vacuum system design and pressure profile calculation for the accelerating tube of a tandem accelerator

In tandem accelerators, charge exchange can be achieved using either foil-based or gas-based methods. this study presents the design of a vacuum system specifically for the gas-based charge exchange method in tandem accelerators, aiming to maintain optimal atomic gas density in the interaction region and minimize gas leakage toward the accelerating tubes. to achieve high charge exchange efficiency, precise design of the beam transfer lines (btl) is essential. in this study, the impact of length and diameter of the btl on the pressure profile along the tube was investigated. a geometry was selected that concentrates gas in the interaction region while minimizing leakage into accelerating tubes. subsequently, gas flow simulations were used to determine the optimal operating window for gas throughput and pumping speed in the charge exchange region, ensuring an atomic gas density of 7.24×1016 cm-2 required for nearly 100% charge exchange efficiency. keeping the gas injection rate fixed, the effective range of pump speeds on charge exchange section and accelerating tubes was then identified to create a pressure ratio of about 10⁻³ mbar between the charge exchange section and accelerating tubes. results showed that beyond a certain threshold, increasing pumping speed does not significantly reduce the pressure due to conductance limitations.