Extreme-ultraviolet(EUV) light sources from compact plasmas are now intensively studied for the next generation of lithography. The emission of multicharged Xe ions has strong peaks near 11 and 13nm and the emission near 13nm is attributed to transitions in Xe¹⁰⁺. Better knowledge of this emission is important for EUV sources and for optimization of a 13.5nm EUV source.
EUV spectra from Xenon ions in LHD have been measured by puffing Xe gas into plasma with a high resolution spectroscopy in the wavelength range 10-17 nm. We analyze the spectral lines near 13nm. We used the spectra without Xe gas puffing for wavelength calibration. Iron ion lines and oxygen ion lines were used as references.
In order to identify the observed lines we have calculated the theoretical data with three different atomic codes, MCDF, Cowan, and Hullac code. We compared the observed spectra with theoretical convoluted spectra and try to identify the spectral lines from Xe¹⁰⁺ ions. We also calculated the lines from Xe²⁵⁺ and Xe²⁶⁺ ions which can emit lines near 13nm. We compared the effective emission rate coefficients for the lines from low charge ions Xe¹⁰⁺ and high charged ions Xe²⁶⁺ to know the contribution from these ions.
We study the time dependent behavior of emission lines and found strong emission during radiative collapse or after radiative collapse. This indicates the line emission is mainly produced from low charged ions.
We can make a benchmark test of computer codes using the observed spectral lines. This is important because the theory has not been extensively tested for such high-Z low charge ions.
We will study plasma conditions which give the best EUV emissions, and will make a collisional radiative model for high-Z many-electron ions.