Measurement of High Ion Temperature using the Doppler Width of the Kr Heb Line (0.8 {angstrom}) from Kr-doped Target Implosions

In a recently-published paper, diagnostic methods for laser implosions were proposed, using Krypton K-shell x-ray lines, particularly the He-? line at 15.43 keV (or 0.8 {angstrom}). Strong Kr K-shell lines were indeed observed on Kr-doped implosions on OMEGA and were used to determine the electron temperature. To determine the ion temperature, on the other hand, would require far greater spectral resolution. It was the purpose of this proposal to use a focusing spectrometer (''Rowland circle spectrometer'') to determine the ion temperature, for the first time using the Doppler broadening. In the OMEGA experiment, electron temperatures of 3 - 4 keV were measured and ion temperatures of up to 13 keV were measured, using neutron spectra. For these conditions and the expected density, the total line profile has been calculated1. There are two diagnostic signatures: (a) The ion temperature can be deduced from the line width, and (b) the density can be deduced from the relative intensity of the ''shoulder'' or the forbidden component calculated to appear on the shorter-wavelength wing of the line. To resolve the details of the profile a spectral resolution E/? E much higher than {approx}550 is required. A flat, non-focusing spectrometer has a resolution of E/? E {approx}300, much less than the minimum required. To address this problem we proposed to use a focusing Rowland spectrometer, whose resolution was predicted to be typically E/? E {approx}2000 - 3000. this is sufficient resolution to resolve the profile of the Kr He-? line