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Title: Wire Initiation Studies at the University of Nevada-Reno: An LDRD Report

Abstract

Wire explosion experiments have been carried out at the University of Nevada, Reno. These experiments investigated the explosion phase of wires with properties and current-driving conditions comparable to that used in the initial stage of wire array z-pinch implosions on the Z machine at Sandia National Laboratories. Specifically, current pulses similar to and faster than the pre-pulse current on Z (current prior to fast rise in current pulse) were applied to single wire loads to study wire heating and the early development of plasmas in the wire initiation process. Understanding such issues are important to larger pulsed power machines that implode cylindrical wire array loads comprised of many wires. It is thought that the topology of an array prior to its acceleration influences the implosion and final stagnation properties, and therefore may depend on the initiation phase of the wires. Single wires ranging from 4 to 40 pm in diameter and comprised of material ranging from AI to W were investigated. Several diagnostics were employed to determine wire current, voltage, total emitted-light energy and power, along with the wire expansion velocity throughout the explosion. In a number of cases, the explosion process was also observed with x-ray backlighting using x-pinches.more » The experimental data indicates that the characteristics of a wire explosion depend dramatically on the rate of rise of the current, on the diameter of the wire, and on the heat of vaporization of the wire material. In this report, these characteristics will be described in detail. Of particular interest is the result that a faster current rise produces a higher energy deposition into the wire prior to explosion. This result introduces a different means of increasing the efficiency of wire heating. In this case, the energy deposition along the wire and its subsequent expansion, is uniform compared to a ''slow'' current rise (170 A/ns compared to 22 A /s current rise into a short circuit) and the expansion velocity is larger. The energy deposition and wire expansion is further modified by the wire diameter and material. Investigations of wire diameter indicate that the diameter primarily effects the expansion velocity and energy deposition; thicker wires explode with greater velocities but absorb less energy per atom. The heat of vaporization also categorizes the wire explosion; wires with a low heat of vaporization expand faster and emit less radiation than their high heat of vaporization counterparts.« less

Authors:
;
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
791889
Report Number(s):
SAND2001-3361
TRN: US0200698
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Nov 2001
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; PINCH EFFECT; EXPLODING WIRES; ACCELERATION; HEATING; IMPLOSIONS; STAGNATION; VAPORIZATION HEAT; LINEAR Z PINCH DEVICES

Citation Formats

DOUGLAS, MELISSA R, and BAUER, BRUNO. Wire Initiation Studies at the University of Nevada-Reno: An LDRD Report. United States: N. p., 2001. Web. doi:10.2172/791889.
DOUGLAS, MELISSA R, & BAUER, BRUNO. Wire Initiation Studies at the University of Nevada-Reno: An LDRD Report. United States. doi:10.2172/791889.
DOUGLAS, MELISSA R, and BAUER, BRUNO. Thu . "Wire Initiation Studies at the University of Nevada-Reno: An LDRD Report". United States. doi:10.2172/791889. https://www.osti.gov/servlets/purl/791889.
@article{osti_791889,
title = {Wire Initiation Studies at the University of Nevada-Reno: An LDRD Report},
author = {DOUGLAS, MELISSA R and BAUER, BRUNO},
abstractNote = {Wire explosion experiments have been carried out at the University of Nevada, Reno. These experiments investigated the explosion phase of wires with properties and current-driving conditions comparable to that used in the initial stage of wire array z-pinch implosions on the Z machine at Sandia National Laboratories. Specifically, current pulses similar to and faster than the pre-pulse current on Z (current prior to fast rise in current pulse) were applied to single wire loads to study wire heating and the early development of plasmas in the wire initiation process. Understanding such issues are important to larger pulsed power machines that implode cylindrical wire array loads comprised of many wires. It is thought that the topology of an array prior to its acceleration influences the implosion and final stagnation properties, and therefore may depend on the initiation phase of the wires. Single wires ranging from 4 to 40 pm in diameter and comprised of material ranging from AI to W were investigated. Several diagnostics were employed to determine wire current, voltage, total emitted-light energy and power, along with the wire expansion velocity throughout the explosion. In a number of cases, the explosion process was also observed with x-ray backlighting using x-pinches. The experimental data indicates that the characteristics of a wire explosion depend dramatically on the rate of rise of the current, on the diameter of the wire, and on the heat of vaporization of the wire material. In this report, these characteristics will be described in detail. Of particular interest is the result that a faster current rise produces a higher energy deposition into the wire prior to explosion. This result introduces a different means of increasing the efficiency of wire heating. In this case, the energy deposition along the wire and its subsequent expansion, is uniform compared to a ''slow'' current rise (170 A/ns compared to 22 A /s current rise into a short circuit) and the expansion velocity is larger. The energy deposition and wire expansion is further modified by the wire diameter and material. Investigations of wire diameter indicate that the diameter primarily effects the expansion velocity and energy deposition; thicker wires explode with greater velocities but absorb less energy per atom. The heat of vaporization also categorizes the wire explosion; wires with a low heat of vaporization expand faster and emit less radiation than their high heat of vaporization counterparts.},
doi = {10.2172/791889},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2001},
month = {11}
}

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