A GAS SCINTILLATION DRIFT CHAMBER FOR THE N-14(N, P)C-14 MEASUREMENT

A gas scintillation drift chamber was developed to measure the cross section of the N-14(n, p)C-14 reaction at the keV region. Since it contains N-2 gas in addition to He gas, the reaction events can be detected with an acceptance of 4 pi. The He-3 in the He gas is enriched to 0.2% in order to normalize the measurement. The chamber uses primary scintillation photons to determine the neutron energies by the time-of-flight method, and uses the trajectories of charged particles to discriminate the true events from events due to both the background and the He-3(n, p)H-3 reaction. It was shown for the first time that N-2 gas works not only as a sample, as a wavelength shifter, but also as a discharge suppressor for the electron avalanche. The basic properties of the chamber were investigated experimentally: good time- (similar to 1.7 ns), spatial- (similar to 2 mm) and energy-(similar to 16% at 600 keV) resolutions were obtained. From these results, it was estimated that the N-14(n, p)C-14 cross section can be measured with an error of 10 similar to 15%.