Recent developments have shown that coupling a Micromegas gaseous detector on a glass substrate with a transparent anode and a CMOS camera enables the optical readout of Micromegas detectors with a ...good spatial resolution, demonstrating that the glass Micromegas detector is well-suited for imaging. This feasibility test has been effectuated with low-energy X-ray photons also permitting energy resolved imaging. This test opens the way to different applications. Here we will focus on two applications. Namely, neutron imaging for non-destructive examination of highly gamma-ray emitting objects, such as irradiated nuclear fuel or radioactive waste. And secondly, we are developing a beta imager for the cell tagging in the field of anticancerous drug studies.
Both applications require to design the detectors in view of the specific constraints of reactor dismantling and medical applications: spatial resolution and strong gamma suppression for neutron imaging and precise rate and energy spectrum measurements for the beta.
A dedicated system consisting of a glass Micromegas detector and an ultrasensitive camera has been designed and assembled. Here we present the first results from the characterization of the detectors, as well as the first acquired images.
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.
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.
Implementation of the VMM ASIC in the Scalable Readout System Lupberger, M.; Bartels, L.; Brunbauer, F.M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2018, Volume:
903
Journal Article
Peer reviewed
Open access
The Scalable Readout System (SRS) developed by the RD51 collaboration is a versatile and multi-purpose approach, which is used with different front-end chips to transfer data from detectors to ...computers. Targeting mainly micro-pattern gaseous detectors, the system is also applicable for silicon strip or pad detectors. The most frequently used front-end chip today is the APV25, originally developed for the CMS pixel detector. In the scope of the ATLAS New Small Wheel upgrade, a new front-end chip, the VMM, is developed, which has significantly improved specifications compared to the APV25.
We report on the implementation of the VMM in the Scalable Readout System carried out by the RD51 collaboration in the framework of a detector project related to the European Spallation Source ERIC. Due to the hierarchical design of the Scalable Readout System, only specific parts of the readout chain need to be adapted or designed, which is the carrier board for the front-end chip, an adapter card that connects to the common hardware of the system and the firmware for a field programmable gate array. In addition, we have developed dedicated software for slow control, data acquisition and online monitoring. The readout system has been tested in the laboratory and in particle beams and we present results which proof the functioning of the system, even though it is still in a prototype state.
Radiation imaging with glass Micromegas Brunbauer, F.M.; Desforge, D.; Ferrer-Ribas, E. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2020, Volume:
955
Journal Article
Peer reviewed
Open access
Optically recording scintillation light emitted by MicroPattern Gaseous Detectors (MPGDs) with imaging sensors is a versatile and performant readout modality taking advantage of modern high ...granularity imaging sensors. To allow scintillation light readout of a detector based on MicroMesh Gaseous Structure (Micromegas) technology, we have integrated a Micromegas on a glass substrate with a transparent anode. In addition to optical detection of scintillation light emitted during electron avalanche multiplication between the micromesh and the anode, this setup also achieves a good energy resolution. A glass Micromegas detector was operated in an Ar/CF4 gas mixture and showed a response comparable to conventional Micromegas detectors. The spectrum of the emitted scintillation light was recorded and shown to be equivalent to the one obtained with other gaseous detectors in the same gas mixture. Optically read out images were recorded with CCD cameras and integrated X-ray radiographic imaging with good spatial resolution was demonstrated. A spatial resolution of 440μm (10% MTF) was found. Single X-ray photon detection with a high-sensitivity camera was achieved, which potentially permits energy-resolved X-ray fluorescence imaging.
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.
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, Volume:
961
Journal Article
Peer reviewed
Open access
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.
Live event reconstruction in an optically read out GEM-based TPC Brunbauer, F.M.; Galgóczi, G.; Gonzalez Diaz, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2018, Volume:
886
Journal Article
Peer reviewed
Open access
Combining strong signal amplification made possible by Gaseous Electron Multipliers (GEMs) with the high spatial resolution provided by optical readout, highly performing radiation detectors can be ...realized. An optically read out GEM-based Time Projection Chamber (TPC) is presented. The device permits 3D track reconstruction by combining the 2D projections obtained with a CCD camera with timing information from a photomultiplier tube. Owing to the intuitive 2D representation of the tracks in the images and to automated control, data acquisition and event reconstruction algorithms, the optically read out TPC permits live display of reconstructed tracks in three dimensions. An Ar/CF4 (80/20%) gas mixture was used to maximize scintillation yield in the visible wavelength region matching the quantum efficiency of the camera. The device is integrated in a UHV-grade vessel allowing for precise control of the gas composition and purity. Long term studies in sealed mode operation revealed a minor decrease in the scintillation light intensity.
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