Instability heating of a solid fiber Z-pinch

Abstract

A dense Z-pinch formed by the electrical breakdown of solid CD 2 fibers in an 800 kA, 100 ns risetime pulse generator has been studied with optical and radiation diagnostics. It has been found that, contrary to calculations based on classical joule heating of the plasma that predict approximate dynamic equilibrium, the pinch always expands explosively while displaying intense mϭ0 hydromagnetic instability activity. Excellent agreement with the observed expansion rate as well as with measured electron temperatures and neutron yield has been obtained by including in a simulation code the direct heating of ions by turbulence arising from instability growth.

Carbon fiber Z-pinch driven by microsecond-long capacitive discharge

“…As this means that the plasma pressure rapidly increased, we argued that the expansion was caused by the rise of plasma heating (the growth of a plasma temperature), and/or a transfer of the current in the vicinity of a fiber (the growth of a plasma density). The theory of flux-limited heat flow from a Joule heated corona [15] and the direct heating of ions by the turbulence in an m = 0 instability [10] were suggested as possible explanations of energy deposition into the dense core of a fiber. In addition let it be said that besides the thermal energy, the kinetic energy of the imploded coronal plasma should be considered.…”

“…The first experiments were performed at Naval Research Laboratory [1] and Los Alamos National Laboratory [2,3]. Z-pinch plasma in these experiments seemed to be stable for many radial Alfvén transit times whereas the neutron yield approached 10 10 . This promising result led to the modification of the Z-pinch theory when the arbitrary current distribution, resistivity, viscosity, and thermal conduction were included in MHD.…”

“…Similarly discouraging results were obtained from further and better diagnosed experiments on new generators at NRL [6] and Los Alamos [7] as well as on KALIF at Kernforschungszentrum Karlsruhe [8] and on MAG-PIE at Imperial College in London [9]. The fibers from carbon and deuterated polyethylene were also employed because their discharge behaviour was roughly the same [9,10], and at the same time they were easily available and could be handled much easier than the frozen deuterium ones. To our knowledge, the last experiments with deuterium fibers were performed in the late of 1990's and the idea of nuclear fusion and radiative collapse in fiber Z-pinches was abandoned.…”

Imploding$Z$-Pinch Plasmas Formed From a Carbon Fiber

“…The fibers from the carbon were also tried in these fiber Z-pinch experiments, because their discharge behavior was roughly the same as the frozen deuterium ones (see [7] and [11]); at the same time, they were easily available and could be handled much easier. Most of the experiments utilized highvoltage pulsed-power systems with a fast current rise time, so as to prevent the early expansion of a plasma column [14].…”

Influence of gap length on the gas‐puff z‐pinch plasma produced by an inductive pulsed power system

“…Research on gas-puff z-pinch plasma soft x-ray sources using pinching of a plasma column has recently been undertaken. It is believed that the soft x-rays from the z-pinch plasma are emitted not only by thermal radiation from the high-temperature plasma column formed in the maximum pinch phase, but also from high-temperature high-density plasma regions (hot spots) that are formed locally by the occurrence of plasma instability during the pinching process [8][9][10][11][12][13]. In particular, the spatial stability of hot spots is important in proximity-exposure lithography, since the spatial scatter of hot spots is proportional to the size of the "blurs" in the exposure pattern.…”