HIGH VOLTAGE — COMPTON 



261 



every time the voltage is applied the electrons are speeded up by just 

 that amount. Thus, by applying only a few thousand volts, protons 

 have been obtained with energy corresponding to nearly 2i/2 million 

 volts. 



Figure 4 shows a diagram of the apparatus. The protons or other 

 ions are liberated, by a suitable device, near the center of a flat, 

 hollow cylinder, which is divided into two ftarts separated from each 



OiCillator I 1 1 ' 'y- 



FiocKB 4. — Diagram of Professor Lawrence's apparatus for prociucinj; liigh sijced 



electrified particles. 



other. The oscillating high-frequency voltage is applied to these 

 two parts, and at the same time the whole cylinder is placed between 

 the poles of a powerful magnet. An ion starting at a is pulled by 

 the momentary electric field across the gap and it takes, in the mag- 

 netic field, a circular path around to h. The frequency is adjusted 

 so that by the time it reaches Z> the direction of the voltage has re- 

 versed so that the ion is again speeded up as it crosses h back into 

 the half-cylinder from which it started. Then by the time it reaches 

 c the voltage has again reversed to its original direction and it is 



