We have determined the mass profiles of dark halos in 83 objects observed by ASCA .
The point spread function of X-ray telescope was deconvoled by the Richardson-Lucy algorithm and the temperature profiles were calculated to obtain the mass profiles .
The derived mass profiles are consistent with the NFW model in 0.01 - 1.0 r _ { virial } .
We found a good correlation between the scale radius r _ { s } and the characteristic mass density \delta _ { c } , which indicates the self-similarity of dark halos .
The spectrum index of primordial density fluctuation , P ( k ) \propto k ^ { n } , was determined from the slope of r _ { s } - \delta _ { c } relation .
For M _ { 200 } = 10 ^ { 12 } -10 ^ { 15 } M _ { \odot } , our analysis gives n = -1.2 \pm 0.3 with a confidence level of 90 \% .
The mass density of dark halos is a good indicator of the mean mass density of the universe at the time when the halos were assembled , z = z _ { f } .
Assuming \delta _ { c } \propto ( 1 + z _ { f } ) ^ { 3 } , we have determined the epoch when each dark halo was assembled .
Our analysis indicates that the field elliptical galaxies and groups of galaxies formed approximately at 1 + z _ { f } \simeq 15 and at 1 + z _ { f } \simeq 7 - 10 respectively .