The variation with altitude of the production of bursts of cosmic-ray ionization
2
146 THE BARTOLRESEARCH FOUNDATION. [J. F. I. also shown in curve C, Fig. 3, in which the “density of blackening,” D, is plotted against time. D is defined thus: D = log10 Lo/L. FIG. 3. EXPOSURE TIME. MIN. CURVE c IO 15 20 25 30 35 0045 50 55 60 10 9 8 7 6 5 0 3 2 I NUMBER OF PILM, N CURVES A,B Blackening of films through which the x-ray beam passed successively. In another series of exposures, the beam of x-rays passed successively through IO thicknesses of film. The blackening of successive films was then measured with a densitometer. Curves A and 23, Fig. 3, show the results for exposures of 60 and 30 minutes. THE VARIATION WITH ALTITUDE OF THE PRODUCTION OF BURSTS OF COSMIC-RAY IONIZATION.* BY C. G. and D. D. MONTGOMERY. The rate of occurrence of bursts of ionization from 140 pounds of lead shot was measured in a 50 liter magnesium ionization chamber filled with nitrogen at 14.5 atmospheres pressure at four elevations between sea level and the summit of Pike’s Peak (4,300 meters). The ionization chamber was * The Physical Review, March 15, 1935.
Transcript of The variation with altitude of the production of bursts of cosmic-ray ionization
146 THE BARTOL RESEARCH FOUNDATION. [J. F. I.
also shown in curve C, Fig. 3, in which the “density of blackening,” D, is plotted against time. D is defined thus: D = log10 Lo/L.
FIG. 3.
EXPOSURE TIME. MIN. CURVE c
IO 15 20 25 30 35 0045 50 55 60
10 9 8 7 6 5 0 3 2 I
NUMBER OF PILM, N CURVES A,B
Blackening of films through which the x-ray beam passed successively.
In another series of exposures, the beam of x-rays passed successively through IO thicknesses of film. The blackening of successive films was then measured with a densitometer. Curves A and 23, Fig. 3, show the results for exposures of 60 and 30 minutes.
THE VARIATION WITH ALTITUDE OF THE PRODUCTION OF BURSTS OF COSMIC-RAY IONIZATION.*
BY
C. G. and D. D. MONTGOMERY.
The rate of occurrence of bursts of ionization from 140 pounds of lead shot was measured in a 50 liter magnesium ionization chamber filled with nitrogen at 14.5 atmospheres pressure at four elevations between sea level and the summit of Pike’s Peak (4,300 meters). The ionization chamber was
* The Physical Review, March 15, 1935.
Jan., 1936.1 THE BAKTOI, RESEARCH FOUNDATION. I47
so designed as to minimize the random fluctuations of the cosmic-ray ionization allowing bursts of relatively small sizes to be measured.
The variation with elevation of the rate of occurrence of bursts of all sizes greater than 1.5 X 10~ ions was found to be the same. The increase in the rate of occurrence with eleva- tion was found to be very large, and increasingly greater at higher elevations. It was found that the relative frequency of bursts at any elevation was approximately proportional to the square of the total cosmic-ray ionization. The following table indicates the results.
Elevation (meters). 61 1860 3500 Depth below top of atmos. (m. of water)
4300 10.27 8.25 6.73 6.04
Relative number of bursts. I 3.04 13.8 26.6 Relative ionization squared I 3.24 12.3 22.8
The variation with elevation shown above has a simple interpretation in the light of a recent theory of W. F. G. Swarm.’
THE SIGNIFICANCE OF J. CLAY’S IONIZATION DEPTH DATA IN RELATION TO THE NATURE OF THE PRIMARY COSMIC
RADIATION.*
BY
W. F. G. SWANN. Director
The latitude and directional effects in cosmic radiation necessitate the existence of charged particles entering our atmosphere with energies greater than 10’~ electron-volts. These particles, if of electron type, would, in passage through the atmosphere, lose but a fraction of their energy, so that they would arrive at the earth’s surface with energies com- parable with 10’~ volts.
The latitude and directional effects necessitate the assump- tion that about 14 per cent. of the rays observed at sea-level are of energy greater than 10’~ volts. On the other hand, it has been frequently asserted that cloud-chamber experiments
1 W. F. G. Swann, Phys. Rev. 47, 575 (193.5). * The Physical Review, Sept. I, 1934.
