Composition of medium energy cosmic rays from silicon to nickel measured with nuclear emulsion

The cosmic ray charge spectrum has been studied in three nuclear emulsion stacks exposed in balloon flights from Fort Churchill, Canada, in 1967 and 1970. The charge region is 14 <= Z <E 28 and the energy interval is about 400-800 MeV/Nucleon. The particles are identified by measurements with a nuclear track photometer which is described in some detail. The charge spectrum is extrapolated to the top of the atmosphere and comparisons with other measurements are made. Special emphasis is put on the abundance ratios (Sc-Mn)/Fe, (Sc+Ti)/(V+Cr) and Ni/Fe. (Auth.)