5,480 research outputs found
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
Scintillator detectors with long WLS fibers and multi-pixel photodiodes
We have studied the possibility of using Geiger mode multi-pixel photodiodes
to read out long scintillator bars with a single wavelength-shifting fiber
embedded along the bar. This detector configuration can be used in large volume
detectors in future long baseline neutrino oscillation experiments. Prototype
bars of 0.7 cm thickness and different widths have been produced and tested
using two types of multi-pixel photodiodes: MRS APD (CPTA, Moscow) and MPPC
(Hamamatsu). A minimum light yield of 7.2 p.e./MeV was obtained for a 4 cm wide
bar
Rearrangement of the vortex lattice due to instabilities of vortex flow
With increasing applied current we show that the moving vortex lattice
changes its structure from a triangular one to a set of parallel vortex rows in
a pinning free superconductor. This effect originates from the change of the
shape of the vortex core due to non-equilibrium effects (similar to the
mechanism of vortex motion instability in the Larkin-Ovchinnikov theory). The
moving vortex creates a deficit of quasiparticles in front of its motion and an
excess of quasiparticles behind the core of the moving vortex. This results in
the appearance of a wake (region with suppressed order parameter) behind the
vortex which attracts other vortices resulting in an effective
direction-dependent interaction between vortices. When the vortex velocity
reaches the critical value quasi-phase slip lines (lines with fast vortex
motion) appear which may coexist with slowly moving vortices between such
lines. Our results are found within the framework of the time-dependent
Ginzburg-Landau equations and are strictly valid when the coherence length
is larger or comparable with the decay length of the
non-equilibrium quasiparticle distribution function. We qualitatively explain
experiments on the instability of vortex flow at low magnetic fields when the
distance between vortices . We speculate that a
similar instability of the vortex lattice should exist for even when
.Comment: 10 pages, 11 figure
Hadron calorimeter with MAPD readout in the NA61/SHINE experiment
The modular hadron calorimeter with micro-pixel avalanche photodiodes readout
for the NA61/SHINE experiment at the CERN SPS is presented. The calorimeter
consists of 44 independent modules with lead-scintillator sandwich structure.
The light from the scintillator tiles is captured by and transported with
WLS-fibers embedded in scintillator grooves. The construction provides a
longitudinal segmentation of the module in 10 sections with independent MAPD
readout. MAPDs with pixel density of /mm ensure good linearity of
calorimeter response in a wide dynamical range. The performance of the
calorimeter prototype in a beam test is reported
Avalanche photodiodes for the CMS electromagnetic calorimeter
Avalanche photodiodes(APD's) will be used as photodetectors in the CMS barrel electromagnetic crystal calorimeter for high precision energy measurements in a hostile radiation environment. Significant progress has been made in the characteristics of these devices being expressly developed for CMS. Parameters of the final structure APD's together with demonstrations of radiation hardness and plans for quality assurance/control during the production phase are presented
Scintillator counters with multi-pixel avalanche photodiode readout for the ND280 detector of the T2K experiment
The Tokai-to-Kamioka (T2K) experiment is a second generation long baseline neutrino oscillation experiment which aims at a sensitive search for νe appearance. The main design features of the T2K near neutrino detectors located at 280 m from the target are presented, and the scintillator counters are described. The counters are readout via WLS fibers embedded into S-shaped grooves in the scintillator from both ends by multi-pixel avalanche photodiodes operating in a limited Geiger mode. Operating principles and results of tests of photosensors with a sensitive area of 1 mm2 are presented. A time resolution of 1.75 ns, a spatial resolution of 9.9 - 12.4 cm, and a detection efficiency for minimum ionizing particles of more than 99% were obtained for scintillator detectors in a beam test. © 2007 Elsevier B.V. All rights reserved
Scintillator counters with WLS fiber/MPPC readout for the side muon range detector (SMRD)of the T2K experiment
The T2K neutrino experiment at J-PARC uses a set of near detectors to measure
the properties of an unoscillated neutrino beam and neutrino interaction
cross-sections. One of the sub-detectors of the near-detector complex, the side
muon range detector (SMRD), is described in the paper. The detector is designed
to help measure the neutrino energy spectrum, to identify background and to
calibrate the other detectors. The active elements of the SMRD consist of 0.7
cm thick extruded scintillator slabs inserted into air gaps of the UA1 magnet
yokes. The readout of each scintillator slab is provided through a single WLS
fiber embedded into a serpentine shaped groove. Two Hamamatsu multi-pixel
avalanche photodiodes (MPPC's) are coupled to both ends of the WLS fiber. This
design allows us to achieve a high MIP detection efficiency of greater than
99%. A light yield of 25-50 p.e./MIP, a time resolution of about 1 ns and a
spatial resolution along the slab better than 10 cm were obtained for the SMRD
counters.Comment: 7 pages, 4 figures; talk at TIPP09, March 12-17, Tsukuba, Japan; to
be published in the conference proceeding
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