116 



BELL SYSTEM TECHNICAL JOURNAL 



half-box B opposite the charged electrode D, which deflects them 

 enough to bring them into the cup-shaped receptacle at the far end of 

 which the crystals of lithium fluoride are spread. The fragments of 

 lithium nuclei which are observed are those which escape to the left 

 in such directions as to enter the Geiger counter G. In this apparatus 

 the radius of the outermost circle was 11.5 cm., the magnetic field 

 14,000 gauss; the potential-difference between the half-boxes never 

 attained as much as 5000 volts, but it was reversed 4.2 millions of 



Fig. 5 — The Lawrence apparatus for cumulative acceleration, beside the colossal 

 magnet between the poles of which it is placed. (Lawrence) 



times in a second, so that after three hundred reversals the protons 

 had arrived at the limit of the box and were ready to strike the lithium 

 nuclei with an energy of 1.23 MEV. By using a bigger pair of half- 

 boxes in a more extensive magnetic field, this energy could be aug- 

 mented; and by viewing the size of the magnet in Fig. 5 one sees 

 what an augmentation is now imminent. The currents were inferior 

 to those achieved by the apparatus of the Cavendish school, being 

 mostly of the order of a few millimicroamperes (one millimicroampere 

 or mixa = 10~* na). 



I 



