IMPROVEMENTS OF RF CHARACTERISTICS IN THE SDTL OF THE J-PARC PROTON LINAC

A separated drift tube linac (SDTL) was adopted as an accelerating structure of Japan Proton Accelerator Complex (J-PARC), which follows the DTL. The SDTL of J-PARC consists of 32 five-cell short tanks, ranging from 1.5 to 2.5 m in length. A design of frequency tuners of the SDTL was performed by taking account of 3-D field distribution calculated with MAFIA. The effects of stems on the resonant frequency and field distribution were also analyzed. An easy and effective compensation method for perturbation by stems of both end cells was proposed and applied to the SDTL tanks