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?