• C. Mitsuda, K. Fukami, K. Kobayashi, M. Oishi, Y. Okayasu, M. Shoji, K. Soutome, H. Yonehara
  JASRI/SPring-8, Hyogo-ken
• T. Nakanishi
  SES, Hyogo-pref.
• T. Ohshima
  RIKEN/SPring-8, Hyogo

In top-up operation at SPring-8 the horizontal beam oscillation had been excited because the injection bump orbit is not closed perfectly. For this problem, we had made an effort to reduce the residual beam oscillation by the improvement of bump magnet design, reducing the effect due to the nonlinearity of sextupole magnet and introducing pulsed corrector magnet, etc. By these improvements the average amplitude of residual oscillation has now been suppressed to the level of less than 0.1 mm. Still remaining relatively large residual oscillation comes from a non-similarity of a temporal shape of magnetic field of four bump magnets. We then started development fast kicker magnet system to give a counter kick to this part of residual beam oscillation. A key technology in this development is how to generate a large pulsed current in a short period to meet the oscillation characteristic. A newly developed fast pulsed power supply can generate a current of about 300 A, or corresponding magnetic field of 4.61 mT, with a pulse width of 1.2 us. Recently, we succeeded in the reduction of the horizontal beam oscillation at the timing of firing bump magnets by using this kicker system.

• K. Soutome, K. Fukami, M. Oishi, Y. Okayasu, J. Schimizu, Y. Shimosaki, M. Shoji, M. Takao, H. Yonehara
  JASRI/SPring-8, Hyogo-ken

A set of three in-vacuum undulators is going to be installed in one of four long straight sections of the SPring-8 storage ring. In order to make the undulator gap as narrow as possible, we plan to divide this long straight section into three sub-sections and install quadrupole magnets between these sub-sections to lower the vertical betatron function. In the modified lattice, however, the symmetry of the ring is lowered and in general it becomes difficult to keep a sufficient dynamic aperture for on- and off-momentum electrons. The long straight sections were originally introduced in the year 2000 and at that time we developed a method of "quasi-transparent matching of sextupole fields" where two key concepts of betatron phase matching and local chromaticity correction were combined to obtain a sufficient dynamic aperture and momentum acceptance. Then, in the year 2007 "counter-sextupole magnets" were further installed to cancel the effect due to non-linear kick by sextupole magnets used for local chromaticity correction. In designing the new lattice with a modified long straight section, we followed the same line and could recover the dynamic aperture and momentum acceptance.