On the failure of neutron yield scaling in the Dense Plasma Focus

The observed scaling of neutron yield in the Dense Plasma Focus (DPF) as the fourth power of the current in the plasma was the principal driver of the growth of DPF research in its early days. Subsequent discovery of failure of this scaling law was also the principal reason for its abandonment by major laboratories. Attempts to understand this failure of scaling have so far been inconclusive. This letter looks at this failure in the context of the recently introduced Generalized Plasma Focus (GPF) problem and suggests a possible reason that can be experimentally examined using small plasma focus devices. This involves restrictions placed on the drive parameter by conservation laws for mass, momentum and energy. A suggested empirical workaround to the problem of neutron yield scaling failure could also be configured as a method for increasing the pressure range for neutron emission in small DPF devices.Comment: Accepted for publication in Physics of Plasmas on 14th July 202

Electronic Structure and Bulk Spin Valve Behavior in Ca3_3Ru2_2O7_7

We report density functional calculations of the magnetic properties and Fermiology of Ca$_3$Ru$_2$O$_7$. The ground state consists of ferromagnetic bilayers, stacked antiferromagnetically. The bilayers are almost but not exactly half-metallic. In the ferromagnetic state opposite spin polarizations are found for in-plane and out-of-plane transport. Relatively high out of plane conductivity is found for the majority spin, which is relatively weakly conductive in-plane. In the ground state in-plane quantities are essentially the same, but the out of plane transport is strongly reduced.Comment: 5 page