Persistence of the Polarization in a Fusion Process

We propose an experiment to test the persistence of the polarization in a fusion process, using a terawatt laser hitting a polarized high density (HD) target. The polarized protons and deuterons heated in the plasma induced by the laser have a significant probability to fuse producing a3He and a γ-ray or a neutron in the final state. The angular distribution of the radiated γ-rays and the change in the corresponding total cross-section are related to the polarization persistence, but the resulting signal turns out to be weak. By comparison, the neutrons are produced hadronically with a larger cross-section and it is much easier to detect them. A significant reduction of the cross-section by parallel polarization of the deuterons as well as a structured angular distribution of the emitted neutrons is reliably predicted by the theory. Therefore, it is expected that the corresponding signal on the neutron counting rate could be seen experimentally. Magnetic fields, relaxation times and possibilities of local investigations are discussed.

Study of Template Measurement of Plutonium Pit Based on Gamma-Ray Detection

Template measurement is an important method in deep nuclear disarmament. The gamma-ray spectrum of Plutonium pit shows unique property due to age, abundance, amounts and thickness of the Plutonium pit; that is, same designed pits yield similar gamma-ray spectra while different design give distinct spectra. Useful information is extracted from gamma-ray spectrum generated by the reliable Plutonium pit radiation as ‘template’. Comparison of the data from inspected objects with the template can give conclusion whether they are of the same type. This paper studies how to choose template data from gamma-ray spectrum and discusses the limits of the gamma-ray measurement. Because of the strong self-absorption of Plutonium, some characteristics of Plutonium pit can’t be identified only by gamma spectrum. MCNP simulation was employed to prove that in some cases, template depending on gamma-ray spectrum from the reliable Plutonium pit alone can’t effectively distinguish the spurious objects. And a further approach indicates that enhancing neutron counting rate of spontaneous fission of Plutonium can improve the problem. Neutron counting rate can be indirectly acquired by spontaneous fissile neutrons bombarding a 10B target. 478 keV γ rays are concomitant with the nuclear reaction 10B(n,α)7Li* from 7Li* nuclei’s deexcitation. Neutron information is gathered by detecting 478 keV γ photons. Using HPGe γ detector can both detect γ-ray spectrum and acquire neutron counting rate. This method efficiently increases confidence of template measurement and also ensures the dismantling process without revealing sensitive nuclear warhead design information.