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Simulations of X-ray spectra in order to determine the parameters
of high-temperature plasma

Łukasz Syrocki

Department of Nuclear Fusion and Plasma Spectroscopy,
Institute of Plasma Physics and Laser Microfusion, Hery 23, 01-497 Warsaw, Poland

The future ITER tokamak ("The way" in Latin) will include plasma facing components that contain tungsten [1]. Some of this tungsten will end up in the center of the machine, where it will ionize and radiate x-rays. The resulting energy loss is undesirable, but on the bright side the x-ray spectrum offers an additional diagnostics of the plasma itself, and is an excellent way to quantify the tungsten impurity. Radiation from tungsten that migrates into the hot, dense center of the plasma reaches the spectrometer from all locations along the line of sight, but is registered only within a specific wavelength window. The tungsten emits into this window only from certain ionization states, so that the resulting spectrum represents some average of properly ionized tungsten over the line of sight. Irrespective of the spectral details, the intensity of the radiation is proportional to the amount of tungsten; sufficiently high spectral resolution may make it possible to determine a local electron temperature, electron density and fractional abundance in addition. An instrument for such purposes is planned for ITER, as e.g., described in [2].
The highly resolved x-ray spectra can be interpreted in terms of interesting plasma parameters only when the theoretical radiation models first identify, and then take into account, all the relevant factors that affect the spectrum [3-9].

[1] R. A. Pitts, A. Kukushkin, A. Loarte, A. Martin, M. Merola, C. E. Kessel, V. Komarov, and M. Shimada, Phys. Scr. T138, 014001, 2009.
[2] T. Pütterich, R. Neu, R. Dux, A. D. Whiteford, and M. G. O’Mullane, the ASDEX Upgrade Team, Plasma Phys. Control. Fusion 50, 085016, 2008.
[3] K. Słabkowska, M. Polasik, E. Szymańska, J. Starosta, Ł. Syrocki, J. Rzadkiewicz, N. R. Pereira, Phys. Scr., T161:014015 (5pp), 2014.
[4] K. Słabkowska, J. Rzadkiewicz, Ł. Syrocki, E. Szymańska, A. Shumack, M. Polasik, N. R. Pereira. J. Phys. B: At. Mol. Phys., 48, 144028 (7pp), 2015.
[5] K. Słabkowska, Ł. Syrocki, E. Szymańska, J. Rzadkiewicz, G. Pestka, M. Polasik, High Energy Dens. Phys., 14:44-46, 2015.
[6] Ł. Syrocki, E. Szymańska, K. Słabkowska, M. Polasik, G. Pestka, Nukleonika, 61:433-436, 2016.
[7] K. Słabkowska, Ł. Syrocki, E. Węder, M. Polasik, Nucl. Instr. Meth. Phys. Res. B, 408:265-270, 2017.
[8] Ł. Syrocki, K. Słabkowska, E. Węder, J. Starosta-Sztuczka, M. Polasik, Nucl. Instr. Meth. Phys. Res. B, 408: 257-264, 2017.
[9] Ł. Syrocki, K. Słabkowska, E. Węder, M. Polasik, J. Rzadkiewicz, Fusion Energy 39, 194-201, 2020.