Ionization balance in EBIT and tokamak plasmas

Abstract

The equilibrium state in tokamak core plasmas has been studied using the relative intensities of resonance x-ray lines, for example Ly ␣ ͑H-like͒, ''w'' ͑He-like͒, and ''q'' ͑Li-like͒ from test ions such as Ar ϩ15 , Ar ϩ16 , and Ar ϩ17. A full spatial analysis involves comparison of the line intensities with ion diffusion calculations, including relevant atomic rates. A zero-dimensional model using a global ion loss rate approximation has also been demonstrated by comparison with the data collected from a Johann configuration spectrometer with a charged coupled device ͑CCD͒ detector. Since the lines are nearly monoenergetic, their intensities are independent of the instrument sensitivity and are directly proportional to the ion abundances. This method has recently been applied to Ar in the Oxford electron beam ion trap ͑EBIT͒ with a beam energy in the range 3-10 keV. Taking into account the cross sections for monoenergetic electron collisions and polarization effects, model calculations agree with the observed line ratios at 4.1 keV beam energy. This work will be expanded to provide nomograms of ionization state versus line intensity ratios as a function of EBIT beam energy.

High-resolution crystal spectrometer for the 10–60 Å extreme ultraviolet region

“…[5][6][7] Bent-crystal spectrometers have also been used at electron beam ion traps at other institutions. 8,9 However, crystal spectrometers built for the Livermore electron beam ion traps operating in the ultra soft x-ray region between about 5 and 20 Å have used the flatcrystal geometry, [10][11][12][13] despite the fact that the flat-crystal geometry provides less throughput than bent-crystal spectrometers. Flat-crystal spectrometers are easy to set-up for observing different wavelength regions by simply rotating the crystal and detector around a common pivot point.…”

Applications of EBIT to magnetic fusion diagnostics

“…The abundance of different ionization stages in a tokamak plasma depends on the ionization and recombination rates and particle confinement. Calculations of ionization balance for argon ions were validated by EBIT and tokamak observations [31].…”

Line ratios and wavelengths of helium-like argon n =2 satellite transitions and resonance lines

“…For He-like argon we compare our measurement of R = z/(x + y) in Fig. 2 with values from other EBIT facilities [11,12], the Alcator C tokamak [1], and theoretical predictions. The theoretical value using excitation rates by Pradhan [1] and the predictions by HULLAC collisional radiative rate coefficients with modifications including the two-photon decay of the 1s 2s 1 S 0 level (HULLAC w 2hν) or a variation of the collisional data (HULLAC col) demonstrate the insensitivity of the ratio R for argon.…”