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Register a new userPerformance of a large size triple GEM detector at high particle rate for CBM Experiment at FAIR
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In CBM Experiment at FAIR, dimuons will be detected by a Muon Chamber (MUCH) consisting of segmented absorbers of varying widths and tracking chambers sandwiched between the absorber-pairs. In this fixed target heavy-ion collision experiment, operating at highest interaction rate of $10~MHz$ for $Au+Au$ collision, after the first MUCH detector station in its inner radial ring will face a particle rate of $1~MHz/cm^2$. To operate at such a high particle density, GEM technology based detectors have been selected for the first two stations of MUCH. We have reported earlier the performance of several small-size GEM detector prototypes built at VECC for use in MUCH. In this work, we report on a large GEM chamber prototype tested with proton beam of momentum $2.36~GeV/c$ at COSY-J{u}elich Germany. The detector was read out using nXYTER ASIC operated in self-triggering mode. An efficiency higher than $96%$ at $Delta V_{GEM}~=~375.2~V$ was achieved. The variation of efficiency with the rate of incoming protons has been found to vary within $2%$ when tested up to a maximum rate of $2.8~MHz/cm^2$. The gain was found to be stable at high particle rate with a maximum variation of $sim~9%$.
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Gaseous detectors are used in high energy physics as trackers or, more generally, as devices for the measurement of the particle position. For this reason, they must provide high spatial resolution and they have to be able to operate in regions of intense radiation, i.e. around the interaction point of collider machines. Among these, Micro Pattern Gaseous Detectors (MPGD) are the latest frontier and allow to overcome many limitations of the pre-existing detectors, such as the radiation tolerance and the rate capability. The gas Electron Multiplier (GEM) is a MPGD that exploits an intense electric field in a reduced amplification region in order to prevent discharges. Several amplification stages, like in a triple-GEM, allow to increase the detector gain and to reduce the discharge probability. Reconstruction techniques such as charge centroid (CC) and micro-Time Projection Chamber ($upmu$TPC) are used to perform the position measurement. From literature triple-GEMs show a stable behaviour up to $10^8,$Hz/cm$^2$. A testbeam with four planar triple-GEMs has been performed at the Mainz Microtron (MAMI) facility and their performance was evaluated in different beam conditions. In this article a focus on the time performance for the $upmu$TPC clusterization is given and a new measurement of the triple-GEM limits at high rate will be presented.
The Phase-II high luminosity upgrade to the Large Hadron Collider (LHC) is planned for 2023, significantly increasing the collision rate and therefore the background rate, particularly in the high $eta$ region. To improve both the tracking and triggering of muons, the Compact Muon Solenoid (CMS) Collaboration plans to install triple-layer Gas Electron Multiplier (GEM) detectors in the CMS muon endcaps. Demonstrator GEM detectors were installed in CMS during 2017 to gain operational experience and perform a preliminary investigation of detector performance. We present the results of triple-GEM detector performance studies performed in situ during normal CMS and LHC operations in 2018. The distribution of cluster size and the efficiency to reconstruct high $p_T$ muons in proton--proton collisions are presented as well as the measurement of the environmental background rate to produce hits in the GEM detector.
Characteristics of triple GEM detector have been studied systematically. The variation of the effective gain and energy resolution of GEM with variation of the applied voltage has been measured with Fe55 X-ray source for different gas mixtures and with different gas flow rates. Long-term test of the GEM has also been performed.
Gas detectors are one of the pillars of the research in fundamental physics. Since many years, a new concept of detectors, the Micro Pattern Gas Detectors, allows to overcome many of the problems of other types of commonly used detectors, as drift chambers and microstrips, reducing the discharge rate and increasing the radiation tolerance. Among these, one of the most commonly used is the Gas Electron Multiplier. Commonly deployed as fast timing detectors and triggers, due to their fast response, high rate capability and high radiation hardness, they can also be used as trackers. The center of gravity readout technique allows to overcome the limit of the digital pads, whose spatial resolution is constrained by the pitch size. The presence of a high external magnetic field can distort the electronic cloud and affect the spatial resolution. The micro-TPC reconstruction method allows to reconstruct the three dimensional particle position as in a traditional Time Projection Chamber, but within a drift gap of a few millimeters. This method brings these detectors into a new perspective for what concerns the spatial resolution in strong magnetic field. In this report, the basis of this new technique will be shown and it will be compared to the traditional center of gravity. The results of a series of test beam performed with 10 x 10 cm2 planar prototypes in magnetic field will also be presented. This is one of the first implementations of this technique for GEM detectors in magnetic field and allows to reach unprecedented performance for gas detectors, up to a limit of 120 micron at 1T, one of the worlds best results for MPGDs in strong magnetic field. The micro-TPC reconstruction has been recently tested at very high rates in a test beam at the MAMI facility; preliminary results of the test will be presented.
Many experiments are currently using or proposing to use large area GEM foils in their detectors, which is creating a need for commercially available GEM foils. Currently CERN is the only main distributor of large GEM foils, however with the growing interest in GEM technology keeping up with the increasing demand for GEMs will be difficult. We present here an update on the assembly and testing of triple-GEM tracking detectors utilizing single-masked $40 times 40$ cm$^2$ commercial GEM foils produced by Tech-Etch. The triple-GEM detectors will allow us to characterize the overall quality of these Tech-Etch foils through gain, efficiency, and energy resolution measurements. This will be done by constructing four single-mask triple-GEM detectors, using foils manufactured by Tech-Etch, which follow the design used by the STAR Forward GEM Tracker (FGT). The stack is formed by gluing the foils to the frames and then gluing the frames together. The stack also includes a Tech-Etch produced high voltage foil and a 2D $r-phi$ readout foil. While one of the four triple-GEM detectors will be built identically to the STAR FGT, the other three will investigate ways in which to further decrease the material budget and increase the efficiency of the detector by incorporating perforated Kapton spacer rings rather than G10 spacing grids to reduce the dead area of the detector.
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