141 research outputs found
Characterization of microbulk detectors in argon- and neon-based mixtures
A recent Micromegas manufacturing technique, so called Microbulk, has been
developed, improving the uniformity and stability of this kind of detectors.
Excellent energy resolutions have been obtained, reaching values as low as 11%
FWHM at 5.9 keV in Ar+5%iC4H10. This detector has other advantages like its
flexible structure, low material budget and high radio-purity. Two microbulk
detectors with gaps of 50 and 25 um have been characterized in argon- and
neon-based mixtures with ethane, isobutane and cyclohexane. The results will be
presented and discussed. The gain curves have been fitted to the Rose-Korff
gain model and dependences of the electron mean free path and the threshold
energy for ionization have been obtained. The possible relation between these
two parameters and the energy resolution will be also discussed.Comment: Submitted to the Journal of Instrumentatio
Performance of the Micromegas detector in the CAST experiment
The gaseous Micromegas detector designed for the CERN Axion search experiment
CAST, operated smoothly during Phase-I, which included the 2003 and 2004
running periods. It exhibited linear response in the energy range of interest
(1-10keV), good spatial sensitivity and energy resolution (15-19% FWHM at
5.9keV)as well as remarkable stability. The detector's upgrade for the 2004
run, supported by the development of advanced offline analysis tools, improved
the background rejection capability, leading to an average rate 5x10^-5
counts/sec/cm^2/keV with 94% cut efficiency. Also, the origin of the detected
background was studied with a Monte Carlo simulation, using the GEANT4 package.Comment: Prepared for PSD7: The Seventh International Conference on Position
Sensitive Detectors, Liverpool, United Kingdom, 12-16 Sep. 200
Spatial Resolution of a Micromegas-TPC Using the Charge Dispersion Signal
The Time Projection Chamber (TPC) for the International Linear Collider will
need to measure about 200 track points with a resolution close to 100 m. A
Micro Pattern Gas Detector (MPGD) readout TPC could achieve the desired
resolution with existing techniques using sub-millimeter width pads at the
expense of a large increase in the detector cost and complexity. We have
recently applied a new MPGD readout concept of charge dispersion to a prototype
GEM-TPC and demonstrated the feasibility of achieving good resolution with pads
similar in width to the ones used for the proportional wire TPC. The charge
dispersion studies were repeated with a Micromegas TPC amplification stage. We
present here our first results on the Micromegas-TPC resolution with charge
dispersion. The TPC resolution with the Micromegas readout is compared to our
earlier GEM results and to the resolution expected from electron statistics and
transverse diffusion in a gaseous TPC.Comment: 5 pages, 8 figures, to appar in the Proceedings of the 2005
International Linear Collider Workshop (LCWS05), Stanford, 18-22 March 200
Micromegas TPC studies at high magnetic fields using the charge dispersion signal
The International Linear Collider (ILC) Time Projection Chamber (TPC)
transverse space-point resolution goal is 100 microns for all tracks including
stiff 90 degree tracks with the full 2 meter drift. A Micro Pattern Gas
Detector (MPGD) readout TPC can achieve the target resolution with existing
techniques using 1 mm or narrower pads at the expense of increased detector
cost and complexity. The new MPGD readout technique of charge dispersion can
achieve good resolution without resorting to narrow pads. This has been
demonstrated previously for 2 mm x 6 mm pads with GEMs and Micromegas in cosmic
ray tests and in a KEK beam test in a 1 Tesla magnet. We have recently tested a
Micromegas-TPC using the charge dispersion readout concept in a high field
super-conducting magnet at DESY. The measured Micromegas gain was found to be
constant within 0.5% for magnetic fields up to 5 Tesla. With the strong
suppression of transverse diffusion at high magnetic fields, we measure a flat
50 micron resolution at 5 Tesla over the full 15 cm drift length of our
prototype TPC.Comment: 7 pages, 3 figure
New pixelized Micromegas detector for the COMPASS experiment
New Micromegas (Micro-mesh gaseous detectors) are being developed in view of
the future physics projects planned by the COMPASS collaboration at CERN.
Several major upgrades compared to present detectors are being studied:
detectors standing five times higher luminosity with hadron beams, detection of
beam particles (flux up to a few hundred of kHz/mm^2, 10 times larger than for
the present detectors) with pixelized read-out in the central part, light and
integrated electronics, and improved robustness. Studies were done with the
present detectors moved in the beam, and two first pixelized prototypes are
being tested with muon and hadron beams in real conditions at COMPASS. We
present here this new project and report on two series of tests, with old
detectors moved into the beam and with pixelized prototypes operated in real
data taking condition with both muon and hadron beams.Comment: 11 pages, 5 figures, proceedings to the Micro-Pattern Gaseous
Detectors conference (MPGD2009), 12-15 June 2009, Kolympari, Crete, Greece
Minor details added and language corrections don
Performances of Anode-resistive Micromegas for HL-LHC
Micromegas technology is a promising candidate to replace Atlas forward muon
chambers -tracking and trigger- for future HL-LHC upgrade of the experiment.
The increase on background and pile-up event probability requires detector
performances which are currently under studies in intensive RD activities.
We studied performances of four different resistive Micromegas detectors with
different read-out strip pitches. These chambers were tested using \sim120 GeV
momentum pions, at H6 CERN-SPS beam line in autumn 2010. For a strip pitch 500
micrometers we measure a resolution of \sim90 micrometers and a efficiency of
~98%. The track angle effect on the efficiency was also studied. Our results
show that resistive techniques induce no degradation on the efficiency or
resolution, with respect to the standard Micromegas. In some configuration the
resistive coating is able to reduce the discharge currents at least by a factor
of 100.Micromegas technology is a promising candidate to replace Atlas forward
muon chambers -tracking and trigger- for future HL-LHC upgrade of the
experiment. The increase on background and pile-up event probability requires
detector performances which are currently under studies in intensive RD
activities. We studied performances of four different resistive Micromegas
detectors with different read-out strip pitches. These chambers were tested
using \sim120 GeV momentum pions, at H6 CERN-SPS beam line in autumn 2010. For
a strip pitch 500 micrometers we measure a resolution of \sim90 micrometers and
a efficiency of \sim98%. The track angle effect on the efficiency was also
studied. Our results show that resistive techniques induce no degradation on
the efficiency or resolution, with respect to the standard Micromegas. In some
configuration the resistive coating is able to reduce the discharge currents at
least by a factor of 100.Comment: "Presented at the 2011 Hadron Collider Physics symposium (HCP-2011),
Paris, France, November 14-18 2011, 3 pages, 6 figures.
Micromegas in a Bulk
In this paper we present a novel way to manufacture the bulk Micromegas
detector. A simple process based on the PCB (Printed Circuit Board) technology
is employed to produce the entire sensitive detector. Such fabrication process
could be extended to very large area detectors made by the industry. The low
cost fabrication together with the robustness of the electrode materials will
make it extremely attractive for several applications ranging from particle
physics and astrophysics to medicineComment: 6 pages, 4 figure
Neutron imaging with a Micromegas detector
The micropattern gaseous detector Micromegas has been developed for several
years in Saclay and presents good performance for neutron detection. A
prototype for neutron imaging has been designed and new results obtained in
thermal neutron beams are presented. Based on previous results demonstrating a
good 1D spatial resolution, a tomographic image of a multiwire cable has been
performed using a 1D Micromegas prototype. The number of pillars supporting the
micromesh is too large and leads to local losses of efficiency that distort the
tomographic reconstruction. Nevertheless, this first tomographic image achieved
with this kind of detector is very encouraging. The next worthwhile development
for neutron imaging is to achieve a bi-dimensional detector, which is presented
in the second part of this study. The purpose of measurements was to
investigate various operational parameters to optimize the spatial resolution.
Through these measurements the optimum spatial resolution has been found to be
around 160 microns (standard deviation) using Micromegas operating in double
amplification mode. Several 2D imaging tests have been carried out. Some of
these results have revealed fabrication defects that occurred during the
manufacture of Micromegas and that are limiting the full potential of the
present neutron imaging system.Comment: 6 pages, 10 figures, presented at IEEE 2004 conference in Roma, Ital
New pixelized Micromegas detector with low discharge rate for the COMPASS experiment
New Micromegas (Micro-mesh gaseous detectors) are being developed in view of
the future physics projects planned by the COMPASS collaboration at CERN.
Several major upgrades compared to present detectors are being studied:
detectors standing five times higher luminosity with hadron beams, detection of
beam particles (flux up to a few hundred of kHz/mm^{2}, 10 times larger than
for the present Micromegas detectors) with pixelized read-out in the central
part, light and integrated electronics, and improved robustness. Two solutions
of reduction of discharge impact have been studied, with Micromegas detectors
using resistive layers and using an additional GEM foil. Performance of such
detectors has also been measured. A large size prototypes with nominal active
area and pixelized read-out has been produced and installed at COMPASS in 2010.
In 2011 prototypes featuring an additional GEM foil, as well as an resistive
prototype, are installed at COMPASS and preliminary results from those
detectors presented very good performance. We present here the project and
report on its status, in particular the performance of large size prototypes
with an additional GEM foil.Comment: 11 pages, 5 figures, proceedings to the Micro-Pattern Gaseous
Detectors conference (MPGD2011), 29-31 August 2011, Kobe, Japa
A low background Micromegas detector for the CAST experiment
A low background Micromegas detector has been operating on the CAST
experiment at CERN for the search of solar axions during the first phase of the
experiment (2002-2004). The detector operated efficiently and achieved a very
low level of background rejection ( counts
keVcms) thanks to its good spatial and energy resolution
as well as the low radioactivity materials used in the construction of the
detector. For the second phase of the experiment (2005-2007), the detector will
be upgraded by adding a shielding and including focusing optics. These
improvements should allow for a background rejection better than two orders of
magnitude.Comment: 6 pages, 3 figures To appear on the proceedings of the 9th ICATPP
Conference on AStroparticle, Particle, Space Physics, Detectors and Medical
Physics Application
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