The performance of MicroMegas (MM) has been extensively studied during several test beam campaigns with high energy particle beams at CERN up to the year 2012, and more recently (June 2013) with ...electron beams at DESY. Main objectives of the tests were to demonstrate that the requirements could be achieved for the upgrade of the ATLAS Muon Spectrometer, where the MicroMegas will be mounted (along with small-strip Thin Gap Chambers - sTGC) on the New Small Wheel for forward muon detection. The MM layout and operating settings have then been chosen to satisfy the ATLAS upgrade requirements and trigger timing constraints. Results for efficiencies, time resolution and spatial resolution for perpendicular and inclined tracks are presented. Moreover, in ATLAS the MM will operate in a non-uniform magnetic field up to 0.3 T. Dedicated test beam measurements have been carried out in a variable magnetic field between 0 and 1 T. The performance of MM in magnetic fields is also reported along with a comparison to simulations.
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.
Design, fabrication, and characterization of an asymmetric metal-semiconductor-metal photodetector, based on internal photoemission effect and integrated into a silicon-on-insulator waveguide, are ...reported. For this photodetector, a responsivity of 4.5 mA/W has been measured at 1550 nm, making it suitable for power monitoring applications. Because the absorbing metal is deposited strictly around the vertical output facet of the waveguide, a very small contact area of about 3 µm2 is obtained and a transit-time-limited bandwidth of about 1 GHz is demonstrated. Taking advantage of this small area and electrode asymmetry, a significant reduction in the dark current (2.2 nA at -21 V) is achieved. Interestingly, applying reverse voltage, the photodetector is able to tune its cut-off wavelength, extending its range of application into the MID infrared regime.
Through the years the Micromegas (MICRO MEsh GAseous Structure) devices have proven to be reliable detectors with excellent space resolution and high rate capability. Large area Micromegas will be ...employed for the first time in high-energy physics for the Muon Spectrometer upgrade of the ATLAS experiment at the CERN LHC. A total surface of about 150 m super(2) of the forward regions of the Muon Spectrometer will be equipped with 8 layers of Micromegas modules. Each module covers a surface from 2 to 3 m super(2) for a total active area of 1200 m super(2). Together with the small-strips Thin Gap Chambers, they will compose the two New Small Wheels, which will replace the innermost stations of the ATLAS Endcap Muon tracking system in the 2018/19 shutdown. The breakthroughs and developments of this type of Micro Pattern Gas Detector will be reviewed, along with the path towards the construction of the modules, which will take place in several production sites starting in 2015. An overview of the detector performance obtained in the test beam campaigns in recent years at CERN will be also presented.
Damage in a pavement structure is usually initiated in the asphalt layers, making the Rayleigh wave ideally suited to the detection of shallow surface defects. However, the practical application of ...crack detection methods in asphalt is hampered by the dispersive behaviour of the road pavement. A new digital signal processing technique for the measurement of the amplitude and phase of the direct and reflected Rayleigh waves, scattered from the boundaries of a vertical crack in asphalt, is presented in this paper for the first time. The method uses multiple receivers and hence it finds an approximate solution with a least square optimisation. The resonant peak frequencies of the reflection coefficient and the cut-off frequencies of the transmission coefficient are used for assessing the depth of the crack. The method proved to be successful for the in-situ assessment of the depth of cracks both numerically and experimentally, since it can cope with the dispersive and heterogeneous nature of asphalt. This work supports a paradigm-shifting approach to the in-situ crack evaluation of roads, for which the road is holistically treated as a dispersive medium.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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.
In the last two decades there has been growing interest in silicon photonics and in the possibility to integrate new materials to overcome the silicon intrinsic limitations. Erbium has represented a ...viable solution for the realization of light sources at telecommunications wavelengths opening the path to the investigation of various photonic devices based on rare earth.
In this work we investigate a photodetector operating at 1550 nm whose detection mechanism is based on the internal photoemission effect through an Er/Si Schottky junction. The Er/Si junction has been carefully electrically characterized showing a potential barrier and cut-off wavelength of 0.59 eV and 2105 nm, respectively. Moreover, a responsivity of 0.62 mA/W has been measured for a 3 μm-width waveguide at 1550 nm and at reverse voltage of -8 V. Finally, the noise equivalent power of the device has been evaluated as high as 0.53 nW/(Hz)
1/2
at -8 V.
Even if device responsivity is still low, we believe that our insights may suggest Er/Si as a new platform for the integration of various optical functionalities on the same chip opening new frontiers in the field of low-cost silicon micro and nanophotonics.
Abstract After exploring different solutions and testing several options, the high granularity resistive Micromegas technology is now mature enough to offer an efficient operation up to particle ...rates of 10 MHz/cm 2 , maintaining the gas amplification above 10 4 , with a large margin before breakdown in order to ensure a stable and reliable operation. The detector exploits small-size readout pads for occupancy reduction and a double Diamond-Like Carbon (DLC) resistive layer with a network of dot-connections to ground for a fast charge evacuation. The double-layer allows preserving the minimum resistance to suppress the discharge intensity for stable operations. The performance measured with particle beams at CERN have shown a spatial resolution below 100 μm for mm-wide readout pads and a few ns time resolution. Now, the technology is being scaled to larger areas, with the construction of detectors with an active area of ∼20×20 cm 2 (already achieved) and new ∼40×50 cm 2 prototypes under construction. An overview of the detector technology, including the latest results, is presented in terms of the gain and rate capability (measured in the laboratory) and efficiency, time and spatial resolution (measured at the CERN SPS). Possible applications in HEP experiments, as well as future developments, are also reported.
The R&D project being presented aims to improve the use of resistive Micromegastechnology in high-energy physics experiments. The project focuses on achieving stable, reliable,and high-gain operation ...at particle flow rates above 1 MHz/cm2 on largesurfaces. To achieve this, the project uses a configuration with small pads readout and requiresinnovative solutions for the spark protection resistive scheme. Different resistive patterns wereinvestigated, and finally the solution based on a double layer of DLC foils was chosen,demonstrating the capability to perform equally for low and high rates under irradiation of X-rayson the full surface of 25 cm2 of the prototype detectors. With this technologyand layout, a detector with an active area of 400 cm2 was recently built. Inthis work we present the results of high-rate capability, robustness, dependence on the irradiatedarea, obtained with high intensity X-rays measurements, as well as the results on efficiency andspatial resolution obtained, at low rates, at CERN SPS with high energy particlebeams. Additionally, preliminary results of pixelized resistive Micromegas time response arereported. With the successful achievements of this detector and the construction of even largersmall-pad resistive Micromegas next year, the project will establish the technology for future usein particle physics and other applications.
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