Computational Study of Emitted Spectra from the Neon Plasma Focus
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ORIGINAL RESEARCH
Computational Study of Emitted Spectra from the Neon Plasma Focus M. Akel • S. Alsheikh Salo • C. S. Wong
Published online: 16 March 2013 Ó Springer Science+Business Media New York 2013
Abstract The expected emission spectra (full, Bremsstrahlung, recombination, and line) of neon focussed plasma have been studied for different conditions. Expected neon plasma spectra at certain electron temperature range have been plotted. The suitable electron temperatures ranges for neon plasma soft X-ray emission and extreme ultraviolet emission have been investigated. The X-ray ratio curves for various electron temperatures with probable electron and ion densities of the neon plasma produced have been computed with the assumption of non-local thermodynamic equilibrium model for the distribution of the ionic species. These ratio curves could be used for electron temperatures deduction of neon plasma focus. Keywords Neon plasma Soft X-ray EUV emission X-rays ratio method
Introduction The plasma focus device has been studied intensively as a plasma source capable of producing high density high temperature plasma that emits intense radiation ranging from hard and soft X-rays, UV and extreme ultraviolet (EUV) [1–4]. The radiation output and the emission spectra that may be obtained depend on the operating parameters of the plasma focus discharge, which include the discharge M. Akel (&) S. Alsheikh Salo Department of Physics, Atomic Energy Commission, P. O. Box 6091, Damascus, Syria e-mail: [email protected] C. S. Wong Physics Department, Plasma Technology Research Center, University of Malaya, 50603 Kuala Lumpur, Malaysia
energy, operating pressure and electrode geometry [5, 6]. The dense plasma focus pinch discharge has recently been considered as a possible light source for extreme ultraviolet lithography (EUVL) [6]. This is of interest to the semiconductor manufacturing industry due to the expectation that the Next Generation Lithography (NGL) will be using ˚ [7, 8]. Various types of EUV the wavelength of 135 A radiation sources, including the laser produced plasma and pulsed discharge sources such as the capillary discharge [9, 10], vacuum spark [11, 12] and plasma focus [13, 14] are being considered. These radiation sources, especially the pulsed discharge sources are favorable as X-ray and EUV radiation sources because of their lower cost and simplicity in operation when compared to other radiation sources. The X-ray emission from dense plasma focus is characterized by high intensity and a wide spectral range, the emission times ranging from a few to a few tens of nanoseconds for a small focus. The predominant spectral range that is actually radiated can be controlled by using a specific gas at a specific temperature. Good soft X-ray yield can be achieved by neon as a filling gas with characteristic spectral energies around 1 keV. Based on corona model incorporated in Lee model code, it is shown that for operation in neon, a focus pinch compression temperature of 200–500 eV is suitable for gen
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