论文标题
混合多弯曲的Achromat晶格在直截面上取消六极
Hybrid multi-bend achromat lattice with sextupole cancellation across straight section
论文作者
论文摘要
在一些衍射限制的储物环设计中采用了混合多弯曲的Achromat(HMBA)晶格概念,该设计可以允许相对较大的动态动态孔径和相对较弱的七分光灯。在典型的HMBA晶格中,主弧截面受到横时的进步-i转换取消的横时。在本文中,提出了一个新的HMBA晶格概念,并在直截面上取消了六极的取消,其中-i是在两个晶格细胞的相邻分散凸起之间进行的。这使主弧截面没有相位前进的约束,因此,可以轻松更改晶格单元格和单元格中的弯曲磁体(弯曲)数量,从而为晶格设计提供了更多选择。为了实现-i在这个新概念中所需的大相位进步,分开弯曲被用作匹配弯曲,这是弯曲弯曲的弯曲,将弯曲分为两块,介于两者之间。分裂弯曲还可以减少发射率,并且在直截面中,较大的阶段进步还具有较低的beta功能,从而增强了插入装置的亮度。此外,对于给定的发射率目标,由于对弯曲单元细胞的聚焦更强,这种新的HMBA晶格的弯曲可能比典型的HMBA晶格较小,这有助于节省空间和抑制光束内散射效果。给出了两个晶格作为证明这一新概念并显示其线性和非线性特性的示例,还讨论了进一步的扩展。
The hybrid multi-bend achromat (HMBA) lattice concept is adopted in some diffraction-limited storage ring designs, which can permit relatively large on-momentum dynamic aperture and relatively weak sextupoles. In a typical HMBA lattice, the main arc section is constrained by the transverse phase advances making -I transformation for sextupole cancellation. In this paper, a new HMBA lattice concept with sextupole cancellation across straight section is proposed, where -I is made between adjacent dispersion bumps of two lattice cells. This makes the main arc section free of the phase advance constraint, and as a result, the number of bending magnets (bends) in the lattice cell and the cell tunes can be easily changed, thus providing more choices for lattice design. To achieve the large phase advances required for -I in this new concept, split bend is used as the matching bend, which is a bend split into two pieces with a quadrupole in between. The split bend also serves to reduce the emittance, and the large phase advances also give low beta functions in the straight section enhancing the insertion device brightness. Besides, for a given emittance goal, this new HMBA lattice can have less bends than the typical HMBA lattice due to stronger focusing in bend unit cells, which is beneficial for saving space and suppressing intra-beam scattering effect. Two lattices are given as examples to demonstrate this new concept and show its linear and nonlinear properties, and further extension is also discussed.