PSFC/RR-12-1 Diagnosing Inertial Confinement Fusion Implosions at OMEGA and the NIF Using Novel Neutron Spectrometry D. T. Casey January, 2012 Plasma Science and Fusion Center Massachusetts Institute of Technology Cambridge MA 02139 USA This work was supported in part by the U.S. Department of Energy (DE-NA0000877 and DE-FG52-09NA29553), the Fusion Science Center at the University of Rochester (PO #415023-G, UR Account #5-24431), the Laboratory for Laser Energetics at the University of Rochester (414090-G), and the Lawrence Livermore National Laboratory (B580243). Reproduction, translation, publication, use and disposal, in whole or in part, by or for the United States government is permitted. Diagnosing Inertial Confinement Fusion Implosions at OMEGA and the NIF Using Novel Neutron Spectrometry by Daniel Thomas Casey B.S. Nuclear Engineering (2005) University of New Mexico SUBMITTED TO THE DEPARTMENT OF NUCLEAR SCIENCE AND ENGINEERING IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPY IN NUCLEAR SCIENCE AND ENGINEERING AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY February 2012 ©2012 Massachusetts Institute of Technology. All rights reserved. Signature of Author:_____________________________________________ Department of Nuclear Science and Engineering February 15th, 2012 Certified by:___________________________________________________ Richard Petrasso Senior Research Scientist Thesis Supervisor Accepted by:__________________________________________________ Ronald Parker Professor of Nuclear Science and Electrical Engineering Thesis Reader Accepted by:__________________________________________________ Mujid S. Kazimi TEPCO Professor of Nuclear Science and Engineering Chair, Department Committee on Graduate Students Diagnosing Inertial Confinement Fusion Implosions at OMEGA and the NIF Using Novel Neutron Spectrometry by Daniel Thomas Casey Submitted to the Department of Nuclear Science and Engineering on December 9, 2011, in partial fulfillment of the requirements for the degree of Doctor of Philosophy ABSTRACT A novel neutron spectrometer, called the Magnetic Recoil Spectrometer (MRS), was designed, built, and implemented on the OMEGA laser facility and the National Ignition Facility (NIF) to measure the neutron spectra from inertial confinement fusion (ICF) implosions. Using the MRS, the down-scattered neutron (DSn) spectrum has been used to infer the areal density (ρR) of ICF implosions for the first time. The DSn technique is essential for diagnosing high ρR (>180mg/cm2) cryogenic deuterium-tritium (DT) implosions, where most other methods fail. The MRS has helped to guide the cryogenic campaign toward the highest ρRs ever achieved at OMEGA. In addition, the MRS is currently being used to diagnose the DSn spectrum from cryogenic implosions at the NIF during the beginning phases of the National Ignition Campaign (NIC). MRS data have already been essential for tuning these implosions to the highest ρRs ever achieved in an ICF implosion (>1 g/cm2), and thus for guiding the NIC toward the realization of thermonuclear ignition. The first measurements of the T(t,2n)4He (TT) neutron spectrum in DT implosions at OMEGA have also been conducted using the MRS. The TT-neutron (TTn) spectrum was measured at low reactant central-mass energies of ~23 keV. The results from these measurements indicate that the TT reaction proceeds primarily through the direct three-body reaction channel, which is in contrast to the results obtained in higher energy accelerator experiments. Measurements of the TTn and DD proton yields were also conducted and compared to the DT neutron yield in DT implosions. From these measurements, it is concluded that the DD yield is anomalously low and the TTn yield is anomalously high, relative to the DT yield. These results have been explained by a stratification of the fuel in the core of an ICF implosion. Thesis Supervisor: Richard D. Petrasso Senior Research Scientist Plasma Science and Fusion Center, Massachusetts Institute of Technology 2 Acknowledgments First, I thank my advisor Richard Petrasso whose enthusiasm and scientific rigor are both motivating and, at times, even awe-inspiring. I also thank Johan Frenje, whose leadership of the OMEGA and NIF MRS projects directly led to their successful realization and whose supervision of my thesis research, was both supportive and educational. I also thank Johan for carefully reviewing this thesis manuscript. I am most appreciative for the many contributions of the entire high-energy-density physics division at MIT. This includes Fredrick Seguin, whose masterful experience and attention to detail was essential for many aspects of this project, including the development of the novel processing techniques of the MRS systems. I also thank Fredrick for his efforts in developing and maintaining the microscope and data analysis systems for all of the MIT diagnostics, including the MRS. I thank Chikang Li for always being available for questions and being supportive of this work. I thank Maria Gatu Johnson for developing powerful new analysis techniques and taking over most of the OMEGA and NIF MRS related responsibilities, while I was writing this thesis. I also thank my good friends Nathan Howard, Mario Manuel, Nareg Sinenian, (and so many others they cannot all be named here) for illuminating conversations both on physics and all facets of life. I also thank Jocelyn Schaeffer, Irina Cashen, Robert Frankel, and Ernie Doeg, who skillfully managed many aspects of the MIT etch/lab and are responsible for much of the data processing that was required to both commission the MRS diagnostics and perform the experiments described in this thesis. This thesis work could not have been possible without the enormous support it received from LLE. The OMEGA operations, engineering, and scientific staff, along with their management, all supported this project. I thank David Meyerhofer and Craig Sangster for supporting the MRS projects, Vladimir Glebov for countless ride-along shot opportunities, Radha Bahukutumbi for enormous simulation support, and Michelle Burke and Joe Katz for managing the OMEGA MRS and the LLE etch/scan lab. I thank Jeff Ulreich and Bill Owens for providing the engineering support of the OMEGA MRS system. In particular, I also thank Sam Roberts, without whom, the OMEGA MRS would not have been successful. His experience and knowledge of OMEGA and its diagnostics are responsible for much of the success of this project. In addition, Sam’s resilience and strength, after his terrible accident, will forever continue to inspire me. At LLNL, I am very appreciative to Richard Bionta and Mark Mckernan for their support and for establishing and flawlessly running the LLNL MRS etch/scan lab. I also thank Mark for designing much of the NIF MRS detector hardware. I also thank Rick Ashabranner and Jason Magoon for their engineering support of the NIF MRS. I also thank Rick for his continued support of the NIF MRS. I also thank Dennis McNabb, whose involvement in the tt project contributed enormously to its success and fostered new collaborations in plasma nuclear science. I thank Ray Leeper at Sandia, for many insightful and entertaining conversations and for his continued interest in this work. 3 I thank my thesis reader, Professor Ron Parker, for reviewing this thesis, along with Professors Ian Hutchinson, Jeffrey Freidberg, and Miklos Porkolab for excellent courses in plasma physics and fusion energy. I also thank my parents, Cheryl and Mike Horne, my brother Adam Horne, my Grandparents Don and Judi Horne and the many other members of my family, for their love, support, and pride, which inspired me to work hard. Lastly, and most importantly, I thank my beautiful and wonderful wife Maxine Casey. Her love and support during these long and arduous years of graduate school managed to make them the most rewarding and enjoyable years of my life. 4 TABLE OF CONTENTS Acknowledgments 3 List of figures 1-10 1 - Introduction 1-16 1.1Nuclear Energy ................................................................................................................................. 1-16 1.2 Stellar nucleosynthesis .................................................................................................................... 1-17 1.3 Realization of thermonuclear energy on earth ............................................................................... 1-18 1.4 Historical remarks on Inertial Confinement Fusion (ICF) ............................................................. 1-22 1.5 Thesis Overview .............................................................................................................................. 1-23 2 - Inertial Confinement Fusion (ICF) 2-25 2.1 Ideal ignition condition in ICF ........................................................................................................ 2-25 2.2 ICF drive configurations ................................................................................................................. 2-27 2.3 Challenges in ICF ............................................................................................................................ 2-29 2.4 The OMEGA laser facility .............................................................................................................. 2-30 2.5 The National Ignition Facility (NIF) .............................................................................................. 2-31 2.6 ICF Diagnostics ..............................................................................................................................