In a generalized beam-target model, the "Gyrating Particle Model" (GPM), the strong suprathermal fusion production of both dynamic phases of the plasma focus POSEIDON (W o = 280 kJ, U o = 60 kV, Mather type) is considered to be due to the fast accelerated deuterons gyrating in pinch structures. The results of this new model are compared with spectrally and spatially resolved measurements of fusion protons and accelerated deuterons, to give evidence of the validity of this generalized beam-target model for both phases. Statements are obtained on the number and distribution function of accelerated deuterons, necessary to explain the observed fusion yield.

The paper presents a comparison of the main characteristics and experimental results obtained in plasma focus (PF) experiments in the POSEIDON 500 kJ facility in Stuttgart and the PF-360 kJ device in Świerk. Parameters of various electrodes and insulators are given, and studies on the evolution of the discharges are summarized. Selected data on X-ray, ion and neutron emission are given. Also presented are recent experimental results — a maximum neutron yield of up to 2.5 × 1011 for 500 kJ/80 kV runs with a new ceramic insulator in POSEIDON and an average neutron yield of 1.2 × 1011 for operation at 171 kJ/36 kV in PF-360. Particular attention is paid to the neutron scaling and the saturation effects observed at higher energy and current levels. Proposals are made for new experimental studies which can facilitate further progress in PF research.

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The energy and mass analysis of ions emitted from a 50-kJ, 18-kV, plasma focus machine was performed with a Thomson analyzer. Energy distribution functions offast deuterons (E>350 keV) and those of impurity ions have been determined. The energy distributions of the 0, N, and C impurity ions in different ionization states have similar character. They usually increase exponentially and after reaching the maximum at E /Z;:::: 1.0 Me V they decrease exponentially to E /Z;:::: 1.8 MeV. For deuterons at lower operating pressures (Po<2 mbar) the energy distribution measured decreases exponentially from 0.35 to about 3.0 MeV. In some cases, independent of the operating pressure, the maximum energies of the distribution extend to 0.5-1.5 MeV only. With an argon admixture (up to 4.5%) Ar+ -Ar7+ ions of energy from 0.5 to 14 MeV are produced.

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