Beam Dynamics in Superconducting Proton Linac

Beam loss control is a crucial research direction in high-current superconducting linear accelerators (SCL). The research findings include firstly, for continuous beams, when tune depression eta > 0.7, zero current periodic phase advance (σ0t) can partially exceed 90° during transport in solenoid and quadrupole doublet periodic focusing channels. Different results occur when eta 0.7. Secondly, in the solenoid system, σ0t can partially exceed 90° without significant impact on beam quality. In the quadrupole doublet focusing system, the partial breakdown of 90° affects beam quality. Thirdly, Similar conclusions hold for acceleration effects. Fourthly, numerical analysis shows that double-period structures have more stringent design criteria than fully period structures. The double-period structure can cause envelope instability even if σ0t 90°. Fifthly, the primary factor causing halo is the 2:1 resonance. Additionally, when eta is small, higher-order resonances can also cause halo.