The structure in the collapse stage of a linear Z-pinch discharge in helium has been studied by optical methods. Observations with a framing camera, rotating mirror spectrograph, and monochromator have been correlated with magnetic field and current distributions determined by Tam (1967). The luminous regions in a helium pinch are very faint. Therefore, up to twenty exposures have to be superimposed on the same framing camera or rotating mirror record. This requires a high degree of reproducibility in the initiation of the discharge. At high initial pressures, a non-luminous shock wave at the inner edge of the collapsing current shell precedes the luminous plasma layer towards the centre of the discharge vessel. This shock front is followed by a region of predominantly Hel emission, while most of the Hell radiation occurs in the outer regions of the collapsing plasma shell. The separation into Hel and Hell radiating regions is consistent with spectroscopic measurements of temperature: higher temperatures occur at larger radii. Pressure and density in the non-radiating shock wave region are determined by calculations based on a simple model. At low filling pressures, the Hel and Hell regions coincide. The position of maximum luminosity is observed to correspond with the position of maximum current density. The luminosity and current shells coincide with no shock wave preceding the luminous front. Strong continuum radiation is emitted from the centre of the discharge tube as soon as the leading edge of the current shell reaches the axis. This leading edge is luminous at low initial pressures, but becomes a non-radiating shock front at higher filling pressures. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The formative phase of a 40 kV Z-pinch has been investigated in the pressure range from 10 mtorr to 80 mtorr in hydrogen. The energy spectrum of the electrons on the axis of the vessel, the spatial distribution of the current at the face of the anode, the total discharge current and the voltage across the discharge have all been monitored. For the pressures examined, the formative phase lasts a few hundred nanoseconds. At the initiation of the discharge, a current of electrons with energies in excess of 20 keV is observed on the axis. As time progresses, the average energy of the electrons decreases to a few keV and the current density increases to about 300 amps/cm². At pressures of 30 and 50 mtorr-H(2), the electron velocity distribution appears to relax to a Maxwellian [formula omitted]. This result is in agreement with the theoretical description of a weakly ionized gas in a strong electric field. However, it should be noted that the influence of plasma-turbulence has been neglected. The current to the central region of the electrode initially carries more than 50% of the total current through the discharge. This observation indicates that ionization initially occurs throughout the entire discharge vessel. However, shortly after the current of energetic electrons reaches its maximum value, the current to the central region of the electrode disappears. Simultaneously, a transient voltage of up to 20 kV appears across the discharge and the rate of increase of the current exhibits a sharp drop in value. The combination of these phenomena has been interpreted as the formation of the boundary layer. The boundary layer or current sheet is not completely formed until the end of the formative phase. Measurements of the pinch time support this conclusion. At low pressures, the time of formation of the boundary layer is considerably shortened by the enhancement of ionization at the wall. This is caused by the presence of the magnetic field of the current flowing in the central region of the vessel. The experiment has led to better comprehension of the mechanism of boundary layer formation in low pressure Z-pinches. The overall understanding of ionization in Z-pinch discharges has been improved and can be extrapolated to higher pressures. In addition, the observations indicate that the detailed nature of the current sheet collapse can be strongly affected by the formative phase. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 186-193).

Thesis (Ph. D.)--University of Nevada, Reno, 2007. / "May, 2007." Includes bibliographical references (leaves 213-218). Online version available on the World Wide Web.

The microwave resonator technique has been successfully employed in the study of a liquid model of a z pinch. A liquid column has formed an integral part of a microwave cavity, and changes in the frequency of such a cavity have been used to study the growth rates of the current driven instability. The growth rates of the instability are seen to be in agreement with the standard theory for the wavelength equal to three centimeters. It is also seen that a definite stabilization is reached for a finite pinch amplitude. A simple theory balancing compressive streamline forces and magnetic pressure show that the maximum pinched amplitude should grow as the square of the axial current, which is what was observed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No description available.

No description available.

Thesis--University of California, Berkeley, 1960. / "Controlled Thermonuclear Processes, UC-20" -t.p. "TID-4500 (15th Ed.)" -t.p. Includes bibliographical references (p. 13).

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (p. 129-132).

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 128-134).