Bulk Micromegas Detectors Research Articles

Aging test of resistive Micromegas detectors operated with and without hydrocarbons

A long-term irradiation and longevity test was conducted on two bulk-Micromegas detectors with screen-printed resistive strips, working with Ar:CO2 gas mixture at the CERN GIF++ facility between 2015 and 2018.The results of the test, for a total integrated charge of about 0.3 C/cm2, have been recently published.One of the detectors exposed at GIF++ was then irradiated with X-rays from Cu, this time with an Ar:CO2:iC4H10 mixture to study the effect of hydrocarbons like isobutane to the detector longevity.The resistive Micromegas under test has accumulated a total charge of 1.5 C/cm2.A second detector with identical construction and characteristics, operated at the same voltages and with the same gas but not irradiated, has been used as reference chamber. Charge spectra with an 55Fe source were acquired at regular intervals for both detectors to monitor the evolution of the gain and energy resolution.The accelerated ageing test has been subsequently repeated with the same detector operated with hydrocarbon-free Ar:CO2 mixture.The paper describes the experimental setup and test procedure, and focuses on the main results and their interpretation.

Charge sensitive preamplifier design optimization for low-pressure Micro-Megas gaseous detector operations

Using a bulk Micro-Megas (MM) detector an energy measurement can be obtained collecting the total charge reaching the mesh electrode connected to a low noise charge sensitive preamplifier. When operating such a device in a low-pressure gas regime, it is necessary to modify the amplification gap geometry to reach the optimal detector gain. This implies changes in the input capacitance of the preamplifier influencing its signal to noise ratio and thus the detector energy resolution. An ad-hoc high-gain and low-noise charge preamplifier has been developed to cope with the requirements of our application field. In this short report, we present the development activities focused to the study of a configurable charge amplifier to be connected to a MM detector having different mesh capacitances.

Encapsulated resistive anode bulk Micromegas detectors for the T2K experiment TPC upgrade

In order to establish accurate leptonic CP violation at 3 σ level for a significant fraction of the possible δCP values, the T2K collaboration plan to upgrade the beam intensity and to upgrade the near detector ND280.The T2K experiment consists of a totally active Super-Fine-Grained-Detector, two High Angle Time Projection Chamber and six time of flight planes. The HA-TPC will be used for 3D track reconstruction, momentum measurement and particle identification. These time projection chambers, with overall dimensions of 2 × 2 × 0.8 m3, will be equipped with 32 encapsulated resistive anode bulk Micromegas detectors. The thin field cage (3 cm thickness, 4% radiation length) will consist of composite material with a Kapton foil with copper strips as inner layer. The 42 × 34 cm2 ERAM detector will use a 400 kΩ/sq diamond-like carbon foil to spread the charge over the pad plane, each pad being approximately 1 cm2. New front-end electronic cards, based on the AFTER chip, directly mounted on the back of the detector and parallel to its plane have been developed and used for the signal readout.The first production ERAM detector modules have been tested in a lab using a X-ray bench and a cosmic bench. In July 2021, data have also been taken in a test beam at DESY in 0.2 T magnetic field. Performance characterization and results from these measurement campaigns will be shown.

Characterization of a low-pressure Micro-Megas-like gaseous detector with low energy x-ray sources

Within the family of the Micro Strip Gas Detectors (MSGD), the intrinsic characteristics of the bulk Micro-Megas (MM) device represent the most promising features for the construction of a new instrument to be operated as a TPC gas chamber in a low-pressure regime. In this study, we present the main properties of a low-pressure bulk MM detector in which the amplification gap was slightly increased to improve the gas gain. Two configurations have been deeply studied: the first one with a gap of 128μm and a second one with a 192μm gap, both filled and operated with a gas mixture (Ar-CO2) at pressures below 100 mbar. The dependence of the gain and the energy resolution on the amplification field, gas pressure and drift field have been evaluated. The reliability of the measured performance, combined with the simple and robust structure of the detector even with an increased length of amplification gap, make it an attractive choice for applications where the track length of low energy particles is detected by using a low-pressure filling gas.

Bulk Micromegas fabrication at JINR

Bulk Micromegas detectors are well known for their good spatial and time resolution, and simplicity of manufacturing and maintenance. They are widely applied in various experiments. Recently, the infrastructure for Bulk Micromegas development was established at the Joint Institute for Nuclear Research. The fabrication technology is described in this article, as well as the performance of the first assembled prototype is presented.

Performance studies of resistive-strip bulk micromegas detectors in view of the ATLAS New Small Wheel upgrade

Abstract The ATLAS collaboration at the Large Hadron Collider at CERN has endorsed the resistive-strip micromegas technology for the high luminosity upgrade of the first muon station in the high-rapidity region, the so called “New Small Wheel” project. It requires detectors with a spatial resolution of ∼ 100 μ m , fully efficient up to a particle rate of ∼ 20 kHz/cm 2 . In order to demonstrate that the resistive-strip micromegas technology fulfils these requirements, small resistive bulk micromegas have been studied with radioactive sources and with high energy beams. The micromegas chambers were operated with an Ar+7%CO 2 gas mixture and read out using the APV25 chip. Results on the detection efficiency and the position resolution are presented for track impact angles from 0° to 40°. A position reconstruction method has been developed for inclined tracks, called the “micro-TPC method”. A description of the method along with performance studies is presented. In addition, the impact of the unavoidable presence of pillars and the relative alignment of readout and resistive strips on the micromegas performance has been quantified. In view of the fact that the micromegas detectors will also contribute to the trigger in ATLAS their time response has been studied.

Experimental and numerical simulation of a TPC like set up for the measurement of ion backflow

Ion backflow is one of the effects limiting the operation of a gaseous detector at high flux, by giving rise to space charge which perturbs the electric field. The natural ability of bulk Micromegas to suppress ion feedback is very effective and can help the TPC drift volume to remain relatively free of space charge build-up. An efficient and precise measurement of the backflow fraction is necessary to cope up with the track distortion due to the space charge effect. In a subtle but significant modification of the usual approach, we have made use of two drift meshes in order to measure the ion backflow fraction for bulk Micromegas detector. This helps to truly represent the backflow fraction for a TPC. Moreover, attempt is taken to optimize the field configuration between the drift meshes. In conjunction with the experimental measurement, Garfield simulation framework has been used to simulate the related physics processes numerically.

Investigation of ion backflow in bulk micromegas detectors

The operation of gas detectors is often limited by secondary effects, originating from avalanche-induced photons and ions. Ion backflow is one of the effects limiting the operation of a gas detector at high flux, by giving rise to space charge which disturbs the electric field locally. For the Micromegas detector, a large fraction of the secondary positive ions created in the avalanche can be stopped at the micro-mesh. The present work involves measurements of the ion backflow fraction (using an experimental setup comprising of two drift planes) in bulk Micromegas detectors as a function of detector design parameters. These measured characteristics have also been compared in detail to numerical simulations using the Garfield framework that combines packages such as neBEM, Magboltz and Heed. Further, the effect of using a second micro-mesh on ion backflow and other parameters has been studied numerically.

Investigation of ion backflow in bulk micromegas detectors

The operation of gas detectors is often limited by secondary effects, originating from avalanche-induced photons and ions. Ion backflow is one of the effects limiting the operation of a gas detector at high flux, by giving rise to space charge which disturbs the electric field locally. For the Micromegas detector, a large fraction of the secondary positive ions created in the avalanche can be stopped at the micro-mesh. The present work involves measurements of the ion backflow fraction (using an experimental setup comprising of two drift planes) in bulk Micromegas detectors as a function of detector design parameters. These measured characteristics have also been compared in detail to numerical simulations using the Garfield framework that combines packages such as neBEM, Magboltz and Heed. Further, the effect of using a second micro-mesh on ion backflow and other parameters has been studied numerically.

Performance studies of bulk Micromegas of different design parameters

The present work involves the comparison of various bulk Micromegas detectors having different design parameters.Six detectors with amplification gaps of 64,128,192,220μm and mesh hole pitch of 63,78μm were tested at room temperature and normal gas pressure.Two setups were built to evaluate the effect of the variation of the amplification gap and mesh hole pitch on different detector characteristics.The gain, energy resolution and electron transmission of these Micromegas detectors were measured in Argon-Isobutane (90:10) gas mixture while the measurements of the ion backflow were carried out in P10 gas.These measured characteristics have been compared in detail to numerical simulations using the Garfield framework that combines packages such as neBEM, Magboltz and Heed.

Investigation of GEM-Micromegas detector on X-ray beam of synchrotron radiation

To reduce the discharge of the standard bulk Micromegas and GEM detectors, a GEM-Micromegas detector was developed at the Institute of High Energy Physics. Taking into account the advantages of the two detectors, one GEM foil was set as a preamplifier on the mesh of Micromegas in the structure and the GEM preamplification decreased the working voltage of Micromegas to significantly reduce the effect of the discharge. At the same gain, the spark probability of the GEM-Micromegas detector can be reduced to a factor 0.01 compared to the standard Micromegas detector, and an even higher gain could be obtained. This paper describes the performance of the X-ray beam detector that was studied at 1W2B Laboratory of Beijing Synchrotron Radiation Facility. Finally, the result of the energy resolution under various X-ray energies was given in different working gases. This indicates that the GEM-Micromegas detector has an energy response capability in an energy range from 6 keV to 20 keV and it could work better than the standard bulk-Micromegas.

Comparison of bulk Micromegas with different amplification gaps

The bulk Micromegas detector is considered to be a promising candidate for building TPCs for several future experiments including the projected linear collider. The standard bulk with a spacing of 128μm has already established itself as a good choice for its performances in terms of gas gain uniformity, energy and space point resolution, and its capability to efficiently pave large readout surfaces with minimum dead zone. The present work involves the comparison of this standard bulk with a relatively less used bulk Micromegas detector having a larger amplification gap of 192μm. Detector gain, energy resolution and electron transparency of these Micromegas have been measured under different conditions in various Argon-based gas mixtures to evaluate their performance. These measured characteristics have also been compared in detail to numerical simulations using the Garfield framework that combines packages such as neBEM, Magboltz and Heed. Further, we have carried out another numerical study to determine the effect of dielectric spacers on different detector features. A comprehensive comparison of the two detectors has been presented and analyzed in this work.

Development of a High-Resolution Muon Tracking System Based on Micropattern Detectors

A muon tracking system consisting of four 9cm x 10cm sized bulk Micromegas detectors with 128um amplification-gap and two 10cm x 10cm triple GEM detectors is foreseen for high-precision tracking of 140GeV muons at the H8 beamline at CERN with a rate of up to 10kHz and an overall resolution below 40um. Larger detectors with an active area of 0.5m^2 and more are under development for detector studies in high neutron or gamma ray background environments at the Gamma Irradiation Facility at CERN and the Munich tandem accelerator. Signal studies of both detector types have been performed by recording cosmic muon and 5.9keV X-ray signals with a single charge-sensitive preamplifier using several gas-mixtures of Ar:CO_2. The signals were digitized using 1GHz VME based flashADCs with 2520 sampling points. The analysis of the complete signal-cycles allows for the determination of rise times, pulse heights, timing fluctuations and discrimination of background, resulting in a FWHM energy resolution of about 20% and detection efficiencies of 99% and more. Models for signal formation in both detector types will be presented. The single detector spatial resolution of 80um was measured using a fast Gassiplex based strip readout with readout strips of 150um width and a pitch of 250um. The Gassiplex readout, formerly used at the HERMES experiment, had to be substantially adapted. No more crosstalk or non-linearities were observed after reconfiguration of the multiplexing amplifier on the frontend boards. The observed spatial resolution is limited by multiple scattering of the cosmic muons used in the laboratory. We also report on the sensitivity to gamma- and neutron background and on the behaviour of spatial resolution as a function of background rates.

Experience with the Time Projection Chambers for the T2K Near Detectors

The Near Detector at 280m (ND280) has been operating for over a year in the Tokai to Kamioka (T2K) neutrino beam. The detector is designed to provide a good knowledge of the neutrino beam before the neutrinos oscillate, including measuring the backgrounds and their energy dependence. An important feature of ND280 is the tracker which consists of two active scintillator-bar target systems sandwiched between three large time projection chambers (TPCs), and surrounded by calorimeters and a large dipole magnet for charged particle tracking. Novel features of the TPCs are the rectangular construction from composite panels, the bulk micromegas detectors for gas amplification, electronics readout based on a new ASIC, and the photoelectron calibration system. This article will review the design, operation and performance of the TPCs as deduced from measurements with particle beams, cosmic rays, and the photoelectron calibration system.

Micromegas for charge readout of double phase Liquid Argon TPCs

The 128 μm bulk-micromegas detector is a mature semi-industrial technology well suited for high quality and large scale production of large active area MPGDs as illustrated by its use in the Time Projection Chambers (TPCs) of the ND280 near detector of the T2K experiment. The cooling of a 128 μm bulk-micromegas detector down to 77 K proves its robustness at low temperatures and that is therefore a natural candidate for charge readout in Giant Liquid Argon TPCs.We propose the use of bulk-micromegas technology as charge readout in the vapour phase of a double phase Liquid Argon TPC. We have made a series of gain measurements with bulk and micro-bulk micromegas at room temperature up to 4.5 bars to predict the behaviour and performances of micromegas in the double-phase Liquid Argon TPC conditions at 87 K. Gas gains of up to 500 were measured in pure Argon at room temperature and 3.5 bars with a 50 μm standard micro-bulk. But the large diffusion of electrons in pure argon demands the operation of the detector with sufficiently low drift over amplification field ratios in order to fully transfer primary electrons in the amplification gap. Gain simulations are in good agreement with these measurements and a gain of 100 in a 128 μm bulk-micromegas is expected in pure Argon at 87 K. Such a large effective gain should be sufficient for charge readout of double-phase liquid Argon TPCs.

Micromegas detector developments for Dark Matter directional detection with MIMAC

The aim of the MIMAC project is to detect non-baryonic Dark Matter with a directional TPC using a high precision Micromegas readout plane. We will describe in detail the recent developments done with bulk Micromegas detectors as well as the characterisation measurements performed in an Argon(95%)-Isobutane(5%) mixture. Track measurements with alpha particles will be shown.

Time projection chambers for the T2K near detectors

The T2K experiment is designed to study neutrino oscillation properties by directing a high intensity neutrino beam produced at J-PARC in Tokai, Japan, towards the large Super-Kamiokande detector located 295 km away, in Kamioka, Japan. The experiment includes a sophisticated near detector complex, 280 m downstream of the neutrino production target in order to measure the properties of the neutrino beam and to better understand neutrino interactions at the energy scale below a few GeV. A key element of the near detectors is the ND280 tracker, consisting of two active scintillator–bar target systems surrounded by three large time projection chambers (TPCs) for charged particle tracking. The data collected with the tracker are used to study charged current neutrino interaction rates and kinematics prior to oscillation, in order to reduce uncertainties in the oscillation measurements by the far detector. The tracker is surrounded by the former UA1/NOMAD dipole magnet and the TPCs measure the charges, momenta, and particle types of charged particles passing through them. Novel features of the TPC design include its rectangular box layout constructed from composite panels, the use of bulk micromegas detectors for gas amplification, electronics readout based on a new ASIC, and a photoelectron calibration system. This paper describes the design and construction of the TPCs, the micromegas modules, the readout electronics, the gas handling system, and shows the performance of the TPCs as deduced from measurements with particle beams, cosmic rays, and the calibration system.

Production and calibration of 9 m2 of bulk-micromegas detectors for the readout of the ND280/TPCs of the T2K experiment

The near detector ND280 of the long baseline neutrino experiment T2K (JPARC, Japan) will contain three large 5m3 time projection chambers (TPC) for charged particles tracking and identification. These TPCs will be the first large TPCs readout by micro pattern gaseous detectors (MPGD). The bulk-Micromegas MPGD is a micro mesh gaseous structure (MicroMeGaS) in which the woven micromesh is embedded on top of the segmented anode plane of the MPGD by use of standard photolithographic techniques. This MPGD was chosen for its performances in terms of gas gain uniformity, energy resolution and space point resolution, and for its capability to efficiently pave large readout surfaces with minimized dead zones. We developed and improved the bulk-micromegas production methods to be suitable for a uniform, cheap and high quality mass production of 34×36cm2 bulk-micromegas modules of 1726 pads. Production of 72 bulk-micromegas modules, for an equivalent total readout surface of 9m2, began in may 2008 at CERN. After the description of a module and its production, we report on the pad per pad calibration with a strong 55Fe X-ray source of the 32 bulk-micromegas produced so far. Gas gain and 5.9keV energy resolution are presented to illustrate their good uniformity within the whole surface of each module (2.8% and 6% r.m.s dispersion, respectively) and their good reproducibility from one module to another (8% and 3% r.m.s, respectively).

Time projection chambers for the T2K experiment

The T2K experiment will study neutrino oscillation properties by directing a high intensity neutrino beam produced at J-PARC in Tokai, Japan, towards the large super-Kamiokande detector located 295km away, in Kamioka, Japan. The experiment includes a sophisticated near detector complex, 280m downstream of the neutrino production target. A key element of the near detectors is the ND280 tracker consisting of two active scintillator-bar target systems surrounded by three large time projection chambers (TPCs) for charged particle tracking. The tracker will provide high statistics samples for studying charged current neutrino interaction rates and kinematics prior to oscillation, so as to better understand backgrounds in the far detector. The tracker is surrounded by the UA1/Nomad dipole magnet and the TPCs will measure the charge, momentum, particle type (through ionization energy loss in the gas) of particles passing through them. Novel features of these TPCs include the rectangular box design, constructed from composite panels, the use of bulk micromegas detectors for gas amplification, electronics readout based on a new ASIC, and a photoelectron calibration system. This paper describes the design and construction of the TPCs, the readout electronics, the gas handling system and shows the performance of a completed TPC as deduced from measurements with particle beams, cosmic rays, and the calibration system.

A MICROMEGAS chamber with embedded DIRAC ASIC for hadronic calorimeter

DIRAC is a 64 channel mixed-signal readout integrated circuit designed for Micro-Pattern Gaseous Detectors (MICROMEGAS, Gas Electron Multiplier) or Resistive Plate Chambers. These detectors are foreseen as the active part of a hadronic calorimeter for a high energy physics experiment at the International Linear Collider. Physics requirements lead to a highly granular hadronic calorimeter with up to thirty million channels, and probably only one or two bits channel readout (so-called digital calorimeter). The DIRAC ASIC has been especially designed for these constraints. Each channel of the DIRAC chip is made of a 4 gains charge preamplifier, a DC-servo loop, 3 switched comparators and a digital memory, thus providing additional energy information for a hit. A bulk MICROMEGAS detector with embedded DIRAC ASIC has been build. The tests of this assembly, both in laboratory with X-Rays and in a beam at CERN are presented, demonstrating the feasibility of a bulk MICROMEGAS detector with embedded electronics. The second version of the ASIC, with improved noise and additional functionalities, has just been received and preliminary results are reported in details.