Smithsonian Report, 1945. — Spear 



l. Close-up View of the Medical Cyclotron (No. 3 of Table 1). 



Showing the 5-foot glow produced when the 16-mev. beam of deutrons is allowed to escape into the air 

 through a thin aluminum foil window which permits passage of the beam but maintains the vacuum 

 in the cyclotron. The beam flares at the end of its path because the deutrons slow down, scatter more 

 easily, and ionize more heavily (15b). A steel plate placed in the beam was melted (14). (Reproduced 

 by permission from Radiology.) 



2. Wilson Cloud-Chamber Photograph (1/100 Sec). 



Showing the intensity of the ionization a few feet from the cyclotron (No. 2b of table 1) when producing 



neutrons. 



