AVS 56th International Symposium & Exhibition
    Vacuum Technology Tuesday Sessions
       Session VT-TuP

Paper VT-TuP14
Study of Secondary Electron Yield for KEKB Positron Ring

Tuesday, November 10, 2009, 6:00 pm, Room Hall 3

Session: Vacuum Technology Posters and Student-Built Vacuum Systems Poster Competition
Presenter: S. Kato, KEK, Japan
Authors: S. Kato, KEK, Japan
M. Nishiwaki, KEK, Japan
Correspondent: Click to Email
In order to mitigate electron cloud instability in high-intensity positron and proton accelerators, material surface with a low secondary electron yield (SEY) for the beam ducts is highly desired. In-situ SEY measuring system in the straight section of the KEKB positron ring was reported where one can measure SEYs of sample coupons exposed to electron cloud during the KEKB operation. In this study we aim to develop a mobile UHV system for sample coupon transfer from an arc section of the positron ring to a load lock chamber of XPS at our laboratory in order to carry out SEY measurements and surface analyses without exposing coupons to the air. There are two sample ports with a size of 8x8 mm2 at the side and the bottom of the positron beam duct for comparison. While both of samples are exposed to electron cloud caused by strong synchrotron light from a bending magnet of the ring, the light directly hits only the sample positioned at the side port. Sample coupons exposed to electron cloud can be transferred to UHV suitcases 1 and 2 through isolation gave valves installed between the beam duct and the suitcases. An amount of electron cloud is measured with the electron monitor. The UHV suitcase consists of a gate valve, linear and rotary motion drives to transfer the coupons, an ion pump with its power supply and drive batteries. The total weight is about 10kg. Two suitcases are almost identical. These suitcases are moved and connected to the second load lock chamber where the coupons up to 12 can be kept in UHV before the measurement. In this paper, the detail of the SEY measuring system is mentioned with its experimental results after a long time exposure of the coupons to the electron cloud during the KEKB operation.