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).
Response-function measurement of an NE213 scintillator using the 2H(d, n)3He reaction
The response function of a 12.5 cm diameter NE213 scintillator detector has been measured over neutron energies ranging from 4.9 to 16.6 MeV. Beams of monoenergetic neutrons were produced using the 2H(d, n)3He reaction. The response function is about 12% lower than previously reported values for a similar detector obtained using a continuous spectrum of neutrons from a 252Cf fission source. However, the present response function agrees with portions of data sets obtained in published work that used monoenergetic neutron source reactions.