micro-pattern Gas Detectors Research Articles

PICOSEC: Charged particle timing to 24 picosecond precision with MicroPattern gas detectors

The prospect of pileup induced backgrounds at the High Luminosity LHC (HL-LHC) has stimulated intense interest in technology for charged particle timing at high rates. In contrast to the role of timing for particle identification, which has driven incremental improvements in timing, the LHC timing challenge dictates a specific level of timing performance—roughly 20 to 30 picoseconds (ps). Since the elapsed time for an LHC bunch crossing (with standard design book parameters) has an rms spread of 170 ps, the ∼50 to 100 ps resolution now commonly achieved in time-of-flight systems would be insufficient to resolve multiple “in-time” pileup. Here we present a MicroMegas based structure which achieves the required time precision (i.e. 24 ps for 150 GeV muons) and could potentially offer an inexpensive solution covering large areas with ∼1 cm2 pixel size. We present here a proof-of-principle which motivates further work in our group toward realizing a practical design capable of long-term survival in a high rate experiment.

Gain characteristics of a 100 μm thick GEM in Krypton-CO2 mixtures

The operation of a Micropattern Gaseous Detector (MPGD) comprising a cascade of two non-standard Gas Electron Multipliers (GEM) made from a 100 μm kapton foil was evaluated in pure krypton and in krypton-CO2 mixtures. The final avalanche charge was collected in a 2D strip readout, providing an active area of 10×10 cm2 for the entire detection system. For each mixture, the effective gain and energy resolution were measured as a function of the electric field in the drift, transfer and induction regions. Using X-rays from a 55Fe radioactive source (5.9 keV), gains close to 104 and energy resolution of 22% (FWHM) were achieved in pure krypton under stable conditions, showing the potential of the experimental setup for the following imaging studies.

Reconstruction of Micropattern Detector Signals using Convolutional Neural Networks

Micropattern gaseous detector (MPGD) technologies, such as GEMs or MicroMegas, are particularly suitable for precision tracking and triggering in high rate environments. Given their relatively low production costs, MPGDs are an exemplary candidate for the next generation of particle detectors. Having acknowledged these advantages, both the ATLAS and CMS collaborations at the LHC are exploiting these new technologies for their detector upgrade programs in the coming years. When MPGDs are utilized for triggering purposes, the measured signals need to be precisely reconstructed within less than 200 ns, which can be achieved by the usage of FPGAs.In this work, we present a novel approach to identify reconstructed signals, their timing and the corresponding spatial position on the detector. In particular, we study the effect of noise and dead readout strips on the reconstruction performance. Our approach leverages the potential of convolutional neural network (CNNs), which have recently manifested an outstanding performance in a range of modeling tasks. The proposed neural network architecture of our CNN is designed simply enough, so that it can be modeled directly by an FPGA and thus provide precise information on reconstructed signals already in trigger level.

Abstract ID: 5 Monte Carlo simulation studies on a beam monitor based on MPGD detectors for hadron therapy

Remarkable scientific and technological progress during the last years has led to the construction of accelerator based facilities dedicated to hadron therapy. This kind of technology requires precise and continuous control of position, intensity and shape of the ions or protons used to irradiate cancers. Patient safety, accelerator operation and dose delivery should be optimized by a real time monitoring of beam intensity and profile before and during the treatment, by using non-destructive, high spatial resolution detectors. The authors have studied, developed and initially tested a beam monitor based on Micro Pattern Gaseous Detectors (MPGDs) called TPC-GEM (TPG) detector, characterized by high spatial resolution and rate capability. Due to the low amount of material in the active volume, it is “not invasive”, therefore the beam characteristics are preserved, so minimizing the uncertainties on beam position, intensity, energy and stability. Computer simulation could be done as a preliminary step for analyzing the basic characteristics of a detector, and Monte Carlo simulation is one approach that can be established. For a better understanding of the first TPG prototype design, and its further improvements, several Monte Carlo simulations were performed. The aim of this presentation is to give an overview of the full and specific Monte Carlo simulation framework, including different tools (GEANT4, FLUKA/FLAIR, Garfield++, ANSYS and ROOT), developed in order to study in detail the interaction of a therapeutic proton beam with the detector sensitive volume in a typical hadron therapy environment and the performance of the chamber, especially for the calculation of the primary ionization, charge transport through the amplification stages and signal creation. The results obtained will be presented, as well as the future perspectives.

The planispherical chamber: A parallax-free gaseous X-ray detector for imaging applications

Crystallography or X-ray fluorescence experiments which require good signal to noise ratios and high position resolution can take advantage of the outstanding signal amplification capabilities of MicroPattern Gaseous Detectors (MPGDs) such as Gaseous Electron Multipliers (GEMs) coupled with the position resolution achieved by optical readout realized with CCD or CMOS cameras. Increasing the detection probability of incident radiation with thicker drift volumes in these detectors leads to a spatial resolution-limiting parallax error when employing parallel electric field lines in the drift region.We describe a new GEM-based detector concept, consisting of a cathode, GEM electrodes and field shaping rings suitably segmented and powered to create a radial electric field, thus minimizing the parallax error. A CCD camera is used to record scintillation light originating from charge multiplication in the high field of the GEM holes in an Ar/CF4 (80/20%) gas mixture. Assembled as pinhole camera, the device permits to obtain high detection efficiencies for soft X-rays, exempt from the parallax error intrinsic in the use of standard gaseous detectors with thick conversion layers. The use of several GEMs in cascade allows for high charge multiplication factors. Switching from straight to radially focused drift field lines, a significant reduction of the parallax error as well as an increased signal-to-noise ratio were achieved, effectively paving the way for applications such as X-ray crystallography realized with optically read out GEMs.

Gain stabilization in Micro Pattern Gaseous Detectors: methodology and results

The phenomenon of avalanche-gain variations over time, particularly in Micro Pattern Gaseous Detectors (MPGD) incorporating insulator materials, have been generally attributed to electric-field modifications resulting from “charging-up” effects of the insulator. A robust methodology for characterization of gain-transients in such detectors is presented. It comprises three guidelines: detector initialization, long gain-stabilization monitoring and imposing transients by applying abrupt changes in operation conditions. Using THWELL and RPWELL detectors, we validated the proposed methodology by assessing a charging-up/charging-down model describing the governing processes of gain stabilization. The results provide a deeper insight into these processes, reflected by different transients upon abrupt variations of detector gain or the irradiation rate. This methodology provides a handle for future investigations of the involved physics phenomena in MPGD detectors comprising insulating components.

A large high-efficiency multi-layered Micromegas thermal neutron detector

Due to the so-called 3He shortage crisis, many detection techniques used nowadays for thermal neutrons are based on alternative converters. Thin films of 10B or 10B4C are used to convert neutrons into ionizing particles which are subsequently detected in gas proportional counters, but only for small or medium sensitive areas so far. The micro-pattern gaseous detector Micromegas has been developed for several years in Saclay and is used in a wide variety of neutron experiments combining high accuracy, high rate capability, excellent timing properties and robustness. We propose here a large high-efficiency Micromegas-based neutron detector with several 10B4C thin layers mounted inside the gas volume for thermal neutron detection. The principle and the fabrication of a single detector unit prototype with overall dimension of ∼ 15 × 15 cm2 and a flexibility of modifying the number of layers of 10B4C neutron converters are described and simulated results are reported, demonstrating that typically five 10B4C layers of 1–2 μm thickness can lead to a detection efficiency of 20–40% for thermal neutrons and a spatial resolution of sub-mm. The design is well adapted to large sizes making possible the construction of a mosaic of several such detector units with a large area coverage and a high detection efficiency, showing the good potential of this novel technique.

High resolution micro-pattern gas detectors for particle physics

Micro-pattern gaseous detectors (MPGDs) allow operation at very high background particle flux with high efficiency and spatial resolution. This combination of parameters determines the main application of these detectors in particle physics experiments: precise tracking in the areas close to the beam and in the end-cap regions of general-purpose detectors. MPGDs of different configurations have been developed and are under development for several experiments in the Budker INP. The system of eight two-coordinate detectors based on a cascade of Gas Electron Multipliers (GEM) is working in the KEDR experiment at the VEPP-4M collider in the tagging system that detects electrons and positrons that lost their energy in two-photon interactions and left the equilibrium orbit due to a dedicated magnetic system. Another set of cascaded GEM detectors is developed for the almost-real Photon Tagging System (PTS) of the DEUTRON facility at the VEPP-3 storage ring. The PTS contains three very light detectors with very high spatial resolution (below 50 μm). Dedicated detectors based on cascaded GEMs are developed for the extracted electron beam facility at the VEPP-4M collider. These devices will allow precise particle tracking with minimal multiple scattering due to very low material content. An upgrade of the coordinate system of the CMD-3 detector at the VEPP-2000 collider is proposed on the basis of the resistive micro-WELL (μ-rWELL). A research activity on this subject has just started.

Overview of the data analysis and new micro-pattern gas detector development for the Active Target Time Projection Chamber (AT-TPC) project.

The Active Target Time Projection Chamber (AT-TPC) project at the NSCL (National Superconducting Cyclotron Laboratory, Michigan State University) is a novel active target detector tailored for low-energy nuclear reactions in inverse kinematics with radioactive ion beams. The AT-TPC allows for a full three dimensional reconstruction of the reaction and provides high luminosity without degradation of resolution by the thickness of the target. Since all the particles (and also the reaction vertex) are tracked inside the detector, the AT-TPC has full 4π efficiency. The AT-TPC can operate under a magnetic field (2 T) that improves the identification of the particles and the energy resolution through the measurement of the magnetic rigidity. Another important characteristic of the AT-TPC is the high-gain operation achieved by the hybrid thick Gas Electron Multipliers (THGEM)-Micromegas pad plane, that allow operation also in pure elemental gas. These two features make the AT-TPC a unique high resolution spectrometer with full acceptance for nuclear physics reactions. This work presents an overview of the project, focused on the data analysis and the development of new micro-pattern gas detectors.

2-D Encoded Multiplexing Readout for THGEM

Micropattern gas detectors (MPGDs) have a wide application in high-energy physics, astrophysics, nuclear physics, medical imaging, and so on. The demand for large area and good spatial resolution requires a large number of channels. The conventional 2-D tracking for MPGDs requires a large number of electronic channels, and in consequence poses a big challenge for the integration, power consumption, cooling, and cost, which has become a problem to the further applications of MPGDs. In this paper, a new tracking method for MPGDs based on 2-D encoded multiplexing readout is presented, which is easily extensible and can significantly reduce the number of electronic readout channels.

The μ-RWELL detector

The μ-RWELL has been conceived as a compact, simple and robust Micro-Pattern-Gaseous-Detector (MPGD) for very large area HEP applications requiring the operation in harsh environment. The detector amplification stage, similar to a GEM foil, is realized with a polyimide structure micro-patterned with a blind-hole matrix, embedded through a thin Diamond Like Carbon (DLC) resistive layer in the readout PCB. The introduction of the resistive layer strongly suppressing the transition from streamer to spark gives the possibility to achieve large gains (> 104), without significantly affecting the capability to stand high particle fluxes. In this work we give an overview of the two detector layouts designed for low and high rate applications, presenting the results of a systematic study of the detector performance as a function of the surface resistivity and discussing the status of the Technology Transfer towards the industry for large area detector manufacturing.

Development of Micro-Pattern Gas Detectors for the Upgrade of the Muon System of the CMS Experiment at the Large Hadron Collider

After the discovery of the long awaited Higgs boson in 2012, the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) and its two general purpose experiments (ATLAS and CMS) are preparing to break new grounds in High Energy Physics (HEP). The international HEP collaboration has established a rigorous research program of exploring new physics at the high energy frontiers. The program includes substantial increase in the luminosity of the LHC putting detectors into a completely new and unprecedented harsh environment. In order to maintain their excellent performance, an upgrade of the existing detectors is mandatory. In this work we will describe ongoing efforts for the upgrade of the CMS muon detection system, in particular the addition of detection layers based on the Gas Electron Multiplier (GEM) technology. We will summarize the past 5-year R&D program and the future installation and operation plans.

THCOBRA X-ray imaging detector operating in pure Kr

MicroPattern Gaseous Detectors (MPGD) have been explored for X-ray imaging, namely for photon counting imaging which allows the improvement of image quality and the collection of more information than the conventional commercial systems. A 2D-THCOBRA based detector was developed, studied and used to acquire X-ray transmission images. The 2D-THCOBRA structure used has an active area of 2.8 × 2.8 cm2 and allows obtaining the position and energy information of each single photon that interacts with the detector. It is filled with pure Kr at 1 bar operating in a sealed mode. Within this work the performance of the detector is evaluated in terms of charge gain, count rate, time stability, energy and spatial resolutions. The detector presents a charge gain of 2 × 104 and an energy resolution of 23% for 5.9 keV, showing gain stability along time for a count rate of about 1 × 105 Hz/mm2. It presents a spatial resolution of 600 μm (σ = 255 μm) and 500 μm (σ = 213 μm) for x and y directions, respectively, and, considering energy bins about 650 μm (σ = 277 μm) for approximately 16.5 keV. X-ray transmission images of some samples presented here show good prospects for X-ray imaging applications.

Toward the Pixel-TPC: Construction and Operation of a Large Area GridPix Detector

We report on the construction of the largest GridPix detector to date and its successful operation as readout of a time projection chamber (TPC). By combining a charge sensitive pixelized readout chip with a micropattern gaseous detector, the GridPix features a high granularity with single electron detection and integrated signal processing. The readout structure consists of 160 GridPixes with a total of 10.5 million pixels, each of a size of $55 \times 55~\mu \text{m}^{ {2}}$ . With a sensitive area of 320 cm $^{ {2}}$ , it is a factor 20 larger than previously operated systems. We report on the integration of such a large number of GridPixes into a single compact detector, including cooling, readout electronics, and low-voltage and high-voltage power supply, and on the performance during a two weeks test beam campaign at DESY. The large area pixelated readout for gaseous detectors can be applied for different detectors. In our developments, we focused on an application for a TPC.

PandaX-III: Searching for neutrinoless double beta decay with high pressure 136Xe gas time projection chambers

Searching for the Neutrinoless Double Beta Decay (NLDBD) is now regarded as the topmost promising technique to explore the nature of neutrinos after the discovery of neutrino masses in oscillation experiments. PandaX-III (Particle And Astrophysical Xenon Experiment III) will search for the NLDBD of $^{136}$Xe at the China Jin Ping underground Laboratory (CJPL). In the first phase of the experiment, a high pressure gas Time Projection Chamber (TPC) will contain 200 kg, 90% $^{136}$Xe enriched gas operated at 10 bar. Fine pitch micro-pattern gas detector (Microbulk Micromegas) will be used at both ends of the TPC for the charge readout with a cathode in the middle. Charge signals can be used to reconstruct tracks of NLDBD events and provide good energy and spatial resolution. The detector will be immersed in a large water tank to ensure $\sim$5 m of water shielding in all directions. The second phase, a ton-scale experiment, will consist of five TPCs in the same water tank, with improved energy resolution and better control over backgrounds.

MIP suppression with ThickGEM based Cherenkov detectors

Micropattern Gaseous Detectors opened a novel way for photon detection for RICH applications; mostly using hole-type amplifiers like GEM and ThickGEM in cascaded or hybrid structures. The main features are low ion backflow, high gain, and possibility for suppressing the MIP signal. This suppression can enhance the dynamic range, and allow for high gain operation, while using cost effective electronics.A ThickGEM and wire chamber based hybrid was constructed, and tested in particle beam as RICH detector. Systematic studies on the MIP suppression with the usage of ThickGEMs were carried out. The dependence on field configuration and the effective gain of the ThichGEM were measured and quantified.

Study of the Performance of the Micromegas Chambers for the ATLAS Muon Spectrometer Upgrade

Micromegas (MICRO MEsh GAseous Structure) chambers are Micro-Pattern Gaseous Detectors designed to provide a high spatial resolution in highly irradiated environments. In 2007 an ambitious long-term R&D activity was started in the context of the ATLAS experiment, at CERN: the Muon ATLAS Micromegas Activity (MAMMA). After years of tests on prototypes and technology breakthroughs, Micromegas chambers were chosen as tracking detectors for an upgrade of the ATLAS Muon Spectrometer. These novel detectors will be installed in 2018 and 2019 during the second long shutdown of the Large Hadron Collider, and will serve as precision detectors in the innermost part of the ATLAS Muon Spectrometer. Eight layers of Micromegas modules of unprecedented size, up to $3~\boldsymbol { {m^{2}}}$ , will cover a surface of $150~\boldsymbol { {m^{2}}}$ for a total active area of about $1200~\boldsymbol { {m^{2}}}$ . This upgrade will be crucial to ensure high quality performance for the ATLAS Muon Spectrometer in view of the third run of the Large Hadron Collider and of the High-Luminosity LHC, as the luminosity of the collider will significantly exceed the one the machine was originally designed for. To meet the demanding performance requirements of the ATLAS Muon Spectrometer, Micromegas chambers are required to achieve a single plane resolution of $100~\boldsymbol {\mu {}}{\mathbf {m}}$ with an efficiency better than 95% for tracks up to an inclination of 32° and in a magnetic field up to 0.3 T. A thorough test program on Micromegas prototypes has been performed during the past years and is still ongoing, with the goal of driving the design of the ATLAS Micromegas chambers and of fully characterising and certifying their performance. These tests produced excellent results, proving that the prototypes fully meet the performance requirements. The methodology and the results of this activity will be reviewed in this paper.

Study of the two dimensional imaging performance for the gas electron multiplier using the resistive anode readout method

The new type of micro-pattern gaseous detector (MPGD) like the gas electron multiplier (GEM), features the advantage of good spatial resolution ( 100 m). However, abundant and high density electronic channels are needed to obtain the high spatial resolution, which will lead to a great pressure on the detector construction, power consumption, spatial utilization, etc. The resistive anode readout method can help to obtain a good spatial resolution comparable to the pixel readout structure with an enormous reduction of the electronic channels. By using the thick film resistor technology, a new type of resistive structure, composed of high resistive square pad array with low resistive narrow border strips, is developed and applied to the readout anode of the triple GEM detector. For the resistive anode readout board used in the experiment, there are 66 resistive cells, which means that the detector needs only 49 electronics channels. To obtain a good spatial resolution, the cell size is set to be 6 mm6 mm. The surface resistivity of the pads and the strips are 150 k/□ and 1 k/□, respectively. The performances of the detector, especially the two-dimensional imaging performance, are studied by using a 55Fe (5.9 keV) source and an X ray tube (8 keV). The test results show that the spatial resolution of the detector is better than 80 m () by using the imaging of a 40 m wide slot, and the nonlinearity is better than 1.5% by the scanning along the x-axis of the readout board in the steps of 1 mm. Furthermore, quite a good two-dimensional imaging capability is achieved by the detector. These good performances of the detector show the feasibility of the resistive anode readout method for the GEM detector with large area and other detectors with similar structures in the two-dimensional imaging applications.

Bivariate normal distribution for finding inliers in Hough space for a Time Projection Chamber

A Time Projection Chamber (TPC) is foreseen as the main tracking detector for the International Large Detector (ILD), one of the two detectors for the next candidate collider named International Linear Collider (ILC) [1].GridPix, a combination of a micropattern gaseous detector with a pixelized readout, is one of the candidate readout systems for the TPC [2] [3]. One of the challenges in the track reconstruction is the large number of individual hits along a track (around 100 per cm). Due to the small pixel size of 55 x 55 μ m2 , the distance between the individual ionization processes in the gas is larger than the size of the pixels. Consequently, the hits in the GridPix are not contiguous. This leads to the challenge of assigning the individual hits to the correct track. Hits within a given distance from a reconstructed track are called inliers. Consequently, finding inliers within the large number of hits and in the presence of noise is difficult for pattern recognition. This difficulty is increased by diffusion effects in the TPC.One of the current algorithms which are utilized for track finding is the Hough transform. Using a bivariate normal distribution based on the covariance matrix calculated from the diffusion effect improves collecting inliers in the Hough space directly [5].

A time projection chamber with GEM-based readout

For the International Large Detector concept at the planned International Linear Collider, the use of time projection chambers (TPC) with micro-pattern gas detector readout as the main tracking detector is investigated. In this paper, results from a prototype TPC, placed in a 1T solenoidal field and read out with three independent Gas Electron Multiplier (GEM) based readout modules, are reported. The TPC was exposed to a 6GeV electron beam at the DESY II synchrotron. The efficiency for reconstructing hits, the measurement of the drift velocity, the space point resolution and the control of field inhomogeneities are presented.