Neutron suppression in polarized dd fusion reaction

We report a model-independent partial-wave analysis of polarized dd fusion reactions at low energies. The radial transition amplitudes, designated by the central, spin-orbit, and tensor forces, are determined by fitting angular distributions of the tensor and vector analyzing powers A_xz(θ), A_ZZ(θ), A_xx-YY(θ), and A_Y(θ), and the unpolarized cross section σ₀(θ). The polarized fusion cross section σ_1.1(θ) is then predicted from these radial transition amplitudes. We stress that this is feasible only when these amplitudes are separated according to the tensor rank of the interaction. This study includes the D-state components of the deuteron, triton, and ³He, and the partial-wave expansion is done up to the d wave for both the entrance and exit channels. Experimental data at E_lab=30, 50, 70, and 90 keV for the d(d,p)t reaction are very well fitted with this method. It is found that the ratio of polarized to unpolarized cross sections is about 86% at 30 keV and goes down to 22% at 90 keV. The implication of the suppression of a polarized dd fusion reaction is discussed in the context of the neutron-lean fusion reactor with polarized D-³He fuel. It turns out that the important range of energy for suppressing the d(d,p)t and d(d,n)³He reactions at the plasma temperature T=60 keV is E_d = 80-600 keV. More experimental data are needed in this range to make a detailed study of the neutron suppression.