Publication Details (including relevant citation information):
J. Vac. Sci. Technol. A 18(2), 492 - 496 (2000).
|29.27.-a||Beams in particle accelerators|
|29.20.db||Storage rings and colliders|
Microparticle trapping phenomena were observed during beam lifetime decreases in some previously constructed electron storage rings. Fortunately, these harmful phenomena have been rarely observed in recently constructed rings (ESRF, APS, SRRC, SPring-8, etc.) where the vacuum systems are under stricter control for contamination. However, if these phenomena occur in spite of the frequent cleaning of vacuum equipment and stricter contamination controls for the vacuum environment, the harmful particles should be removed. Therefore, we carried out analyses to find the removal conditions for trapped particles using simple electrostatic electrodes for which a voltage is applied during the entire revolution time, except when the bunched electron beam is passing. In the case of the TRISTAN accumulation ring, it was found that trapped microparticles in the range of the continuous trapping condition can be adequately removed using electrodes 30 cm in length, and an applied potential of 30 V, in the passing time of the particle through the electrodes, if the passing time of the particle is more than 0.2 s. The longitudinal motion of the trapped microparticle is also discussed, using a newly developed equation for the longitudinal velocity of a trapped particle. The velocity decides the residence time of the trapped particle passing through the electrodes and the residence time is a key point to remove the particle using the electrostatic electrodes.