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Ohkuma, H.

Paper Title Page
WEPEA032 Design Study of a very Low-emittance Storage Ring for the Future Upgrade Plan of SPring-8 2555
 
  • K. Soutome, H. Ohkuma, J. Schimizu, Y. Shimosaki, M. Takao
    JASRI/SPring-8, Hyogo-ken
 
 

The SPring-8 storage ring has been operated for more than ten years and provided brilliant hard X-ray radiation to users. In recent years there are some discussions on upgrade plans of existing synchrotron radiation facilities and proposals of new facilities. In these the target brilliance of photons is set to be comparable or even higher, in some energy range, than that of the present value of SPring-8. At SPring-8 a design study of a new storage ring is now in progress for the future upgrade plan. The lattice structure will be changed from the present double-bend type to the multi-bend one, keeping the source position of all insertion devices unchanged. The emittance will be lowered from the present value of 3.4nmrad at 8GeV to 0.4nmrad at 6GeV (or 0.8nmrad at 8GeV) in the case of triple-bend lattice and 0.2nmrad at 6GeV (or 0.3nmrad at 8GeV) in the case of quadruple-bend lattice. We will report the present state of our preliminary work on lattice design. Nonlinear resonance correction to enlarge the dynamic aperture for on- and off-momentum electrons will also be discussed.

 
THOBRA02 Suppression of Transverse Instabilities by Chromaticity Modulation 3647
 
  • T. Nakamura, N. Kumagai, S. Matsui, H. Ohkuma, T. Ohshima, H. Takebe
    JASRI/SPring-8, Hyogo-ken
  • A. Ando, S. Hashimoto, Y. Shoji
    NewSUBARU/SPring-8, Laboratory of Advanced Science and Technology for Industry (LASTI), Hyogo
  • K. Kumagai
    RIKEN Nishina Center, Wako
 
 

Transverse beam instabilities were suppressed with chromaticity modulation (CM)* in the electron storage ring, New SUBARU. The horizontal and vertical betatron tune spread inside a bunch were introduced by CM with synchrotron oscillation frequency driven by an AC sextuple magnet**, to obtain Landau damping of the coherent bunch motion. The tune spread in a bunch is usually introduced by octupole field, however, its high nonlinearity reduces the dynamic aperture. And usual feedback against instabilities work only on m=0 mode and it is not easy to be applied to hadron synchrotrons because of their varying revolution period. The CM scheme has not such disadvantages. The damping time of coherent motion excited by external kick was measured and was found as less than 1ms, one order faster than that without CM. To observe the effect on instabilities, we intentionally tuned an HOM in a cavity to excite a horizontal multi-bunch instability. The instability peak in the spectrum of the beam motion was vanished with CM turned on and the instability was suppressed. We also observed the increase of the threshold current of the vertical single-bunch mode-coupling instability by factor 3 with CM.


* T. Nakamura, Proc. of PAC'95, p.3100 (1995).
** T. Nakamura, et al., Appl. Superconduct., IEEE Trans. Vol. 18, p.326 (2008).

 

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