The energy dependence of the abundance of lithium, beryllium, and boron in the primary cosmic radiation: Observations at Fort Churchill

The relative abundances of lithium, beryllium, boron, and the S-group nuclei have been determined at two different energies by means of a pure nuclear emulsion stack flown from Fort Churchill, Canada (λ = 70.5°), on August 4, 1962, under a total of 4.7 g/cm2 of residual atmosphere. The ratio of the L to S nuclei, , at the top of the atmosphere between 200 and 70 Mev/n and >700 Mev/n was determined to be 0.41±0.08 and 0.19±0.03, respectively. The results of both the absolute flux values of L- and S-group nuclei, as well as their ratios, are in accord with other investigations. Combined with the evidence from the measurements of in the same stack, our results indicate that low energy cosmic ray nuclei have traversed about twice as much hydrogen as high energy particles. The results rule out an accelerating mechanism of the Fermi type but can be explained by a source-trapping mechanism.