An algorithm for the design and tuning of RF accelerating structures with variable cell lengths

摘要

An algorithm is proposed for the design of aπmode standing wave buncher structure with variable cell lengths. It employs a two-parameter, multi-step approach for the design of the structure with desired resonant frequency and field flatness. The algorithm, along with analytical scaling laws for the design of the RF power coupling slot, makes it possible to accurately design the structure employing a freely available electromagnetic code like SUPERFISH. To compensate for machining errors, a tuning method has been devised to achieve desired RF parameters for the structure, which has been qualified by the successful tuning of a 7-cell buncher toπmode frequency of 2856 MHz with field flatness<3% and RF coupling coefficient close to unity.The proposed design algorithm and tuning method have demonstrated the feasibility of developing an S-band accelerating structure for desired RF parameters with a relatively relaxed machining tolerance of∼25μm. This paper discusses the algorithm for the design and tuning of an RF accelerating structure with variable cell lengths.