10,668 research outputs found
Performances of silicone coated high resistive bakelite RPC
Performances of several single gap (gas gap 2 mm) prototype Resistive Plate
Chambers (RPC) made of high resistive ({\rho} \sim 1010 - 1012 {\Omega} cm)
bakelite, commercially available in India have been studied in recent times. To
make the inner electrode surfaces smooth, a thin coating of silicone has been
applied. An efficiency > 90% and time resolution \sim 2 ns (FWHM) have been
obtained for both the streamer and the avalanche mode. The induced charge
distributions of those silicone coated RPC are studied and the results are
presented. A numerical study on the effect of surface roughness of the
resistive electrodes on the electric field of the device has been carried out
using Garfield-neBEM code. A few results for a simplified model representing
surface roughness, measured using a surface profilometer for the bakelite
surfaces, have also been presented
The Complex Time WKB Approximation And Particle Production
The complex time WKB (CWKB) approximation has been an effective technique to
understand particle production in curved as well as in flat spacetime. Earlier
we obtained the standard results on particle production in time dependent gauge
in various curved spacetime. In the present work we generalize the technique of
CWKB to the equivalent problems in space dependent gauge. Using CWKB, we first
obtain the gauge invariant result for particle production in Minkowski
spacetime in strong electric field. We then carry out particle production in
de-Sitter spacetime in space dependent gauge and obtain the same result that we
obtained earlier in time dependent gauge. The results obtained for de-Sitter
spacetime has a obvious extension to particle production in black hole
spacetime. It is found that the origin of Planckian spectrum is due to repeated
reflections between the turning points. As mentioned earlier, it is now
explicitly shown that particle production is accompanied by rotation of
currents.Comment: 12 pages, Revte
Detector calibration of the Indian cosmic ray experiment (IONS) in Space-Shuttle Spacelab-13
In the Indian cosmic ray experiment (IONS) in Spacelab-3 the intention is to study nuclei up to iron in low energy cosmic rays, using CR-39 (DOP) detectors. CR-39 (DOP) was exposed to He4, C12, O16, Ne20, Si28, Ar40, Cr52 and Fe56 accelerated beams from various accelerator facilities available around the world. Different beam energies and exposure angles were used. From these exposures, the charge resolution and energy resolution for the detector in the region of interest were studied. The effect of pre-annealing and depth on the response of our detector was studied. For isotopic resolution, exposed the detector samples were exposed to Ne2O and Ne22 accelerated beams. Samples of CR-39 (DOP) exposed to different accelerated heavy ions were kept in the detector module to take into account the effect of ambient conditions on detector response during the flight
On bouncing solutions in non-local gravity
A non-local modified gravity model with an analytic function of the
d'Alembert operator is considered. This model has been recently proposed as a
possible way of resolving the singularities problem in cosmology. We present an
exact bouncing solution, which is simpler compared to the already known one in
this model in the sense it does not require an additional matter to satisfy all
the gravitational equations.Comment: 5 pages; v2: matching the jounral versio
Relative abundances of sub-iron to iron nuclei in low energy (50-250 MeV/N) cosmic rays as observed in the Skylab experiment
A Lexan polycarbonate detector exposed on the exterior of Skylab-3 for 73 days during a solar quiet period was used to study the relative abundances of calcium to nickel ions in low energy cosmic rays of 50 to 250 MeV/N. The method of charge identification is based on the measurement of conelength (L) and residual range (R) of these particles in various Lexan sheets. Since more than one cone (sometimes as many as five) is observed and is measured, the charge accuracy becomes precise and accurate. The ratio of (calcium to manganese) to (iron and cobalt) obtained at three energy intervals of 50 to 80, 80 to 150, 150 to 250 and 50 to 250 MeV/N are 7.6 plus or minus 3.8, 2.7 plus or minus 0.8, 1.4 plus or minus 0.6 and 3.3 plus or minus 0.7 respectively. These data thus indicate a large increase of this ratio with decreasing energy. The origin of this strong energy dependence is not understood at present
The CWKB Method of Particle Production in Periodic Potential
In this work we study the particle production in time dependent periodic
potential using the method of complex time WKB (CWKB) approximation. In the
inflationary cosmology at the end of inflationary stage, the potential becomes
time dependent as well as periodic. Reheating occurs due to particle production
by the oscillating inflaton field. Using CWKB we obtain almost identical
results on catastrophic particle production as obtained by others.Comment: 17 pages, latex, 2 figure
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