IPAC2011 - List of Authors (Cai, Y.)

Paper

Title

Page

Beam Breakup Simulation for the PEP-X ERL

805

Y. Jiao, Y. Cai, A. Chao
SLAC, Menlo Park, California, USA

Funding: The work is supported by the U.S. Department of Energy under contract No. DE-AC02-76SF00515.
The transverse beam breakup (BBU) is one of the dominant factors in ERL for the available beam current. A tracking code built in Matlab is developed and benchmarked by comparing with the analytical solutions with the simple model. Study on the threshold current and emittance growth due to the transverse BBU for PEP-X ERL are presented in this paper.

MOPS090

Observation of Beam Ion Instability in SPEAR3

814

L. Wang, Y. Cai, W.J. Corbett, T.O. Raubenheimer, J.A. Safranek, J.F. Schmerge, J.J. Sebek
SLAC, Menlo Park, California, USA
D. Teytelman
Dimtel, San Jose, USA

Weak vertical coupled bunch instability with oscillation amplitude at μm level has been observed in SPEAR3. The instability becomes stronger when there is a vacuum pressure rise by partially turning off vacuum pumps and it becomes weaker when the vertical beam emittance is increased by turning off the skew quadrupole magnets. These confirmed that the instability was driven by ions in the vacuum. The threshold of the beam ion instability when running with a single bunch train is just under 200 mA. This paper presents the comprehensive observations of the beam ion instability in SPEAR3. The effects of vacuum pressure, beam current, beam filling pattern, chromaticity, beam emittance and bunch-by-bunch feedback are investigated in great detail.pattern, chromaticity, beam emittance and bunch-by-bunch feedback are investigated in great detail.

WEPC045

Transverse Emittance Reduction with Tapered Foil

2112

Y. Jiao, Y. Cai, A. Chao
SLAC, Menlo Park, California, USA

Funding: The work is supported by the U.S. Department of Energy under contract No. DE-AC02-76SF00515.
The idea of reducing transverse emittance with tapered energy-loss foil is proposed by J.M. Peterson in 1980s and recently by B. Carlsten. In present paper, we present the physical model of tapered energy-loss foil and analyze the emittance reduction using the concept of eigen emittance. The study shows that, to reduce transverse emittance, one should collimate at least 4% of particles which has either much low energy or large transverse divergence. The multiple coulomb scattering is not trivial, leading to a limited emittance reduction ratio.

THPC074

Dynamic Aperture and Tolerances for PEP-X Ultimate Storage Ring Design

3065

M.-H. Wang, Y. Cai, R.O. Hettel, Y. Nosochkov
SLAC, Menlo Park, California, USA
M. Borland
ANL, Argonne, USA

Funding: Work supported by the Department of Energy Contract DE-AC02-76SF00515.
A lattice for the PEP-X ultimate storage ring light source[1], having 11 pm-rad natural emittance at a beam energy of 4.5 GeV at zero current, using 90 m of damping wiggler and fitting into the existing 2.2-km PEP-II tunnel, has been recently designed[2]. Such a low emittance lattice requires very strong sextupoles for chromaticity correction, which in turn introduce strong non-linear field effects that limit the beam dynamic aperture. In order to maximize the dynamic aperture we choose the cell phases to cancel the third and fourth order geometric resonances in each 8-cell arc. Four families of chromatic sextupoles and six families of geometric (or harmonic) sextupoles are added to correct the chromatic and amplitude-dependent tunes. To find the best settings of the ten sextupole families, we use a Multi-Objective Genetic Optimizer employing elegant[3] to optimize the beam lifetime and dynamic aperture simultaneously. Then we evaluate dynamic aperture reduction caused by magnetic field multipole errors, magnet fabrication errors and misalignments. A sufficient dynamic aperture is obtained for injection, as well as workable beam lifetime[2].

THPC075

Lattice Design for PEP-X Ultimate Storage Ring Light Source

3068

Y. Nosochkov, K.L.F. Bane, Y. Cai, R.O. Hettel, M.-H. Wang
SLAC, Menlo Park, California, USA

Funding: Work supported by the Department of Energy Contract DE-AC02-76SF00515.
SLAC expertise in designing and operating high current storage rings and the availability of the 2.2-km PEP-II tunnel present an opportunity for building a next generation light source – PEP-X – that would replace the SPEAR3 storage ring in the future. The "baseline" design for PEP-X, with 164 pm-rad emittance at 4.5 GeV beam energy and a current of 1.5 A, was completed in 2010. As a next step in the study, a so-called "ultimate" PEP-X lattice having another order of magnitude reduction in emittance from the baseline design has been investigated. The beam emittance approaches the diffraction limited photon emittance for multi-keV photons, providing near maximum photon brightness and high coherence. In this design, the ring arcs contain seven-bend achromat cells yielding 29 pm-rad natural emittance and up to 9 insertion device straights per arc. Another factor of two emittance reduction is achieved with an 89.3-m damping wiggler installed in one of the six long straights. Details of the lattice design, the sextupole correction scheme, dynamic aperture simulations, and calculation of the intra-beam scattering effect and Touschek lifetime at a nominal 200-mA current are presented.

FRXAA01

Theory of Microwave Instability and Coherent Synchrotron Radiation in Electron Storage Rings

3774

Y. Cai
SLAC, Menlo Park, California, USA

Funding: This work was supported by Department of Energy Contract No. DE-AC02-76SF00515.
Bursting of coherent synchrotron radiation has been observed and in fact used to generate THz radiation in many electron storage rings. In order to understand and control the bursting, we return to the study of the microwave instability. In this talk, we will report on the theoretical understanding, including recent developments, of the microwave instability in electron storage rings. The historical progress of the theories will be surveyed, starting from the dispersion relation of coasting beams, to the work of Sacherer on a bunched beam, and ending with the Oide and Yokoya method of discretization. This theoretical survey will be supplemented with key experimental results over the years. Finally, we will describe the recent theoretical development of utilizing the Laguerre polynomials in the presence of potential-well distortion. This self-consistent method will be applied to study the microwave instability driven by commonly known impedances, including that of coherent synchrotron radiation.

Slides FRXAA01 [0.948 MB]

THPZ003

The SuperB Project: Accelerator Status and R&D

3684

M.E. Biagini, S. Bini, R. Boni, M. Boscolo, B. Buonomo, T. Demma, E. Di Pasquale, A. Drago, L.G. Foggetta, S. Guiducci, S.M. Liuzzo, G. Mazzitelli, L. Pellegrino, M.A. Preger, P. Raimondi, U. Rotundo, C. Sanelli, M. Serio, A. Stecchi, A. Stella, S. Tomassini, M. Zobov
INFN/LNF, Frascati (Roma), Italy
M.A. Baylac, O. Bourrion, J.-M. De Conto, N. Monseu, C. Vescovi
LPSC, Grenoble, France
K.J. Bertsche, A. Brachmann, Y. Cai, A. Chao, M.H. Donald, R.C. Field, A.S. Fisher, D. Kharakh, A. Krasnykh, K.C. Moffeit, Y. Nosochkov, A. Novokhatski, M.T.F. Pivi, J.T. Seeman, M.K. Sullivan, S.P. Weathersby, A.W. Weidemann, U. Wienands, W. Wittmer, G. Yocky
SLAC, Menlo Park, California, USA
S. Bettoni
PSI, Villigen, Switzerland
A.V. Bogomyagkov, I. Koop, E.B. Levichev, S.A. Nikitin, I.N. Okunev, P.A. Piminov, D.N. Shatilov, S.V. Sinyatkin, P. Vobly
BINP SB RAS, Novosibirsk, Russia
B. Bolzon, M. Esposito
CERN, Geneva, Switzerland
F. Bosi
INFN-Pisa, Pisa, Italy
L. Brunetti, A. Jeremie
IN2P3-LAPP, Annecy-le-Vieux, France
A. Chancé
CEA, Gif-sur-Yvette, France
P. Fabbricatore, S. Farinon, R. Musenich
INFN Genova, Genova, Italy
E. Paoloni
University of Pisa and INFN, Pisa, Italy
C. Rimbault, A. Variola
LAL, Orsay, France
Y. Zhang
IHEP Beijing, Beijing, People's Republic of China

The SuperB collider project has been recently approved by the Italian Government as part of the National Research Plan. SuperB is a high luminosity (10³6 cm^-2 s^-1) asymmetric e⁺e⁻ collider at the Y(4S) energy. The design is based on a “large Piwinski angle and Crab Waist” scheme already successfully tested at the DAΦNE Phi-Factory in Frascati, Italy. The project combines the challenges of high luminosity colliders and state-of-the-art synchrotron light sources, with two beams (e⁺ at 6.7 and e^- at 4.2 GeV) with extremely low emittances and small beam sizes at the Interaction Point. As unique features, the electron beam will be longitudinally polarized at the IP and the rings will be able to ramp down to collide at the tau/charm energy threshold with one tenth the luminosity. The relatively low beam currents (about 2 A) will allow for low running (power) costs compared to similar machines. The insertion of beam lines for synchrotron radiation users is the latest feature included in the design. The lattice has been recently modified to accommodate insertion devices for X-rays production. A status of the project and a description of R&D in progress will be presented.

Paper	Title	Page
MOPS086	Beam Breakup Simulation for the PEP-X ERL	805
	Y. Jiao, Y. Cai, A. Chao SLAC, Menlo Park, California, USA
	Funding: The work is supported by the U.S. Department of Energy under contract No. DE-AC02-76SF00515. The transverse beam breakup (BBU) is one of the dominant factors in ERL for the available beam current. A tracking code built in Matlab is developed and benchmarked by comparing with the analytical solutions with the simple model. Study on the threshold current and emittance growth due to the transverse BBU for PEP-X ERL are presented in this paper.

MOPS090	Observation of Beam Ion Instability in SPEAR3	814
	L. Wang, Y. Cai, W.J. Corbett, T.O. Raubenheimer, J.A. Safranek, J.F. Schmerge, J.J. Sebek SLAC, Menlo Park, California, USA D. Teytelman Dimtel, San Jose, USA
	Weak vertical coupled bunch instability with oscillation amplitude at μm level has been observed in SPEAR3. The instability becomes stronger when there is a vacuum pressure rise by partially turning off vacuum pumps and it becomes weaker when the vertical beam emittance is increased by turning off the skew quadrupole magnets. These confirmed that the instability was driven by ions in the vacuum. The threshold of the beam ion instability when running with a single bunch train is just under 200 mA. This paper presents the comprehensive observations of the beam ion instability in SPEAR3. The effects of vacuum pressure, beam current, beam filling pattern, chromaticity, beam emittance and bunch-by-bunch feedback are investigated in great detail.pattern, chromaticity, beam emittance and bunch-by-bunch feedback are investigated in great detail.

WEPC045	Transverse Emittance Reduction with Tapered Foil	2112
	Y. Jiao, Y. Cai, A. Chao SLAC, Menlo Park, California, USA
	Funding: The work is supported by the U.S. Department of Energy under contract No. DE-AC02-76SF00515. The idea of reducing transverse emittance with tapered energy-loss foil is proposed by J.M. Peterson in 1980s and recently by B. Carlsten. In present paper, we present the physical model of tapered energy-loss foil and analyze the emittance reduction using the concept of eigen emittance. The study shows that, to reduce transverse emittance, one should collimate at least 4% of particles which has either much low energy or large transverse divergence. The multiple coulomb scattering is not trivial, leading to a limited emittance reduction ratio.

THPC074	Dynamic Aperture and Tolerances for PEP-X Ultimate Storage Ring Design	3065
	M.-H. Wang, Y. Cai, R.O. Hettel, Y. Nosochkov SLAC, Menlo Park, California, USA M. Borland ANL, Argonne, USA
	Funding: Work supported by the Department of Energy Contract DE-AC02-76SF00515. A lattice for the PEP-X ultimate storage ring light source[1], having 11 pm-rad natural emittance at a beam energy of 4.5 GeV at zero current, using 90 m of damping wiggler and fitting into the existing 2.2-km PEP-II tunnel, has been recently designed[2]. Such a low emittance lattice requires very strong sextupoles for chromaticity correction, which in turn introduce strong non-linear field effects that limit the beam dynamic aperture. In order to maximize the dynamic aperture we choose the cell phases to cancel the third and fourth order geometric resonances in each 8-cell arc. Four families of chromatic sextupoles and six families of geometric (or harmonic) sextupoles are added to correct the chromatic and amplitude-dependent tunes. To find the best settings of the ten sextupole families, we use a Multi-Objective Genetic Optimizer employing elegant[3] to optimize the beam lifetime and dynamic aperture simultaneously. Then we evaluate dynamic aperture reduction caused by magnetic field multipole errors, magnet fabrication errors and misalignments. A sufficient dynamic aperture is obtained for injection, as well as workable beam lifetime[2].

THPC075	Lattice Design for PEP-X Ultimate Storage Ring Light Source	3068
	Y. Nosochkov, K.L.F. Bane, Y. Cai, R.O. Hettel, M.-H. Wang SLAC, Menlo Park, California, USA
	Funding: Work supported by the Department of Energy Contract DE-AC02-76SF00515. SLAC expertise in designing and operating high current storage rings and the availability of the 2.2-km PEP-II tunnel present an opportunity for building a next generation light source – PEP-X – that would replace the SPEAR3 storage ring in the future. The "baseline" design for PEP-X, with 164 pm-rad emittance at 4.5 GeV beam energy and a current of 1.5 A, was completed in 2010. As a next step in the study, a so-called "ultimate" PEP-X lattice having another order of magnitude reduction in emittance from the baseline design has been investigated. The beam emittance approaches the diffraction limited photon emittance for multi-keV photons, providing near maximum photon brightness and high coherence. In this design, the ring arcs contain seven-bend achromat cells yielding 29 pm-rad natural emittance and up to 9 insertion device straights per arc. Another factor of two emittance reduction is achieved with an 89.3-m damping wiggler installed in one of the six long straights. Details of the lattice design, the sextupole correction scheme, dynamic aperture simulations, and calculation of the intra-beam scattering effect and Touschek lifetime at a nominal 200-mA current are presented.

FRXAA01	Theory of Microwave Instability and Coherent Synchrotron Radiation in Electron Storage Rings	3774
	Y. Cai SLAC, Menlo Park, California, USA
	Funding: This work was supported by Department of Energy Contract No. DE-AC02-76SF00515. Bursting of coherent synchrotron radiation has been observed and in fact used to generate THz radiation in many electron storage rings. In order to understand and control the bursting, we return to the study of the microwave instability. In this talk, we will report on the theoretical understanding, including recent developments, of the microwave instability in electron storage rings. The historical progress of the theories will be surveyed, starting from the dispersion relation of coasting beams, to the work of Sacherer on a bunched beam, and ending with the Oide and Yokoya method of discretization. This theoretical survey will be supplemented with key experimental results over the years. Finally, we will describe the recent theoretical development of utilizing the Laguerre polynomials in the presence of potential-well distortion. This self-consistent method will be applied to study the microwave instability driven by commonly known impedances, including that of coherent synchrotron radiation.
	Slides FRXAA01 [0.948 MB]

THPZ003	The SuperB Project: Accelerator Status and R&D	3684
	M.E. Biagini, S. Bini, R. Boni, M. Boscolo, B. Buonomo, T. Demma, E. Di Pasquale, A. Drago, L.G. Foggetta, S. Guiducci, S.M. Liuzzo, G. Mazzitelli, L. Pellegrino, M.A. Preger, P. Raimondi, U. Rotundo, C. Sanelli, M. Serio, A. Stecchi, A. Stella, S. Tomassini, M. Zobov INFN/LNF, Frascati (Roma), Italy M.A. Baylac, O. Bourrion, J.-M. De Conto, N. Monseu, C. Vescovi LPSC, Grenoble, France K.J. Bertsche, A. Brachmann, Y. Cai, A. Chao, M.H. Donald, R.C. Field, A.S. Fisher, D. Kharakh, A. Krasnykh, K.C. Moffeit, Y. Nosochkov, A. Novokhatski, M.T.F. Pivi, J.T. Seeman, M.K. Sullivan, S.P. Weathersby, A.W. Weidemann, U. Wienands, W. Wittmer, G. Yocky SLAC, Menlo Park, California, USA S. Bettoni PSI, Villigen, Switzerland A.V. Bogomyagkov, I. Koop, E.B. Levichev, S.A. Nikitin, I.N. Okunev, P.A. Piminov, D.N. Shatilov, S.V. Sinyatkin, P. Vobly BINP SB RAS, Novosibirsk, Russia B. Bolzon, M. Esposito CERN, Geneva, Switzerland F. Bosi INFN-Pisa, Pisa, Italy L. Brunetti, A. Jeremie IN2P3-LAPP, Annecy-le-Vieux, France A. Chancé CEA, Gif-sur-Yvette, France P. Fabbricatore, S. Farinon, R. Musenich INFN Genova, Genova, Italy E. Paoloni University of Pisa and INFN, Pisa, Italy C. Rimbault, A. Variola LAL, Orsay, France Y. Zhang IHEP Beijing, Beijing, People's Republic of China
	The SuperB collider project has been recently approved by the Italian Government as part of the National Research Plan. SuperB is a high luminosity (10³6 cm^-2 s^-1) asymmetric e⁺e⁻ collider at the Y(4S) energy. The design is based on a “large Piwinski angle and Crab Waist” scheme already successfully tested at the DAΦNE Phi-Factory in Frascati, Italy. The project combines the challenges of high luminosity colliders and state-of-the-art synchrotron light sources, with two beams (e⁺ at 6.7 and e^- at 4.2 GeV) with extremely low emittances and small beam sizes at the Interaction Point. As unique features, the electron beam will be longitudinally polarized at the IP and the rings will be able to ramp down to collide at the tau/charm energy threshold with one tenth the luminosity. The relatively low beam currents (about 2 A) will allow for low running (power) costs compared to similar machines. The insertion of beam lines for synchrotron radiation users is the latest feature included in the design. The lattice has been recently modified to accommodate insertion devices for X-rays production. A status of the project and a description of R&D in progress will be presented.