Title: Monte Carlo Simulations of Neutron Resonance Transmission Analysis with the Dense Plasma Focus

We explore the feasibility of using Feynman moments as attributes of fissile material in warhead authentication measurements. We present results of computer simulations of neutron correlation measurements to validate and inform the application of the method to measurements in an arms control scenario. We establish the robustness of the method for use in automated measuring equipment that protects classified or sensitive data using an information barrier. Drawing from our results, we define high-level requirements to govern the design process, and guide the construction of a prototype.

New path integral Monte Carlo simulation (PIMC) techniques will be developed and applied to derive the equation of state (EOS) for the regime of warm dense matter and dense plasmas where existing first-principles methods cannot be applied. While standard density functional theory has been used to accurately predict the structure of many solids and liquids up to temperatures on the order of 10,000 K, this method is not applicable at much higher temperature where electronic excitations become important because the number of partially occupied electronic orbitals reaches intractably large numbers and, more importantly, the use of zero-temperature exchange-correlation functionals introducesmore » an uncontrolled approximation. Here we focus on PIMC methods that become more and more efficient with increasing temperatures and still include all electronic correlation effects. In this approach, electronic excitations increase the efficiency rather than reduce it. While it has commonly been assumed such methods can only be applied to elements without core electrons like hydrogen and helium, we recently showed how to extend PIMC to heavier elements by performing the first PIMC simulations of carbon and water plasmas [Driver, Militzer, Phys. Rev. Lett. 108 (2012) 115502]. Here we propose to continue this important development to extend the reach of PIMC simulations to yet heavier elements and also lower temperatures. The goal is to provide a robust first-principles simulation method that can accurately and efficiently study materials with excited electrons at solid-state densities in order to access parts of the phase diagram such the regime of warm dense matter and plasmas where so far only more approximate, semi-analytical methods could be applied.« less

We have carried out 2D simulations of three dense plasma focus (DPF) devices using the ALEGRA-HEDP code and validated the results against experiments. The three devices included two Mather-type machines described by Bernard et. al. and the Tallboy device currently in operation at NSTec in North Las Vegas. We present simulation results and compare to detailed plasma measurements for one Bernard device and to current and neutron yields for all three. We also describe a new ALEGRA capability to import data from particle-in-cell calculations of initial gas breakdown, which will allow the first ever simulations of DPF operation from themore » beginning of the voltage discharge to the pinch phase for arbitrary operating conditions and without assumptions about the early sheath structure. The next step in understanding DPF pinch physics must be three-dimensional modeling of conditions going into the pinch, and we have just launched our first 3D simulation of the best-diagnosed Bernard device.« less