My primary research focus is now on Inertial Confinement Fusion (ICF). The goal of ICF is to use high-powered lasers to rapidly compress and heat a spherical capsule of deuterium/tritium fuel until it is hotter and denser than the center of the sun.
My research in ICF is broad and includes present and past work on fusion ignition at NIF, nuclear astrophysics, the basic physics of dense plasmas, and the development of nuclear diagnostics for laser-fusion facilities. This 'portfolio' gives an overview of my contributions to these national and international collaborations, which has resulted in a large number of publications.
Since joining Los Alamos, my main work has been on implosion physics experiments conducted on NIF as part of the national campaign studying inertial confinement fusion ignition. Specifically I am currently the experimental campaign leader for beryllium ablator implosions, which have several potential advantages for reaching fusion conditions. I have also contributed to studies using liquid fuel layer implosions and several projects led by LLNL scientists (e.g. Variable convergence liquid layer implosions on the National Ignition Facility).
For fusion ignition to work, the fuel must remain clean - any introduction of other materials, such as the surrounding capsule, is very detrimental. I have led a series of experiments at the OMEGA laser studying mix using novel techniques on the target fabrication, and by improving our measurement techniques using gamma rays (see Simultaneous measurement of the HT and DT fusion burn histories in inertial fusion implosions).
A newer effort within a multi-institution collaboration has been to study nuclear physics using our inertially-confined plasmas at laser facilities, coupled with available nuclear diagnostics. In particular, I have led several experiments to study nuclear reactions relevant to astrophysics:
I have also led experiments to study the stopping of charged particles in dense plasma, which is theoretically complex and has not been tested experimentally. Using existing technology at the OMEGA laser, great data was obtained, which wasbe used to constrain these theories in a recent paper in Phys. Rev. Lett. (Measurement of Charged-Particle Stopping in Warm Dense Plasma). Additional experiments are underway at the NIF and OMEGA.
As a graduate student I participated in ignition experiments at the NIF. In particular, I led the effort to implement and use proton spectroscopy on 'surrogate' NIF implosions with D+³He fuel (see Charged-particle spectroscopy for diagnosing shock ϱR and strength in NIF implosions). My role at NIF was as the Responsible Scientist for these 'Wedge Range Filter' (WRF) proton spectrometers, responsible for managing their use on experiments and analysis of the data.
Over several years, the WRF recorded data on a large number of NIF shots. Using a data-mining analysis, I identified a subset of shots with reasonable similarity to study the shock dynamics. In a NIF implosion, several shocks are launched into the target; these shocks coalesce and converge at the center several hundred ps before the main fusion burn. By studying the convergence at the shock flash and the strength of the shock, I identified some key physics mysteries in the behavior of this shock at very extreme conditions (see The effect of shock dynamics on compressibility of ignition-scale National Ignition Facility implosions). Additional, multiple spectrometer views can be used to study asymmetries in the implosion (see In-flight observations of low-mode ϱR asymmetries in NIF implosions).
A large role of my grad school group group within the ICF community is in the development and fielding of nuclear diagnostics. To support these efforts, I led several projects to extend our capabilities. First, I designed and implemented a new and compact neutron spectrometer (see A compact neutron spectrometer for characterizing inertial confinement fusion implosions at OMEGA and the NIF). Additional work I have done has extended our capabilities for using CR-39 solid-state nuclear track detectors (see two papers). Finally, our group used a linear electrostatic ion accelerator for diagnostic development and testing. I contributed to the upgrades, control software development, and operation of the facility throughout my graduate career.