Study of gas-puff Z-pinches on COBRA

Abstract

Gas-puff Z-pinch experiments were conducted on the 1 MA, 200 ns pulse duration Cornell Beam Research Accelerator (COBRA) pulsed power generator in order to achieve an understanding of the dynamics and instability development in the imploding and stagnating plasma. The triplenozzle gas-puff valve, pre-ionizer, and load hardware are described. Specific diagnostics for the gas-puff experiments, including a Planar Laser Induced Fluorescence system for measuring the radial neutral density profiles along with a Laser Shearing Interferometer and Laser Wavefront Analyzer for electron density measurements, are also described. The results of a series of experiments using two annular argon (Ar) and/or neon (Ne) gas shells (puff-on-puff) with or without an on-(or near-) axis wire are presented. For all of these experiments, plenum pressures were adjusted to hold the radial mass density profile as similar as possible. Initial implosion stability studies were performed using various combinations of the heavier (Ar) and lighter (Ne) gasses. Implosions with Ne in the outer shell and Ar in the inner were more stable than the opposite arrangement. Current waveforms can be adjusted on COBRA and it was found that the particular shape of the 200 ns current pulse affected on the duration and diameter of the stagnated pinched column and the x-ray yield. V C 2014 AIP Publishing LLC. [http://dx.

The Generation of Warm Dense Matter Samples Using Fast Magnetic Compression

“…In this case, the current stays in the shell or switch to the rod. Experiments using a Ne-on-Ar gas-puff Z -pinch [27] showed that the pinch column is much tighter when an aluminum wire is placed on axis (see [27,Fig. 21]) compared with the case without wire [27, Fig.…”

MA-class linear transformer driver for Z -pinch research

“…If the driver has a sizable prepulse, then the prepulse may be able to produce enough ionization through the gas before the main pulse arrives. Alternatively, an external system can be used to preionize the gas before the driver pulse; several methods have been reported in the literature, including the use of microwaves [55], electron beams [56], or UV irradiation [57,58]. A uniform initial ionization is thought to improve the reproducibility and symmetry of the pinch [52].…”

“…Because of zippering and MRT instability growth, the plasma column disrupts first near the cathode electrode, coincident in time with the K-shell x-ray emission peak (Ti-filtered photodiode). Mitigation of MRT instability growth has received significant attention in the literature, and several techniques have been investigated to reduce the impact of MRT instability on Z pinches, including sheared flow [65], field-line tension via addition of an external axial magnetic field B z [66,67], and tailored or multishell density profiles [58,[68][69][70].…”