arXiv subjects

Wallace Manheimer

Publications and source records attributed to Wallace Manheimer.

5 recordsLinked to original sources

arXiv2026

On modeling energetic electrons in laser fusion plasmas

It has been known for decades that laser fusion can be, and often is plagued by the production of energetic electrons.produced either by a instability or by the production of energetic electrons, produced either by an instability or by the energetic tail of a Maxwellian distribution. Despite more than 25 years of a variety of efforts, there is still no generally accepted way to address this issue. This work hopes to advance the progress by developing a Fokker Planck model which is simple enough to be used at every time step of a rad-hydro simulation, and accurate enough to be useful. It makes several approximations, the main one being that the percentage of these energetic electrons is small. Recent experiments confirm this so far that this is the case for plasmas subject to a laser plasma instability. Hence energetic electons interact with the background plasma, but not with each other. This work makes no attempt to solve for the entire electron distribution function. It makes a variety of tohter approximations to solve the resulting Fokker Planck equation. This rather elngthy report both summarizes the author's work with the NRL group, and presents new advances since the termination of the NRL laser fusion project. An important tentative conclusion is that energetic electrons may not be such a big problem for laser fusion.

physics.plasm-ph↗

arXiv2025

For a New Department of Energy lab to examine laser fusion for energy

This paper gives a summary of a talk by the author at the mini-conference entitled Progress in Making IFE-based Concepts a Reality at the APS-DPP meeting in Atlanta in October, 2024. It argues principally for a new DoE lab to examine the potential opportunity of laser fusion for civilian energy, by direct drive, with an excimer laser. This work is motivated mostly by the demonstration of a burning plasma in an indirect drive configuration, by the Lawrence Livermore National laboratory with its NIF laser. Also, it briefly gives some impressions of the mini conference.

physics.plasm-ph↗

arXiv2024

Fusion It is time to color outside the lines

There has been some good news, and some bad news in the controlled fusion community recently. The good news is that the Lawrence Livermore National Laboratory (LLNL) has recently produced a burning plasma. It succeeded on several of its shots where ~1.5-2 megajoules from its laser (National Ignition Facility, or NIF) has generated ~ 1.3-3 megajoules of fusion products. The highest ratio of fusion energy to laser energy it achieved, defined as its Q, was 1.5 at the time of this writing. While LLNL is sponsored by nuclear stockpile stewardship, this author sees a likely path from their result to fusion for energy for the world, a path using a very different laser and a very different target configuration. The bad news is that the International Tokamak Experimental Reactor (ITER) has continued to stumble on more and more delays and cost overruns, as its capital cost has mushroomed from ~$5 billion to ~ $25B. This paper argues that the American fusion effort, for energy for the civilian economy, should switch its emphasis not only from magnetic fusion to inertial fusion but should also take much more seriously fusion breeding. Over the next few decades, the world might well be setting up more and more thermal nuclear reactors, and these might need fuel which only fusion breeders can supply. In other words, fusion should begin to color outside the lines.

physics.plasm-ph↗

arXiv2023

Analytic insights into nonlocal energy transport: Steady State Fokker Planck theory in arbitrary Z plasmas

The generation of energetic electrons in laser fusion in an important issue. The electrons may either arise from a laser plasma instability, or from the uncoupled high temperature tail of a Maxwellian distribution. To study these in a laser fusion context, it is important to find a method accurate enough to be useful, and simple enough to be incorporated into a radiation hydrodynamics numerical simulation, the main workhorse for studying the laser fusion target. That is why analytic insights become important, they allow one to simplify the Fokker Planck theory so that a solution of it can be incorporated into a radiation hydrodynamic (rad-hydro) simulation. This work develops and analyzes a steady state Fokker Planck theory for plasmas of arbitrary Z. It developes a method of solving the simplified Fokker Planck method with a technique called sparse eigenfunction analysis. This method appears to work reasonably well when compared to the experimental results from the Rochester/NIF on plastic spherical targets with and without a silicon layer.

physics.plasm-ph↗

arXiv2022

Fusion breeding and pure fusion development perceptions and misperceptions

This paper examines fusion breeding, namely the use of 14 MeV fusion neutrons to breed $^{233}$U fuel for thermal nuclear reactors. This can be accomplished much more quickly than pure fusion. It can become main component of a power architecture that is economical, enviromentally sound and has little if any proliferation risk.

physics.plasm-ph↗