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, Volume:
958
Journal Article
Peer reviewed
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.
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.
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, Volume:
1041
Journal Article
Peer reviewed
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.
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