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On the annihilation radiation of the positron

  • Otto Klemperer

Boron and carbon activated by diplon and proton bombardment have been used as positron emitting sources in experiments on the annihilation radiation.

By coincidence counting with two Geiger-Müller tubes it has been established that the radiation is emitted in pairs.

By the coincidence method of Becker and Bothe it has been shown that the annihilation radiation consists only of “soft” quanta.

By ordinary absorption measurements it has been shown that the annihilation radiation is homogeneous with a hardness corresponding to 0·5 million e-volt.

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* Dirac, P. A. M., Proc. Camb. Phil. Soc. 26 (1930), 361 and 30 (1934), 150; Proc. Roy. Soc. 133 (1931), 60.

Chadwick, J., Blackett, P. M. S. and Occhialini, G. P. S., Proc. Roy. Soc. 144 (1934), 235.

Oppenheimer, J. R. and Plesset, M. S., Phys. Rev. 44 (1933), 53.

§ Perrin, F., Comptes Rendus, 197 (1933), 1302.

Fermi, E. and Uhlenbeck, G. E., Phys. Rev. 44 (1933), 510.

* Cockcroft, J. D., Gilbert, C. W. and Walton, E. T. S., Nature, 133 (1934), 328.

I am very much indebted to Dr E. T. S. Walton for preparing several sources.

* Rossi, B., Nature, 125 (1930), 636; de Bruyne, N. A. and Webster, H. C., Proc. Camb. Phil. Soc. 27 (1931), 113; Fussel, L. and Johnson, Th. H., J. Frankl. Inst. 217 (1934), 517. The modification of such a circuit used in this paper has been worked out in the Cavendish Laboratory by Mr D. E. Lea.

The best resistance was here 3 × 109ω, both 2 × 109 and 4 × 109ω were less satisfactory. Since the counter had no “flat place” in its count-voltage curve, particular care was taken to hold the voltage applied to the tube constant.

* The number of positrons emitted from the source was measured by means of a tube counter provided with a thin mica window. A small correction was made to allow for the reflection of positrons from the graphite. I am indebted to Mr C. W. Gilbert for the loan of the tube counter.

Becker, H. and Bothe, W., Zeits. f. Phys. 76 (1932), 421.

Thibaud, J., Comptes Rendus, 197 (1933), 1629.

* Joliot, F., Comptes Rendus, 197 (1933), 1622; 198 (1934), 81.

Crane, H. R. and Lauritsen, C. C., Phys. Rev. 45 (1934), 430.

* Klein, O. and Nishina, Y., Zeits. f. Phys. 52 (1928), 853.

Gray, L. H., Proc. Camb. Phil. Soc. 27 (1931), 103.

* Kohlrausch, K. W. F., Wiener Ber. 126 (1917), 441; Handb. d. exp. Phys. 15 (1928), 72.

Gray, L. H. and Tarrant, G. T. P., Proc. Roy. Soc. 143 (1934), 681 and 706.

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Mathematical Proceedings of the Cambridge Philosophical Society
  • ISSN: 0305-0041
  • EISSN: 1469-8064
  • URL: /core/journals/mathematical-proceedings-of-the-cambridge-philosophical-society
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