Tuning of the RF field of the DTL for the J-PARC

Tuning of the accelerating field of the DTL first tank for the Japan Proton Accelerator Research Complex (J-PARC) has been done. The first DTL tank consists of 75 full drift tubes, 37 post-couplers and 10 fixed tuners. The resonant frequency of the tank is 324 MHz. An uniform accelerating field has been achieved by the fine adjustment of the post-couplers and the fixed tuners. The field stabilization by the post-couplers against perturbations has been confirmed also. In order to achieve the stabilized-uniform distribution of the average field for each accelerating gap, the following techniques have been applied for the post-coupler tuning: (1) non-uniform insertion length of the post-coupler from the tank wall; (2) increment of the diameter of several post-couplers. The recipe of the fine post-coupler tuning is described.