The Summary for Optimization of the Annular Coupled Structure Accelerating Module Physical Design for High Intensity Hadron Linac

Abstract

The normal conducting Annular Coupled Structure (ACS) is applied for 190-400 MeV part of high intensity proton linac for the J-PARC. The ACS operating frequency is 972 MHz. The J-PARC ACS is strongly based on the results of previous investigations, especially results of Japan Hadron Project (JHP) research program in KEK. However, the design was revised and optimized to meet the requirements of reliability, operation efficiency and cost reduction. The cells shape of accelerating cells was optimized in total energy range to have high shunt impedance value together with the careful matching with the decreased coupling cells. The design of the bridge coupler cells was optimized to simplify mass production and shape of RF input cell together with matching window were optimized for higher operational reliability. Collected and adjusted all together, these modifications result in the significant effect. The ACS module design doesn't lose to another possible accelerating structures in RF parameters and dimensions. Previously developed for L-band ACS fabrication technique is applied to 972 MHz ACS construction. The realized solutions have the reserve for ACS module use with very high heat loading during operations with 15% duty factor, the highest heat loading at present time, as compared to accelerating modules with another normal conducting accelerating structures, realized in hadron linacs. This report contains the descriptions and explanations of changes in the ACS module physical design for the J-PARC linac.