Necessity of D's in a Cyclotron

[jackferry]

Are the D's necessary in a cyclotron? It seems to me that the same effect could be achieved without the discontinuity, which would eliminate the need for a high operating voltage. If the D's are replaced by a complete conducting circle of metal, you could just apply the alternating voltage to either side of the circle, accelerating the electrons around it without the need to push them across the gap between the D's. Am I wrong in thinking that the gap isn't necessary? If not, where did I go wrong thinking about it?

 

[mfb]

Applying a high voltage to metal draws a high current, and potentially melts the metal or other equipment. I would also expect that the orbit gets less stable with electric fields in odd directions during the orbit.

 

[lychette]

Are the D's necessary in a cyclotron? It seems to me that the same effect could be achieved without the discontinuity, which would eliminate the need for a high operating voltage. If the D's are replaced by a complete conducting circle of metal, you could just apply the alternating voltage to either side of the circle, accelerating the electrons around it without the need to push them across the gap between the D's. Am I wrong in thinking that the gap isn't necessary? If not, where did I go wrong thinking about it?

The acceleration of the charged particles occurs as they pass across the gap between the Ds. In effect the gap is like the spacing of parallel plates with a high voltage across the gap.