AVS 58th Annual International Symposium and Exhibition
    Vacuum Technology Division Tuesday Sessions
       Session VT-TuM

Paper VT-TuM5
Design and Construction of the Vacuum System for SuperKEKB

Tuesday, November 1, 2011, 9:20 am, Room 111

Session: Accelerator and Large Vacuum System Design, Outgassing and Pumping
Presenter: Yusuke Suetsugu, KEK, Japan
Authors: Y. Suetsugu, KEK, Japan
K. Shibata, KEK, Japan
H. Hisamatsu, KEK, Japan
M. Shirai, KEK, Japan
T. Ishibashi, KEK, Japan
K. Kanazawa, KEK, Japan
Correspondent: Click to Email
The upgrade project of KEKB B-factory, that is SuperKEKB, has started last year. The SuperKEKB is a two-ring electron-positron collider with 7.0 GeV electrons and 4 GeV positrons aiming a goal luminosity of 8.0x1035 cm-2s-1, which is approximately 80 times higher than that of KEKB. In order to realize the unprecedented luminosity, the stored beam currents are increased to 2.4 A and 3.6 A for electrons and positrons, respectively. The vertical beam sizes at the collision point are also squeezed to approximately 60 and 50 nm with the beam emittances of 5/13 and 3/9 nm/pm (horizontal/vertical) for electrons and positrons, respectively. The vacuum system is accordingly improved to achieve the challenging goal. Beam pipes with antechambers are adopted for the reduction in the beam impedance of beam channel and also in the irradiation power density of synchrotron radiation from intense stored beams. Various vacuum components adaptable to the antechamber scheme with low beam impedance and high thermal strength had been developed. The bellows chambers, for example, have a comb-type RF-shield, and the main vacuum pump is NEG strips inserted into one of antechambers. Special attention is paid for the mitigation of the electron cloud issues in the positron ring to avoid unwanted increase in the beam emittance. In order to reduce secondary electron emission, the inner surface of beam pipes is coated with TiN, the grooved surface is prepared in dipole magnets, and the newly developed clearing electrodes are introduced in wiggler magnets. The antechamber scheme is also effective to suppress the photoelectron effect. The beam pipes in drift spaces, furthermore, are winded by solenoid coils. The design of vacuum system has been mostly completed, and the mass production of beam pipes has started. Copper beam pipes with clearing electrodes for wiggler magnets had been already delivered. Aluminum beam pipes for arc section of positron ring are under manufacturing, together with bellows chambers, gate valves, NEG pumps, and so on. The installation to the ring will start next year after TiN coating, expecting the start of commissioning from 2014. The overall vacuum system design and some key issues for SuperKEKB together with the present status will be reported here.