Search

The calibration of high-purity germanium gamma-ray cylindrical detectors using bar (parallelepiped) sources is carried out analytically using the probability correction approach. Improved expressions for the source self-attenuation coefficient have been included in the present algorithm based on the accurate calculation of all possible path lengths covered by the gamma ray inside the bulky source. Moreover, the full-energy peak attenuation coefficient ftp is included in the present algorithm. The sources were positioned at long distances from the detector window so that the coincidence summing effects could be neglected. Remarkable agreement between the measured efficiency values and the corrected efficiency values calculated by the present technique was observed. The percentage relative differences for the results calculated in this way from experimental values are at least 25% smaller than those observed and reported by the direct mathematical method in previous work. [ABSTRACT FROM AUTHOR]

In this work, the scintillation properties of Cs3LaCl6 and Cs3LaBr6 single crystals doped with various Ce concentrations (0.5 at.%–40 at.%) were studied. In the decay time profiles, both the fast (\sim 50 ns) and slow (\sim 500 ns) components decrease with increasing Ce concentration. The fast decay component dominates with high Ce concentration. Cs3LaCl6:Ce has a light yield of \sim 20\ 000 photons/MeV for 20 at.% Ce, while Cs3LaBr6:Ce has a light yield of 35 000 photons/MeV for 10% Ce. Energy resolution was improved from 20 at.% to 8 at.% with higher Ce concentration. Cs3LaCl6:Ce and Cs3LaBr6:Ce are 30 and 8 times less hygroscopic than LaBr3:Ce. [ABSTRACT FROM PUBLISHER]

We examine the effects of time dilation on the temporal profiles of gamma-ray burst (GRB) pulses. By using prescriptions for the shape and evolution of prompt gamma-ray spectra, we can generate a simulated population of single-pulsed GRBs at a variety of redshifts and observe how their light curves would appear to a gamma-ray detector here on Earth.We find that the observer frame duration of individual pulses does not increase with redshift as 1 + z, which one would expect from cosmological expansion. This time dilation is masked by an opposite and often stronger effect: with increasing redshift and decreasing signal-to-noise ratio only the brightest portion of the light curve can be detected. The results of our simulation are consistent with the fact that the simple time dilation of GRB light curves has not materialized in either the Swift or Fermi detected GRBs with known redshift.We show that the measured durations and associated Eiso estimates for GRBs detected near the instrument's detection threshold should be considered lower limits to the true values. Furthermore, we conclude that attempts at distinguishing between long and short GRBs, at even moderate redshifts, cannot be done based on a burst's temporal properties alone. [ABSTRACT FROM AUTHOR]