Tuning and measuring of RFQ with resonantly coupled segments

Tuning and measuring on a 3-meter aluminum RFQ cold model with three resonantly coupled segments is carried out, RF electric field distribution with flatness better than 4 percent is obtained. The reason for the formation of RF electric distribution steps at the location of coupling cells is described, and the relation of the step size and the local resonant frequency difference between the two sides of coupling cell is also given. With this relation, the RF electric field distribution steps at the location of coupling cells can be removed in one tuning operation. The best tuning procedure is finally determined. Following this procedure, the tuning of RFQ with several resonantly coupled segments is easy and fast.