The cross section of the ¹⁶O(n,α)¹³C reaction in the MeV energy range

Abstract

Abstract.A novel spectrometer was developed and used to measure the cross section for the 16 O(n,α) reaction at IRMM. The basic parts of the new instrument are an ionisation chamber, a gas oxygen target, and signal digitisation. It is shown that simultaneous digitisation of the anode and cathode signals allows an effective background suppression and the accurate determination of the number of reaction events and the number of atoms in the gas target. Cross section values for the 16 O(n,α) reaction measured in the energy range 3.95-9.0 MeV are presented. None of the existing nuclear data libraries describes well the IRMM data in the entire energy range.

Radionuclide neutron source characterization techniques

“…For 241 Am-Be sources the variation is large enough to change the calculated source emission rate by up to 0.8% [11], which makes it one of the dominant uncertainty components in a calibration of this type of source. It is hoped that ongoing and future measurements of the 16 O(n, α) 13 C reaction, such as those at the Institute for Reference Materials and Measurements (IRMM) [12], will lead to a more reliable evaluated cross-section which will resolve the problem.…”

16O(n,α) cross section investigation using LENZ instrument at LANSCE

“…As discussed in Section 2, the previous (n,α) measurements [2,9] discussed the difficulty from the poor neutron energy resolution, since the neutrons were produced from D(d,n) 3 He or 3 H(p,n) reactions. The combination of the production gas cell and entrance and exit windows could add large energy straggling and broadening.…”

“…This has been recognized and is the motivation for its inclusion as part of the Collaborative International Evaluated Library Organization (CIELO) project [1] looking at improving the nuclear data for key isotopes. At the heart of the questions on the oxygen-16 data is a 30-50% discrepancy between various (n,α) cross section measurements.…”

“…Previously measured cross sections (The subsets are shown in Figure 2) were performed by two different approaches . One is to measure the 16 O(n,α) reaction directly [2,[7][8][9][10]. Gas detectors like a Frisch-gridded ionization counter or a proportional counter were used in a gas mixture, which contained oxygen in order to measure 16 O(n,α) 13 C reaction cross section.…”

Measurement of (n,α) cross section for set of structural material isotopes

“…To minimize the background, we used the experience of investigations of (n,α) reactions on the components of the ionization chamber's working gas [1,2]. The target was mounted on gold filaments fastened to the chamber's first guard electrode.…”