For detectors with resistive elements, the time dependence of the signals is not solely given by the movement of the charges in the drift medium but also by the time-dependent reaction of the ...resistive materials. In this report, we present a numerical way to capture this contribution by using the extended form of the Ramo–Shockley theorem for conductive media. As an example, the methodology will be applied to the MicroCAT two-dimensional interpolation readout to calculate the center of gravity position reconstruction distortion map of its readout cells.
We describe the development of a position-sensitive Gas Electron Multiplier detector prototype, providing for each ionizing event three coordinates: the cartesian X and Y, and U at 45°. Simultaneous ...recording of the three projections permits ambiguity-free reconstruction of multiple tracks, and aims at operation in very high intensity radiation fields.
The VMM3a is an Application Specific Integrated Circuit (ASIC), specifically developed for the readout of gaseous detectors. Originally developed within the ATLAS New Small Wheel (NSW) upgrade, it ...has been successfully integrated into the Scalable Readout System (SRS) of the RD51 collaboration. This allows, to use the VMM3a also in small laboratory set-ups and mid-scale experiments, which make use of Micro-Pattern Gaseous Detectors (MPGDs). As part of the integration of the VMM3a into the SRS, the readout and data transfer scheme was optimised to reach a high rate-capability of the entire readout system and profit from the VMM3a’s high single-channel rate-capability of 3.6Mhits/s. The optimisation focused mainly on the handling of the data output stream of the VMM3a, but also on the development of a trigger-logic between the front-end cards and the DAQ computer. In this article, two firmware implementations of the non-ATLAS continuous readout mode are presented, as well as the implementation of the trigger-logic. Afterwards, a short overview on X-ray imaging results is presented, to illustrate the high rate-capability from an application point-of-view.
This work explores the use of multichannel readout electronics, already in use for quality assurance in gain uniformity studies, to measure the uniformity of the induction gap in Gas Electron ...Multipliers (GEM) based detectors. The devised procedure also provides a qualification of the readout electrodes in terms of disconnected or shorted channels. The measurement is based on inducing a signal on the readout strips by pulsing the bottom layer of the GEM foil, and measuring the amplitude of the induced signal. In this work, signals are readout using the analog APV25 front-end chip and the Scalable Readout System (SRS) developed by the RD51 collaboration at CERN. Studies on small and large area GEM detectors, effects of mechanical stress, and of electric fields are presented. Sensitivity to defects in the readout plane is also verified.
The implementation of the VMM3a Application-Specific Integrated Circuit (ASIC) into the Scalable Readout System (SRS) has opened a new domain for measurements with Micro-Pattern Gaseous Detectors ...(MPGDs). In the presented studies we demonstrate the capabilities of this system, specifically the time-resolution in the nanosecond regime in combination with a continuous multichannel readout and a 10-bit ADC. We can now resolve the interaction of argon fluorescence X-ray photons created in a gaseous detector and utilise these interactions to determine the electron drift velocity in our detector and to investigate the attenuation length of the fluorescence photons.
X-ray imaging with gaseous detectors using the VMM3a and the SRS Scharenberg, L.; Bortfeldt, J.; Brunbauer, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2021, Letnik:
1011
Journal Article
Recenzirano
Odprti dostop
The integration of the VMM3a Application-Specific Integrated Circuit (ASIC) into RD51’s Scalable Readout System (SRS) provides a versatile tool for the readout of Micro-Pattern Gaseous Detectors ...(MPGDs). With its self-triggered high-rate readout, its analogue part that allows to get information on the deposited energy in the detector, and its so-called neighbouring-logic that allows to recover information on the charge distribution, this new system has features of particular interest for digital X-ray imaging. In the present article, we want to emphasise the capabilities of VMM3a/SRS by presenting results of X-ray imaging studies. We will highlight the advantages on the energy and the spatial resolution provided by the neighbouring-logic. In the first part, we focus on spatial resolution studies. We show how segmented readout structures introduce a repeating pattern in the distribution of the reconstructed positions (using the centre-of-gravity method) and how this behaviour can be mitigated with the neighbouring-logic. As part of these studies, we explore as well an alternative position reconstruction algorithm. In the second part of the article, we present the energy resolution studies.
Abstract
As demonstrated by the ATLAS New Small Wheel community with their MicroMegas (MM) design,
resistive electrodes are now used in different detector types within the Micro Pattern Gaseous
...Detector family to improve their robustness. The extended form of the Ramo-Shockley theorem for
conductive media has been applied to a 1 MΩ/□ 2D resistive strip bulk MM to calculate
the signal spreading over neighbouring channels using an 80 GeV/c muon track. For this geometry,
the dynamic weighting potential was obtained numerically using a finite element solver by applying
a junction condition and coordinate scaling technique to accurately represent the boundary
conditions of a 10 × 10 cm
2
active area. Using test beam measurements, the results of
this model will be used to benchmark this microscopic modelling methodology for signal induction
in resistive particle detectors.
Minimizing distortions with sectored GEM electrodes Marques, A.P.; Brunbauer, F.M.; Müller, H. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2020, Letnik:
961
Journal Article
Recenzirano
Odprti dostop
Electrode sectorization is an important design principle for large area GEM based detectors. It reduces the energy of discharges and permits to disconnect defective or shorted sectors, but induces a ...local signal distortion and a potential efficiency loss. We implemented and evaluated a new design approach for the insulating gaps between electrode sectors, to minimize or mitigate distortions and dead regions. By preserving the hole pattern of GEMs even in the insulating region between electrode sectors, the response of the detector in these regions was partly recovered resulting in reduced distortions. Single-side sectored GEMs were optically read out to study the influence of different sectorization patterns. Recorded images show a clear improvement with full holes both aligned with the rows and with a random alignment as compared to the traditional blank insulating strip between sectors. A sectored GEM manufactured on a substrate coated with a resistive DLC layer was evaluated and shown to minimize distortions. The investigated sectorization patterns provide a way of recovering signals in the insulating or resistive regions between sectors in GEM-based detectors.
Abstract Gas Electron Multipliers (GEMs) are used in many particle physics experiments, employing their `standard' configuration with amplification holes of 140 μ m pitch in a hexagonal pattern. ...However, the collection of the charge cloud from the primary ionisation electrons from the drift region of the detector into the GEM holes affects the position information from the initial interacting particle. In this paper, the results from studies with a triple-GEM detector with an X-Y-strip readout anode are presented. It is demonstrated that GEMs with a finer hole pitch of here 90 μ m improve the detector's spatial resolution. Within these studies, also the impact of the front-end electronics on the spatial resolution was investigated, which is briefly discussed in the paper.
Timing performance of a multi-pad PICOSEC-Micromegas detector prototype Aune, S.; Bortfeldt, J.; Brunbauer, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2021, Letnik:
993, Številka:
C
Journal Article
Recenzirano
Odprti dostop
The multi-pad PICOSEC-Micromegas is an improved detector prototype with a segmented anode, consisting of 19 hexagonal pads. Detailed studies are performed with data collected in a muon beam over four ...representative pads. We demonstrate that such a device, scalable to a larger area, provides excellent time resolution and detection efficiency. As expected from earlier single-cell device studies, we measure a time resolution of approximately 25 picoseconds for charged particles hitting near the anode pad centres, and up to 30 picoseconds at the pad edges. Here, we study in detail the effect of drift gap thickness non-uniformity on the timing performance and evaluate impact position based corrections to obtain a uniform timing response over the full detector coverage.
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