Dopants for High Density Carbon

Tom Braun | 21-ERD-048

Project Overview

Diamond, or high-density carbon (HDC), is currently used in many industrial and research applications due to its outstanding physical and chemical properties. Its high density and low atomic number make it an attractive Inertial Confinement Fusion (ICF) ablator material, and it was recently used in the major achievement of fusion ignition at Lawrence Livermore National Laboratory. Most ablator shells require doping to control the M-band preheat by providing a shield for the DT fuel. However, doping of diamond is notoriously challenging due to its record high atomic density and, therefore, small lattice dimensions to accommodate dopants. The goal of the project was to study the incorporation of high concentrations of dopants into diamond, with the focus on dopant gradients and a new low-Z dopants silicon. As a starting point for our work, we used the established W dopant process for HDC, developed by Diamond Materials GmbH, Germany. We used a combination of microwave plasma enhanced chemical vapor deposition, in-situ process and plasma diagnostics and ex-situ characterization to gain a better understanding of film growth, control of dopant concentration, and film growth using Tungsten and Silicon. We studied dependencies of film properties on process parameters and synthesized a gradient dopant film on a spherical shell with National Ignition Facility (NIF) shot dimensions.

Mission Impact

This project focused on the incorporation of novel dopants into HDC and directly supported Core Competencies  of High Energy Density Science and Advanced Materials and Manufacturing, and two key areas of interest within the mission focus area of Nuclear Weapons Science. It benefited ICF and High Energy Density experiments at the NIF and advanced one of Lawrence Livermore National Laboratory's Core Competencies as leadership in materials synthesis.

Publications, Presentations, and Patents

T. Braun et. al., "High Density Carbon Capsule Development at NIF" (Presentation, Target Fabrication Specialist Meeting 2022, Virtual, Los Alamos National Laboratory, Los Alamos, NM, June 8, 2022).

T. Braun, "Diamond (HDC) capsules at LLNL" (Technical Presentation, Virtual, 2021). 

R. Wheeler, Ariel Lighty, Sean Hayes, Daniel Behne, Chantel Aracne-Ruddle, and Tom Braun,"Diamonds are the NIF's best friend" (Presentation, 2021 Summer SLAM - Special Edition, Livermore Lab Foundation - Selected Top 10 Presentation, 2021). 

R. Wheeler, Chantel Aracne-Ruddle, Daniel Behne, Jonathan Crowhurst, Sean Hayes, Annie Kritcher, Ariel Lighty, Edward Lindsey, Christoph Wild, and Tom Braun, "Diamond Capsule Material Analysis" (Presentation, U.S. Department of Energy Science Undergraduate Laboratory Internship Presentation, 2021).

R. Wheeler, Ariel Lighty, Chantel Aracne-Ruddle, Christoph Wild, Daniel Behne, Edward Lindsey, Jonathan Crowhurst, Sean Hayes, and Tom Braun. 2021. "Material characterization of tungsten doped high-density carbon capsules for the National Ignition Facility." U.S. Department of Energy Science Undergraduate Laboratory Internship Final Report.