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Coincidence counter studies of the corpuscular component of the cosmic radiation
Dec., ~934.]
T H E BARTOL RESEARCH FOUNDATION.
769
be more protons in the nucleus t h a n neutrons, e.g., the series, HID2T3He *. These rules indicate t h a t T 3 should have a v e r y small chance of forming a pair with the subsequent formation of He 3 and the emission of a free electron whereas T 3 should react readily with neutrons to form He 4 with the emission of a free electron. W h e t h e r the excess energy will appear as energy of the free electron or as hard ~/-rays it is impossible to state. We shall t a k e as our final example, the case of the n e u t r o n b o m b a r d m e n t of carbon. T h e reaction C613 ~ - n o t - , C614 -~N7 ~4 + e- is possible on this model but a radioactive reaction following the formation of C613C612 + n o t - , C~ts is improbable as C613 cannot m a k e a transition to a n o t h e r existing element with the emission of an electron. T h e process by which the nuclear electron, formed as one e n t i t y of the pair, escapes from the nucleus, is difficult to imagine. It m a y be t h a t the nuclear barrier for electrons is m u c h lower t h a n we have supposed: the calculations of Kemble and Present 4 on the fine structure of H a indicate an effective nuclear radius of 5 X Io -~2 cm.; the calculations of the writer 5 on the formation of x-rays b y high energy electrons lead to a similar conclusion; the reaction D 2 q - D 2 - , T ~ q- H ~ requires an even larger effective collision radius to explain the rate of reaction.
COINCIDENCE COUNTER STUDIES OF THE CORPUSCULAR COMPONENT OF THE COSMIC RADIATION.* BY THOMAS H. JOHNSON, Assistant Director. (ABSTRACT.)
T h e directional distribution of the cosmic radiation has been investigated in Peru, geomagnetic latitude Xo°, atmospheric depths h = 6, 6.8, a n d IO meters of equivalent water; in P a n a m a , X2o °, h = IO meters; in Mexico, X29°, h = 6.8, 7.2, and IO meters; a n d in P e n n s y l v a n i a a n d Colorado, X5o°, Kemble and Present, Phys. Rev., 44, xo3I (1933). s Bramley, Nature, x33, 259 (x934). * Published in full in Physical Review, May I, I934.
770
TIlE BARTOL RESEARCH FOUNDATION.
[J. F. I.
h = Io, and 7.2 meters. At each location the west intensity exceeded the east and the per cent. asymmetry was maxim u m near zenith-angles of 45 °, falling off towards the horizon. At h = Io meters the maximum asymmetry varied from 2 or 3 per cent. at X5o° to 8 or io per cent. at the equator and at h = 6 meters it attained I6 per cent. at the equator. It is shown that the observations cannot be accounted for as an effect of secondary rays, and from the Lemaitre-Vallarta theory expressions have been derived which relate both asymmetry and latitude-intensity-variations to a primary corpuscular component. The discovery of the asymmetry therefore establishes beyond doubt the existence of this component, already indicated by the latitude effect. Consistency between magnitudes of the two effects can be established only if the corpuscular component is exclusively positive. The magnitude and the absorption coefficient of this component associate it with the intense soft component of the absorption curve analyses of Millikan and Regener, with coefficient o.55 per meter of water and containing some 98 per cent. of the radiation incident at the top of the atmosphere. Although the corpuscular radiation is widely distributed in energy, close analysis shows a band of greaterthan-average intensity in the range of positron or proton energies from I to 1.8 X IO1° volts. Independent determinations of energy and absorption coefficient show disagreement in order of magnitude with the theory of energy loss by ionization, and the atmospheric range of the asymmetrical radiation is anomalously independent of primary energy. Both characteristics point to some other process for dissipation of energy. Studies have been made of the shower-produclng radiation, and it is found that its absorption coefficient in the atmosphere agrees with that of the corpuscular component. The directions of shower-producing rays are likewise asymmetrically distributed showing them to be of positive corpuscular origin. Hence it is suggested t h a t shower-production possibly accounts for the absorption anomalies. Studies of the shower-producing mechanism at high elevations have shown the existence of relatively soft intermediary rays which are also ionizing corpuscles. Studies of the zenith-angle distributions at high and low elevations have shown that
Dec., I934.]
T H E ]~ARTOL RESEARCH t?0UNDATION.
771
the ratio of counts to electroscope ionization is less for the soft than for the harder components and a correction for this effect, probably arising from shower production, brings zenithangle distributions into fair agreement with the absorption curve analysis of Bowen, Millikan and Neher. Difficulties in accounting for exclusively positive radiation by radioactive and secondary processes are enumerated and the existence of a radial cosmic electric field with the earth near its center is suggested. Acknowledgment is made of the support and co6peration of the Carnegie Institution, the Bartol Foundation, and of many individuals. A POSSIBLE EXPLANATION OF THE FREQUENCY DISTRIBUTION OF SIZES OF HOFFMANN ST~SSE.* BY C. G. MONTGOMERY.
The cloud chamber photographs of Blackett and Occhialini, Anderson, and Locher ~ have brought to light the suggestion that Hoffmann St6sse may not originate in a single atom, but m a y arise from several atoms as the result of a primary cosmic ray acting through intermediaries. Each of these observers finds groups of ray tracks, apparently all formed simultaneously. These tracks are possibly produced by the particles which give rise to the bursts of ions observed in a pressure chamber. However, these tracks do not diverge from a common point, but seem, in many cases, to be formed in several groups, each group of tracks diverging from a separate point. The existence of these multiple centers has been attributed by Locher ~ to the action of neutrons which, coming from any one nuclear disintegration, serve to precipitate others. Experiments by W. F. G. Swann and the author are in progress at the present time for the purpose of testing this conclusion further and particularly to ascertain whether the size of a Stoss depends upon the amount of material involved. * Reprinted from the Physical Review, 45, No. I, 62-63, January I, I934. 1 p. M. S. Blackett and G. Occhiallni, Proc. Roy. Soc. Long,, Ax39, 699 0[933); C. D. Anderson, Phys. Rev., 43, 368 (I933); G. L. Loeher, Phys. Rev., 44, 779 (I933).
T H E BARTOL RESEARCH FOUNDATION.
769
be more protons in the nucleus t h a n neutrons, e.g., the series, HID2T3He *. These rules indicate t h a t T 3 should have a v e r y small chance of forming a pair with the subsequent formation of He 3 and the emission of a free electron whereas T 3 should react readily with neutrons to form He 4 with the emission of a free electron. W h e t h e r the excess energy will appear as energy of the free electron or as hard ~/-rays it is impossible to state. We shall t a k e as our final example, the case of the n e u t r o n b o m b a r d m e n t of carbon. T h e reaction C613 ~ - n o t - , C614 -~N7 ~4 + e- is possible on this model but a radioactive reaction following the formation of C613C612 + n o t - , C~ts is improbable as C613 cannot m a k e a transition to a n o t h e r existing element with the emission of an electron. T h e process by which the nuclear electron, formed as one e n t i t y of the pair, escapes from the nucleus, is difficult to imagine. It m a y be t h a t the nuclear barrier for electrons is m u c h lower t h a n we have supposed: the calculations of Kemble and Present 4 on the fine structure of H a indicate an effective nuclear radius of 5 X Io -~2 cm.; the calculations of the writer 5 on the formation of x-rays b y high energy electrons lead to a similar conclusion; the reaction D 2 q - D 2 - , T ~ q- H ~ requires an even larger effective collision radius to explain the rate of reaction.
COINCIDENCE COUNTER STUDIES OF THE CORPUSCULAR COMPONENT OF THE COSMIC RADIATION.* BY THOMAS H. JOHNSON, Assistant Director. (ABSTRACT.)
T h e directional distribution of the cosmic radiation has been investigated in Peru, geomagnetic latitude Xo°, atmospheric depths h = 6, 6.8, a n d IO meters of equivalent water; in P a n a m a , X2o °, h = IO meters; in Mexico, X29°, h = 6.8, 7.2, and IO meters; a n d in P e n n s y l v a n i a a n d Colorado, X5o°, Kemble and Present, Phys. Rev., 44, xo3I (1933). s Bramley, Nature, x33, 259 (x934). * Published in full in Physical Review, May I, I934.
770
TIlE BARTOL RESEARCH FOUNDATION.
[J. F. I.
h = Io, and 7.2 meters. At each location the west intensity exceeded the east and the per cent. asymmetry was maxim u m near zenith-angles of 45 °, falling off towards the horizon. At h = Io meters the maximum asymmetry varied from 2 or 3 per cent. at X5o° to 8 or io per cent. at the equator and at h = 6 meters it attained I6 per cent. at the equator. It is shown that the observations cannot be accounted for as an effect of secondary rays, and from the Lemaitre-Vallarta theory expressions have been derived which relate both asymmetry and latitude-intensity-variations to a primary corpuscular component. The discovery of the asymmetry therefore establishes beyond doubt the existence of this component, already indicated by the latitude effect. Consistency between magnitudes of the two effects can be established only if the corpuscular component is exclusively positive. The magnitude and the absorption coefficient of this component associate it with the intense soft component of the absorption curve analyses of Millikan and Regener, with coefficient o.55 per meter of water and containing some 98 per cent. of the radiation incident at the top of the atmosphere. Although the corpuscular radiation is widely distributed in energy, close analysis shows a band of greaterthan-average intensity in the range of positron or proton energies from I to 1.8 X IO1° volts. Independent determinations of energy and absorption coefficient show disagreement in order of magnitude with the theory of energy loss by ionization, and the atmospheric range of the asymmetrical radiation is anomalously independent of primary energy. Both characteristics point to some other process for dissipation of energy. Studies have been made of the shower-produclng radiation, and it is found that its absorption coefficient in the atmosphere agrees with that of the corpuscular component. The directions of shower-producing rays are likewise asymmetrically distributed showing them to be of positive corpuscular origin. Hence it is suggested t h a t shower-production possibly accounts for the absorption anomalies. Studies of the shower-producing mechanism at high elevations have shown the existence of relatively soft intermediary rays which are also ionizing corpuscles. Studies of the zenith-angle distributions at high and low elevations have shown that
Dec., I934.]
T H E ]~ARTOL RESEARCH t?0UNDATION.
771
the ratio of counts to electroscope ionization is less for the soft than for the harder components and a correction for this effect, probably arising from shower production, brings zenithangle distributions into fair agreement with the absorption curve analysis of Bowen, Millikan and Neher. Difficulties in accounting for exclusively positive radiation by radioactive and secondary processes are enumerated and the existence of a radial cosmic electric field with the earth near its center is suggested. Acknowledgment is made of the support and co6peration of the Carnegie Institution, the Bartol Foundation, and of many individuals. A POSSIBLE EXPLANATION OF THE FREQUENCY DISTRIBUTION OF SIZES OF HOFFMANN ST~SSE.* BY C. G. MONTGOMERY.
The cloud chamber photographs of Blackett and Occhialini, Anderson, and Locher ~ have brought to light the suggestion that Hoffmann St6sse may not originate in a single atom, but m a y arise from several atoms as the result of a primary cosmic ray acting through intermediaries. Each of these observers finds groups of ray tracks, apparently all formed simultaneously. These tracks are possibly produced by the particles which give rise to the bursts of ions observed in a pressure chamber. However, these tracks do not diverge from a common point, but seem, in many cases, to be formed in several groups, each group of tracks diverging from a separate point. The existence of these multiple centers has been attributed by Locher ~ to the action of neutrons which, coming from any one nuclear disintegration, serve to precipitate others. Experiments by W. F. G. Swann and the author are in progress at the present time for the purpose of testing this conclusion further and particularly to ascertain whether the size of a Stoss depends upon the amount of material involved. * Reprinted from the Physical Review, 45, No. I, 62-63, January I, I934. 1 p. M. S. Blackett and G. Occhiallni, Proc. Roy. Soc. Long,, Ax39, 699 0[933); C. D. Anderson, Phys. Rev., 43, 368 (I933); G. L. Loeher, Phys. Rev., 44, 779 (I933).