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TitleEarly History of Cosmic Ray Studies: Personal Reminiscences with Old Photographs
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Page 1

EARLY HISTORY OF COSMIC RA Y STUDIES

Page 2

ASTROPHYSICS AND
SPACE SCIENCE LIBRARY

A SERIES OF BOOKS ON THE RECENT DEVELOPMENTS

OF SPACE SCIENCE AND OF GENERAL GEOPHYSICS AND ASTROPHYSICS

PUBLISHED IN CONNECTION WITH THE JOURNAL

SPACE SCIENCE REVIEWS

Editorial Board

R. L. F. BOYD, University College, London, England

L. GOLDBERG, Kitt Peak National Observatory, Tucson, Ariz., U.S.A.

C. DE JAGER, University of Utrecht, The Netherlands

J. KLECZEK, Czechoslovak Academy of Sciences, Ondrejov, Czechoslovakia

Z. KOPAL, University of Manchester, England

L. I. SEDOV, Academy of Sciences of the U.S.S.R., Moscow, U.S.S.R.

Z. SVESTKA, Laboratory for Space Research, Utrecht, The Netherlands

VOLUME 118

PROCEEDINGS

Page 215

216 P. Auger

photographs, due probably to slow protons, and suggesting the presence of neutrons in
the beam. But the striking feature was the density of electron tracks, sometimes so
thick that the cloud chamber looked like filled with a heavy rainfall (see Fig. 3): in
this case we thought that the chamber had been striken by the axial part of the
shower, probably the direction of the incoming primary particle. Some photographs
showed much less dense tracks, characteristic of the periphery of the showers. We did
also some work with two chambers, situated vertically above one another and
separated by screen of lead, and could make visible the multiplication effect of the
screen.

But the main surprise came when I tried to evaluate the energy of the incoming
primary particles. For that purpose I had to evaluate the total number of electrons,
and also the mean value of their energy. The total number could be deduced from the
density of tracks per square meter and the distance at which the coincidences could be
obtained. For that last variation of number of showers with distance, it was clear that
showers of much more extension did exist. Anyway, with a total surface of between 104

and 105 square meters this meant a munimum of 106 particles in the showers of large
extension. Now as to the energy of the electron, not having at my disposal at that
time a cloud chamber in a magnetic field, I had to admit that they had at least the
critical energy in air, that is 108 eV. By another method, the consideration of the total
screen of air between the origin of the showers and the instruments, the same value
can be derived from the Bhabha-Heitler calculations.

Taking that mean value of 1011 eV and the total number of 106 electrons and taking
into account the loss of energy by crossing the atmosphere, I came to the conclusion,
rather astonishing at that time, that particles of at least 1015 eV arrived at the top of
the atmosphere (Auger et al., 1938, 1939a, b, 1948, 1949). The number per square
meter of these primary particles could also be evaluated, and taking only the particles

Fig. 2. Au sol (Labo.).

Page 216

Proof of the Very High Energies Carried by Some of the Primary Particles 217

Fig. 3

with an energy higher than 1015 eV their number was found of the ordered one per
day on 10 square meters. Of course the number of particles with smaller energy, say
1012 eV, was more than 10 times larger.

As for the energy spectrum of the primaries responsible for the extensive showers we
tried to deduce it from the number of showers obtained at different altitudes. Having
done some experiments with three to nine coincidence counters installed in an airplane
with a total horizontal extension of 15 meters, we found at the altitude of 7250
meters a fifty fold increase. We found also a strong increase of the density of the tracks
in the big showers. At first sight, the spectrum seemed to be of an exponential form,
the number of showers with an energy higher than E being roughly proportional to
£-2.

Anyway the existence of a large number of particles striking our atmosphere with
an energy of that magnitude could not be easily explained. Since the time of our
discovery, in 1938, the existence of these high energy particles has been confirmed and
even much higher energies have been measured by different authors, 1018 and perhaps
even 10 20 in very exceptional cases. How particles with such energies are produced is
not fully understood even if some interesting theories have been proposed, for instance
by Fermi, involving large and extended magnetic fields in space. It is presently admitted
that the primary particles responsible for the EAS are nuclei, mostly protons, and
some heavier ones. The initiation of the shower takes place at very high altitude, say
20 km above ground, and consists in a first collision between the high energy primary
particle and the nucleus of an atom of the air. All sorts of particles are then produced,
but the main part of the shower after a few km of atmosphere, are electrons and
positrons, with a certain proportion of muons, - those which are counted under
10-20 cm of lead -, of pions, of light nuclei and hadrons. So the total analysis of the
phenomenon tends to be rather complicated, and has been studied by a large number
of physicists. Many publications have been made since our first observation of long
distance coincidences leading to the discovery of the extensive showers.

Page 430

Name Index 443

Stozhkov, 367
Street, J. c., 125, 140, 141, 155-157,288,387
Suga, K., 222-224, 244, 245
Sugerman, N., 401
Swann, W. F. G., 265, 267, 387,428
Swetnick, 260
Syrovatskii, S. 1.,418-420,423
Szilard, L., 385

Takagi, S., 347
Taketani, M., 192, 210, 221, 285, 287, 290,

292, 293, 340
Takeuchi, M., 137, 138, 140, 142, 189, 197,

220,288
Takibayev, 234
Tamaki, H., 197,290,292,293
Tamm, 1.,134,227,286,339,340,342
Tamura, Y., 188
Tanaka, 224
Tanikawa, Y., 290-292
Tarrant, G. T. P., 100
Tate, J. T., 263
Telegdi, V., 401
Teller, E., 267, 387, 388, 428
Terada, T., 187
Thales, 9, 10, 14
Thambyahpillai, T., 383
Thiesoen,381
Thompson, R. W., 129, 311, 313, 317-319
Thomson, J. J., 10, 12
Tidman, D. A., 324, 328
Tinlot, J., 251
Tomonoga, S., 188, 189, 192, 197-199, 285,

286, 289-293
Tongiorgi, V. C., 394
Torney, 243
Townsend, 65
Trabacchi, 65
Treiman, S. B., 394
Tremblay, J., 251
Tripp, R. D., 330
Trost, 193
Turkot,349
Turner, R., 195
Tuve, M., 255
Tuvim, 47, 225
Tverskoy, B. A., 368
Tyapkin, A. A., 334

Uhlenbeck, G., 289, 340, 343
Umeda, K., 286
Unsold, 414, 416
Urey, H. c., 388,401

Viiisiilii, 107

Valera, de, 308
Vallarta, M. S., 68, 200, 205, 265, 270, 380,

387,389,394,398,428
Vallauri,65
Valley, G., 265
Van Allen, J., 225, 270,406,421
Van Heerden, I. J., 383
Varfolomeev, A. A., 330, 334
Vashakidze, 416
Vavilov, 226, 234, 372
Vavilov, S. I., 359
Veksler, V., 227,228, 345, 363
Verigo, A. B., 225
Vernov, N., 357, 359, 360, 362-367, 371, 372
Vernov, 225, 227
Vick, F. A., 304
Victor, 79
Vieweg,29
Vityaz,365
Vladimirskii, 414, 415
Vogt,270
Volkov, E. I., 350, 351
Von Halban, 257

Wada, M., 196, 200, 203
Waddington, J., 272-274
Wallace, 423
Walraven, 418
Wambacher, H., 28, 29, 210
Wataghin, G., 344
Wataghin,65
Watagin, 235, 299
Watanabe, S., 223, 291
Watase, Y., 197-199, 219-224, 289
Webster, 422
Wegener, 384
Weicziicher, 222
Weischedel, 83
Weisskopf, V. F., 343
Weizsiicker, C. F., 51,152,341
Wentzel, G., 291, 394, 399
Weyssennoff, J., 295
Wheeler, J. A., 112, 265, 295, 297, 387
Wick, G., 340, 342
Wienberg, L., 263
Wigand, 76
Wigner, E., 385
Wilkinson, D. H., 332
Williams, E. J., 126, 152, 156-158,341
Williams, R., 222, 239, 299
Wilson, A. H., 342
Wilson, C. T. R., 11-14, 17,47,48,50,99, 101,

109, 118, 126, 149, 161, 24~ 349
Wilson, J. G., 145, 149-151, 154-158,299,304,

375,384

Page 431

444

Wilson, V., 385, 387
Winckler, J., 266, 268, 271, 273, 274
Winzen, 0., 263
Wolf, E., 20, 21, 75
Wolfendale, 419
Wollan,E.0.,291,300, 302,387,389
Wood,13
Wordie, J. M., 103, 104, 109, 110
Wright, C., 401
Wulf, Th., 8,14,18,19,75-77
Wynn-Williams, C. E., 100

Yagi, T., 203
Yamaguchi, Y., 220, 221289
Yamasaki, F., 138, 187, 189, 190
York, C. M., 313, 318,401

Name Index

York, H., 273, 287
Yoshida, S., 202
Yuan, L. C. L., 391
Yukawa, H., 10, 126, 127, 133, 134, 157-159,

161, 163, 164, 187, 188, 195, 210, 220,
285, 286, 288, 289, 291, 292, 302, 340-
342,344

Zachariasen, W., 385,401
Zatsepin, G. T., 51, 225, 229, 230, 345, 347,

367
Zeleny, 107
Zhdanov, A. P., 228,231,233,234
Zhirov, O. V., 348
Zwicky, F., 412, 419

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