High-precision wavelength measurements of x-ray lines emitted from TS-tokamak plasmas

X-ray line spectra from highly charged impurity ions have been taken with a high-resolution Bragg-crystal spectrometer on the Tore Supra (`TS') tokamak. By cross-checking the wavelengths of reference lines from the helium-like ions (2.6 Å) and (3.95 Å) we first demonstrate that it is possible to measure wavelengths with a precision, , of better than 50 000. We then determine the wavelengths of n = 3 to n = 2 transitions of neon-like in the 4 Å spectral range.