371 research outputs found
Long-term stability test of a triple GEM detector
The main aim of the study is to perform the long-term stability test of gain
of the single mask triple GEM detector. A simple method is used for this long-
term stability test using a radioactive X-ray source with high activity. The
test is continued till accumulation of charge per unit area > 12.0 mC/mm2. The
details of the chamber fabrication, the test set-up, the method of measurement
and the test results are presented in this paper.Comment: 8 pages, 5 figure
Efficient transport of femtosecond laser-generated fast electrons in a millimeter thick graphite
We demonstrate efficient transport of fast electrons generated by ∼1018 W/cm2, 30 fs, 800 nm laser pulses through a millimeter thick polycrystalline graphite. Measurements of hot electron spectra at the front side of the graphite target show enhancement in terms of the electron flux and temperature, while the spectra at the rear confirm the ability of the graphite to transport large electron currents over a macroscopic distance of a millimeter. In addition, protons of keV energies are observed at the rear side of such a macroscopically thick target and attributed to the target-normal-sheath-acceleration mechanism
Controlling femtosecond-laser-driven shock-waves in hot, dense plasma
Ultrafast pump-probe reflectometry and Doppler spectrometry of a supercritical density plasma layer excited by 1017-1018 W/cm2 intensity, 30 fs, and 800 nm laser pulses reveal the interplay of laser intensity contrast and inward shock wave strength. The inward shock wave velocity increases with an increase in laser intensity contrast. This trend is supported by simulations as well as by a separate independent experiment employing an external prepulse to control the inward motion of the shock wave. This kind of cost-effective control of shock wave strength using femtosecond pulses could open up new applications in medicine, science, and engineering
Neutrino oscillations with disentanglement of a neutrino from its partners
We bring attention to the fact that in order to understand existing data on
neutrino oscillations, and to design future experiments, it is imperative to
appreciate the role of quantum entanglement. Once this is accounted for, the
resulting energy-momentum conserving phenomenology requires a single new
parameter related to disentanglement of a neutrino from its partners. This
parameter may not be CP symmetric. We illustrate the new ideas, with
potentially measurable effects, in the context of a novel experiment recently
proposed by Gavrin, Gorbachev, Veretenkin, and Cleveland. The strongest impact
of our ideas is on the resolution of various anomalies in neutrino oscillations
and on neutrino propagation in astrophysical environments.Comment: 6 page
Dirac field in topologically massive gravity
We consider a Dirac field coupled minimally to the Mielke-Baekler model of
gravity and investigate cosmological solutions in three dimensions. We arrive
at a family of solutions which exists even in the limit of vanishing
cosmological constant.Comment: 12 pages. Title changed. Conclusion extended. Appendix added. To
appear in Gen. Rel. Gra
Attenuation of electromagnetic radiation in Nuclear Track Detectors
A systematic study of the attenuation of electromagnetic radiation in Nuclear
Track Detectors (NTDs) is carried out. The attenuation of gamma-ray, X-ray, UV,
visible, and infrared radiation in NTDs are investigated using NaI(Tl)
detector, Gas Electron Multiplier (GEM) detector, UV-Vis spectrophotometer, and
FTIR spectrophotometer respectively. The values of some important parameters
(e.g., optical depth, attenuation coefficient, etc.) of three commercially
available NTDs (PET, Makrofol r and CR-39 r ), at the relevant region of the
electromagnetic spectrum, is determined. The details of the experimental
techniques and the results are also presented in this paper.Comment: 10 page
Returns to Foreign Language Skills in a Developing Country: The Case of Turkey
Foreign language skills represent a form of human capital that can be rewarded in the labor market. Drawing on data from the Adult Education Survey of 2007, this is the first study estimating returns to foreign language skills in Turkey. We contribute to the literature on the economic value of language knowledge, with a special focus on a country characterized by fast economic and social development. Although English is the most widely spoken foreign language in Turkey, we initially consider the economic value of different foreign languages among the employed males aged 25 to 65. We find positive and significant returns to proficiency in English and Russian, which increase with the level of competence. Knowledge of French and German also appears to be positively rewarded in the Turkish labor market, although their economic value seems mostly linked to an increased likelihood to hold specific occupations rather than increased earnings within occupations. Focusing on English, we also explore the heterogeneity in returns to different levels of proficiency by frequency of English use at work, birth-cohort, education, occupation and rural/urban location. The results are also robust to the endogenous specification of English language skills
Gravitational field around a screwed superconducting cosmic string in scalar-tensor theories
We obtain the solution that corresponds to a screwed superconducting cosmic
string (SSCS) in the framework of a general scalar-tensor theory including
torsion. We investigate the metric of the SSCS in Brans-Dicke theory with
torsion and analyze the case without torsion. We show that in the case with
torsion the space-time background presents other properties different from that
in which torsion is absent. When the spin vanish, this torsion is a
-gradient and then it propagates outside of the string. We investigate
the effect of torsion on the gravitational force and on the geodesics of a
test-particle moving around the SSCS. The accretion of matter by wakes
formation when a SSCS moves with speed is investigated. We compare our
results with those obtained for cosmic strings in the framework of
scalar-tensor theory.Comment: 22 pages, LaTeX, presented at the "XXII - Encontro Nacional de Fisica
de Particulas e Campos", Sao Lourenco, MG, Brazi
- …