Conceptual Design of Higher-order Achromat Lattice for the Upgrade of Taiwan Photon Source

NuanYa Huang^1*, MauSen Chiu¹, HunJen Tsai¹, PingJung Chou¹

¹NSRRC, Hsinchu, Taiwan

* Presenter:NuanYa Huang, email:nuanyahuang@gmail.com

We plan to upgrade the Taiwan Photon Source (TPS) for a green design with energy saving as the prime objective. The upgrade design is dubbed TPS-II. Several possible schemes for TPS-II lattice design are under study. In this report, one of the schemes based on the multi-bend achromat (MBA) lattice with the inclusion of reverse bending magnet will be reported. Because of the constraint to fix the present source points of undulator beamlines, an ideal MBA lattice design with a higher periodicity could not be fit in the existing accelerator tunnel. To accommodate the constraints imposed by the existing tunnel, we choose the design of higher-order achromat (HOA) lattice which is composed of the 5BA and 4BA cells. The HOA lattice produces a beam emittance about 160 pm-rad. As a result of the ultralow beam emittance, the brightness and coherence fraction of the photon beam are increased significantly, especially in the photon wavelength around 0.1 nm. The challenges and preliminary results of this HOA lattice design will be presented.

Keywords: MBA, emittance, HOA