A pinboard by
Arnab Kar

Research Associate, University of Rochester


To develop an understanding of shock wave dynamics through radiography

Scheme for an alternative source of energy:

The first proposal to use a high energy laser for an efficient thermonuclear burn was laid out 55 years ago (J. Nuckolls, L. Wood, A. Thiessen, and G. Zimmerman, Nature 239, 139 (1972)). Over the years, the development of laser technology and the understanding of the related physics have progressed to an extent that laser-driven fusion energy can be seen as a realistic possibility of a source of energy for the future. However, we are yet to demonstrate experimentally that the fusion energy out is greater than laser energy in.

What has been done so far?

The goal of inertial confinement fusion (ICF) is to compress and maintain (briefly) the fusion fuel to significantly high densities necessary for a nuclear fusion reaction to trigger by its own inertia. One approach to ICF is to shine high energy laser on a pellet containing fusion material to generate the required compression from light pressure.

What is lacking that needs to be done?

The pellets consist of a plastic shell that confines the fusion material. As the laser interacts with the pellets, it generates a shock wave into the pellet. The injection of the plastic from the pellet into the fuel can potentially compromise performance and prevent the nuclear fusion reaction. We are working on an experimental diagnostic (X-ray radiography) to understand the dynamics of shock waves to mitigate the extent of the insertion of the plastic into the fusion material. We hope that this will take us to closer to achieving inertial confinement fusion as a feasible source of energy.


First-principles opacity table of warm dense deuterium for inertial-confinement-fusion applications.

Abstract: Accurate knowledge of the optical properties of a warm dense deuterium-tritium (DT) mixture is important for reliable design of inertial confinement fusion (ICF) implosions using radiation-hydrodynamics simulations. The opacity of a warm dense DT shell essentially determines how much radiation from hot coronal plasmas can be deposited in the DT fuel of an imploding capsule. Even for the simplest species of hydrogen, the accurate calculation of their opacities remains a challenge in the warm-dense matter regime because strong-coupling and quantum effects play an important role in such plasmas. With quantum-molecular-dynamics (QMD) simulations, we have derived a first-principles opacity table (FPOT) of deuterium (and the DT mixture by mass scaling) for a wide range of densities from ρ(D)=0.5 to 673.518g/cm(3) and temperatures from T=5000K up to the Fermi temperature T(F) for each density. Compared with results from the astrophysics opacity table (AOT) currently used in our hydrocodes, the FPOT of deuterium from our QMD calculations has shown a significant increase in opacity for strongly coupled and degenerate plasma conditions by a factor of 3-100 in the ICF-relevant photon-energy range. As conditions approach those of classical plasma, the opacity from the FPOT converges to the corresponding values of the AOT. By implementing the FPOT of deuterium and the DT mixture into our hydrocodes, we have performed radiation-hydrodynamics simulations for low-adiabat cryogenic DT implosions on the OMEGA laser and for direct-drive-ignition designs for the National Ignition Facility. The simulation results using the FPOT show that the target performance (in terms of neutron yield and energy gain) could vary from ∼10% up to a factor of ∼2 depending on the adiabat of the imploding DT capsule; the lower the adiabat, the more variation is seen in the prediction of target performance when compared to the AOT modeling.

Pub.: 15 Oct '14, Pinned: 29 Sep '17

FPEOS: A First-Principles Equation of State Table of Deuterium for Inertial Confinement Fusion Applications

Abstract: Understanding and designing inertial confinement fusion (ICF) implosions through radiation-hydrodynamics simulations rely on the accurate knowledge of the equation of state (EOS) of the deuterium and tritium fuels. To minimize the drive energy for ignition, the imploding shell of DT fuel must be kept as cold as possible. Such low-adiabat ICF implosions can access to coupled and degenerate plasma conditions, in which the analytical or chemical EOS models become inaccurate. Using the path-integral Monte Carlo (PIMC) simulations we have derived a first-principles EOS (FPEOS) table of deuterium that covers typical ICF fuel conditions at densities ranging from 0.002 to 1596 g/cm3 and temperatures of 1.35 eV to 5.5 keV. We report the internal energy and the pressure, and discuss the structure of the plasma in terms of pair-correlation functions. When compared with the widely used SESAME table and the revised Kerley03 table, discrepancies in the internal energy and in the pressure are identified for moderately coupled and degenerate plasma conditions. In contrast to the SESAME table, the revised Kerley03 table is in better agreement with our FPEOS results over a wide range of densities and temperatures. Although subtle differences still exist for lower temperatures (T < 10 eV) and moderate densities (1 to 10 g/cc), hydrodynamics simulations of cryogenic ICF implosions using the FPEOS table and the Kerley03 table have resulted in similar results for the peak density, areal density ({\rho}R), and neutron yield, which are significantly different from the SESAME simulations.

Pub.: 30 Sep '11, Pinned: 16 Aug '17