IPAC2011 - List of Authors (Soutome, K.)

Paper

Title

Page

Lattice Design of a Very Low-emittance Storage Ring for SPring-8-II

942

Y. Shimosaki, K.K. Kaneki, T. Nakamura, H. Ohkuma, J. Schimizu, K. Soutome, M. Takao
JASRI/SPring-8, Hyogo-ken, Japan

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).

Slides TUOAB01 [4.812 MB]

WEPC068

Amplitude Dependent Betatron Oscillation Center Shift by Non-linearity and Beam Instability Interlock

2178

T. Nakamura, K. Kobayashi, J. Schimizu, T. Seike, K. Soutome, M. Takao
JASRI/SPring-8, Hyogo-ken, Japan
T. Hara
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

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

M. Takao, J. Schimizu, Y. Shimosaki, K. Soutome
JASRI/SPring-8, Hyogo-ken, Japan

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.

THPC031

Measurement of Longitudinal Dynamics of Injected Beam in a Storage Ring

2978

T. Watanabe, T. Fujita, M. Masaki, K. Soutome, S. Takano, M. Takao, K. Tamura
JASRI/SPring-8, Hyogo-ken, Japan

Experimental observation of longitudinal dynamics of injected beam in a storage ring has been demonstrated. Since the injected beam undergoes synchrotron oscillation in a longitudinal phase space, two projected values, i.e., a bunch duration and an energy spread, oscillate at twice the synchrotron frequency. At SPring-8, the initial energy spread (~0.126%) at the injection goes up and down until it reaches the equilibrium energy spread (~0.11%). If the injection timing should not be optimized, an asymmetrically enhanced oscillation could distort the injection efficiency. The observation of such an oscillation helps make sure that no significant injection loss occurs. More importantly, the scheme is expected to enable us to observe non-linear longitudinal dynamics of ultra-short bunches injected from the XFEL linac; the bunches are in near future going to be transferred from the linac to the storage ring via 600-meter long transports, in which strong coherent synchrotron radiation and other high peak-current effects will not be ignorable. Experimental results obtained by a dual-scan streak camera and other devices as well as numerical simulations will be presented.

THPC032

Current Status of SPring-8 Upgrade Plan

2981

T. Watanabe, T. Asaka, H. Dewa, H. Ego, T. Fujita, K. Fukami, M. Masaki, C. Mitsuda, A. Mochihashi, T. Nakamura, H. Ohkuma, Y. Okayasu, Y. Shimosaki, K. Soutome, M. Takao
JASRI/SPring-8, Hyogo-ken, Japan
T. Tanaka
RIKEN Spring-8 Harima, Hyogo, Japan

The SPring-8 upgrade plan has been discussed. The main goal is to replace the storage ring in the existing tunnel so that the resulting emittance will get as close to the diffraction limit in hard x-ray region as possible. For 10 keV photons, for instance, the diffraction limit corresponds to the emittance of as small as 10 pm.rad. For the challenging goal, the new ring features a multi-bend lattice with damping wigglers, which presumably enables us to reduce an emittance by two orders of magnitudes or more compared with the current double-bend lattice without damping wigglers. Up to now, a six-bend lattice has been mainly studied, which is supposed to generate a natural emittance of 60–70 pm.rad for 6 GeV. In addition, damping wigglers and coupling control should assist to reduce the emittance even more for approaching the ultimate goal. The major modification requires not only an advanced lattice design via manipulation of non-linear beam dynamics but also extensive technological developments in almost every component such as magnets, monitors, and RF systems. The overall review of the upgrade plan, including some detailed discussions on the critical issues, will be presented.

THPC143

Beam-based Alignment for Injection Bump Magnets of the Storage Ring using Remote Tilt-control System

3221

K. Fukami, K. Kobayashi, C. Mitsuda, T. Nakamura, K. Soutome
JASRI/SPring-8, Hyogo-ken, Japan

Stored beam is oscillated in vertical if the injection-bump magnets have alignment error in rotation around the beam-axis (tilt). In addition, even if the tilt is negligibly small, the beam out of the median plane is kicked in vertical direction. Also, there is a small long-term drift of the vertical beam positions in the bump magnets, which causes the gradual increase of the oscillation. We have already developed a remote tilt-control system to make a smooth realignment*. To observe the oscillation, the beam position was measured bunch-by-bunch and turn-by-turn by using a bunch-by-bunch feedback system** with high resolution strip-line type beam position monitor. To obtain responses to the tilts of each magnet, the oscillations were measured under the condition that the magnets were tilted intentionally. Tilt errors were calculated with least-squares method using the responses. In order to confirm the source of the residual oscillation, a frequency analysis was carried out with FFT method using the position data from 1st to 128th turns. We succeeded in suppressing the vertical oscillation to sub-microns order, the value of less than one tenth of the beam size.
* K. Fukami et al., Proc. of EPAC'08, p. 2172 (2008).
** T. Nakamura et al., Proc. of ICALEPCS'05, PO2.022-2 (2005).

Paper	Title	Page
TUOAB01	Lattice Design of a Very Low-emittance Storage Ring for SPring-8-II	942
	Y. Shimosaki, K.K. Kaneki, T. Nakamura, H. Ohkuma, J. Schimizu, K. Soutome, M. Takao JASRI/SPring-8, Hyogo-ken, Japan
	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).
	Slides TUOAB01 [4.812 MB]

WEPC068	Amplitude Dependent Betatron Oscillation Center Shift by Non-linearity and Beam Instability Interlock	2178
	T. Nakamura, K. Kobayashi, J. Schimizu, T. Seike, K. Soutome, M. Takao JASRI/SPring-8, Hyogo-ken, Japan T. Hara RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	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
	M. Takao, J. Schimizu, Y. Shimosaki, K. Soutome JASRI/SPring-8, Hyogo-ken, Japan
	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.

THPC031	Measurement of Longitudinal Dynamics of Injected Beam in a Storage Ring	2978
	T. Watanabe, T. Fujita, M. Masaki, K. Soutome, S. Takano, M. Takao, K. Tamura JASRI/SPring-8, Hyogo-ken, Japan
	Experimental observation of longitudinal dynamics of injected beam in a storage ring has been demonstrated. Since the injected beam undergoes synchrotron oscillation in a longitudinal phase space, two projected values, i.e., a bunch duration and an energy spread, oscillate at twice the synchrotron frequency. At SPring-8, the initial energy spread (~0.126%) at the injection goes up and down until it reaches the equilibrium energy spread (~0.11%). If the injection timing should not be optimized, an asymmetrically enhanced oscillation could distort the injection efficiency. The observation of such an oscillation helps make sure that no significant injection loss occurs. More importantly, the scheme is expected to enable us to observe non-linear longitudinal dynamics of ultra-short bunches injected from the XFEL linac; the bunches are in near future going to be transferred from the linac to the storage ring via 600-meter long transports, in which strong coherent synchrotron radiation and other high peak-current effects will not be ignorable. Experimental results obtained by a dual-scan streak camera and other devices as well as numerical simulations will be presented.

THPC032	Current Status of SPring-8 Upgrade Plan	2981
	T. Watanabe, T. Asaka, H. Dewa, H. Ego, T. Fujita, K. Fukami, M. Masaki, C. Mitsuda, A. Mochihashi, T. Nakamura, H. Ohkuma, Y. Okayasu, Y. Shimosaki, K. Soutome, M. Takao JASRI/SPring-8, Hyogo-ken, Japan T. Tanaka RIKEN Spring-8 Harima, Hyogo, Japan
	The SPring-8 upgrade plan has been discussed. The main goal is to replace the storage ring in the existing tunnel so that the resulting emittance will get as close to the diffraction limit in hard x-ray region as possible. For 10 keV photons, for instance, the diffraction limit corresponds to the emittance of as small as 10 pm.rad. For the challenging goal, the new ring features a multi-bend lattice with damping wigglers, which presumably enables us to reduce an emittance by two orders of magnitudes or more compared with the current double-bend lattice without damping wigglers. Up to now, a six-bend lattice has been mainly studied, which is supposed to generate a natural emittance of 60–70 pm.rad for 6 GeV. In addition, damping wigglers and coupling control should assist to reduce the emittance even more for approaching the ultimate goal. The major modification requires not only an advanced lattice design via manipulation of non-linear beam dynamics but also extensive technological developments in almost every component such as magnets, monitors, and RF systems. The overall review of the upgrade plan, including some detailed discussions on the critical issues, will be presented.

THPC143	Beam-based Alignment for Injection Bump Magnets of the Storage Ring using Remote Tilt-control System	3221
	K. Fukami, K. Kobayashi, C. Mitsuda, T. Nakamura, K. Soutome JASRI/SPring-8, Hyogo-ken, Japan
	Stored beam is oscillated in vertical if the injection-bump magnets have alignment error in rotation around the beam-axis (tilt). In addition, even if the tilt is negligibly small, the beam out of the median plane is kicked in vertical direction. Also, there is a small long-term drift of the vertical beam positions in the bump magnets, which causes the gradual increase of the oscillation. We have already developed a remote tilt-control system to make a smooth realignment. To observe the oscillation, the beam position was measured bunch-by-bunch and turn-by-turn by using a bunch-by-bunch feedback system* with high resolution strip-line type beam position monitor. To obtain responses to the tilts of each magnet, the oscillations were measured under the condition that the magnets were tilted intentionally. Tilt errors were calculated with least-squares method using the responses. In order to confirm the source of the residual oscillation, a frequency analysis was carried out with FFT method using the position data from 1st to 128th turns. We succeeded in suppressing the vertical oscillation to sub-microns order, the value of less than one tenth of the beam size. * K. Fukami et al., Proc. of EPAC'08, p. 2172 (2008). ** T. Nakamura et al., Proc. of ICALEPCS'05, PO2.022-2 (2005).