High-repetition-rate electron accelerators face beam instabilities induced by wake fields from beam-vacuum chamber interactions. Geometric discontinuities at ubiquitous con flat (CF) knife-edge flange connections are a dominant source of beam-induced impedance in all-metal vacuum chambers.

To mitigate this impedance, this paper presents the design of an RF-shielded flange-gasket connection structure that achieves a smooth post-tightening transition at the interface, thereby minimizing impedance.

Electromagnetic simulation: 3D simulations (CST) analyzed impedance effects of radial step heights and axial gaps at the transition, establishing allowable parameter ranges. Deformation simulation: ANSYS simulations modeled the shielded flange-copper gasket assembly to preliminarily determine inner diameter specifications for various gasket models. Vacuum sealing tests: Verified ultra-high vacuum integrity under applied tightening torque. Transition geometry testing: Measured the achieved radial step and axial gap post-tightening to define optimal copper gasket dimensions and tightening torque. Comparative simulation: CST simulations compared power loss and impedance for smooth chambers, standard flange-gasket transitions, and the proposed shielded transition.

Electromagnetic simulations were used to define critical tolerance ranges for radial step and axial gap. Deformation simulations were utilized to provide initial gasket inner diameter specifications. Vacuum tests confirmed effective sealing at a tightening torque ≥6 N·m. Transition testing established the optimal tightening torque and key copper gasket dimensions ensuring minimal geometric discontinuity. Comparative simulations demonstrated that the RF-shielded flange-gasket transition significantly reduces power loss and impedance compared to a standard CF transition, achieving performance close to that of a smooth vacuum chamber.

The designed RF-shielded flange-gasket connection structure effectively minimizes geometric discontinuity at the joint. Through combined electromagnetic, mechanical, and vacuum testing, critical parameters, including radial step, axial gap, gasket dimensions, and tightening torque, were optimized.. Electromagnetic verification confirms this design provides effective impedance shielding, offering a solution to mitigate wake-field-induced instabilities at flange connections in high-energy accelerators.