The High-Energy-Density Physics Division, headed by Dr. Richard Petrasso, studies the physics of inertial-confinement fusion (ICF) plasmas and high-energy-density plasmas using experimental and theoretical methods developed by MIT and collaborators.
| An MIT-designed charged-particle spectrometer (upper right) being installed on the target chamber of the OMEGA laser at the University of Rochester Laboratory for Laser Energetics (LLE). (Photo courtesy of LLE)
ICF experiments utilizing special nuclear diagnostics are currently performed at the OMEGA laser facility at the University of Rochester Laboratory for Laser Energetics and at the National Ignition Facility at the Lawrence Livermore National Laboratory. Special nuclear diagnostics make it possible to determine the spatial and temporal variations in fusion burn and in plasma areal densities through spectral, temporal, and imaging measurements of fusion products and other ions. These measurements are then used to study a wide variety of physics processes and issues such as laser-plasma interactions, the relationship of implosion symmetry to laser drive symmetry, the timing of shock wave coalescence, the effects of mix on convergence and burn profiles, the effects of hydrodynamic instabilities, and the accuracy of hydrodynamic simulations.
In addition, experiments are being designed for studying the transport of energetic electrons in materials relevant for “Fast Ignitor” ICF scenarios. Theoretical work has involved studies of the slowing down of charged particles in plasmas and the transport of energetic electrons in solids and plasmas. The focus of the work is developing novel diagnostics,
furthering the understanding of ICF physics, and pursuing ignition. Another important goal is the education and training of young scientists and students.
MIT PhD Thesis Research at the National Ignition Facility
mentioned in the Strategic Studies Quarterly (SSQ)
Four Massachusettes Institute of Technology (MIT) PhD students played an important role in the highly successful implosion at the National Ignition Facility (NIF) on March 12, 2013, in which a record deuterium-deuterium (D-D) fusion yield (5x1012) was achieved. The four students, Hans Rinderknecht, Mike Rosenberg, Alex Zylstra, and Hong Sio, all from the MIT Physics Department and the MIT Plasma Science and Fusion Center, were part of the team responsible for fielding nuclear spectrometers that revealed critical internal plasma conditions of the implosion.
For this deuterium-fueled implosion, the D-D fusion reaction has the following two equally probable branches.
D + D → n (2.5 MeV) + 3He (0.8 MeV) (1a)
→ p (3.0 MeV) + T (1.0 MeV) (1b)
As the very energetic 3He or T fusion products slow down in the background D plasma, they have a probability of about 1x10-3 of undergoing in-flight fusion with the plasma D, thus generating the following fusion products:
3He (0.8 MeV ) + D → P (12 MeV - 17.6 MeV) + alpha (2a)
T (1.0 MeV) + D → n (12 - 17 MeV) + alpha (2b)
By carefully analyzing the spectra of both the energetic protons and neutrons from these latter reactions, and doing such in a novel and integrated fashion, the MIT PhD students were able to infer the D fuel areal density (15 mg/cm2) and electron temperature (1.8 keV), and the total (fuel and shell) areal density (45 mg/cm2). The figure below shows a recent photo of the four MIT PhD students at the NIF facility, together with the director of the NIF facility, Dr. Ed Moses.
Four current MIT PhD students (2nd from left, Rinderknecht; 4th, Zylstra; 6th, Rosenberg; and 7th, Sio), with their advisor, Dr. Richard Petrasso (far left), former MIT PhD student Dr. Dan Casey (3rd from left), and Dr. Ed Moses, Director of the NIF Facility (5th from left). Dr. Casey was the first student to use NIF data in his PhD thesis, and recently joined LLNL as a staff scientist. The NIF target chamber is in the background. The MIT-LLE-LLNL designed high resolution neutron spectrometer, used by Dr. Casey in his thesis research, is in the middle.
MIT Team mentioned in the January 13, 2013 issue of Photons & Fusion a monthly review of science and technology at the National Ignition Facility & Photon Science Directorate
The article says in part that the MIT team has delivered key NIF diagnostics: “Twenty new wedge range filter (WRF) precision compact proton spectrometers developed at MIT have been delivered to NIF. The WRF is one of three diagnostic devices created at MIT that are designed to measure the spectrum and timing of NIF neutrons and protons.”
Members of the MIT-NIF team responsible for the development, testing, and calibration of the wedge range filter (WRF) proton spectrometers. PhD student Mike Rosenberg, an active participant in NIF experiments, holds a tray of the spectrometers next to the accelerator used in their final calibration.
Joint Press Release from MIT, Lawrence Livermore National Laboratory (LLNL), and the University of Rochester's Laboratory for Laser Energetics (LLE)
The joint press release heralds the recent paper published in the Physical Review Letters by group members Johan Frenje, C.K. Li, Fredrick Séquin, Dan Casey, and Richard Petrasso and their collaborators at LLE and LLNL. The paper "Measurements of the Differential Cross Sections for the Elastic n-3H and n-2H Scattering at 14.1 MeV by Using an Inertial Confinement Fusion Facility", represents the first fundamental nuclear physics result obtained from a high-energy-density facility. "With this class of experiments imminent, a new and exciting field of research is ushered in: plasma nuclear science, blending the disciplines of plasma and nuclear physics," said lead researcher Johan Frenje of MIT.
National Ignition Facility and Photon Science Awards
Congratulations to Johan Frenje, Hans Rinderknecht, Alex Zylstra and team members for receiving NIF Directorate Performance Awards. Three members in the MIT-HEDP division received the National Ignition Facility and Photon Science Award for their outstanding contributions in designing and implementing diagnostics that have been essential to the progress of the National Ignition Campaign (NIC). "Dr. Johan Frenje received the award for outstanding contributions in designing and implementing large scope, advanced neutron spectrometer in support of characterizing NIC implosions". PhD student "Hans Rinderknecht received the award for outstanding contributions in designing and implementing particle time-of-flight detector in support of characterizing NIC implosions.", and PhD student "Alex Zylstra received the award for outstanding contributions in designing and implementing proton spectrometer in support of characterizing NIC implosions".
New Paper by Chikang Li et al. in Science!
(A) Schematic of the experimental setup, with proton backlighter, hohlraum-driven implosion, CR-39 imaging detector, and laser drive beams. Fifteen laser beams entered each end of the hohlraum: 5 with incident angle 42° and 10 with angle 58.8°. The colors shown on the hohlraum wall indicate the laser intensity distribution [modeled by VISRAD]. The proton backlighter was driven by 30 laser beams with total laser energy ~ 11 kJ in a 1-ns square pulse. The 15 MeV D3He backlighting protons passed through the laser-driven hohlraum, sampling plasma conditions and capsule implosions at different times. Images in (B) show proton fluence (within each image, darker means higher fluence), while images in (C) show proton energy (within each image, darker means more proton energy loss and therefore more matter traversed). The gray-scale mapping for image display is different in each image. The capsule mounting stalk appears in the upper left corner of each image. Click the image to see the Science paper.
The HEDP Division was also featured in MIT-News
See also Ryan Rygg et al., 2008 in Science
This schematic drawing shows the monoenergetic proton radiography system MIT physicists
are using to study inertial confinement fusion capsule implosions. Protons created by
fusion reactions in the capsule shown at the far left travel through magnetic and
electric fields generated by the other implosion. On the right is the resulting image of the fields, with the compressed hydrogen pellet in the center. Click the image to see the Science paper.
Members of the HEDP/ICF team in the experiment planning room, around 11 PM,
on shot day (13
March 2008) for the MIT NLUF experiments at the OMEGA laser facility.