Preliminary design of the beam transport system for the Super Tau-Charm Facility

The injector of the Super Tau-Charm Facility (STCF) should provide high-quality electron and positron beams for the collider ring according to different injection schemes, which is one of the key systems to ensure the high brightness of STCF. This paper presents the preliminary physical design and beam dynamics optimization of the complex beam transport system, which interconnects the main accelerator components over approximately 550 meters. The design encompasses three major segments: the injection line from the positron linac to the damping ring (PL2DR), the extraction and transport line from the damping ring to the main linac (DR2ML), and the final transport lines from the main linac to the collider rings (ML2CR). Each segment addresses unique challenges, including transverse emittance preservation, Twiss parameter matching, sophisticated phase-space manipulation and tight restrictions on the geometrical conditions. Through detailed optics design and particle tracking simulations, these results demonstrate the feasibility of the transport system in maintaining the high beam quality essential for the STCF's physics program.