Parameter scaling and practical design of TME lattice

[Abstract] It is a challenge to produce a practical design of an electron storage ring with a theoretical minimum emittance (TME) lattice of ultra low emittance, e.g. down to a level of several pico-meters, due to the very strong focusing and the extremely large natural chromaticity associated with the lattice design. To help dealing with this challenge, it is customary to scale the parameters and look for a best solution guided by these scaling properties. In this paper, the parameter scaling is summarized, and it is argued that, with the lattice configuration with defocusing quadrupoles closer to the dipoles or simply with combined-function defocusing dipoles, one can reach a good balance of the low emittance and relatively small natural chromaticity, with phase advance per half cell below π/2. A 10 pm TME lattice for PEP-X is shown as demonstration of the design procedure.