Investigation of the possibility of L-band SRF cavities for medium-beta heavy ion multi-charge-state beams

The possibility of 1288 MHz (L-band) SRF elliptical cavity to accelerate heavy ion multi-charge-state (up to 5 charge states) beams is being investigated for accelerating energy higher than 200 MeV/u. This cavity is a potential energy upgrade for heavy ions linac accelerators such as the Facility for Rare Isotope Beams (FRIB) in the United States of America and Rare Isotope Science Project (RISP) in Korea. One of possible disadvantages of the L-band frequency structure is its small longitudinal acceptance. It should be sufficiently large for transporting the ions with the limited beam loss ensuring accelerator hands-on maintenance. The analytic study was performed and it showed a promising result using 1288 MHz cavities. In addition, from beam loss point of view, the study deduced that 1288 MHz linac frequency could be the limit for mediumbeta heavy ion up to 5 charge states beam accelerators. This paper is the result of the detailed beam dynamics simulation for the linac performance using TRACK code to confirm the analytic result. The result shows that the longitudinal acceptance is large enough for medium-beta heavy ion with 5 charge state beams.