Airplane Cosmic-Ray Intensity Measurements

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Abstract
With the help of the United States Air Corps and particularly of Captain A. W. Stevens of Wright Field the following cosmic-ray measurements have been made: (1) day-time intensity curve from 1000 to 27,000 feet, (2) night-time intensity curve up to 27,000 feet, (3) absorption in a few cm of lead at various elevations, (4) intensity measurement at 27,000 feet during the solar eclipse of August 31, 1932. A change with altitude in the character of the "uebergangs" effect for cosmic-rays passing from air into lead is shown from the absorption-in-lead curves. Comparison with the earlier high altitude measurements, notably those of Kolhoerster, indicates that the present curve is steeper at 27,000 feet so that the marked decrease in the absorption coefficient above 20,000 feet is not observed. No significant decrease in intensity was observed during the night-time observation even at the highest altitudes. In accord with all previous eclipse measurements, no change in intensity was observed during the solar eclipse. The construction and technique of operation of the high-pressure Wulf-type electroscope used in these measurements are described.