Discharge behaviour of resistive Micromegas Alviggi, M.; Iengo, P.; Iodice, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
958
Journal Article
Recenzirano
As other gaseous detectors with planar geometry, resistive Micromegas suffer of possible discharges between the cathode (mesh) and the anode planes. As the probability of appearance may depend on the ...mesh structure and the gas mixture, a systematic study is on-going to test meshes of different wire diameter, weft opening and production technique. The mesh with the best performance has been additionally tested in different gas mixtures, changing the percentages of Ar and CO2 in the mixture and/or adding small quantities of additional quenchers. In this paper we present the preliminary results obtained on the present small, but growing, sets of meshes and gas mixtures, which seem to favour meshes with small openings and the addition of isobutane.
•Smaller mesh wires/openings result in a higher high voltage stability.•Calendered meshes, helping in improving field uniformity, perform better.•The increase of the quencher in Ar-CO2 mixtures improves the detector stability.•A small quantity of Isobutane further improves the detector stability.
The LHC experiments are undergoing important upgrades for the High Luminosity LHC project. Experiments will be required to operate under three times higher instantaneous luminosity and higher levels ...of radiation when compared to LHC Run2. The integrated luminosity will increase by a factor ten. To cope with these conditions resistive Micromegas chambers were chosen by the ATLAS experiment as one of the technologies for the upgrade of the first forward muon stations. This paper describes the results of two prototype Micromegas detectors that were installed in the CERN Gamma Irradiation Facility with the aim to evaluate the detector performance under high-rate irradiation and to assess ageing effects over a 2.5 year long irradiation period and an accumulated charge in excess of 0.3 C/cm2.
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 ∼100μm, fully efficient up to a particle rate of ∼20kHz/cm2. 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%CO2 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.
Pixelated resistive Micromegas detector for high-rate environment Alviggi, M.; Camerlingo, M.T.; Pietra, M. Della ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2022, Letnik:
1041
Journal Article
Recenzirano
The R&D work reported in this paper has been devoted to the production and test of pixelated resistive micromegas detectors able to track particles in a high-rate environment, up to 10MHz/cm2, ...keeping a stable gain and a good spatial resolution. To pursue our goal, we had to reduce the occupancy by increasing the detector granularity and this has been done by changing the read-out anodes from the usual strips to pads. This minor change in the electrodes layout drastically increased the difficulty of implementing a resistive structure to protect the anodes from sparking. We present the results of the tests performed on four prototypes, with different protection schemes, showing it is possible to reach the desired rate with high gain, high efficiency and good position resolution. The response to X-rays from low (55Fe source) to high (X-rays generator) rates, as well as to beams of ionizing particles is reported.
The results of the study of a large-size, multilayer Micromegas detector with X-ray source Cd-109 are discussed. The detector consists of 4 layers, each of them is a Micromegas detector with ...resistive anode and strip-based read-out structure. The gas volume of the chamber is split to 4 parts interconnected in 6 points. Results of the measurements of the gas gain curves and the 1st Townsend coefficient as well as the E_amp/E_drift characteristics are presented and discussed. The detector presented a non-negligible gas leak, affecting the reported results. The influence of the leak on operation of the module is estimated.
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.
During the last decade, a major improvement in the field of the Micro-Pattern Gaseous Detectors has been reached by adding a layer of resistive strips above the readout strips to reduce drastically ...the effect of discharges. The resistive strips are separated from the readout strips by a thin layer of insulator. When the detector is operated some gain reduction is observed over the first seconds or minutes after switch-on, stabilising after some time. Is this related to the presence of the insulator or are there other mechanisms at work? We report here the results of a detailed study of this effect and compare resistive-strip and Diamond Like Carbon (DLC) Micromegas detectors. We will present and quantify the main characteristics of this effect, i.e, the relative gain drop and the time to reach a stable regime, as a function of the detector configuration and rate. In addition we studied the influence of the pillars that support the mesh on the behaviour of bulk and non-bulk Micromegas detectors.
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