119251181
Understanding Ultracold Neutron Production in Oxygen Solids from Volume and Temperature Dependent Yields
We present experimental data on ultracold neutron (UCN) production in solid oxygen from 5 K to 50 K. The experiment used 3 cells of different dimensions in order to study the excess UCN elastic scattering in s-O$_2$ due to source density non-uniformities. We present a combined $\chi^2$ analysis with the aid of Monte-Carlo simulations which contain the detailed physics of UCN transport as well as cold neutron attenuation. The results validate the UCN production and upscattering cross-sections extracted from the dynamic structure function derived from inelastic neutron scattering, and illustrate the role of magnetic scattering in enhancing UCN production in s-O$_2$.
121470821
The one-loop effective potential in nuclear matter and nuclei
Abstract The lowest-order quantum corrections to the Walecka model are approximated by the one-loop effective potential. The model is considered with and without scalar self-interactions. In contrast to previous work, quantum corrections from the nonlinear scalar self-interactions are included. The resulting equations of motion for the mesons and nucleons are solved self-consistently for nuclear matter and spherical nuclei. Comparison is made to linear mean-field results for several sets of cubic and quartic self-couplings; all sets are consistent with renormalizability and the existence of a stable mean field ground state. Because of these restrictions on the self-couplings, it is impossible to improve the nuclear systematics over those obtained without self-couplings or in the mean-field theory.
14462919
An obliquely propagating electromagnetic drift instability in the lower hybrid frequency range
[1] By employing a local two-fluid theory, we investigate an obliquely propagating electromagnetic instability in the lower hybrid frequency range driven by cross-field current or relative drifts between electrons and ions. The theory self-consistently takes into account local cross-field current and accompanying pressure gradients. It is found that the instability is caused by reactive coupling between the backward propagating whistler (fast) wave in the electron frame and the forward propagating sound (slow) wave in the ion frame when the relative drifts are large. The unstable waves we consider propagate obliquely to the unperturbed magnetic field and have mixed polarization with significant electromagnetic components. A physical picture of the instability emerges in the limit of a large wave number characteristic of the local approximation. The primary positive feedback mechanism is based on reinforcement of initial electron density perturbations by compression of electron fluid via induced Lorentz force. The resultant waves are qualitatively consistent with the measured electromagnetic fluctuations in reconnecting current sheet in a laboratory plasma.