METHOD OF IRRADIATION 



361 



5000 



15,000 



20,000 



10,000 

 Range, mg crrf^in Al 



Fig. 2. Bragg curve in Al of 190-mev deuterons. The total ionization increases as 

 the particles slow down, reaching a maximum about 43^^ times the value at 190 mev. 

 The number of particles in the beam decreases simultaneously as indicated on the 

 Faraday curve. The mean relative ionization per particle is the ratio of the total 

 ionization divided by the number of particles present. 



Microorganism exposures 

 184" cyclotron 



rQuadrant chamber 

 •Monitor 



Motor 



Telescope 



^ 



Biological sample 

 Absorber 



^ — Absorber wheel 



Lucite cap 

 Lucite 

 Agar blocks 



Microorganism 



Fig. 3. The experimental arrangement for exposure of microorganisms at the 184-in. 

 cyclotron. The beam first penetrates two monitoring ionization chambers and then 

 passes through absorbers of variable thicknesses. The microorganisms are mounted 

 in a Lucite chamber on agar blocks and are'rotated in the beam so that all receive 



uniform exposure. 



