Dynamic pressure monitoring in the front-end vacuum systems at the TPS facility

Abstract The Taiwan Photon Source Front End (TPS FE) vacuum systems are located between the storage ring and beam lines and include various high-heat-load (HHL) components. We investigate the change in dynamic pressure over time in the FE vacuum system, including measurements of HHL component temperatures, residual gas analyzer (RGA) data analysis, and the effect of changing the insertion device (ID) gap during beam current operation. Our results reveal that the exponential slopes of dynamic pressures in the FE versus accumulated beam dose is nearly −0.5 for all cases. With beam current at 400 mA and ID gap close to 7 mm, the dynamic pressure and HHL component temperature are 1.5 × 10 −8  Pa and 45 °C, respectively. The RGA data show that the main dynamic pressure contributions are H 2 , H 2 O, CO and CO 2 . H 2 O, CO and CO 2 come from the chamber surface, while H 2 comes from the vacuum chamber materials. The dynamic pressure was ∼2.3 × 10 −11  Pa/mA at 1000 Ah, and it continues to decrease with an increase in accumulated beam dose. These results indicate that the total dynamic pressure reaches to a value of 10 −7  Pa at full operation current in the FE systems.