1,778 research outputs found

    Micromegas for Imaging Calorimetry

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    International audienceTwo Micromegas chambers of 1 m2 size and 1 cm2 cell segmentation have recently been built. Designed for Particle-Flow hadron calorimetry, each chamber features ten thousand channels with embedded front-end electronics and three readout thresholds (concept of semi-digital hadron calorimeter or SDHCAL). The chambers have been tested in a muon beam and also exposed to hadron showers inside a steel structure. Excellent performance such as low noise, high efficiency and very uniform spatial response have been measured and will be reported. The measurements will be confronted to the predictions of a Monte Carlo simulation for which a complete digitisation procedure has been established. Finally, prospects towards the use of a Micromegas SDHCAL at a future linear collider will be discussed based on the scalability of current prototypes to larger sizes and on the expected energy resolution and linearity of such a device

    RD51, a world-wide collaboration for the development of Micro Pattern Gaseous Detectors

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    International audienceOriginally introduced to improve the rate capability of traditional wire chambers, Micro Pattern Gaseous Detectors (MPGD) actually demonstrate many more benefits. Be it for medical and industry imaging, collider experiments or more interestingly in the framework of this conference for the search of rare events, they are the subject of constant research and development in several laboratories over the world. The RD51 collaboration has been coordinating this work since April 2008 and is meant to advance the technological development and application of MPGD. The collaboration is presented and emphasis is put on its latest achievements which do make these devices an attractive option for the detection of low energy rare events: the possibility to instrument large area and to detect UV photons

    Environmental study of a Micromegas detector

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    We report on measurements of the basic performance of a Micromegas detector for a digital hadronic calorimeter. Electron collection efficiency, energy resolution and gas gain were measured in various mixtures of Ar and CO2. Also the dependence of the gain on environmental variables (pressure, temperature), gas parameters (flow, mixing ratio) and geometry (amplication gap size) is studied. Eventually, predictions on the impact of these variables on the detection efficiency of thin Micromegas detectors are drawn

    Status of the Micromegas semi-DHCAL

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    The activities towards the fabrication and test of a 1 m3 semi-digital hadronic calorime- ter are reviewed. The prototype sampling planes would consist of 1 m2 Micromegas chambers with 1 cm2 granularity and embedded 2 bits readout suitable for PFA calorime- try at an ILC detector. The design of the 1 m2 chamber is presented first, followed by an overview of the basic performance of small prototypes. The basic units composing the 1 m2 chamber are 32 \times 48 cm2 boards with integrated electronics and a micro-mesh. Results of character- ization tests of such boards are shown. Micromegas as a proportional detector is well suited for semi-digital hadronic calorimetry. In order to quantify the gain in perfor- mance when using one or more thresholds, simulation studies are being carried out, some of which will be reported in this contribution

    Readout of GEM Detectors Using the Medipix2 CMOS Pixel Chip

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    We have operated a Medipix2 CMOS readout chip, with amplifying, shaping and charge discriminating front-end electronics integrated on the pixel-level, as a highly segmented direct charge collecting anode in a three-stage gas electron multiplier (Triple-GEM) to detect the ionization from 55^{55}Fe X-rays and electrons from 106^{106}Ru. The device allows to perform moderate energy spectroscopy measurements (20 % FWHM at 5.9 keV XX-rays) using only digital readout and two discriminator thresholds. Being a truly 2D-detector, it allows to observe individual clusters of minimum ionizing charged particles in Ar/CO2Ar/CO_2 (70:30) and He/CO2He/CO_2 (70:30) mixtures and to achieve excellent spatial resolution for position reconstruction of primary clusters down to ‚ąľ50őľm\sim 50 \mu m, based on the binary centroid determination method.Comment: 18 pages, 14 pictures. submitted to Nuclear Instruments and Methods in Physics Research

    Characterization of microbulk detectors in argon- and neon-based mixtures

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    A recent Micromegas manufacturing technique, so called Microbulk, has been developed, improving the uniformity and stability of this kind of detectors. Excellent energy resolutions have been obtained, reaching values as low as 11% FWHM at 5.9 keV in Ar+5%iC4H10. This detector has other advantages like its flexible structure, low material budget and high radio-purity. Two microbulk detectors with gaps of 50 and 25 um have been characterized in argon- and neon-based mixtures with ethane, isobutane and cyclohexane. The results will be presented and discussed. The gain curves have been fitted to the Rose-Korff gain model and dependences of the electron mean free path and the threshold energy for ionization have been obtained. The possible relation between these two parameters and the energy resolution will be also discussed.Comment: Submitted to the Journal of Instrumentatio

    THGEM-based detectors for sampling elements in DHCAL: laboratory and beam evaluation

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    We report on the results of an extensive R&D program aimed at the evaluation of Thick-Gas Electron Multipliers (THGEM) as potential active elements for Digital Hadron Calorimetry (DHCAL). Results are presented on efficiency, pad multiplicity and discharge probability of a 10x10 cm2 prototype detector with 1 cm2 readout pads. The detector is comprised of single- or double-THGEM multipliers coupled to the pad electrode either directly or via a resistive anode. Investigations employing standard discrete electronics and the KPiX readout system have been carried out both under laboratory conditions and with muons and pions at the CERN RD51 test beam. For detectors having a charge-induction gap, it has been shown that even a ~6 mm thick single-THGEM detector reached detection efficiencies above 95%, with pad-hit multiplicity of 1.1-1.2 per event; discharge probabilities were of the order of 1e-6 - 1e-5 sparks/trigger, depending on the detector structure and gain. Preliminary beam tests with a WELL hole-structure, closed by a resistive anode, yielded discharge probabilities of <2e-6 for an efficiency of ~95%. Methods are presented to reduce charge-spread and pad multiplicity with resistive anodes. The new method showed good prospects for further evaluation of very thin THGEM-based detectors as potential active elements for DHCAL, with competitive performances, simplicity and robustness. Further developments are in course.Comment: 15 pages, 11 figures, MPGD2011 conference proceedin

    DIRAC v2: a DIgital Readout Asic for hadronic Calorimeter

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    International audienceThis mixed-signal circuit is a 64 channels readout R&D ASIC for Micro-Pattern Gaseous Detectors (Micromegas, Gas Electron Multiplier) or Resistive Plate Chambers. These detectors are foreseen as the active part of a digital 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 fifty millions channels with probably only hit information (digital calorimeter). Each channel of the 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. For detector characterization, a multiplexed analog readout has been implemented. Configuration and readout are fully digital, indeed six 8-bit DACs are embedded to set comparators thresholds. Power-down circuitry has been included, decreasing the power consumption to 10 őľW per channel. To achieve a low cost electronics, a cheap full CMOS 0.35 őľm foundry process has been chosen and the floorplan has been designed to reduce Printed Circuit Board costs. The SPS beam tests of the DIRAC first version embedded in a bulk Micromegas will be presented. The second version has just been received and preliminary results will be detailed. Large area detectors equipped with these chips are planned to be put in the PS beam this year

    Resistive micromegas for sampling calorimetry

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    MicromegasInternational audienceMicromegas is an attractive option for a gaseous sampling calorimeter. It delivers proportional and fast signals, achieves high efficiency to minimum ionising particles with a compact design and shows well-uniform performance over meter-square areas. The current R&D focuses on large- size spark-protected Micromegas with integrated front-end electronics. It targets an application at future linear colliders (LC) and possible upgrades of LHC experiments for the running at high luminosity. In the later case, occasional sparking should be suppressed to avoid dead-time and technical solutions using resistive coatings are investigated. Small prototypes of resistive and non-resistive Micromegas were constructed and tested in a beam at DESY. Results are reported with emphasis on the impact of the resistive layer on the detector performance
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