Millikan, R. A. and Cameron, G. Harvey (1926) High frequency rays of cosmic origin III. Measurements in snow-fed lakes at high altitudes. Physical Review, 28 (5). pp. 851-868. ISSN 0031-899X. http://resolver.caltech.edu/CaltechAUTHORS:MILpr26b
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1. Absorption experiments in Muir Lake (alt. 11,800 feet).—The sinking of sealed electroscope No. 3 in Muir Lake showed an ionization decreasing steadily with depth from 13.3 ions per cc per sec. at the surface to 3.6 ions at 50 feet below the surface, below which there was no further decrease. The absorption curve of electroscope No. 3 was in excellent agreement with that of No. 1. 2. Absorption experiments in Arrowhead Lake (alt. 5,100 feet).—The electroscope readings in Arrowhead Lake correspond uniformly to readings six feet deeper in Muir Lake. This difference is the exact water equivalent of the absorption of the atmosphere between the two elevations. All readings of both electroscopes fit satisfactorily upon a single curve relating ionization to depth beneath the surface of the atmosphere in equivalent meters of water. 3. Rays of cosmic origin.—1 and 2 combined with the failure to detect any systematic diurnal variation, in tests of a number of days duration at high altitudes, constitute new and quite unambiguous evidence for the existence of very hard etherial rays of cosmic origin entering the earth uniformly from all directions. 4. Spectral distribution of cosmic rays.—No single absorption coefficient is found to fit the absorption curve, the lower end of which requires a coefficient of.18 per meter of water; the upper end a coefficient,.30 per meter of water. These coefficients correspond, by Compton's equations, to wave-lengths λ=.00038A and λ=.00063A. These are fifty times the frequencies of ordinary gamma rays, λ=.025A, and the former corresponds to an energy of 32,000,000 volts. 5. Number of pairs of ions due to cosmic rays.—The observed number of pairs of ions in electroscope No. 1 due to cosmic rays is about 1.4 at sea level, 2.6 at 1600 meters, 4.8 at 3600 meters, 5.9 at 4300 meters. 6. Stimulated secondary rays.—Theoretically, cosmic rays of the foregoing energy should not stimulate ether waves of gamma ray hardness, but should produce beta rays capable of penetrating brass walls 5 mm thick. The observations present evidence of rays of about this hardness increasing systematically with altitude in rough proportionality to the intensity of the cosmic rays. This evidence is not completely convincing because of inability thus far to eliminate the effects of the gamma rays from the underlying rocks. 7. Origin of cosmic rays.—Evidence is presented that these rays do not result from the union of protons with negative electrons, but they are rather due to nuclear changes of about one-thirtieth the energy corresponding to such union, taking place throughout the depths of the universe.
|Additional Information:||©1926 The American Physical Society. Received 7 August 1926.|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||25 Mar 2006|
|Last Modified:||26 Dec 2012 08:48|
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