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Abstract
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Characteristics of the energetic argon ions emitted by a 90 kJ Filippov-type plasma focus are
studied by employing an array of Faraday cups. The Faraday cups are designed to minimize the
secondary electron emission effects on their response. Angular distribution of the ions is measured,
and the results indicate a highly anisotropic emission with a dip at the device axis and a local
maximum at the angle of 7 with respect to the axis. It has been argued that this kind of anisotropic
emission may be related to the surfatron acceleration mechanism and shown that this behavior is
independent of the working gas pressure. It has been also demonstrated that this mechanism is
responsible for the generation of MeV ions. Measuring the total ion number at different working
gas pressures gives an optimum pressure of 0.3 Torr. In addition, the energy spectrum of ions is
measured by taking into account of the ambient gas effects on the energy and charge of the ions.
The current neutralization effect of electrons trapped in the ion beam as well as the effect of
conducting boundaries surrounding the beam, on the detected signals are investigated.
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