Measurements of the Differential Cross Sections for the Elastic $n\mathrm{\text{−}}{}^3\mathrm{H}$ and $n\mathrm{\text{−}}{}^2\mathrm{H}$ Scattering at 14.1 MeV by Using an Inertial Confinement Fusion Facility

For the first time the differential cross section for the elastic neutron-triton ($n\mathrm{\text{−}}{}^3\mathrm{H}$) and neutron-deuteron ($n\mathrm{\text{−}}{}^2\mathrm{H}$) scattering at 14.1 MeV has been measured by using an inertial confinement fusion facility. In these experiments, which were carried out by simultaneously measuring elastically scattered ${}^3\mathrm{H}$ and ${}^2\mathrm{H}$ ions from a deuterium-tritium gas-filled inertial confinement fusion capsule implosion, the differential cross section for the elastic $n\mathrm{\text{−}}{}^3\mathrm{H}$ scattering was obtained with significantly higher accuracy than achieved in previous accelerator experiments. The results compare well with calculations that combine the resonating-group method with an ab initio no-core shell model, which demonstrate that recent advances in ab initio theory can provide an accurate description of light-ion reactions.

Figure 1

(a) The CPS on the OMEGA chamber for simultaneous measurements of deuterons and tritons elastically scattered by 14.1-MeV neutrons, and protons from $dd$ reactions in a deuterium-tritium-gas-filled thin-glass capsule implosion. A bending magnet (gray) was used for momentum analysis. (b) Schematic drawing of the CPS, which uses a 2-mm wide aperture in front of a 7.6-kG permanent magnet (Nd-Fe-B) for dispersion and high-resolution measurements of the charged particles. Two pieces of CR-39 were used for detection of the $dd$ protons and the elastically scattered deuterons and tritons. The energies are given in MeV for protons.

Figure 2

(a)–(c) $d^{\prime }$ and $t^{\prime }$ spectra measured simultaneously on three different OMEGA shots. The broadening of these spectra is due to the Doppler-effect and CPS-spectrometer response. (d) $dd$-proton spectrum measured for shot 31753 illustrates that the average energy is similar to the birth energy of 3.05 MeV.

Figure 3

(a) Measured differential cross section for the elastic $n\mathrm{\text{−}}{}^2\mathrm{H}$ scattering, which has been normalized to a Faddeev calculation. (b) Measured and calculated differential cross section for the elastic $n\mathrm{\text{−}}{}^3\mathrm{H}$ scattering. The experimental data have been normalized with the deuterium-tritium fuel-ratio modified normalization factor derived in (a). The blue solid curve represents an ab initio NCSM/RGM calculation, and the red dashed curve represents an $R$-matrix calculated $n\mathrm{\text{−}}{}^3\mathrm{H}$ cross section.