Abstract

Damages induced on the tungsten surface at two different operating conditions of a kilojoule plasma focus device are studied. In one condition, the tungsten samples were exposed to axial plasma shocks that are formed after pinch disruption, and in the other condition, the pinch phenomenon was absent or weak. Melting, craters, and cracking on the surfaces were observed in both cases. In the former case, the charged particle beams and post-pinch material ejection will play a role in impacting the surface; however, in the latter case those phenomena will have small contributions because of the absence or weak formation of the pinch. A damage factor of similar to 10(9) W m(-2) s(0.5) was estimated at a distance of 3 cm from the pinch exit using the method given in Akel et al. [J. Fusion Energy 35, 694-701 (2016)] and Klimov et al. [J. Nucl. Mater. 390, 721-726 (2009)] for the former case. The present work suggests that at pressures lower than the pinch-occurring pressure, only axial plasma shock effects on the targeted surface can be studied and that they can be separated from the effects produced by the charged particle beams mixed with axial plasma shocks in the case of pinch occurrence.