Experimental evidence of more than one ions acceleration mechanisms in plasma focus device: Observations and interpretations

Abstract

Charged particle (CP) measurements in dense plasma focus (DPF) devices are important to understand the fundamentals of the CP acceleration mechanism, which is under active investigation. In this work, the results of the CP (ion) measurements obtained from a kilojoule DPF device, PF-2 kJ, are presented. The ion signals were observed in the pressure range of 3–11 mbar of hydrogen gas. The ion signals were recorded by means of Faraday cups (FCs). One FC was mounted in the axial direction, and two FCs were mounted in radial directions (at 180° to each other). Three distinct signals of ions were observed in the FC that was in the axial direction and two in the FCs that were in the radial direction. Later, the ion signals were converted into number densities [NDs (m−3)] at each pressure. The maximum NDs were found at 3 mbar in both directions. The variation in the NDs with pressures suggests the existence of more than one ion acceleration mechanism in the PF-2 kJ. Moreover, at the lower pressures (3 mbar), ion emissions are observed before the dip in the current derivative, which suggests that there are acceleration mechanisms acting not only in the pinch stage but also during the radial compression.