Gregory A. Moses

Improved treatment of electron thermal conduction in plasma hydrodynamics calculations

The classical transport law for the hydrodynamic description of the electron heat flux breaks down in the nonequilibrium laser fusion plasma and an alternative expression for the electron heat flux vector must be used. The ad‐hoc flux limit treatment used in present production level codes is analyzed and shown to provide physically plausible results but without providing any further insight into the properties of the plasma. Grad’s 13 moment method is proposed as an alternative to the conventional Fourier’s law expression for the heat flux. Numerical calculations confirm that this approach not only provides physically plausible results but provides them within a more fundamental framework than the ad‐hoc flux limiting schemes and thus offers the possibility of gaining more insight into the flux limiting mechanism.

Timely Delivery of Laser Inertial Fusion Energy (LIFE)

Abstract The National Ignition Facility (NIF), the world’s largest and most energetic laser system, is now operational at Lawrence Livermore National Laboratory. A key goal of the NIF is to demonstrate fusion ignition for the first time in the laboratory. Its flexibility allows multiple target designs (both indirect and direct drive) to be fielded, offering substantial scope for optimization of a robust target design. In this paper we discuss an approach to generating gigawatt levels of electrical power from a laser-driven source of fusion neutrons based on these demonstration experiments. This “LIFE” concept enables rapid time-to-market for a commercial power plant, assuming success with ignition and a technology demonstration program that links directly to a facility design and construction project. The LIFE design makes use of recent advances in diode-pumped, solid-state laser technology. It adopts the paradigm of Line Replaceable Units utilized on the NIF to provide high levels of availability and maintainability and mitigate the need for advanced materials development. A demonstration LIFE plant based on these design principles is described, along with the areas of technology development required prior to plant construction.

Inertial fusion energy target output and chamber response: Calculations and experiments

The emission of photons and energetic ions by the burn and subsequent explosion of inertial fusion energy (IFE) targets poses a threat to the survival of the target chambers in future IFE power plants. Immediately after the deposition of target output, the chamber can experience sufficient heating to cause vaporization, melting, and shock loading on chamber walls. Until high-yield targets can be ignited in laboratory experiments, predictions of the nature of the target output and the response of the target chamber must be made with radiation-hydrodynamics computer codes that need to be validated with relevant smaller scale experiments. Physical models of equation of state, opacity, and radiation transport are in special need of validation. Issues of target output and chamber response requiring experiments and computer modeling are discussed and initial results from experiments are presented. Calculations of x ray and debris output from direct-drive IFE targets are shown and sensitivity of the output spect...

Effective Teaching with Technology

A course entitled effective teaching with technology (ETT) has been taught to PhD candidates and postdoctoral students in science, technology, engineering, and mathematics (STEM) during the Spring semester of 2004, 2005, and 2006, at the University of Wisconsin-Madison. The course is supported by the NSF-sponsored Center for Integration of Research, Teaching, and Learning (CIRTL). The course employs the three CIRTL pillars of teaching-as-research, learning-through-diversity, and learning communities as its basis. The ETT course introduces students to the idea that they critically evaluate technology options with the overarching goal of improved student learning. In this paper we describe: (1) development of this unique course, (2) operational experiences, and (3) student outcomes and effectiveness of the teaching-as-research approach to motivate future faculty (i.e. graduate students) to view teaching and the classroom with the same critical eye and scientific method that they use in their own research

HIBALL—A conceptual design study of a heavy-ion driven inertial confinement fusion power plant

Abstract A preliminary concept for a heavy-ion beam driven inertial confinement fusion power plant is presented. The high repetition rate of the RF accelerator driver is utilized to serve four reactor chambers alternatingly. In the chambers a novel first-wall protection scheme is used. At a target gain of 83 the total net electrical output is 3.8 GW. The recirculating power fraction is below 15%. The main goal of the comprehensive HIBALL study (which is continuing) is to demonstrate the compatibility of the design of the driver, the target and the reactor chambers. Though preliminary, the present design is essentially self-consistent. Tentative cost estimates are given. The costs compare well with those found in similar studies on magnetic confinement fusion reactors.

CHAMBER DESIGN FOR THE LASER INERTIAL FUSION ENERGY (LIFE) ENGINE

Abstract The Laser Inertial Fusion Energy (LIFE) concept is being designed to operate as either a pure fusion or hybrid fusion-fission system. The present work focuses on the pure fusion option. A key component of a LIFE engine is the fusion chamber subsystem. It must absorb the fusion energy, produce fusion fuel to replace that burned in previous targets, and enable both target and laser beam transport to the ignition point. The chamber system also must mitigate target emissions, including ions, x-rays and neutrons and reset itself to enable operation at 10-15 Hz. Finally, the chamber must offer a high level of availability, which implies both a reasonable lifetime and the ability to rapidly replace damaged components. An integrated design that meets all of these requirements is described herein.

RADIATION TRANSPORT FOR EXPLOSIVE OUTFLOWS: A MULTIGROUP HYBRID MONTE CARLO METHOD

We explore Implicit Monte Carlo (IMC) and discrete diffusion Monte Carlo (DDMC) for radiation transport in high-velocity outflows with structured opacity. The IMC method is a stochastic computational technique for nonlinear radiation transport. IMC is partially implicit in time and may suffer in efficiency when tracking MC particles through optically thick materials. DDMC accelerates IMC in diffusive domains. Abdikamalov extended IMC and DDMC to multigroup, velocity-dependent transport with the intent of modeling neutrino dynamics in core-collapse supernovae. Densmore has also formulated a multifrequency extension to the originally gray DDMC method. We rigorously formulate IMC and DDMC over a high-velocity Lagrangian grid for possible application to photon transport in the post-explosion phase of Type Ia supernovae. This formulation includes an analysis that yields an additional factor in the standard IMC-to-DDMC spatial interface condition. To our knowledge the new boundary condition is distinct from others presented in prior DDMC literature. The method is suitable for a variety of opacity distributions and may be applied to semi-relativistic radiation transport in simple fluids and geometries. Additionally, we test the code, called SuperNu, using an analytic solution having static material, as well as with a manufactured solution for moving material with structured opacities. Finally, we demonstrate with a simple source and 10 group logarithmic wavelength grid that IMC-DDMC performs better than pure IMC in terms of accuracy and speed when there are large disparities between the magnitudes of opacities in adjacent groups. We also present and test our implementation of the new boundary condition.

Vapor condensation in the presence of a noncondensable gas

Kinetic theory principles are used to study one‐dimensional steady‐state vapor condensation phenomena in the presence of a noncondensable gas. The results have been fitted to an interpolation formula describing the condensation flux that reduces to the one obtained by Labuntsov and Kryukov [Int. J. Heat Mass Transfer 22, 989 (1979)] in the limit of no noncondensable gas.Kinetic theory principles are used to study one‐dimensional steady‐state vapor condensation phenomena in the presence of a noncondensable gas. The results have been fitted to an interpolation formula describing the condensation flux that reduces to the one obtained by Labuntsov and Kryukov [Int. J. Heat Mass Transfer 22, 989 (1979)] in the limit of no noncondensable gas.

Improved non-local electron thermal transport model for two-dimensional radiation hydrodynamics simulations

An implicit, non-local thermal conduction algorithm based on the algorithm developed by Schurtz, Nicolai, and Busquet (SNB) [Schurtz et al., Phys. Plasmas 7, 4238 (2000)] for non-local electron transport is presented and has been implemented in the radiation-hydrodynamics code DRACO. To study the models effect on DRACOs predictive capability, simulations of shot 60 303 from OMEGA are completed using the iSNB model, and the computed shock speed vs. time is compared to experiment. Temperature outputs from the iSNB model are compared with the non-local transport model of Goncharov et al. [Phys. Plasmas 13, 012702 (2006)]. Effects on adiabat are also examined in a polar drive surrogate simulation. Results show that the iSNB model is not only capable of flux-limitation but also preheat prediction while remaining numerically robust and sacrificing little computational speed. Additionally, the results provide strong incentive to further modify key parameters within the SNB theory, namely, the newly introduced non-local mean free path. This research was supported by the Laboratory for Laser Energetics of the University of Rochester.

Overview of the LIBRA light ion beam fusion conceptual design

The LIBRA light ion beam fusion commercial reactor study is a self-consistent conceptual design of a 330 MWe power plant with an accompanying economic analysis. Fusion targets are imploded by 4 MJ shaped pulses of 30 MeV Li ions at a rate of 3 Hz. The target gain is 80, leading to a yield of 320 MJ. The high intensity part of the ion plate is delivered by 16 diodes through 16 separate z-pinch plasma channels formed in 100 torr of helium with trace amounts of lithium. The blanket is an array of porous flexible silicon carbide tubes with Li/sub 17/Pb/sub 83/ flowing downward through them. These tubes (INPORT units) shield the target chamber wall from both neutron damage and the shock overpressure of the target explosion. The target chamber is self-pumped by the target explosion generated overpressure into a surge tank partially filled with Li/sub 17/Pb/sub 83/ that surrounds the target chamber. This scheme refreshes the chamber at the desired 3 Hz frequency without excessive pumping demands. The blanket multiplication is 1.2 and the tritium breeding ratio is 1.4. The direct capital cost of LIBRA is estimated to be