A measurement in nuclear emulsion of the isotopic abundance of cosmic ray nitrogen and oxygen

This report discusses a measurement of the isotopic composition of the cosmic ray nitrogen and oxygen. The detector is a stack of nuclear emulsions which was exposed in a balloon flight in northern Canada. The particle energy is 220-450 MeV/n. The particle masses are determined from photometric measurements of track widths. The standard deviation in the mass determination is calculated to 0.46 AMU for nitrogen and 0.50 AMU for oxygen. Special checks of possible errors originating from emulsion disturbances are made. The mass scale of nitrogen is calibrated with an accuracy of +- 0.1 AMU. The calibration is made by using the concept of restricted energy loss. The following results are obtained of the isotopic quotients extrapolated to the top of the atmosphere 17O/O=0.05+-0.03, 18O/O=0.08+-0.03, 15N/N=0.33+-0.09. (Auth.)