4,249 research outputs found
The MRPC-based ALICE Time-Of-Flight detector: status and performance
The large Time-Of-Flight (TOF) array is one of the main detectors devoted to
charged hadron identification in the mid-rapidity region of the ALICE
experiment at the LHC. It allows separation among pions, kaons and protons up
to a few GeV/c, covering the full azimuthal angle and -0.9 < eta < 0.9. The TOF
exploits the innovative MRPC technology capable of an intrinsic time resolution
better than 50 ps with an efficiency close to 100% and a large operational
plateau; the full array consists of 1593 MRPCs covering a cylindrical surface
of 141 m2. The TOF detector has been efficiently taking data since the first pp
collisions recorded in ALICE in December 2009. In this report, the status of
the TOF detector and the performance achieved for both pp and Pb--Pb collisions
are described.Comment: 4 pages, 6 figure
Long-term operation of a multi-channel cosmic muon system based on scintillation counters with MRS APD light readout
A Cosmic Ray Test Facility (CRTF) is the first large-scale implementation of
a scintillation triggering system based on a new scintillation technique known
as START. In START, the scintillation light is collected and transported by WLS
optical fibers, while light detection is performed by pairs of avalanche
photodiodes with the Metal-Resistor-Semiconductor structure operated in the
Geiger mode (MRS APD). START delivers 100% efficiency of cosmic muon detection,
while its intrinsic noise level is less than 10^{-2} Hz. CRTF, consisting of
160 START channels, has been continuously operated by the ALICE TOF
collaboration for more than 25 000 hours, and has demonstrated a high level of
stability. Fewer than 10% of MRS APDs had to be replaced during this period.Comment: Proceedings of NDIP-2008. 8 pages, 8 figures, 6 reference
Scintillation counter with MRS APD light readout
START, a high-efficiency and low-noise scintillation detector for ionizing
particles, was developed for the purpose of creating a high-granular system for
triggering cosmic muons. Scintillation light in START is detected by MRS APDs
(Avalanche Photo-Diodes with Metal-Resistance-Semiconductor structure),
operated in the Geiger mode, which have 1 mm^2 sensitive areas. START is
assembled from a 15 x 15 x 1 cm^3 scintillating plastic plate, two MRS APDs and
two pieces of wavelength-shifting optical fiber stacked in circular coils
inside the plastic. The front-end electronic card is mounted directly on the
detector. Tests with START have confirmed its operational consistency, over 99%
efficiency of MIP registration and good homogeneity. START demonstrates a low
intrinsic noise of about 10^{-2} Hz. If these detectors are to be
mass-produced, the cost of a mosaic array of STARTs is estimated at a moderate
level of 2-3 kUSD/m^2.Comment: 6 pages, 5 figure
Design, development and performance study of six-gap glass MRPC detectors
The Multigap Resistive Plate Chambers (MRPCs) are gas ionization detectors
with multiple gas sub-gaps made of resistive electrodes. The high voltage (HV)
is applied on the outer surfaces of outermost resistive plates only, while the
interior plates are left electrically floating. The presence of multiple narrow
sub--gaps with high electric field results in faster signals on the outer
electrodes, thus improving the detector's time resolution. Due to their
excellent performance and relatively low cost, the MRPC detector has found
potential application in Time-of-Flight (TOF) systems. Here we present the
design, fabrication, optimization of the operating parameters such as the HV,
the gas mixture composition, and, performance of six--gap glass MRPC detectors
of area 27cm 27 cm, which are developed in order to find application
as trigger detectors, in TOF measurement etc. The design has been optimized
with unique spacers and blockers to ensure a proper gas flow through the narrow
sub-gaps, which are 250 m wide. The gas mixture consisting of R134A,
Isobutane and SF, and the fraction of each constituting gases has been
optimized after studying the MRPC performance for a set of different
concentrations. The counting efficiency of the MRPC is about 95% at kV.
At the same operating voltage, the time resolution, after correcting for the
walk effect, is found to be about ps.Comment: Revised version with 15 pages, 14 figures, 2 tables. Accepted for
publication in the European Physical Journal
RPC with low-resistive phosphate glass electrodes as a candidate for the CBM TOF
Usage of electrodes made of glass with low bulk resistivity seems to be a
promising way to adapt the Resistive Plate Chambers (RPC) to the high-rate
environment of the upcoming CBM experiment. A pilot four-gap RPC sample with
electrodes made of phosphate glass, which has bulk resistivity in the order of
10^10 Ohm cm, has been studied with MIP beam for TOF applications. The tests
have yielded satisfactory results: the efficiency remains above 95% and the
time resolution stays within 120 ps up to the particle rate of 18 kHz/cm2. The
increase in rate from 2.25 to 18 kHz/cm2 leads to an increase of estimated
"tails" fraction in the time spectrum from 1.5% to 4%.Comment: 8 pages, 6 figures, submitted to Elsevier Scienc
Kaon pair production in proton-nucleus collisions at 2.83 GeV kinetic energy
The production of non-phi K+K- pairs by protons of 2.83 GeV kinetic energy on
C, Cu, Ag, and Au targets has been investigated using the COSY-ANKE magnetic
spectrometer. The K- momentum dependence of the differential cross section has
been measured at small angles over the 0.2--0.9 GeV/c range. The comparison of
the data with detailed model calculations indicates an attractive K- -nucleus
potential of about -60 MeV at normal nuclear matter density at a mean momentum
of 0.5 GeV/c. However, this approach has difficulty in reproducing the
smallness of the observed cross sections at low K- momenta.Comment: 7 pages, 5 figures, 1 tabl
START as the detector of choice for large-scale muon triggering systems
Further progress in building high-granular large-scale systems based on Scintillation Tiles with MRS APD light readout (START) became possible thanks to the creation of an improved version of MRS APD. The cost of the system may now be significantly reduced by using inexpensive extruded scintillator. More than 160 START samples were assembled based on this design modification and proved to possess 100% MIP detection efficiency and the intrinsic noise rate of less than 0.08 Hz. Long-term stability of START characteristics was confirmed after 3.5 months of operation
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