Speaker
Description
The Super Tau-Charm Facility is a new-generation electron-positron collider in the beam energy range of 1-3.5 GeV, with a target luminosity exceeding $5×10^{34}\ \text{cm}^{−2}\text{s}^{−1}$ at 2 GeV using a large Piwinski angle and crab-waist collision scheme. However, the required sub-millimeter vertical beta function ($\beta_y^*$ < 1 mm) induce strong nonlinear chromaticity, which severely limits the momentum aperture of the collider rings and leads to a very short Touschek lifetime. To achieve the necessary 1.5% momentum aperture, local correction of the nonlinear chromaticity from the final‑focus quadrupoles is essential. In this paper, we derive the theoretical origin of the nonlinear chromaticity and demonstrate dedicated measures to systematically mitigate these nonlinearities order by order. Specifically, we present an updated modular linear lattice for the interaction region to facilitate nonlinear chromaticity optimization. The second‑order dispersion at the crab sextupoles is also reduced to nearly zero. By implementing a local chromaticity correction scheme up to the third order, we obtain a momentum aperture of 2% for the interaction region.
Funding Agency
This work is supported by the National Natural Science Foundation of China (Project No.
12341501, No. 12405174)
| Paper status | Resubmitted proceeding files received and assigned to an editor. Accepted. |
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