382 SECTIONAL TRANSACTIONS.— A. 



generator, and a 2 million volt generator is being installed. These genera- 

 tors speed up streams of charged particles for use in transmutation experi- 

 ments. 



The Cyclotron accelerates particles by giving them a succession of im- 

 pulses as they move in the field of a powerful electromagnet. The magnet 

 of the Cavendish equipment has pole pieces 90 cm. in diameter and should 

 make possible the production of deuterons of energy up to 10 million volts. 



The Cyclotron seems likely to find its most important application in 

 providing very strong sources of the new radioactive substances produced 

 by transmutation. It also makes possible a much wider range of trans- 

 mutations than can be produced by ions of only 2 million volts energy. 

 The D.c. generator, on the other hand, provides much more homogeneous 

 beams of particles and is more suitable for precision work on the details of 

 nuclear processes. 



Dr, P. I. Dee. — Excited states of light nuclei (11.45). 



Recent experimental work wliich has been carried out in the Cavendish 

 High Voltage Laboratory has given evidence of the existence of many new 

 excited states of certain light nuclei. The bombardment of fluorine with 

 artificially accelerated deuterons, for example, has been shown to result in 

 the production of five homogeneous groups of a-particles, four of which 

 may be associated with the formation of excited states of ^'O nuclei. 



Evidence in support of the existence of these excited states of ^'O has also 

 been obtained by Dr. C. W. Gilbert from cloud track photographs of the 

 disintegration of neon by fast neutrons. 



The energies of excitation of a number of other light nuclei have been 

 determined by the investigation of the excitation functions of the y-rays 

 which result from processes of proton capture. The resonance character 

 of the excitation of the y-radiation which results from the capture of pro- 

 tons by carbon, for example, has been shown to be more complex than had 

 previously been supposed. An intense production of y-rays at a proton 

 energy of 560 K. v. has been proved to be due to the capture of protons by 

 "C, which results in the formation of excited ^*N nuclei having an energy 

 of excitation of about 8 -o M.v. 



Dr, N. Feather. Some neutron-produced radioactivities (12.05). 



The radioactivities of various substances irradiated by the neutrons pro- 

 duced by bombarding lithium by deuterons have been studied by a combina- 

 tion of the absorption and coincidence methods, using tube counters. 

 Information has been obtained regarding certain cases of nuclear isomerism 

 and also regarding the long-lived products formed by bombarding thorium. 

 The P and y radiations from a number of other radioelements have also 

 been investigated. 



Dr. E. Bretscher and Mr. J. V. Dunworthhave collaborated in the experi- 

 mental work, and members of the personnel of the Cavendish High Voltage 

 Laboratory have been responsible for carrying out the irradiations. 



General Discussion (12.25) {continued on Friday afternoon). 



Afternoon. 



Visits to [a) Cavendish and Mend Laboratories ; {b) Mathematical- 

 Laboratory (for details see under Department A*). Film illustrating solar 

 prominences. 



