3,804 research outputs found
On the limited amplitude resolution of multipixel Geiger-mode APDs
The limited number of active pixels in a Geiger-mode Avalanche Photodiode
(G-APD) results not only in a non-linearity but also in an additional
fluctuation of its response. Both these effects are taken into account to
calculate the amplitude resolution of an ideal G-APD, which is shown to be
finite. As one of the consequences, the energy resolution of a scintillation
detector based on a G-APD is shown to be limited to some minimum value defined
by the number of pixels in the G-APD.Comment: 5 pages, 3 figure
Radiation Damage Studies of Silicon Photomultipliers
We report on the measurement of the radiation hardness of silicon
photomultipliers (SiPMs) manufactured by
Fondazione Bruno Kessler in Italy (1 mm and 6.2 mm), Center of
Perspective Technology and Apparatus in Russia (1 mm and 4.4 mm), and
Hamamatsu Corporation in Japan (1 mm). The SiPMs were irradiated using a
beam of 212 MeV protons at Massachusetts General Hospital, receiving fluences
of up to protons per cm with the SiPMs at operating
voltage. Leakage currents were read continuously during the irradiation. The
delivery of the protons was paused periodically to record scope traces in
response to calibrated light pulses to monitor the gains, photon detection
efficiencies, and dark counts of the SiPMs. The leakage current and dark noise
are found to increase with fluence. Te leakage current is found to be
proportional to the mean square deviation of the noise distribution, indicating
the dark counts are due to increased random individual pixel activation, while
SiPMs remain fully functional as photon detectors. The SiPMs are found to
anneal at room temperature with a reduction in the leakage current by a factor
of 2 in about 100 days.Comment: 35 pages, 25 figure
Performance Studies of Prototype II for the CASTOR forward Calorimeter at the CMS Experiment
We present results of the performance of the second prototype of the CASTOR
quartz-tungsten sampling calorimeter, to be installed in the very forward
region of the CMS experiment at the LHC. The energy linearity and resolution,
as well as the spatial resolution of the prototype to electromagnetic and
hadronic showers are studied with E=20-200 GeV electrons, E=20-350 GeV pions,
and E=50,150 GeV muons from beam tests carried out at CERN/SPS in 2004. The
responses of the calorimeter using two different types of photodetectors
(avalanche photodiodes APDs, and photomultiplier tubes PMTs) are compared.Comment: 16 pages, 22 figs., submitted to EPJ-
Proposal for SPS beam time for the baby MIND and TASD neutrino detector prototypes
The design, construction and testing of neutrino detector prototypes at CERN
are ongoing activities. This document reports on the design of solid state baby
MIND and TASD detector prototypes and outlines requirements for a test beam at
CERN to test these, tentatively planned on the H8 beamline in the North Area,
which is equipped with a large aperture magnet. The current proposal is
submitted to be considered in light of the recently approved projects related
to neutrino activities with the SPS in the North Area in the medium term
2015-2020
First performance studies of a prototype for the CASTOR forward calorimeter at the CMS experiment
We present results on the performance of the first prototype of the CASTOR quartz-tungsten sampling calorimeter, to be installed in the very forward region of the CMS experiment at the LHC. This study includes GEANT Monte Carlo simulations of the Cherenkov light transmission efficiency of different types of air-core light guides, as well as analysis of the calorimeter linearity and resolution as a function of energy and impact-point, obtained with 20-200 GeV electron beams from CERN/SPS tests in 2003. Several configurations of the calorimeter have been tested and compared, including different combinations of (i) structures for the active material of the calorimeter (quartz plates and fibres), (ii) various light-guide reflecting materials (glass and foil reflectors) and (iii) photodetector devices (photomultipliers and avalanche photodiodes)
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
Activation of spinal locomotor circuits in the decerebrated cat by spinal epidural and/or intraspinal electrical stimulation
The present study was designed to further compare the stepping-like movements generated via epidural (ES) and/or intraspinal (IS) stimulation. We examined the ability to generate stepping-like movements in response to ES and/or IS of spinal lumbar segments L1-L7 in decerebrate cats. ES (5-10 Hz) of the dorsal surface of the spinal cord at L3-L7 induced hindlimb stepping-like movements on a moving treadmill belt, but with no rhythmic activity in the forelimbs. IS (60 Hz) of the dorsolateral funiculus at L1-L3 (depth of 0.5-1.0 mm from the dorsal surface of the spinal cord) induced quadrupedal stepping-like movements. Forelimb movements appeared first, followed by stepping-like movements in the hindlimbs. ES and IS simultaneously enhanced the rhythmic performance of the hindlimbs more robustly than ES or IS alone. The differences in the stimulation parameters, site of stimulation, and motor outputs observed during ES vs. IS suggest that different neural mechanisms were activated to induce stepping-like movements. The effects of ES may be mediated more via dorsal structures in the lumbosacral region of the spinal cord, whereas the effects of IS may be mediated via more ventral propriospinal networks and/or brainstem locomotor areas. Furthermore, the more effective facilitation of the motor output during simultaneous ES and IS may reflect some convergence of pathways on the same interneuronal populations involved in the regulation of locomotion
Conserving surgery for iatrogenic defects of the maxillary sinus
A rationale for the choice of the method of primary plastics perforation of the maxillary sinus defects of different etiology. The study Included 292 patients of both sexes aged 19-72 years who in the course of surgical intervention been opened maxillary sinus: at 80 - in the formation of access for the removal of cysts (30 in a conventional manner, endoscopic (FESS) - 30, osteoplastic by ultrasound NV Mishenkin • 30); In 212 - during the removal of the tooth (37 patients without restoring bone wall, 175 with the restoration of the authors' methodology with platelet plasma (patent 2,380,052). When using the osteoplastic ultrasonic method for accessing the maxillary sinus catarrhal, purulent and subatrophic changes in the nasal mucosa observed 4.5 times less than the traditional access and 3.8 times less than in FESS. results perforated plastic defect using the platelet plasma by the method of Al and AA Musienko 12 times better than traditional treatment group.Цель работы - обоснование выбора метода первичной пластики перфорационных дефектов верхнечелюстной пазухи различной этиологии. Под наблюдением находились 292 пациента обоего пола в возрасте 19-72 лет, у которых в процессе хирургического вмешательства вскрывалась верхнечелюстная пазуха: у 80-ти - при формировании доступа для удаления кисты (традиционным способом 30, эндоскопическим (ФЭСХ) - 30, остеопластическим ультразвуковым по Н.В. Мишенькину - 30); у 212 - во время удаления зуба (37 пациентам без восстановления костной стенки, 175 с восстановлением по авторской методике с тромбоцитарной плазмой (патент 2380052). При использовании остеопластического ультразвукового способа для доступа в верхнечелюстную пазуху катаральные, гнойные и субатрофические изменения слизистой оболочки полости носа отмечались в 4,5 раза реже, чем при традиционном доступе и в 3,8 раза реже, чем при ФЭСХ. Результаты пластики перфоративного дефекта с использованием тромбоцитарной плазмы по методике А.И. И А А Мусиенко в 12 раз лучше, чем в группе традиционного лечения
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