Experiments Conducted on the Electron Beam Produced by a Dense Plasma Focus

An experimental investigation was conducted using a 34-kJ Dense Plasma Focus (DPF) in which the possible enhancement of the electron beam was addressed. Electron beams ejected from the DPF have been observed to exceed 30 kA with pulse durations of a few nanoseconds. Enhancement was considered to be either an increase in the probability that the peak beam current exceeded some lower limit, or an increase in the mean energy of the beam electrons. The investigation was divided into two parts, each addressing one of the aspects of enhancement. In the first part of the investigation, an axial magnetic field was introduced into the beam drift region so as to reduce beam loss due to contact with the conductive walls of the drift tube. The beam guiding apparatus was shown to increase the probability of observing a beam with a peak current greater than 10 kA from 10% of the DPF discharges to 20%. The second part of the investigation initially addressed the apparent increase in the beam electron's mean energy produced by the introduction of a secondary discharge in the DPF pinch region prior to pinch formation. However, on the average, the presence in the DPF chamber of a third electrode which was necessary to produce the secondary discharge had an adverse effect on the transmission of the electron beam through the drift tube. This effect, which was shown to be inversely related to the distance between the DPF anode and the third electrode, subsequently became the main emphasis of the second part of the investigation. The diagnostic results obtained during the investigation were not sufficient to conclusively determine the role of the third electrode in the beam disturbance; however, it is speculated that the presence of the third electrode caused internal currents to circulate which magnetically deflected the electron beam from entering the drift tube region.