Scaling Laws of Nitrogen Soft X-Ray Yields from 1 to 200 kJ Plasma Focus

Numerical experiments are carried out systematically to determine the nitrogen soft x-ray yield for optimized nitrogen plasma focus with storage energy E₀ from 1 kJ to 200 kJ. Scaling laws on nitrogen soft x-ray yield, in terms of storage energies E₀, peak discharge current I_peak and focus pinch current I_pinch were found. It was found that the nitrogen x-ray yields scales on average with y_sxr, N= 1.93xE_o¹.21 J (E₀ in kJ) with the scaling showing gradual deterioration as E₀ rises over the range. A more robust scaling is y_sxr = 8x10^-8I⁰3.38_pinch . The optimum nitrogen soft x-ray yield emitted from plasma focus is found to be about 1 kJ for storage energy of 200 kJ. This indicates that nitrogen plasma focus is a good water-window soft x-ray source when properly designed. (author)