DOE OSTI2013
Recent advances in technology has made possible to create matter with extremely high energy density (energy densities and pressure exceeding 10 11 J/m 3 and 1 Mbar respectively). The field is new and complex. The basic question for high energy density physics (HEDP) is how does matter behave under extreme conditions of temperature, pressure, density and electromagnetic radiation? The conditions for studying HEDP are normally produced using high intensity short pulse laser, x-rays, particle beams and pulsed power z-pinches. Most of these installations occupy a large laboratory floor space and require a team consisting of a large number of scientists and engineers. This limits the number of experiments that can be performed to explore and understand the complex physics. A novel way of studying HEDP is with a compact x-pinch in university scale laboratory. The x-pinch is a configuration in which a pulsed current is passed through two or more wires placed between the electrodes making the shape of the letter ‘X’. Extreme conditions of magnetic field (> 200 MGauss for less than 1 ns), temperature (1 keV) and density (~ 10 22 cm -3 ) are produced at the cross-point, where two wires make contact. Further, supersonic jets are produced on either side of the cross-point. The physics of the formation of the plasma at the cross-point is complex. It is not clear what role radiation plays in the formation of high energy density plasma (>> 10 11 J/m 3 ) at the cross-point. Nor it is understood how the supersonic jets are formed. Present numerical codes do not contain complex physics that can take into account some of these aspects. Indeed, a comprehensive experimental study could answer some of the questions, which are relevant to wide-ranging fields such as inertial confinement fusion, astrophysical plasmas, high intensity laser plasma interactions and radiation physics. The main aim of the proposal was to increase the fundamental understanding of high energy density physics and particularly address the key issues associated with x-pinches, which include radiation transport, energetic particle transport, supersonic jet formation, using state-of-the-art compact pulsed power drivers. All the primary objectives of the proposed work were met. These objectives include: • Understanding of the fundamental physics of hot and dense plasma formation, implosion to less than 1 µm size due to the radiation enhanced collapse and energetic electron heating, • Study of the jet formation mechanism, which is of interest due to the astrophysical jets and deposition of energy by energetic electrons in jets, • Characterization of an x-pinch as a point x-ray source for the phase contrast radiography of beryllium cryogenic targets for the National Ignition Facility (NIF) experiments. The work carried out included a strong educational component involving both undergraduate and graduate students. Several undergraduate students from University of California San Diego participated in this project. A post-doctoral fellow, Dr. Simon Bott and two graduate students, David Haas and Erik Shipton contributed to every aspect of this project. The success of the project can be judged from the fact that fifteen peer-reviewed papers were published in high quality journals. In addition several presentations were made to a number of scientific meetings.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗