IHEP, Beijing, People’s Republic of China
HUST, Wuhan, People’s Republic of China
In the beam transfer line which often consists of dipoles to deflect the beam trajectory, longitudinal dispersion effect and emission of coherent synchrotron radiation (CSR) will lead to beam phase space distortion, thus degrading the machine performance. In this study, optimizations of a triple-bend achromat (TBA) cell are conducted using the multi-objective particle swarm optimization (MOPSO) method to suppress the CSR-induced emittance growth and minimize the longitudinal dispersion functions up to high orders, simultaneously. For the longitudinal dispersion function, results of three optimization settings are reported, which makes the TBA design first-order, second-order, and higher-order isochronous. Furthermore, we study the shortest possible beamline length of the higher-order isochronous TBA design, which may pave the way to designing a more compact beam transfer line.
IHEP, Beijing, People’s Republic of China
HUST, Wuhan, People’s Republic of China
Transport of high-brightness beams with minimum degradation of the phase space quality is pursued in modern accelerators. For the beam transfer line which commonly consists of bending magnets, it would be desirable if the transfer line can be isochronous and coherent synchrotron radiation (CSR)-immune. For multi-pass transfer line, the achromatic cell designs with stable optics would bring great convenience. In this paper, based on the transfer matrix formalism and the CSR point-kick model, we report the detailed theoretical analysis and derive the condition for a triple-bend achromat with stable optics in which the first-order longitudinal dispersion (i.e., R56) and the CSR-induced emittance growth can be eliminated. The derived condition suggests a new way of designing the bending magnet beamline that can be applied to the free-electron laser (FEL) spreader and energy recovery linac (ERL) recirculation loop.