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Title: Investigation of ablation and implosion dynamics in linear wire arrays

Abstract

Ablation and implosion dynamics were investigated by optical probing in linear wire arrays of different geometry. Formation of ablation jets begins on the outermost wires. In the beginning of implosion plasma bubbles arise in breaks on the outer wires. Implosion bubbles move to the next wire in the array and hit the plasma column with the speed >250 km/s. Imploding plasma moves to the center of the array cascading from wire to wire. Configuration of magnetic fields in the linear array can be changed by variation of wire spacing. The regimes of ablation and implosion in the wire arrays are found to differ with different wire spacing.

Authors:
; ; ; ; ;  [1];  [2];  [2]
  1. University of Nevada, Reno, 5625 Fox Avenue, Reno, Nevada 89506 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20974884
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 3; Other Information: DOI: 10.1063/1.2716665; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ABLATION; BUBBLES; CONFIGURATION; EXPLODING WIRES; EXPLOSIONS; GEOMETRY; IMPLOSIONS; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; PLASMA; PLASMA DIAGNOSTICS; PLASMA JETS

Citation Formats

Ivanov, V. V., Sotnikov, V. I., Haboub, A., Sarkisov, G. E., Presura, R., Cowan, T. E., Ktech Corporation, Albuquerque, New Mexico 87123, and University of Nevada, Reno, 5625 Fox Avenue, Reno, Nevada 89506. Investigation of ablation and implosion dynamics in linear wire arrays. United States: N. p., 2007. Web. doi:10.1063/1.2716665.
Ivanov, V. V., Sotnikov, V. I., Haboub, A., Sarkisov, G. E., Presura, R., Cowan, T. E., Ktech Corporation, Albuquerque, New Mexico 87123, & University of Nevada, Reno, 5625 Fox Avenue, Reno, Nevada 89506. Investigation of ablation and implosion dynamics in linear wire arrays. United States. doi:10.1063/1.2716665.
Ivanov, V. V., Sotnikov, V. I., Haboub, A., Sarkisov, G. E., Presura, R., Cowan, T. E., Ktech Corporation, Albuquerque, New Mexico 87123, and University of Nevada, Reno, 5625 Fox Avenue, Reno, Nevada 89506. Thu . "Investigation of ablation and implosion dynamics in linear wire arrays". United States. doi:10.1063/1.2716665.
@article{osti_20974884,
title = {Investigation of ablation and implosion dynamics in linear wire arrays},
author = {Ivanov, V. V. and Sotnikov, V. I. and Haboub, A. and Sarkisov, G. E. and Presura, R. and Cowan, T. E. and Ktech Corporation, Albuquerque, New Mexico 87123 and University of Nevada, Reno, 5625 Fox Avenue, Reno, Nevada 89506},
abstractNote = {Ablation and implosion dynamics were investigated by optical probing in linear wire arrays of different geometry. Formation of ablation jets begins on the outermost wires. In the beginning of implosion plasma bubbles arise in breaks on the outer wires. Implosion bubbles move to the next wire in the array and hit the plasma column with the speed >250 km/s. Imploding plasma moves to the center of the array cascading from wire to wire. Configuration of magnetic fields in the linear array can be changed by variation of wire spacing. The regimes of ablation and implosion in the wire arrays are found to differ with different wire spacing.},
doi = {10.1063/1.2716665},
journal = {Physics of Plasmas},
number = 3,
volume = 14,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • Coiled arrays, a cylindrical array in which each wire is formed into a helix, suppress the modulation of ablation at the fundamental wavelength. Outside the vicinity of the wire cores, ablation flow from coiled arrays is modulated at the coil wavelength and has a 2-stream structure in the r,{theta} plane. Within the vicinity of the helical wires, ablation is concentrated at positions with the greatest azimuthal displacement and plasma is axially transported from these positions such that the streams become aligned with sections of the coil furthest from the array axis. The GORGON MHD code accurately reproduces this observed ablationmore » structure, which can be understood in terms of JxB forces that result from the interaction of the global magnetic field with a helical current path as well as additional current paths suggested by the simulations. With this ability to control where ablation streamers occur, large wavelength coils were constructed such that the breaks that form in the wires had sufficient axial separation to prevent perturbations in the implosion sheath from merging. This produces a new mode of implosion in which the global instability can be controlled and perturbations correlated between all wires in an array. For large wavelength 8-wire coiled arrays, this produced a dramatic increase in x-ray power, equalling that of a 32-wire straight array. These experiments were carried out on the MAGPIE generator (1 MA, 240 ns) at Imperial College, and the COBRA generator (1 MA, 100 ns) at Cornell University.« less
  • The results of experiments with combined aluminum (Al) and stainless steel (SS) alloy 304, nested wire arrays from the 1 MA COBRA generator at Cornell University are presented. The loads studied consisted of a 6 mm diameter inner array and a 13 mm diameter outer array with a different material in each array: SS or aluminum. Al implodes before SS in all loads studied, even when Al was on the inner array. The new wire ablation dynamic model and spectroscopic modeling are used to interpret these data. The observed implosion dynamics are likely a result of the higher ablation ratemore » of Al. These initial results suggest that combining wire materials with different ablation rates in wire array loads could be developed into a useful technique for x-ray pulse shaping and radiation yield optimization.« less
  • Results are presented from experimental studies on the implosion of arrays made of wires and metalized fibers under the action of current pulses with an amplitude of up to 3.5 MA at the Angara-5-1 facility. The effect of the parameters of an additional linear mass of bismuth and gold deposited on the wires/fibers is investigated. It is examined how the material of the wires/fibers and the metal coating deposited on them affect the penetration of the plasma with the frozen-in magnetic field into a cylindrical array. Information on the plasma production rate for different metals is obtained by analyzing opticalmore » streak images of imploding arrays. The plasma production rate m-dot{sub m} for cylindrical arrays made of the kapron fibers coated with bismuth is determined. For the initial array radius of R{sub 0} = 1 cm and discharge current of I = 1 MA, the plasma production rate is found to be m-dot{sub m} approx. 0.095 ± 0.015 μg/(cm{sup 2} ns)« less
  • Star and cylindrical wire arrays were studied using laser probing and X-ray radiography at the 1-MA Zebra pulse power generator at the University of Nevada, Reno. The Leopard laser provided backlighting, producing a laser plasma from a Si target which emitted an X-ray probing pulse at the wavelength of 6.65 Å. A spherically bent quartz crystal imaged the backlit wires onto X-ray film. Laser probing diagnostics at the wavelength of 266 nm included a 3-channel polarimeter for Faraday rotation diagnostic and two-frame laser interferometry with two shearing interferometers to study the evolution of the plasma electron density at the ablation and implosionmore » stages. Dynamics of the plasma density profile in Al wire arrays at the ablation stage were directly studied with interferometry, and expansion of wire cores was measured with X-ray radiography. The magnetic field in the imploding plasma was measured with the Faraday rotation diagnostic, and current was reconstructed.« less
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