AVS 59th Annual International Symposium and Exhibition
    Vacuum Technology Tuesday Sessions
       Session VT-TuA

Invited Paper VT-TuA1
Design of the Vacuum System for the SuperKEKB Positron Ring

Tuesday, October 30, 2012, 2:00 pm, Room 14

Session: Accelerator and Ultra-Clean Vacuum Systems
Presenter: Y. Suetsugu, High Energy Accelerator Research Organization, Japan
Authors: Y. Suetsugu, High Energy Accelerator Research Organization, Japan
K. Kanazawa, High Energy Accelerator Research Organization, Japan
K. Shibata, High Energy Accelerator Research Organization, Japan
T. Ishibashi, High Energy Accelerator Research Organization, Japan
H. Hisamatsu, High Energy Accelerator Research Organization, Japan
M. Shirai, High Energy Accelerator Research Organization, Japan
S. Terui, High Energy Accelerator Research Organization, Japan
Correspondent: Click to Email
A two-ring electron-positron collider with asymmetric energies, the SuperKEKB, has been designed as an upgrade of the KEKB B-factory (KEKB). The SuperKEKB aims for a maximum luminosity of 8×1035 cm−2s−1, which is approximately 40 times larger than that of the KEKB. The upgrade of the vacuum system is a key factor that will allow the SuperKEKB to achieve unprecedented high performance. As for the positron ring, most of the beam pipes are newly designed to reduce beam impedance and, especially, to manage the electron cloud effect (ECE), which is essential to keep the low-emittance beam stable. The beam pipes basically have antechambers at the both sides of a beam channel. 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 with the same cross section to the beam pipe, and the main vacuum pump consisting of NEG strips is inserted into one of the antechambers. The antechamber scheme is also effective to mitigate the ECE, that is, it structurally suppresses the photoelectron effect. A side wall of the antechamber, where the synchrotron radiation hit directly, is roughened so as to reduce photon reflections. In order to reduce secondary electron effect, on the other hand, the inner surface of beam channel is coated with titanium nitride (TiN). Furthermore, the longitudinal grooved surface and the clearing electrode are prepared for the beam pipes in dipole magnets and the wiggler magnets in the ring, respectively. In addition, the beam pipes in drift spaces are winded by solenoid coils. These mitigation techniques are the fruits of various theoretical and experimental studies so far. The SuperkKEB positron ring is the first one that will adopt these techniques in a large scale. The design of vacuum system has been mostly completed, and the mass production of beam pipes has started. The vacuum system design and some key issues for SuperKEKB positron ring will be reported here together with the present status.