Mary Ann Sweeney

Chamber dynamic research with pulsed power

In Inertial Fusion Energy (IFE), Target Chamber Dynamics (TCD) is an integral part of the target chamber design and performance. TCD includes target output deposition of target x-rays, ions and neutrons in target chamber gases and structures, vaporization and melting of target chamber materials, radiation-hydrodynamics in target chamber vapors and gases, and chamber conditions at the time of target and beam injections. Pulsed power provides a unique environment for IFE-TCD validation experiments in two important ways: they do not require the very clean conditions which lasers need and they currently provide large x-ray and ion energies.

History of z-pinch research in the U.S.

Over the years, the scientific community has been fascinated with z pinches. Z-pinch references include papers on the quest for fusion, on applications for radiation effects testing, lithography, x-ray microscopy, and pumping x-ray lasers, and on the production of intense magnetic fields. Because much of the research has been pursued elsewhere-in the USSR, Russia, England, Germany, and Chile, among other countries-we must place the U.S. work in an international context. We assert here that the z pinch is a valuable asset for its applications, chiefly those related to the production of x rays, but it is a tool that has sometimes deceived us with its seeming simplicity.

Chapter 9 Memories of Shock Wave Research at Sandia

These individual recollections present a window into the personal experiences of people who participated in the shock wave research program at Sandia. We made a strong effort to contact and encourage as many people as possible to participate. Over 80 people were contacted and about 40 provided recollections of their personal experiences. Each contributor was asked to provide a summary of their role in shock wave research at Sandia, bringing out any interesting events or anecdotes that happened along the way

Chapter 8 Looking to the Future

The synopsis of shock wave science presented in this book describes the pioneering research conducted at Sandia over the past 60 years. The shock wave program was organized and conducted rather differently from that of similar research programs at other institutions. Two separate shock wave research efforts were established in the 1950s, one focused on scientific understanding of shock compression processes and the other on engineering applications.

Chapter 5 The 1980s: Heady Times

The previous two decades of shock wave research at Sandia led to (1) advances in experimental techniques, (2) measurements of dynamic material response for a wide range of materials, (3) state-of-the-art material models, and (4) a family of 1-D and 2-D computer codes that could simulate materials used in weapon components and subsystems with considerable accuracy. However, full three-dimensional (3-D) code capabilities were needed for higher fidelity simulations of weapon components and subsystems.

Chapter 6 The 1990s: Black Monday

The 1990s were turbulent times for shock wave research at Sandia because of the near elimination of experimental shock wave research, including experimental facilities. Three management decisions led to this challenging event. The first decision was implementation of a laboratory-wide restructuring of management in the early 1990s. As a consequence, all Sandia departments, including the second-level (i.e., the original department management level) ones that involved shock wave research managed by George Samara and Jim Asay, were dissolved. The first-level divisions (now renamed departments) that had been supervised by Samara and Asay became individual departments under the direct supervision of two different directors. In addition, Walt Herrmann stepped down as the Director of Engineering Sciences; that was the directorate in which Asay’s shock wave department had resided. The directorate was then eliminated, and the shock wave divisions that Asay had managed were transferred to Ed Barsis, who was the Director of the Computing Research Center. This resulted in a two-level management structure, with each director supervising the direct-reporting managers, as opposed to the previous situation in which three or four second-level managers reported to each director.

Chapter 3 The 1960s: Explosive Growth

The 1960s witnessed phenomenal growth of shock wave capabilities at Sandia. Along with rapidly evolving techniques for producing precisely controlled loading at ever-increasing shock pressures, pivotal improvements in precision diagnostics were occurring at a record rate. The goal was to probe the detailed structure of shock waves to understand specific aspects of dynamic material response, such as the ubiquitous two-wave structure observed in materials that exhibit both elastic and plastic response under shock loading. This information was needed for the new material models being developed. It was important, as well, to apply this new technology to the pressing requirements of the nation’s defense community. In particular, it was necessary to understand the stress response of materials in nuclear environments, such as the stress wave response of materials subjected to pulsed radiation sources, so that appropriate experimental techniques and material models could be developed to simulate effects on weapon components and systems.

Chapter 2 The 1950s: Origins

Shock compression science, in its modern form, evolved from the early work conducted at Los Alamos resulting from the Manhattan Project. That work, of course, was an important aspect of the development of nuclear weapons, first the fission bomb toward the end of World War II and then the fusion bomb, both of which were mainstays of the Cold War era.

Chapter 4 The 1970s: New Opportunities

In 1973 a laboratory-wide reduction in Sandia staff was implemented that caused major reverberations in shock wave research. As Barry Butcher stated in his recollections:

Chapter 7 The 2000s: A New Millennium

After the turn of the century, dramatic changes occurred in experimental and theoretical shock wave research at Sandia. In the 1950s and 1960s, computational capabilities to design and interpret shock wave experiments were extremely limited. Use of slide rules and small desktop calculators was common. In the 1950s instruments to measure the fine details of shock compression and dynamic material response were limited. In those early decades, the innovation and intuition of experimentalists and modelers were critical in advancing shock wave research in spite of these constraints. By the late 1960s, dynamic phenomenological models to describe the shock compression of complex materials such as composites and porous materials were beginning to be established. The pioneering loading and diagnostic technology developed in the 1960s was instrumental in advancing knowledge in the later decades. This was especially true for high-pressure applications until the mid-1970s, when time-resolved gauges became available for routine use at Sandia. Bob Graham and his team concentrated on developing the piezoelectric gauge, which is also known as the quartz gauge (Graham 1961a, b; Graham 1975; Neilson and Benedick 1960; Neilson et al. 1962; Graham and Ingram 1968; Graham and Reed 1978). Meanwhile, Lynn Barker and his team concentrated on developing optical interferometric gauges and, in particular, the velocity interferometer system for any reflector (or VISAR), which grew out of a wide-angle version of the Michelson interferometer (Barker and Hollenbach 1965, 1972; Barker 1968, 2000a). This allowed considerable progress in understanding dynamic compression processes. Among early researchers, there was an excitement in developing pioneering new capabilities and solving complex dynamic material problems using the new gauges.