Hiroshi Saeki - Removal conditions for trapped microparticles in a stored electron beam using electrostatic electrodes

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  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.

  Address (URL): http://avspublications.org/jvsta/resource/1/jvtad6/v18/i2/p492_s1