29 research outputs found
Effects of High Charge Densities in Multi-GEM Detectors
A comprehensive study, supported by systematic measurements and numerical
computations, of the intrinsic limits of multi-GEM detectors when exposed to
very high particle fluxes or operated at very large gains is presented. The
observed variations of the gain, of the ion back-flow, and of the pulse height
spectra are explained in terms of the effects of the spatial distribution of
positive ions and their movement throughout the amplification structure. The
intrinsic dynamic character of the processes involved imposes the use of a
non-standard simulation tool for the interpretation of the measurements.
Computations done with a Finite Element Analysis software reproduce the
observed behaviour of the detector. The impact of this detailed description of
the detector in extreme conditions is multiple: it clarifies some detector
behaviours already observed, it helps in defining intrinsic limits of the GEM
technology, and it suggests ways to extend them.Comment: 5 pages, 6 figures, 2015 IEEE Nuclear Science Symposiu
Charge Transfer Properties Through Graphene Layers in Gas Detectors
Graphene is a single layer of carbon atoms arranged in a honeycomb lattice
with remarkable mechanical, electrical and optical properties. For the first
time graphene layers suspended on copper meshes were installed into a gas
detector equipped with a gaseous electron multiplier. Measurements of low
energy electron and ion transfer through graphene were conducted. In this paper
we describe the sample preparation for suspended graphene layers, the testing
procedures and we discuss the preliminary results followed by a prospect of
further applications.Comment: 2014 IEEE Nuclear Science Symposium and Medical Imaging Conference
with the 21st Symposium on Room-Temperature Semiconductor X-Ray and Gamma-Ray
Detectors, 4 pages, 8 figure
Charge Transfer Properties Through Graphene for Applications in Gaseous Detectors
Graphene is a single layer of carbon atoms arranged in a honeycomb lattice
with remarkable mechanical and electrical properties. Regarded as the thinnest
and narrowest conductive mesh, it has drastically different transmission
behaviours when bombarded with electrons and ions in vacuum. This property, if
confirmed in gas, may be a definitive solution for the ion back-flow problem in
gaseous detectors. In order to ascertain this aspect, graphene layers of
dimensions of about 2x2cm, grown on a copper substrate, are transferred
onto a flat metal surface with holes, so that the graphene layer is freely
suspended. The graphene and the support are installed into a gaseous detector
equipped with a triple Gaseous Electron Multiplier (GEM), and the transparency
properties to electrons and ions are studied in gas as a function of the
electric fields. The techniques to produce the graphene samples are described,
and we report on preliminary tests of graphene-coated GEMs.Comment: 4pages, 3figures, 13th Pisa Meeting on Advanced Detector
Demonstration of Gd-GEM detector design for neutron macromolecular crystallography applications
The European Spallation Source (ESS) in Lund, Sweden will become the world's
most powerful thermal neutron source. The Macromolecular Diffractometer (NMX)
at the ESS requires three 51.2 x 51.2~cm detectors with reasonable
detection efficiency, sub-mm spatial resolution, a narrow point spread function
(PSF) and good time resolution. This work presents measurements with the
improved version of the NMX detector prototype consisting of a Triple-GEM
detector with natural Gd converter and a low material budget readout. The
detector was successfully tested at the neutron reactor of the Budapest Neutron
Centre (BNC) and at the D16 instrument at the Institut Laue-Langevin (ILL) in
Grenoble. The measurements with Cadmium and Gadolinium masks in Budapest
demonstrate that the point spread function of the detector lacks long tails
that could impede the measurement of diffraction spot intensities. On the D16
instrument at ILL, diffraction spots from Triose phosphate isomerase w/
2-phosphoglycolate (PGA) inhibitor were measured both in the D16 Helium-3
detector and the Gd-GEM. The comparison between the two detectors show a
similar point spread function in both detectors, and the expected efficiency
ratio compared to the Helium-3 detector. Both measurements together thus give
good indications that the Gd-GEM detector fits the requirements for the NMX
instrument at ESS
Charge transfer properties through graphene for applications in gaseous detectors
Graphene is a single layer of carbon atoms arranged in a honeycomb lattice with remarkable mechanical and electrical properties. Regarded as the thinnest and narrowest conductive mesh, it has drastically different transmission behaviours when bombarded with electrons and ions in vacuum. This property, if confirmed in gas, may be a definitive solution for the ion back-flow problem in gaseous detectors. In order to ascertain this aspect, graphene layers of dimensions of about 2 x 2 cm(2), grown on a copper substrate, are transferred onto a flat metal surface with holes, so that the graphene layer is freely suspended. The graphene and the support are installed into a gaseous detector equipped with a triple Gaseous Electron Multiplier (GEM), and the transparency properties to electrons and ions are studied in gas as a function of the electric fields. The techniques to produce the graphene samples are described, and we report on preliminary tests of graphene-coated GEMs.UK Research & Innovation (UKRI) - Engineering & Physical Sciences Research Council (EPSRC) - EP/H020055/1 / EP/N004159/
Timing performance of a Micro-Channel-Plate Photomultiplier Tube
The spatial dependence of the timing performance of the R3809U-50 Micro-Channel-Plate PMT (MCP-PMT) by Hamamatsu was studied in high energy muon beams. Particle position information is provided by a GEM tracker telescope, while timing is measured relative to a second MCP-PMT, identical in construction. In the inner part of the circular active area (radius r5.5 mm) the time resolution of the two MCP-PMTs combined is better than 10 ps. The signal amplitude decreases in the outer region due to less light reaching the photocathode, resulting in a worse time resolution. The observed radial dependence is in quantitative agreement with a dedicated simulation. With this characterization, the suitability of MCP-PMTs as t0 reference detectors has been validated.Peer reviewe
Progress on the PICOSEC-Micromegas Detector Development : Towards a precise timing, radiation hard, large-scale particle detector with segmented readout
This contribution describes the PICOSEC-Micromegas detector which achieves a time resolution below 25 ps. In this device the passage of a charged particle produces Cherenkov photons in a radiator, which then generate electrons in a photocathode and these photoelectrons enter a two-stage Micromegas with a reduced drift region and a typical anode region. The results from single-channel prototypes (demonstrating a time resolution of 24 ps for minimum ionizing particles, and 76 ps for single photoelectrons), the understanding of the detector in terms of detailed simulations and a phenomenological model, the issues of robustness and how they are tackled, and preliminary results from a multi-channel prototype are presented (demonstrating that a timing resolution similar to that of the single-channel device is feasible for all points across the area covered by a multi-channel device).Peer reviewe
Precise charged particle timing with the PICOSEC detector
The experimental requirements in near future accelerators (e.g. High Luminosity-LHC) has stimulated intense interestin development of detectors with high precision timing capabilities. With this as a goal, a new detection concept called PICOSEC,which is based to a “two-stage” MicroMegas detector coupled to a Cherenkov radiator equipped with a photocathode has beendeveloped. Results obtained with this new detector yield a time resolution of 24 ps for 150 GeV muons and 76 ps for single pho-toelectrons. In this paper we will report on the performance of the PICOSEC in test beams, as well as simulation studies andmodelling of its timing characteristicsPeer reviewe
Precise timing with the PICOSEC-Micromegas detector
This work presents the concept of the PICOSEC-Micromegas de-tector to achieve a time resolution below 30 ps. PICOSEC consists of a two-stageMicromegas detector coupled to a Cherenkov radiator and equipped with a photo-cathode. The results from single-channel prototypes as well as the understanding ofthe detector in terms of detailed simulations and preliminary results from a multi-channel prototype are presented.Peer reviewe
Charged particle timing at sub-25 picosecond precision : The PICOSEC detection concept
The PICOSEC detection concept consists in a “two-stage” Micromegas detector coupled to a Cherenkov radiator and equipped with a photocathode. A proof of concept has already been tested: a single-photoelectron response of 76 ps has been measured with a femtosecond UV laser at CEA/IRAMIS, while a time resolution of 24 ps with a mean yield of 10.4 photoelectrons has been measured for 150 GeV muons at the CERN SPS H4 secondary line. This work will present the main results of this prototype and the performance of the different detector configurations tested in 2016-18 beam campaigns: readouts (bulk, resistive, multipad) and photocathodes (metallic+CsI, pure metallic, diamond). Finally, the prospects for building a demonstrator based on PICOSEC detection concept for future experiments will be discussed. In particular, the scaling strategies for a large area coverage with a multichannel readout plane, the R&D on solid converters for building a robust photocathode and the different resistive configurations for a robust readout.Peer reviewe