Isotopic composition of cosmic ray B, C, N and O measured by nuclear emulsion technique

The isotopic composition of cosmic ray boron, carbon, nitrogen and oxygen is measured in a stack of nuclear emulsions exposed in a balloon flight from Fort Churchill in 1970 at a mean altitude of about 3 g/cm2. The emulsion stack consisted of 61 sheets of Ilford G5 emulsions. The energies of the entering nuclei cover the interval 200-400 MeV/n. The technique of measurement is based on measurements with a nuclear track photometer of the widths of the tracks in the residual range interval 1 <= R <= 12 mm. The measured quantity, the light absorption caused by the track, is interpreted as the track width. About 300 such measurements are taken for each track on the last 12 mm residual range. Corrections for emulsion disturbances and other effects affecting the absorption values are made. (Auth.)