Designs of High-intensity Proton Linacs with Non-equipartitioning

Superconducting technology is playing more and more important roles in high-power proton linacs. Periodic phase advance less than 90 degrees and equipartitioning design are considered very important principles in linac design. Due to the very high construction and operation costs, it is very important in optimizing the design to lower the costs. In usual, the longitudinal emittance is larger from the front-end, thus the transverse phase advance is designed to have a larger value. However, with the technical advancement, higher accelerating field can be obtained. In order to take this advantage, it is of much interest in increasing the longitudinal phase advance to shorten the linac or reduce the cost. In this paper, we present the design method that keeping the longitudinal phase advance as large as possible but smaller than 90 degree to maximize the use of the available accelerating gradient. Even though this method does not observe the equipartitioning condition, we can also obtain very good beam dynamics results by placing the tunes in resonant-free regions. In this paper, the design and simulation results by applying this method to the SPL and China-ADS linac will be present.