Abstract
As liquid xenon TPCs increase in target mass while pursuing the direct detection of WIMP dark matter, the technical challenges arising due to their size call for new solutions and open the ...discussion on alternative detector concepts. Proportional scintillation in liquid xenon allows for a single-phase design evading problems related to the liquid-gas interface and the precise gas gap required in a dual-phase TPC.
Aside from a different scintillation mechanism, the successful detection- and analysis scheme of state-of-the-art experiments is maintained in this approach.
We study the impact on charge signal analysis in a single-phase detector of DARWIN dimensions, where the fast timing of the proportional scintillation signal allows for the precise identification of the single electrons in the ionisation signal.
Such a discrete electron-counting approach can lead to a better signal resolution for low energies when compared to the classical dual-phase continuous method.
The absence of the liquid-gas interface can further benefit the S2-only energy resolution significantly. This can reduce the uncertainties from the scintillation and signal-detection process to a level significantly below the irreducible fluctuation in the primary ionisation. Exploiting the precise electron arrival time information can further allow for a powerful single vs. multiple site interaction discrimination with 93% rejection efficiency and 98% signal acceptance. This outperforms the design goal of the DARWIN observatory by a reduction factor of 4.2 in non-rejected multiple site neutron events.
For the upcoming upgrade of the forward muon stations of the ATLAS detector, 1280m
2
of Micromegas chambers have to be constructed. The industrialization of anode board production is an essential ...precondition. Design and construction methods of these boards have been optimized towards mass production. In parallel quality control procedures have been developed and established. The first set of large size Micromegas anode boards has finally been produced in industries and demonstrates the feasibility of the project on full-scale.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The reconstruction precision of gaseous detectors is limited by losses of primary electrons during signal formation. In addition to common gas related losses, like attachment, Micromegas suffer from ...electron absorption during its transition through the micro mesh. This study aims for a deepened understanding of electron losses and their dependency on the mesh geometry. It combines experimental results obtained with a novel designed Exchangeable Mesh Micromegas (ExMe) and advanced microscopic-tracking simulations (ANSYS and Garfield++) of electron drift and mesh transition.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Avalanche fluctuations set a limit to the energy and position resolutions that can be reached by gaseous detectors. This paper presents a method based on a laser test-bench to measure the absolute ...gain and the relative gain variance of a Micro-Pattern Gaseous Detector from its single-electron response. A Micromegas detector was operated with three binary gas mixtures, composed of 5% isobutane as a quencher, with argon, neon or helium, at atmospheric pressure. The anode signals were read out by low-noise, high-gain Cremat CR-110 charge preamplifiers to enable single-electron detection down to gain of 5 10 super(3) for the first time. The argon mixture shows the lowest gain at a given amplification field together with the lowest breakdown limit, which is at a gain of 210 super(4) an order of magnitude lower than that of neon or helium. For each gas, the relative gain variance f is almost unchanged in the range of amplification field studied. It was found that f is twice higher (f~0.6) in argon than in the two other mixtures. This hierarchy of gain and relative gain variance agrees with predictions of analytic models, based on gas ionisation yields, and a Monte-Carlo model included in the simulation software Magboltz version 10.1.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Characterization of the ATLAS Micromegas quadruplet prototype Sidiropoulou, O.; Bianco, M.; Danielsson, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2016, Volume:
824
Journal Article
Peer reviewed
A Micromegas 1 detector with four active layers, serving as prototype for the upgrade of the ATLAS muon spectrometer 2, was designed and constructed in 2014 at CERN and represents the first example ...of a Micromegas quadruplet ever built. The detector has been realized using the resistive-strip technology and decoupling the amplification mesh from the readout structure. The four readout layers host overall 4096 strips with a pitch of 415μm; two layers have strips running parallel (η in the ATLAS reference system, for measuring the muon bending coordinate) and two layers have inclined strips by ±1.5° angle with respect to the η coordinate in order to provide measurement of the second coordinate.
A detector characterization carried out with cosmic muons and under X-ray irradiation is presented with the obtained results.
•The Micromegas detector with four readout layers is the first quadruplet ever built.•The characterization of it is valuable for the ATLAS New Small Wheel upgrade.•This is part of the validation procedure for the Micromegas New Small Wheel detectors.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In view of the use of Micromegas detectors for the upgrade of the ATLAS muon system, two detector quadruplets with an area of 0.3 m
2
per plane serving as prototypes for future ATLAS chambers have ...been constructed. They are based on the resistive-strip technology and thus spark tolerant. The detectors were built in a modular way. The quadruplets consist of two double-sided readout panels and three support (or drift) panels equipped with the micromesh and the drift electrode. The panels are bolted together such that the detector can be opened and cleaned, if required. Two of the readout planes are equipped with readout strips inclined by 1.5 degree. In this talk, we present the results of detailed performance studies based on X-Ray and cosmic ray measurements as well as measurements with 855 MeV electrons at the MAMI accelerator. In particular, results on reconstruction efficiencies, track resolution and gain homogeneity is presented.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A resistive-MicroMeGaS quadruplet built at CERN has been installed at the new CERN Gamma Irradiation Facility (GIF++) with the aim of carrying out a long-term ageing study. Two smaller resistive ...bulk-MicroMeGaS produced at the CERN PCB workshop have also been installed at GIF++ in order to provide a comparison of the ageing behavior with the MicroMeGaS quadruplet. We give an overview of the ongoing tests at GIF++ in terms of particle rate, integrated charge and spatial resolution of the MicroMeGaS detectors.
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We report on the first search for nuclear recoils from dark matter in the form of weakly interacting massive particles (WIMPs) with the XENONnT experiment, which is based on a two-phase time ...projection chamber with a sensitive liquid xenon mass of 5.9 ton. During the (1.09±0.03) ton yr exposure used for this search, the intrinsic ^{85}Kr and ^{222}Rn concentrations in the liquid target are reduced to unprecedentedly low levels, giving an electronic recoil background rate of (15.8±1.3) events/ton yr keV in the region of interest. A blind analysis of nuclear recoil events with energies between 3.3 and 60.5 keV finds no significant excess. This leads to a minimum upper limit on the spin-independent WIMP-nucleon cross section of 2.58×10^{-47} cm^{2} for a WIMP mass of 28 GeV/c^{2} at 90% confidence level. Limits for spin-dependent interactions are also provided. Both the limit and the sensitivity for the full range of WIMP masses analyzed here improve on previous results obtained with the XENON1T experiment for the same exposure.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UL, UM
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