Search

Abstract In counting experiments associated with pulsed sources, a high data collection rate can lead to considerably large counting losses, especially in the case of spallation Time-of-Flight facilities equipped with medium and short flight paths where the research interest is focused on higher neutron energies where counting losses can be quite large due to the higher neutron flux, the more compressed time frame compared to the one on lower energies and the higher cross-section depending on the reaction. Examples of such measurements are the neutron induced fission experiments at the new experimental area EAR-2 at the n_TOF facility at CERN. Although analytical expressions to account for this inefficiency exist in literature, the introduced corrections are not always sufficient to retrieve the true reaction rate, therefore a different approach is mandatory. This work explores the possibility to quantify the counting losses using detector emulation devices and exponential fits in waiting time distributions. The methodology is benchmarked in the test case of the standard 238U(n,f) cross-section with reference to 235U(n,f) for bandwidths up to 1.9 MHz and counting losses that exceed 60%. [ABSTRACT FROM AUTHOR]

Abstract: Detectors based on the micromegas principle have already been used in several atomic, nuclear and particle physics experiments. They have also been proposed as one of the options to upgrade the ATLAS muon spectrometer in the very forward/backward region. To meet this end, it is imperative to study their performance in a mixed (neutron and gamma) radiation field. The general-purpose Monte-Carlo code FLUKA has been employed in the present work in order to study the effect of 5.5MeV neutrons impinging on a prototype micromegas detector developed for sLHC. The response of the detector to the photons originating from the inevitable neutron inelastic scattering on the surrounding materials of the experimental facility was also studied, through comparisons with experimental data. [Copyright &y& Elsevier]

Abstract: The response function of a commercial 2in.×2in. BC501A neutron detector has been studied through the general-purpose Monte-Carlo (MC) simulation toolkit GEANT4. For neutron energies below 8MeV, where the dominant detection mechanism originates from the knockout protons, the results of MC calculations reproduce remarkably well the experimental pulse-height spectra. This is not the case, however, at higher neutron energies, where the contribution of heavier charged particles to the detection mechanism becomes significant. The calculated detector efficiency is also compared at three indicative energies to the experimental one via the neutron activation technique. [Copyright &y& Elsevier]

The 232Th(n,2n)231Th reaction cross-section was measured relative to the 56Fe(n,p)56Mn and 27Al(n,α)24Na reaction cross-sections with the activation method for neutron energies up to 11 MeV. Neutrons were produced by the 2H(d,n) reaction in the 5.5 MV Tandem accelerator of the NCSR “Demokritos”. The characteristic γ lines of the product nuclei 231Th (25.646 keV) and 56Mn (846.771 keV) or 24Na (1368 keV) were measured with an 80 mm2 Si(Li) and a 20% reverse-electrode coaxial germanium detector, respectively. The results indicate that our values are in agreement with the JEF2 and BROND2 database values up to 9 MeV and slightly higher than those from all the libraries for higher energies. [Copyright &y& Elsevier]

Within the present work a peak analysis and unfolding method for low energy γ -ray spectroscopy is presented. This method can be used to facilitate the determination of the peak integral of a photopeak, when Ge X-ray escape peaks contaminate the latter and in parallel the source activity and the emission rate of the recorded photons which produce the escape peaks are unknown. It is based on extensive Monte Carlo simulations of the spectra by taking the full advantage of power and accuracy provided by the GEANT4 simulation toolkit. [ABSTRACT FROM AUTHOR]