Below you can find a list of my first-authored papers along with some details about the contents of each, a list of co-authored papers, and select papers available for download. The most up-to-date listing is available via google scholar.

This paper has two main purposes. First it discusses different types of HED implosion targets that access different regimes of energy transfer. The goal is to use these different target types to constrain different physical processes by using a Bayesian model of the implosions. Secondly this paper further develops how Bayesian modelling can be used to inform experimental design and diagnostic choices and presents an example experimental design using a thick-shelled gas-filled implosion.

This work is published in Physics of Plasmas and the is available below with the permission of AIP Publishing.

This paper details the results of using a fully Bayesian model to constrain the energy flow within a thin-shelled gas-filled implosion on the Omega60 laser. The dynamics of this system is dominated by a single spherically converging shock wave. The primary measurement comes form tracking the trajectory of the decompressing shell which is heated by the outgoing shock wave, after collapse, and emits significant x-ray emission. Based on this measurements, along with inital target characteristics, laser pulse details, and conservation laws, the flow of kinetic energy in the shell to internal energy in the gas is constrained using a mechanical model. This also led to a measurement of the pressure at the fuel-shell interface and most interestingly a measurement of the shock wave strength as it hits the shell, independent of thermodynamic path.

This work is published in Physical Review Letter and the is available below with the permission of the American Physical Society Copyright (2020).

This paper, a companion to the PRL paper detailing the results, discussed the virtues of building Bayesian models for the analysis of HED experiments, in particular convergent HED experiments which are necessary to reach the highest pressures. The benefits of Bayesian modelling include explicit statement of model assumptions, full construction of the posterior parameter distributions for proper uncertainty quantification, and a straight-forward way to combine multiple different sources of information in a single self-consistent analysis framework. A common critique that comes up with these methods is that they are model dependent, which is true, but this same critique can be said of virtually every single analysis method that can be applied to physical measurements. The difference with these methods is that the models must be self-consistent and explicitly stated which allows for more scrutiny, another benefit!

This work is published in Physical Review E and the is available below with the permission of the American Physical Society Copyright (2020).

This paper looks at a classic problem in compressible fluid dynamics, the Guderley solution to a converging shock wave, and adds two new constructs in an attempt to make the solution informative for a particular class of problems, laser driven HED implosions. The Guderley solution is an elegant reduction of Euler's equations to a single ordinary differential equation, under the assumption of an adiabatic equation of state, for a converging shock wave in either spherical of cylindrical geometry. This solutions is great for building intuition about how converging shock waves behave. The modifications this paper outlines include introducing a boundary condition so that the flow does not extend to infinity and a method for partitioning the energy between two fluids, electrons and ions, which each have a temperature and come to equilibrium over a characteristic time-scale.

This work is published in Physics of Fluids and the is available below with the permission of AIP Publishing.

This paper details efforts to measure residual velocity in inertial confinement fusion (ICF) implosions using gated x-ray imaging. Residual velocity is any bulk motion during the stagnation phase of an ICF implosion and is an indicator of kinetic energy that is not being used to compress the fuel and therefore represents an inefficiency in the implosions system. This quantity is often measured using the Doppler shift in the thermonuclear fusion neutron spectrum and this work compliments those measurements using a different type of diagnostic.

This work is published in Physics of Plasmas.

- High-resolution x-ray radiography with Fresnel zone plates on the University of Rochester’s OMEGA Laser Systems
- Shock-compressed silicon: Hugoniot and sound speed up to 2100 GPa
- The data-driven future of high energy density physics
- High-intensity laser-accelerated ion beam produced from cryogenic micro-jet target

John J.Ruby IV, PhD