NEW FRONTIERS IN THE ATOM — LAWRENCE 171 



nics were known, and they allowed the possibility of heavier-than-air 

 flight. Moreover, there was an abundance of supporting observa- 

 tional evidence that flight should be possible; there were kites and 

 there were the birds of the air. But man's realization of the dream 

 awaited primarily the development of the combustion engine, a cir- 

 cumstance not so evidently connected with the fundamental problem 

 of flight. Likewise the fundamental laws of nature recently revealed 

 to us allow the possibility of obtaining useful nuclear energy, and 

 radium and the sun and stars bear witness that this vast source of 

 energy is being tapped in nature. Again success in this direction 

 may await the development of a new intrument or technique just as 

 the airplane depended on the gas engine. 



Perhaps the problem awaits a deeper understanding of the forces 

 that hold nuclei together. That there are little-understood forces 

 operative in the nucleus is more than evident ; especially from obser- 

 vations of the cosmic rays, it has been established that particles of 

 matter called mesotrons of intermediate mass between electrons and 

 protons play a dominant role in nuclear structure. Theoretical con- 

 siderations suggest that the mesotrons may be connected with the 

 primary forces in the nucleus, and accordingly, an understanding of 

 mesotron forces may ultimately yield the solution of the practical 

 problem of atomic energy. 



THE GIANT CYCLOTRON 



In order to study experimentally the mesotron problem, it is neces- 

 sary to bombard nuclei with atomic projectiles having energies in 

 the range of 100 million electron-volts rather than in the neighbor- 

 hood of 10 million electron-volts at present available in c3'clotron 

 laboratories. To this end a giant cyclotron is now under construc- 

 tion on Charter Hill in Berkeley ; some pictures of this great machine 

 are shown in plates 8 and 9. Whether it will be the key to the vast 

 store of energy in the atom, what new discoveries, what new insight 

 into nature it will bring — only the future will tell ! 



THE PRINCIPLE OF THE CYCLOTRON 



The principle of the cyclotron has been described as follows in a 

 popular article by Henry Schacht.^ 



A circular chamber was placed between the poles of the magnet. Then all 

 air was removed from the chamber and heavy hydrogen gas allowed to flow in. 

 This so-called heavy hydrogen behaves in the same way as ordinary hydrogen. 

 However, while the nuclei of ordinary hydrogen atoms contain one positively 

 charged particle, or proton, heavy hydrogen nuclei contain two such particles 



' Schacht, Henry, Lawrence's cyclotron, Part I and Part II. California Monthly for 

 May and June, 1940. 



