Theoretical development of x-ray diagnostics of Tungsten ions for fusion and hedp applications

Summary form only given. ITER represents the essential next step in magnetic fusion and is the world´s biggest fusion energy research project. All the main plasma regions of ITER will be probed by an extensive set of spectroscopic diagnostics covering the visible to the X-ray wavelength range. The expected plasma parameters will achieve unprecedented levels. For example, the central electron/ion temperatures may reach 50 keV at an electron density up to ~10¹⁴ cm^-3. Only high-Z impurities may produce diagnostic line radiation at such high temperatures. Tungsten represents a prime candidate element for ITER diagnostics because it may be present in the core due to influx from the tungsten-lined divertor region. A comprehensive theoretical and experimental study of radiation from tungsten ions over a broad spectral and wide temperature range is thus very important. A non-LTE collisional-radiative kinetic model of W is presented to account for M-shell W radiation. Relativistic atomic data implemented in the model as well as the theoretical spectral features that are the most important for x-ray diagnostics are discussed. This model is benchmarked with data from the Livermore EBIT-I electron beam ion trap at densities (Ne ges10¹¹ cm^-3). It is also applied to study radiation from implosions of W wire arrays at higher densities (Ne=10¹⁹-10²¹ cm^-3). The latter experiments were performed on the 1 MA Zebra generator at the University of Nevada, Reno, with planar wire arrays, which consisted of 10-16 W wires with two peripheral wires replaced by Al wires for diagnostic purposes. The spatially resolved X-ray spectra show the distribution of M-shell W spectra from hot plasma (Te>1 keV) together with K-shell spectra from Al from cooler plasma. The model is then used to generate synthetic M-shell W spectra at the ITER-relevant density of Ne=10¹⁴ cm^-3, and the sensitivity of the d- - iagnostically important spectral features to Te and Ne is analyzed. In addition, theoretical L- shell W spectra are presented and discussed along with the further development of these diagnostics.