| Paper | Title | Page |
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| TUOAB01 | Lattice Design of a Very Low-emittance Storage Ring for SPring-8-II | 942 |
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The design work for an upgrade project of the SPring-8, the SPring-8-II, is in progress. Its ultimate goal is to provide a superior brilliance of photons by reducing emittance of electrons until a diffraction limit. A multi-bend lattice has been adopted for the emittance reduction; a double-bend lattice (natural emittance of 2000 pmrad at 6 GeV), a triple-bend lattice (400 pmrad) and a quadruple-bend lattice (170 pmrad) were designed step by step for studying its feasibility*. For an additional emittance reduction, beam dynamic issues for a sextuple-bend lattice have been examined for the first candidate. In this case, the natural emittance is about 70 pmrad. The dynamic aperture has been enlarged by studying beam dynamic phenomena caused by nonlinear dispersion, nonlinear chromaticity, nonlinear resonance, etc., and by optimizing linear and nonlinear optics. The lattice design for the coming upgrade of SPring-8 will be presented in detail.
* K. Soutome et al., "Design Study of a very Low-emittance Storage Ring for the Future Upgrade Plan of SPring-8", Proc. of IPAC10, WEPEA032, p. 2555 (2010). |
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Slides TUOAB01 [4.812 MB] | |
| WEPC016 | Amplitude Dependent Orbit Shift and its Effect on Beam Injection | 2040 |
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| The betatron oscillation amplitude dependent orbit shift was measured at the electron storage ring, NewSUBARU. The result roughly agreed with the theoretical calculation. The effect of this shift on the beam injection is discussed using parameters of NewSUBARU and SPring-8. Generally there exists a better side for the injection, the inner side or the outer side of the ring, which depends on the sign of the orbit shift at the injection septum. In case of the NewSUBARU, the beam is injected from the outer side and the shift is positive. The effective thickness of the septum is reduced by the large oscillation amplitude of the injected beam. On the other hand at SPring-8, the beam is injected from the inner side of the ring while the orbit shift is negative. This means that the two rings are using better side for the injection. | ||
| WEPC068 | Amplitude Dependent Betatron Oscillation Center Shift by Non-linearity and Beam Instability Interlock | 2178 |
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| The center of the betatron oscillation in storage rings shifts as the amplitude of the oscillation increases. This effect is produced by non-linear components like sextupole magnets with its first-order perturbation. This shift can be observed as the shift of the closed orbit with usual slow beam position monitor (BPM) for closed orbit measurement. At the SPring-8 storage ring, the insertion devices (IDs) have their dedicated BPMs for monitoring the beam axis in the IDs. If some amount of the shift of beam axis is observed, the beam is aborted to avoid the damage by the irradiation of the ring components by ID radiation. When a betatron oscillation is excited by a beam transverse instability, the beam axis also oscillates and might produce the damage. Though it is not easy to detect the oscillation amplitude in various bunch current and filling patterns like in SPring-8, the oscillation produces the shift of the center of the betatron oscillation and can be observed by the BPM of IDs, and the beam is aborted. Calculation, tracking simulation and observation will be reported. | ||
| WEPC069 | Impact of Nonlinear Resonances on Beam Dynamics at the SPring-8 Storage Ring | 2181 |
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| For a low emittance storage ring like high brilliant light sources, the improvement of nonlinear beam dynamics is necessary for the stable operation, or for providing large dynamic aperture and momentum acceptance for efficient injection and long Touschek lifetime. At the SPring-8 storage ring it is observed that injection efficiency is affected by the gap heights of the magnet arrays of the in-vacuum insertion devices. The fact that the injected beam of fundamentally oscillating in horizontal direction is limited by the vertical aperture means that coupling resonances influence the beam dynamics. To clarify the phenomena, we studied the nonlinear beam dynamics of transverse betatron motion by means of turn-by-turn method. Then, we found some nonlinear coupling resonances, such as the one by skew sextupole field, are excited to enhance vertical oscillation and to deteriorate the injection efficiency. By analyzing these results, we developed measures to suppress the effect of the nonlinear coupling resonances and to improve the injection efficiency. | ||