AbstractDistributions of line-intensity ratios that correspond to the electron temperature of a laser-created fusion plasma were measured by means of toroidally bent Bragg crystals. Those were determined by seeding the fuel with a tiny amount of argon and by obtaining monochromatic image of Ar+17 (1s−3p) Lyβ and Ar+16 (1 s2−1s3p) Heβ lines. Furthermore, the experimental distribution of the line ratio of Lyβ to Heβ is remarkably different from the post-processed outputs from the one-dimensional implosion code ILESTA-1D with the help of the RATION code.