Modern Physics Letters B, Vol. 16, No. 9 (2002) 309–318 c  World Scientific Publishing Company SOFT X-RAY EMISSION IN THE (1.0–1.5 KEV) WINDOW WITH NITROGEN FILLING IN A LOW ENERGY PLASMA FOCUS M. SHAFIQ, SARTAJ, S. HUSSAIN, M. SHARIF, S. AHMAD and M. ZAKAULLAH Department of Physics, Quaid-i-Azam University, 45320 Islamabad, Pakistan A. WAHEED PINSTECH, P.O. Box 2151, 44000 Islamabad, Pakistan G. MURTAZA Salam Chair in Physics, Government College, 54000 Lahore, Pakistan R. AHMAD Centre for Advanced Studies in Physics, Government College, 54000 Lahore, Pakistan Received 30 March 2002 A study of soft X-ray emission in the 1.0–1.5 keV energy range from a low energy (1.15 kJ) plasma focus has been conducted. X-rays are detected with the combination of Quantrad Si PIN-diodes masked with Al (50 μm), Mg (100 μm) and Ni (17.5 μm) filters and with a pinhole camera. The X-ray flux is found to be measurable within the pressure range of 0.1–1.0 mbar nitrogen. In the 1.0–1.3 keV and 1.0–1.5 keV windows, the X-ray yield in 4π-geometry is 1.03 J and 14.0 J, respectively, at a filling pressure of 0.25 mbar and the corresponding efficiencies are 0.04% and 1.22%. The total X-ray emission in 4π-geometry is 21.8 J, which corresponds to the system efficiency of about 1.9%. The X-ray emission is found dominantly as a result of the interaction of energetic electrons in the current sheath with the anode tip. Images recorded by the pinhole camera confirm the emission of X-rays from the tip of the anode. 1. Introduction The plasma focus is well known as a source of fusion neutrons and X-rays. 1 Besides being a ready source of hot dense plasma and fusion neutrons, the focus also emits plentiful amounts of soft X-rays, especially when operated with high Z gases rather than deuterium. Because of its simple construction, cost-effectiveness and easy maintenance, the plasma focus appears to be a promising device for X-ray generation with enhanced efficiency. 2 Sadowski et al. 3 found the fine structure of soft X-ray (0.8–3 keV) emitting zones in a neutron optimized plasma focus. They investigated the distinct continuous filaments registered during the pinch phase. Their time-resolved X-ray measurements show that the filamentation exists 20– 309