27 research outputs found
Experimental and numerical simulation of a TPC like set up for the measurement of ion backflow
Ion backflow is one of the effects limiting the operation of a gaseous
detector at high flux, by giving rise to space charge which perturbs the
electric field. The natural ability of bulk Micromegas to suppress ion feedback
is very effective and can help the TPC drift volume to remain relatively free
of space charge build-up. An efficient and precise measurement of the backflow
fraction is necessary to cope up with the track distortion due to the space
charge effect. In a subtle but significant modification of the usual approach,
we have made use of two drift meshes in order to measure the ion backflow
fraction for bulk Micromegas detector. This helps to truly represent the
backflow fraction for a TPC. Moreover, attempt is taken to optimize the field
configuration between the drift meshes. In conjunction with the experimental
measurement, Garfield simulation framework has been used to simulate the
related physics processes numerically
A numerical investigation on the track distortion at the Micromegas based LPTPC endplate
Abstract
The R&D activities for the Linear Collider TPC (LCTPC) are currently focused on the adoption of the Micro-Pattern Gaseous Detectors (MPGDs). Different MPGD modules which are commissioned on the endplate of a Large Prototype TPC (LPTPC) at DESY, were tested with a 5 GeV electron beam, under a 1 T magnetic field. During the tests, reduced signal sensitivity as well as distortion in the reconstructed track, were observed at the boundary of these modules.
We have numerically investigated the origin of the track distortions observed close to the edges of the Micromegas modules. The study clearly shows that the electric field non-uniformity near the inter-modular gaps is responsible for such track distortion. We have been able to simulate the observed patterns and magnitudes of distortion successfully. The obtained agreements with 2015 beam test data encourage us to continue with the study and, to propose module design modifications that can alleviate the problem of electrostatic field distortion at the module boundaries
Characterization of LAPPD timing at CERN PS testbeam
Large Area Picosecond PhotoDetectors (LAPPDs) are photosensors based on
microchannel plate technology with about 400 cm sensitive area. The
external readout plane of a capacitively coupled LAPPD can be segmented into
pads providing a spatial resolution down to 1 mm scale. The LAPPD signals have
about 0.5 ns risetime followed by a slightly longer falltime and their
amplitude reaches a few dozens of mV per single photoelectron. In this article,
we report on the measurement of the time resolution of an LAPPD prototype in a
test beam exercise at CERN PS. Most of the previous measurements of LAPPD time
resolution had been performed with laser sources. In this article we report
time resolution measurements obtained through the detection of Cherenkov
radiation emitted by high energy hadrons. Our approach has been demonstrated
capable of measuring time resolutions as fine as 25-30 ps. The available
prototype had performance limitations, which prevented us from applying the
optimal high voltage setting. The measured time resolution for single
photoelectrons is about 80 ps r.m.s.Comment: 35 pages, 23 figure
A Time Projection Chamber with GEM-Based Readout
For the International Large Detector concept at the planned International
Linear Collider, the use of time projection chambers (TPC) with micro-pattern
gas detector readout as the main tracking detector is investigated. In this
paper, results from a prototype TPC, placed in a 1 T solenoidal field and read
out with three independent GEM-based readout modules, are reported. The TPC was
exposed to a 6 GeV electron beam at the DESY II synchrotron. The efficiency for
reconstructing hits, the measurement of the drift velocity, the space point
resolution and the control of field inhomogeneities are presented.Comment: 22 pages, 19 figure
The Micromegas chambers for the ATLAS New Small Wheel upgrade
The ATLAS collaboration at LHC has chosen the resistive Micromegas technology, along with the small-strip Thin Gap Chambers (sTGC), for the high luminosity upgrade of the first muon station in the high-rapidity region, the so called New Small Wheel (NSW) project. After the R&D, design and prototyping phase, the first series production Micromegas quadruplets are being constructed at the involved construction sites in France, Germany, Italy, Russia and Greece. At CERN, the final validation and the integration of the modules in Sectors are in progress. These are big steps forward for the installation of the NSW foreseen for the LHC long shutdown in 2019 and 2020. The construction of the four types of large size quadruplets, all having trapezoidal shapes with surface areas between 2 and 3 m2, will be reviewed. The achievement of the requirements for these detectors revealed to be even more challenging than expected, when scaling from the small prototypes to the large dimensions. We will describe the encountered problems, to a large extent common to other micro-pattern gaseous detectors, and the adopted solutions. Final quality assessment and validation results on the achieved mechanical precision, on the High-Voltage stability during operation with and without irradiation will be presented together with the most relevant steps and results of the modules integration into sectors
Numerical Study of Electrostatic Field Distortion on LPTPC End-Plates based on Bulk Micromegas Modules
The R&D activities for the linear collider TPC (LC-TPC) are currently working on the adoption of the micro pattern devices for the gaseous amplification stage. Several beam tests have been carried out at DESY with a 5 GeV electron beam in a 1 T superconducting magnet. We worked on a large prototype TPC with an end-plate that was built, for the first time, using seven resistive bulk Micromegas modules. During experiments, reduced signal sensitivity was observed at the boundary of these modules. Electrostatic field distortion near the module boundaries was considered to be the possible major reason behind these observations. In the present work, we will explore this hypothesis through numerical simulation. Our aim has been to understand the origin of distortions observed close to the edges of the test beam modules and to explore the possibility of using the Garfield simulation framework for investigating a phenomenon as complex as distortion
Numerical Study of Electrostatic Field Distortion on LPTPC End-Plates based on Bulk Micromegas Modules
The R&D activities for the linear collider TPC (LC-TPC) are currently working on the adoption of the micro pattern devices for the gaseous amplification stage. Several beam tests have been carried out at DESY with a 5 GeV electron beam in a 1 T superconducting magnet. We worked on a large prototype TPC with an end-plate that was built, for the first time, using seven resistive bulk Micromegas modules. During experiments, reduced signal sensitivity was observed at the boundary of these modules. Electrostatic field distortion near the module boundaries was considered to be the possible major reason behind these observations. In the present work, we will explore this hypothesis through numerical simulation. Our aim has been to understand the origin of distortions observed close to the edges of the test beam modules and to explore the possibility of using the Garfield simulation framework for investigating a phenomenon as complex as distortion