Effect of current sheath initiation on the radial collapse and energetic particle acceleration in 10 kJ Dense Plasma Focus
Abstract
The Dense Plasma Focus (DPF) is a pulsed power driven plasma discharge that emits copious X rays and energetic particles, such as electrons, ions and neutrons. The discharge is initialized from a surface breakdown at the insulator sleeve that separates the anode and cathode in a coaxial geometry. Then, the plasma peels off of the insulator surface due to the Lorentz (JxB) force and moves along the coaxial electrodes, sweeping the background gas with it. At the end of this run down phase, when the plasma sheath reaches the end of the electrodes, it turns over and compresses on axis. Charged particles in these devices are accelerated by intense electromagnetic fields produced by instabilities formed during the final radial compression phase. Neutrons, on the other hand, are mainly generated by the beam target mechanism as a byproduct of the instabilities. Even though instability formation and particle acceleration are well known processes in DPFs, open questions regarding particle generation still remain, warranting further investigation. The breakdown and the run down phases in DPF are believed to play a key role on the final radial pinch phase. The breakdown phase depends on several factors, including insulator sleeve dimensions and surface properties. There has been limited work on the study of current initiation. The gas pressure and insulator sleeve dimensions can significantly affect the quality of the pinch and neutron yield. There has not been a comprehensive effort to systematically study the underlying physics and potentially control the initial breakdown phase and its effect on particle energy and yield. Experimental and modeling work is therefore warranted to address the critical aspect of pinch dynamics.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 14, 2022
- Source ID
- FA95501910073
Entities
People
- Farhat Nadeem Beg
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of California, San Diego