In this article, we report the absolute production cross-section of 6.13, 6.92 and 7.12 MeV γ-rays from the 16O(p,p'γ)16O reaction for incident proton energy range of 8-16 MeV. Angular distributions of the three γ-rays have been measured for seven angles at 9 MeV proton energy. A detailed phenomenological optical model potential (OMP) was set up to analyse the cross-section data. The OMP parameters were optimised using elastic, polarization and total reaction data available in the literature for protons and neutrons. Low-lying states of 16O were coupled, the optical potential was deformed using deformation parameters, and several resonances were included in the calculations to account for the nuclear structure effects. The potentials so generated have been used to calculate the differential and total cross sections for both 16O(p,p')16O and 16O(p,p'γ)16O reactions. Our calculated cross-sections are in fairly good agreement with our measured data for 6.13, 6.92 and 7.12 MeV γ-rays. However, there still exist discrepancies in reproduction of the finer details of the cross sections. The comparisons of the calculations with the data bring forth the rather complex roles of channel couplings, resonances in the p+16O system and target deformation in the variation of the cross sections with projectile energy. The increased contribution of nuclear structure effects in light mass nuclei, leads to an apparent loss of predictive power of the theoretical calculation, as we approach the low-energy region of less than 10 MeV projectile energy.

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This communication reports the measurement of direct response for fast and thermal neutrons of a newly marketed scintillation crystal LaBr2.85Cl0.15:Ce, along with the widely used LaBr3:Ce and NaI:Tl crystals. It continues our investigation on the possible utility of LaBr2.85Cl0.15:Ce crystal for the detection of high-energy γ-rays and neutrons. This is the first report of the neutron response of the LaBr2.85Cl0.15:Ce crystal. The neutron response was measured for the three detectors using a calibrated Am-Be source, which emits both neutrons and γ-rays. To eliminate the events due to the interaction of the 4.4 MeV γ-ray emitted from Am-Be, the γ-ray response of all three crystals was simulated using the Monte Carlo simulation toolkit GEANT4. Events due to 2.22 MeV γ-ray produced by the capture of thermal neutrons in the paraffin moderator were also eliminated with the aid of simulations. In addition, the response due to fast neutrons was also simulated using GEANT4 and compared with the measured spectrum. This is the first report of the simulation of fast neutron response of LaBr2.85Cl0.15:Ce using GEANT4. The fast neutron detection efficiency of the three detectors has been obtained from the measured spectra.

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This communication reports about complete characterisation of a small volume 1"x1" cylindrical LaBr2.85Cl0.15:Ce crystal supplied by Scionix Inc. for γ-rays up to 4.4 MeV. The various properties of the crystal studied, are, linearity of response for γ-rays, energy resolution up to 4.4 MeV, timing resolutions, quantification of internal activity, and full energy detection efficiencies for γ-rays from 276 to 4439 keV. Monte Carlo simulation toolkit GEANT4 was used to carry out realistic simulations of the detector’s response for γ-rays. Experimental γ-ray energy spectrum was reproduced in the simulations to estimate the full energy detection efficiency for γ-rays and compared with the measured value. We have obtained energy resolution of ~3.8% at 662 keV using 2" ET-9266B PMT biased at −800 V with the energy signal drawn from the 8th dynode. Timing resolutions of 422 and 364 ps were obtained using 2" ET-9807B PMT for 22Na and 60Co, respectively. To the best of our knowledge, this is the first report on the performance of the newly manufactured and marketed LBC crystal. We do not find any significant difference in the performance of LBC from that of a standard Lanthanum Bromide (Ce activated) crystal of similar volume.

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CeBr3 is emerging as one of the best scintillators having properties almost similar to cerium-doped lanthanum halide scintillators. We have measured, for the first time, the intrinsic energy resolution of Compton electrons in a cylindrical 1"×1" CeBr3 detector using the sources, namely, 137Cs, 22Na, and 60Co employing Compton coincidence technique. We have used the PIXIE-4 data acquisition system that makes the measurement setup quite compact. The measurements of intrinsic energy resolution of Compton electrons were made in the energy range of 0.1-1 MeV. The measurements of intrinsic energy resolution of gamma rays were also made, for the comparison. The preliminary results have clearly suggested that δ-ray component is a major contributor to the intrinsic resolution of CeBr3.

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