Tabletop Fusion Revisited
I do not think that it is possible for R. P. Taleyarkhan et al. (“Evidence for nuclear emissions during acoustic cavitation,” Research Articles, 8 March, p. [1868][1]) to have observed 2.5-MeV neutrons for the simple reason that the pulse-height threshold used in their experiment is greater than
Response function of NE213 scintillator for 0.5-6 MeV neutrons measured by an improved pulse shape discrimination
Abstract Using the pulse shape discrimination method combined with the time of flight technique, we have obtained the response function of a 2″ diameter × 2″ thick NE213 scintillator by measuring directly the proton recoil energy spectrum of 0.5–6 MeV prompt neutrons from a 252 Cf source. Three parameters, time of flight (TOF), pulse shape discrimination (PSD) and recoil energy (RE), were recorded in an event-by-event mode with a TOF gate. We attempted to improve the determination of maximum proton recoil energies equal to incident neutron energies by employing two analysis methods. First, we attempted to separate better neutrons from coexisting gamma rays in the PSD spectrum by projecting neutron channels of the PSD spectrum onto both TOF and RE spectra in a cubic matrix constructed by the three-parameter data. The resulting two-dimensional matrix composed of TOF and RE channels was free from gamma rays and corresponding Compton-recoiled electrons, and then projected with neutron energy bins of 0.05 MeV wide determined by TOF. Finally, to determine the maximum proton recoil energies from each RE spectrum with a realistic function, accounting for the nonlinear response of the NE213 scintillator due to the quenching effect, we performed a least-squares fit to the RE spectrum using the four-parameter function. The response function obtained in the present work agrees well with previous experimental results obtained by Gul et al. (Nucl. Instr. and Meth. A 278 (1989) 470) and a Monte Carlo study by Cecil et al. (Nucl. Instr. and Meth. 161 (1979) 439).
A study of neutron detection efficiency of an organic scintillation detector through simulation of detection processes
Abstract Neutron detection efficiency of an organic scintillation detector has been studied through Rawal Monte Carlo programm coded in FORTRAN IV for energies of 0–15 MeV. The contribution from multiple scattering, carbon break-up and light pile-up have been investigated. The effect of resonances in the total cross-section of carbon on neutron detection efficiency as a function of neutron energy dispersion has also been studied. The comparison of calculated efficiency with reported measurements indicates that evaluated ENDF/B-IV alpha emission cross-sections below 15 MeV are higher and the corresponding evaluation reported by Lachkar et al. leads to better agreement.