MEDICAL USES OF THE CYCLOTRON — SPEAR 139 



Table 1. — The Berkeley cyclotrons 



12 3 4 



a b 



Date (begun) 1929 '1932* 1936 1939 1940 



Housing Physics Radiation Crocker Distant 



laboratory laboratory laboratory hilltop 



Magnet (tons) 1 80 190 4,000 



Pole diameter (inches) 11 27 > 37 2 60 184 



Energy of particles (mev.) 1.25 4 8 » 16 MOO 



Beam in air (feet) 1 5 4 140 



Water protection (feet) 5 25 



1 45 inches available. 



3 72 inches available. 



3 For deuterons; 21 for neutrons. 



* Conjectural, aDoaratus under construction. 



Each apparatus was bigger than its predecessor and capable of 

 producing greater quantities of radioactive material (pi. 1, fig. 1) . In 1 

 day (1940) as much radio sodium, as measured by gamma-ray activity, 

 could be made as would correspond with 100 mg. of radium. For an 

 initial cost of some £10,000 (prewar of course) and with annual run- 

 ning costs of, say, £2,000, a cyclotron could yield energies of 8 million 

 electron-volts or the energy equivalent of gamma radiation from 

 100,000 g. of radium (11). But while the cost was trivial compared 

 with that of radium, the size of the apparatus was becoming consid- 

 erable and much additional space was required for the devices neces- 

 sary to protect those who came near the machine at work. When one 

 looks at a cloud-chamber photograph (pi. 1, fig. 2) "and realizes that 

 it represents the ionization which occurs in a layer of one's body 

 about a thousandth of an inch thick every one-hundredth of a second, 

 the amount of ionization present in the body of anyone standing near 

 the cyclotron becomes impressive" (12) . Stage by stage the technical 

 difficulties of these huge machines were surmounted, and the scientific 

 investigations begun. A study of the properties of artificial radio- 

 active substances is now proceeding apace, and alongside this, work 

 has begun on their effects on the human body. 4 This paper is con- 

 cerned with the constructive applications of the new discovery to 

 medicine and the way in which the cyclotron can be used in "the 

 preparation of medicines." 



Not long before the United States entered the war, the designer of 

 the cyclotron was described to an American audience in these words : 

 "Lawrence and his collaborators are providing medicine, biology, and 

 physics with agents that should revolutionize our knowledge of the 

 structure of the world and everything that lives in it" (13). The 



* This work is being directed by Lawrence's medical brother (J. H. Lawrence) at the 

 Crocker laboratory, built, equipped and staffed for the sole purpose of studying and 

 developing the biological applications of the cyclotron (No. 3 of table 1) housed in the 

 building (10). 



