Radial profiles of ground-state transitions of heliumlike argon from the Alcator-C tokamak

Measurement of the electron and ion temperatures by the x-ray imaging crystal spectrometer on joint Texas experimental tokamak

An x-ray imaging crystal spectrometer has been developed on joint Texas experimental tokamak for the measurement of electron and ion temperatures from the K_α spectra of helium-like argon and its satellite lines. A two-dimensional multi-wire proportional counter has been applied to detect the spectra. The electron and ion temperatures have been obtained from the Voigt fitting with the spectra of helium-like argon ions. The profiles of electron and ion temperatures show the dependence on electron density in ohmic plasmas.

Tangential x-ray imaging crystal spectrometer on J-TEXT tokamak

A tangential x-ray imaging crystal spectrometer (XICS) has been developed for the J-TEXT tokamak to measure the ion temperature and the plasma toroidal rotation velocity. The resonance spectral line and its satellites of Ar XVII in the ranges of 3.94 Å-4.0 Å are detected. A spherically bent quartz crystal with 2d = 4.913 Å is used in this system. The crystal has a dimension of 9 cm high and 3 cm wide and the radius of curvature 3823 mm. The XICS is designed to receive emission of Ar XVII from -10 cm to +10 cm region with a spatial resolution of 3.1 cm in the vertical direction considering the parameters of the J-TEXT plasma. The XICS has a tangential angle of 27° with respect to toroidal direction in the magnetic axis. A two-dimensional 100 mm by 300 mm multi-wire proportional counter is applied to detect the spectra.

Spatially resolved high resolution x-ray spectroscopy for magnetically confined fusion plasmas (invited)

The use of high resolution x-ray crystal spectrometers to diagnose fusion plasmas has been limited by the poor spatial localization associated with chord integrated measurements. Taking advantage of a new x-ray imaging spectrometer concept [M. Bitter et al., Rev. Sci. Instrum. 75, 3660 (2004)], and improvements in x-ray detector technology [Ch. Broennimann et al., J. Synchrotron Radiat. 13, 120 (2006)], a spatially resolving high resolution x-ray spectrometer has been built and installed on the Alcator C-Mod tokamak. This instrument utilizes a spherically bent quartz crystal and a set of two dimensional x-ray detectors arranged in the Johann configuration [H. H. Johann, Z. Phys. 69, 185 (1931)] to image the entire plasma cross section with a spatial resolution of about 1 cm. The spectrometer was designed to measure line emission from H-like and He-like argon in the wavelength range 3.7 and 4.0 A with a resolving power of approximately 10,000 at frame rates up to 200 Hz. Using spectral tomographic techniques [I. Condrea, Phys. Plasmas 11, 2427 (2004)] the line integrated spectra can be inverted to infer profiles of impurity emissivity, velocity, and temperature. From these quantities it is then possible to calculate impurity density and electron temperature profiles. An overview of the instrument, analysis techniques, and example profiles are presented.