New determination of the intensities of primary cosmic ray alpha particles and Li, Be, B Nuclei at λ= 41.5‡ using a čerenkov detector

Abstract

Measurements of the intensities of the α-particles and Li, Be, B nuclei in the primary cosmic radiation have been made at an average atmospheric depth of 18.5 g/cm2 in two « Skyhook » balloon flights at λ = 41.5‡. The measuring instrument consisted of a thin (3.0 g/cm2) cerenkov detector placed within the solid angle of a Geiger counter telescope. This detector yielded unusually good resolution of the α-particle and Li, Be, B components. This fact and the slow rate of rise of the two balloons made possible a detailed determination of the dependence of α-particle intensity on atmospheric depth. The quality of the data justified a new approach to the problem of extrapolating the α-particle intensity to the top of the atmosphere. This extrapolation was carried out by applying a « diffusion » equation of the type previoysly used for nuclei withZ > 2 to the observed pressure-altitude dependence of α-particle intensity. The resulting estimate of the α-particle intensity at the top of the atmosphere is significantly lower than previous estimates. At 18.5 g/cm2 the sum of the vertical intensities of the Li, Be, B components was found to be (3.11 ±0.31) (m2·sr·s)-1 and the intensitiesJLi/JBe/JB were found to be as 3/4/2. The (light nuclei/medium nuclei) intensity ratio at the top of the atmosphere as determined by this experiment was 0.35 ±0.09. The vertical intensities at the top of the atmosphere of the various components of the primary radiation as obtained in this experiment at gl = 41.5dg were: Open image in new window