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Nobel prize to E. O. Lawrence awarded in 1939 "for the invention and development of the cyclotron and for results obtained with it, especially with regard to artifical radioactive elements'' |  |
LAWRENCE 1931B
Lawrence, E.O.; Livingston, M.S.;
The Production of High Speed Protons Without the use of High Voltages
Phys. Rev. 38 (1931) 834;
Full Text
A method for the production of high speed protons without the use of high voltages was described before the meeting of the National Academy of Sciences last September (Lawrence and Edlefson, Science 72, 376-377, 1930). Later before the American Physical Society (Lawrence and Livingston, Phys. Rev 37, 1707, 1931) results of a preliminary study of the practicability of this method were presented. In this preliminary experimental work 80000-volt hydrogen molecule ions were successfully produced in
a vacuum tube in which the maximum applied potential was less than 2000 volts, and the conclusion of the experiments was that there are no serious difficulties in the way of producing 1000000-volt protons in this indirect manner.
This important conclusion has now been confirmed. A magnet having pole faces nine inches in diameter and producing a field of 15000 gauss has recently been constructed and with its aid protons and hydrogen molecule ions having energies in excess of one half million
volt-electrons have been produced.
The magnitudes of the high speed hydrogen ion currents turned out to be surprisingly large, being in excess of one-tenth of one microampere. The proton currents were about one-tenth this value.
The voltage amplification obtained in the present experiment was approximately one hundred. That is to say, about five thousand volts were applied to the tube for the production of five hundred thousand volt ions. This amplification was limited by the slit system
used to select out the high speed ions, and can be greatly increased by better design of this part of the tube.
There can be little doubt that one million volt ions will be produced with intensities as great as here recorded when the present experimental tube is enlarged to make full use of the magnet. This alteration is now being carried out.
These experiments make it evident that with quite ordinary laboratory facilities proton beams having great enough energies for nuclear studies
can be readily produced with intensities far exceeding the intensities of beams of alpha-particles from radioactive sources.
Possibly the most interesting consequence of these experiments is that it appears now that the production of 10000000-volt protons can be readily accomplished when a suitably larger magnet and high frequency oscillator are available. The importance of the production of protons of such speeds can hardly be overestimated and it is our hope that the necessary equipment
for doing this will be made available to us.
Related references
More (later) information appears in
E. O. Lawrence and M. S. Livingston, Phys. Rev. 40 (1932) 19;
See also
W. Bothe and H. Becker, Z. Phys. 66 (1930) 289;
G. Beck, Naturw. 18 (1930) 896;
C. Y. Chao, Phys. Rev. 36 (1930) 1519;
W. Gurney and E. U. Condon, Phys. Rev. 33 (1929) 127;
G. Gamow, Z. Phys. 51 (1928) 204;
G. Gamow, Z. Phys. 52 (1928) 514;
J. Chadwick, J. E. R. Constable, and E. C. Pollard, Proc. Roy. Soc. A130 (1930) 463;
C. C. Lauritsen and R. D. Bennett, Phys. Rev. 32 (1928) 850;
M. A. Tuve et al., Phys. Rev. 35 (1930) 66;
M. A. Tuve et al., Phys. Rev. 39 (1932) 384;
A. Brash and J. Lande, Z. Phys. 70 (1931) 10;
D. H. Sloan and E. O. Lawrence, Phys. Rev. 38 (1931) 2021;
E. O. Lawrence and W. E. Edlefsen, Science 72 (1930) 376;
E. O. Lawrence and M. S. Livingston, Phys. Rev. 37 (1931) 1707;
H. Rose, Z. Phys. 64 (1930) 1;
