2
Relevance of the National Ignition Facility to Science Based Stockpile Stewardship

Ignition is relevant to SBSS, but the NIF will make contributions to SBSS independent of ignition: Its experimental program will help attract and train people in weapons-related skills, provide microphysics data, enhance integrated code validation, and create hohlraum conditions unique in a laboratory setting (high radiation temperatures foremost among them).

PEOPLE

One of the stated goals of the SBSS program is to maintain core intellectual and technical competencies in nuclear weapons in the absence of nuclear testing. Previous reviews1 have recognized that a successful SBSS program requires the ability to sustain and enhance the scientific competence of the National Laboratories. In particular, the National Laboratories must be able to attract, train, and retain competent and creative scientists with the skills necessary to understand nuclear weapons and to certify the stockpile. Appropriate personnel are best attracted and retained by the opportunity to participate in challenging basic research. The maintenance and renewal of technical skills and overall scientific competence can be best fostered through ambitious technical challenges and the opportunity for scientific recognition, both through publication in the open literature and through performance in the classified community. These conditions are important to ensuring an imaginative and high-quality SBSS program. The committee believes that a stewardship program based only on the static knowledge and technology of the past would find it difficult to attract and maintain the necessary scientific talent. The stewardship community must be able to respond to unforeseen challenges, including technical issues in support of treaty negotiations, as well as the recognized issues of safety, security, reliability, aging, remanufacturing, and proliferation monitoring and control.

Maintaining core intellectual and technical competencies requires a challenging theoretical, computational, and experimental program in the areas of implosion hydrodynamics, instabilities and mix, radiation transport, and theormonuclear burn. In the committee's judgment, ICF provides a unique synthesis of these relevant physics areas, and the NIF would provide unique capabilities for basic experiments in atomic physics, radiation flows, plasma physics, and hydrodynamics. In the collective judgment of the committee, the NIF should stimulate the scientific imagination and attract excellent scientists and engineers more than any other proposed element of SBSS. This assertion is supported by the ICF program's history of attracting and retaining high-quality personnel. While it is difficult to quantify how much more successful the NIF would be in attracting personnel than other proposed SBSS facilities, a majority of the committee members are involved in the training of scientists, and their consensus is that they would more strongly encourage their students to work on the NIF than on any other proposed SBSS facility. The attraction of the NIF is so high that, indeed, it may be a management and leadership challenge to keep the ICF program in proper balance with the rest of SBSS.

Universities are the primary source of scientific and technical talent, and the NIEF will provide new opportunities for university-National Laboratory synergism, both in personnel and in science. Beyond the long-standing LLE effort at the University of Rochester, universities have been involved in the ICF program at a modest but increasing rate since recent declassification of much of the program. For example, a new program makes about 10% of the NOVA shots available, at no charge, to university experts in laser-matter interactions and high-energy-density physics, on the basis of brief proposals focused on basic science. Other ICF facilities have similar outreach programs; more than 100 graduate

1  

 Science Based Stockpile Stewardship, JASON report, JSR-94-345, the MITRE Corp., McLean, Virginia, November 1994.



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Review of the Department of Energy's Inertial Confinement Fusion Program: The National Ignition Facility 2 Relevance of the National Ignition Facility to Science Based Stockpile Stewardship Ignition is relevant to SBSS, but the NIF will make contributions to SBSS independent of ignition: Its experimental program will help attract and train people in weapons-related skills, provide microphysics data, enhance integrated code validation, and create hohlraum conditions unique in a laboratory setting (high radiation temperatures foremost among them). PEOPLE One of the stated goals of the SBSS program is to maintain core intellectual and technical competencies in nuclear weapons in the absence of nuclear testing. Previous reviews1 have recognized that a successful SBSS program requires the ability to sustain and enhance the scientific competence of the National Laboratories. In particular, the National Laboratories must be able to attract, train, and retain competent and creative scientists with the skills necessary to understand nuclear weapons and to certify the stockpile. Appropriate personnel are best attracted and retained by the opportunity to participate in challenging basic research. The maintenance and renewal of technical skills and overall scientific competence can be best fostered through ambitious technical challenges and the opportunity for scientific recognition, both through publication in the open literature and through performance in the classified community. These conditions are important to ensuring an imaginative and high-quality SBSS program. The committee believes that a stewardship program based only on the static knowledge and technology of the past would find it difficult to attract and maintain the necessary scientific talent. The stewardship community must be able to respond to unforeseen challenges, including technical issues in support of treaty negotiations, as well as the recognized issues of safety, security, reliability, aging, remanufacturing, and proliferation monitoring and control. Maintaining core intellectual and technical competencies requires a challenging theoretical, computational, and experimental program in the areas of implosion hydrodynamics, instabilities and mix, radiation transport, and theormonuclear burn. In the committee's judgment, ICF provides a unique synthesis of these relevant physics areas, and the NIF would provide unique capabilities for basic experiments in atomic physics, radiation flows, plasma physics, and hydrodynamics. In the collective judgment of the committee, the NIF should stimulate the scientific imagination and attract excellent scientists and engineers more than any other proposed element of SBSS. This assertion is supported by the ICF program's history of attracting and retaining high-quality personnel. While it is difficult to quantify how much more successful the NIF would be in attracting personnel than other proposed SBSS facilities, a majority of the committee members are involved in the training of scientists, and their consensus is that they would more strongly encourage their students to work on the NIF than on any other proposed SBSS facility. The attraction of the NIF is so high that, indeed, it may be a management and leadership challenge to keep the ICF program in proper balance with the rest of SBSS. Universities are the primary source of scientific and technical talent, and the NIEF will provide new opportunities for university-National Laboratory synergism, both in personnel and in science. Beyond the long-standing LLE effort at the University of Rochester, universities have been involved in the ICF program at a modest but increasing rate since recent declassification of much of the program. For example, a new program makes about 10% of the NOVA shots available, at no charge, to university experts in laser-matter interactions and high-energy-density physics, on the basis of brief proposals focused on basic science. Other ICF facilities have similar outreach programs; more than 100 graduate 1    Science Based Stockpile Stewardship, JASON report, JSR-94-345, the MITRE Corp., McLean, Virginia, November 1994.

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Review of the Department of Energy's Inertial Confinement Fusion Program: The National Ignition Facility students and some $5 million in funding are involved. These opportunities can be exploited most effectively by moving from the present National Laboratory-driven university grant program to the very successful user models in nuclear physics, high-energy physics, and basic energy sciences. Here, large facilities are regarded as tools available to both university and National Laboratory scientists for collaborative pursuit of shared scientific goals. Furthermore, university participants have typically been supported by funding independent of the National Laboratories, usually from either the DOE Office of Energy Research or the National Science Foundation. CERTIFICATION OF WEAPONS STEWARDS Predicting ICF results in well-diagnosed experiments and ultimately achieving ignition are in many respects more technically demanding than making a nuclear weapon work. Significant surprises in NIF results might be an objective signal of inadequacies in the SBSS program and would spur efforts to improve basic understanding of weapons physics. Prior to the start of the moratorium on nuclear testing, weapons designers could unambiguously confirm judgment and refine their skills through the success or failure of their devices in underground tests. In the new era of a complete nuclear test ban, the NIF can provide weapons stewards with a similarly challenging alternative for refining and proving their skills. Hydrodynamic motion, radiation flow in diverse geometries, and ultimately capsule ignition and burn would be examined in great detail in NIF experiments. The ability to do "pre-shot" modeling of these phenomena will be a significant certification of weapons stewards' skills and a continuing challenge for those skills. CODE VALIDATION AND MATERIALS PROPERTIES Several relatively new experimental programs exploit lasers and pulsed power to collect data and validate the weapons physics in codes relevant to SBSS. These efforts are aimed at understanding genuinely three-dimensional systems and measuring opacities, equations of state, the dynamic response of materials, hydrodynamics, and radiative transfer. These studies do not have sharp requirements in laser energy or performance; indeed, they have been carried out at NOVA, as well as at the LANL Trident laser facility, NRL's NIKE laser facility, and LLE's OMEGA. However, the NIEF would carry these studies into new and more relevant domains. It is expected that the NIF would provide a controlled environment from which extensive and novel data can be extracted for both ICF and SBSS applications. Such data are critical for the validation of the design codes that are applied to ICF targets and are relevant to the prediction, evaluation, and analysis of weapons physics issues. While other facilities are expected to provide similar data, the NIF would access different regimes of such parameters as temperature, density, and scale length. This full suite of data is required to attempt to meet SBSS objectives under the Comprehensive Test Ban Treaty. The complex physics involved in ICF and SBSS studies implies a corresponding complexity in the radiation-hydrodynamics codes used; these codes push the state of the art in many ways, including differencing methods, parallel computation techniques, and physics modules. Even in the absence of ignition, the NIF has key roles to play in the maturation, maintenance, and advanced development of these codes, which have a use in other DOE technical and scientific programs. In addition to providing data for critical, yet standardized, tests of codes (including grid resolution and convergence studies), the NIF environment would allow some of the physics models involved to be developed, tested, and evaluated. Since a first-principles formulation of such models is generally not possible at this time, the phenomenology used must be calibrated against an extensive and reliable database spanning the range of expected conditions. The NIF may be the best tool to provide this calibration for many of the models of interest. For example, ions with high atomic number have a complex set of electronic configurations and ionization states whose descriptions strain both computational and experimental techniques. A benchmark class of experiments with the NIF will both calibrate and validate advanced computer codes that can be used to extend opacity tables and equation-of-state formulae into regimes important to both

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Review of the Department of Energy's Inertial Confinement Fusion Program: The National Ignition Facility ICF and SBSS. Current computer codes have limited capabilities to treat fully relativistic ionization and impact cross sections and reaction rates that are required to create reliable stand-alone simulation tools for design, analysis, and evaluation. Much of the empiricism in weapons understanding and analysis is related to the fundamental issues of material mix and hydrodynamic instabilities. These issues can be addressed through experiments with the NEF, which would allow the detailed study of instabilities of many materials at densities and temperatures relevant to the stockpile. Experiments that simulate specific weapons-relevant geometries would be of particular interest. Current and former members of the weapons community are debating the extent to which the data to be gained on facilities such as the NIF are applicable to the stockpile. As SBSS is a venture into uncharted technical and organizational territory, this issue can only be resolved by experience. Although many real engineering issues would not be tested directly on facilities such as the NIF, a skilled practitioner could use NIF experiments to develop an understanding of the relevant physics and apply the judgment he develops to analyze stockpile problems as they arise. IGNITION In terrestrial environments to date, significant thermonuclear burn in a dense plasma occurs only in weapons. Achieving ignition on the NIF would thus open a new realm of physical study relevant to weapons science, to basic research, and to energy production. Among the possibilities are the following: The study of burn in the presence of mix. The physics of thermonuclear bum in the presence of mixed materials is central to nuclear weapons and to the consequences of defects and aging. The diagnosis of ICF plasmas. Because of the sensitivity of burn to various plasma conditions (temperature, density, geometries, impurities, and others), the detection of burn products will be a novel diagnostic of ICF plasmas. For example, diagnosing highly compressed, somewhat asymmetric, and partly-mixed targets is very difficult. The copious fusion products, which can be used for imaging and spectral analyses, should provide the best diagnostic for implosion quality. High-energy-density-phenomena. Ignition with the NIF would enable a closer approach to the energy densities of weapons (and some astrophysical situations) than that possible at any other laboratory facility; an x-ray spectrum desired for weapons effects studies would also be produced. In progressing from NOVA to the NIF to ignition with the NIF, each step represents approximately a one-order-of-magnitude increase in x-ray yield. Ignition on the NIF would create laboratory environments at multi-keV temperatures. Proof-of-principle for inertial fusion energy (IFE). Much of the target physics for initial fusion energy (the use of ICF for commercial-scale power production) is driver independent. The NIF would enable study of the relative merits of direct and indirect drive, as well as a range of target designs. These studies will help to quantify the beam energy and beam quality requirements for ignition and for future reactor designs.