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.
We present the development of resistive Micromegas aiming at operation under high rates, up to tens MHz/cm2, focusing on the optimisation of the spark protection resistive layer and the ...miniaturisation of the readout elements. Several Micromegas detectors have been built with an anode plane matrix of 48x16 rectangular readout pads, each pad 0.8x2.8 mm2. The detectors differ for the spark protection resistive schemes being realised with the following techniques: a pad-patterned embedded resistor by screen printing, and uniform DLC (Diamond Like Carbon structure) layers. Characterisation and performance studies of the detectors have been carried out by means of radioactive sources, X-Rays, and test beam. A comparison of the performance obtained with the different resistive layouts is presented, in particular focusing on the response under high irradiation and high rate exposure.
Small-pads resistive Micromegas prototype Di Donato, C.; Alviggi, M.; Camerlingo, M.T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
958
Journal Article
Recenzirano
Detectors at future accelerators will require operation at rates up to three orders of magnitude higher than 15 kHz/cm2 the hit rates expected in the current upgrades forward muon detectors of LHC ...experiments. A resistive Micromegas detectors with modified readout system can achieve rate capability up to few MHz/cm2 low occupancy. We present the development of small-pad Micromegas detectors with a pad resistive readout of few mm2 in size, built with the spark protection resistive layer realized with different techniques.
The new generation of particle physics experiments at current and future colliders demands more and more robust detectors. A proposed solution to the stringent requirements are the Small-pad ...Resistive Micormegas. This technology is being developed during recent years, in the framework of the new R&D project RHUM. Different resistive schemes have been implemented. The different behaviours of the embedded resistor layout and the Diamond-Like Carbon (DLC) uniform layers scheme have been studied. Results at very high rate are shown. HV stability studies with two different gases are reported.
Objectives: Hepatitis C virus (HCV) infection is often associated with cryoglobulinaemia (CG). Peripheral neuropathy (PN) is a comparatively common complication of CG associated with HCV infection ...and it is thought to be attributable to nerve ischaemia. Only few HCV CG patients with PN have been reported. The recent finding of HCV RNA in nerve biopsy specimens has suggested a possible direct role of HCV in the pathogenesis of PN. The authors studied 51 HCV patients to determine the prevalence of CG and to clarify the possible mechanism by which HCV determines the PN. Methods: All the patients were studied clinically, by laboratory tests and electrophysiologically. Twenty eight patients underwent sural nerve biopsy where both morphological and morphometric evaluation of the biopsy specimen was performed, as well as statistical analysis. Results: CG was found in 40 of 51 cases (78%). Polyneuropathy was significantly prevalent in CG+ patients compared with CG− (18 of 40 compared with 1 of 11 patients; p=0.01). HCV CG− patients more frequently developed well defined mononeuropathy or multiple neuropathy when compared with HCV CG+ (10 of 11 compared with 22 of 40; p<0.03). HCV CG+ patients showed significantly higher proportion of rheumatoid factor positivity (p<0.001) and low C4 levels (p=0.001). Nerve biopsy was performed in 25 of 40 HCV CG+ patients and in 3 of 11 HCV CG− patients: epineurial vasculitis was present in 8 of 25 HCV CG+ (32%) and in 2 of 3 HCV CG−. Differential fascicular loss of axons was found in 10 of 25 CG+ (40%) and 1 of 3 CG−, signs of both demyelination and axonal degeneration were present in 7 of 25 CG+ (28%). No significant difference was found in neuropathological features, while histometrical analysis disclosed more severe involvement in CG+ patients. Conclusions: These findings suggest that the presence of CG is a negative predictive factor for the associated PN. Morphological findings in the sural nerve from HCV CG− and CG+ are consistent with an ischaemic mechanism of nerve damage and are against a direct role of the virus in causing the associated PN.
Motivated mainly by future upgrades at high-luminosity LHC (HL-LHC) and detectors at future accelerators, most of the HEP R&D collaborations are focusing on the design of new particle detectors for ...operation under high particle flow. In the field of Micro-Pattern-Gaseous-Detectors, were designed the small-pad resistive Micromegas prototypes, to overcome the limitations of current resistive strip Micromegas chambers. In these new prototypes, pads with 1×3 mm 2 area replace the readout strips to reduce the occupancy. The spark protection resistive layer has been redesigned and optimized with different techniques to permit a safe behavior of the detector, at rates of the order of tens MHz/cm 2 over large surfaces without efficiency loss. The firstly-developed design exploits a pad-patterned embedded resistor layout made by screen-printing, while the most recent technique involves uniform sputtered DLC (Diamond Like Carbon structure) layers, where the charge evacuates through the several vias connected to the ground. Comparative studies have been conducted on the performance of the detectors with two resistive layouts, and between two DLC prototypes with different pitch of vias and surface resistivity. The results of the tests performed with high intensity X-rays and with high-energy charged particle beams will be presented.
In an Italian population of 275 unrelated men affected by adult-onset sporadic progressive cerebellar ataxia, the authors found six patients carrying an FMR1 gene premutation. Age at onset (range, 53 ...to 69 years) and clinical-neuropathologic findings were consistent with the fragile-X tremor ataxia syndrome (FXTAS), although tremor was not as common as previously described. FXTAS accounted for 4.2% of the cases diagnosed at >50 years, suggesting that it is a frequent genetic cause of late-onset sporadic ataxia.
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