IPAC2011 - List of Authors (Nakamura, T.)

Paper

Title

Page

Resonant Strip-line Type Longitudinal Kicker

493

T. Nakamura
JASRI/SPring-8, Hyogo-ken, Japan

The longitudinal feedback for the SPring-8 storage ring is under consideration as the device for suppression of the longitudinal instabilities driven by higher order modes of cavities, observed at test operation with 4 to 6 GeV low energy beam. As the beam energy and the ring circumference are rather high, and the length of the space for the longitudinal kickers is limited, high efficiency kicker per length is required in the our case. As a candidate of such kicker, we propose a resonant strip-line type longitudinal kicker with drive frequency of 13/4 of RF frequency. The shut impedance per length is higher than over-loaded cavities and the drive circuits can be simplified because of higher drive frequency. The design consideration, the result of the simulation and measurement of the prototype model, and the detail of the drive circuit will be reported in the presentation.

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]

TUPC095

Bucket-by-bucket On/Off-axis Injection with Variable Field Fast Kicker

1230

T. Nakamura
JASRI/SPring-8, Hyogo-ken, Japan

Dynamic aperture of ultra-low emittance storage rings is expected to be as small as a few mm; one order smaller than that of current rings, because of their high nonlinearity. The conventional injection scheme with bump formation may not be applied for such small aperture. On-axis injection with fast magnet is one of the solutions, however, it requires the injection beam of long trains of bunches, which impose serious limitation on the injector and the filling pattern. We propose a bucket-by-bucket on-axis/off-axis injection scheme, which manipulates the injection and stored beams bucket-by-bucket with a variable field fast kicker. For on-axis injection, this scheme eliminates the limitation on injectors and filling pattern, and also it can reject the contaminated electrons from the injector to keep the bunch purity. Those advantages allow the SPring-8 XFEL low emittance linac to be an injector matched with ultra-low emittance rings like the SPring-8 II: upgrade plan of SPring-8. By changing the drive power to the kicker, it can also produce position dependent kick required for the off-axis injection, with minimal perturbation on the stored beam achieved by bucket-by-bucket scheme.

WEPC016

Amplitude Dependent Orbit Shift and its Effect on Beam Injection

2040

Y. Shoji
LASTI, Hyogo, Japan
T. Nakamura, J. Schimizu, M. Takao
JASRI/SPring-8, Hyogo-ken, Japan

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

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.

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
MOPO007	Resonant Strip-line Type Longitudinal Kicker	493
	T. Nakamura JASRI/SPring-8, Hyogo-ken, Japan
	The longitudinal feedback for the SPring-8 storage ring is under consideration as the device for suppression of the longitudinal instabilities driven by higher order modes of cavities, observed at test operation with 4 to 6 GeV low energy beam. As the beam energy and the ring circumference are rather high, and the length of the space for the longitudinal kickers is limited, high efficiency kicker per length is required in the our case. As a candidate of such kicker, we propose a resonant strip-line type longitudinal kicker with drive frequency of 13/4 of RF frequency. The shut impedance per length is higher than over-loaded cavities and the drive circuits can be simplified because of higher drive frequency. The design consideration, the result of the simulation and measurement of the prototype model, and the detail of the drive circuit will be reported in the presentation.

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]

TUPC095	Bucket-by-bucket On/Off-axis Injection with Variable Field Fast Kicker	1230
	T. Nakamura JASRI/SPring-8, Hyogo-ken, Japan
	Dynamic aperture of ultra-low emittance storage rings is expected to be as small as a few mm; one order smaller than that of current rings, because of their high nonlinearity. The conventional injection scheme with bump formation may not be applied for such small aperture. On-axis injection with fast magnet is one of the solutions, however, it requires the injection beam of long trains of bunches, which impose serious limitation on the injector and the filling pattern. We propose a bucket-by-bucket on-axis/off-axis injection scheme, which manipulates the injection and stored beams bucket-by-bucket with a variable field fast kicker. For on-axis injection, this scheme eliminates the limitation on injectors and filling pattern, and also it can reject the contaminated electrons from the injector to keep the bunch purity. Those advantages allow the SPring-8 XFEL low emittance linac to be an injector matched with ultra-low emittance rings like the SPring-8 II: upgrade plan of SPring-8. By changing the drive power to the kicker, it can also produce position dependent kick required for the off-axis injection, with minimal perturbation on the stored beam achieved by bucket-by-bucket scheme.

WEPC016	Amplitude Dependent Orbit Shift and its Effect on Beam Injection	2040
	Y. Shoji LASTI, Hyogo, Japan T. Nakamura, J. Schimizu, M. Takao JASRI/SPring-8, Hyogo-ken, Japan
	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
	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.

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).