IPAC2017 - List of Authors (Li, Y.)

Paper	Title	Page
MOPAB151	Techniques for Transparent Lattice Measurement and Correction	483
	W.X. Cheng, K. Ha, Y. Li BNL, Upton, Long Island, New York, USA
	Funding: Work supported by DOE contract No: DE-SC0012704 NSLS-II storage ring started top off operation since Oct 2015. It has been noticed during the user operation that machine lattice was affected by insertion devices (ID). The storage ring coupling, emittance and lifetime vary when ID gap changes. Lattice characterization was typically carried out with dedicated machine study time with low storage current. Due to collective effect, the lattice at high operation current is different. To characterize the machine lattice during normal user operation with little disturbance, a small portion of beam (~1%) filled in the ion gap can be excited by the bunch by bunch feedback system near betatron frequency. Recent development on BPM electronics enables the gate function to detect partial beam motion in the ring. With the gated BPM turn by turn data from excited bunches, storage ring lattice can be measured and corrected with the well-developed tools. We present in the paper preliminary test results with these tools to characterize the lattice and how it improves the machine performance during user operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB151
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MOPAB155	Characterization of the Longitudinal Acceptance in a Storage Ring with RF Pinger	497
	G.M. Wang, B. Holub, Y. Li, J. Rose, T.V. Shaftan BNL, Upton, Long Island, New York, USA
	In modern generation light sources, it is desired to have SR performance at high beam current, low horizontal emittance with small coupling, resulting in intense Touschek scattering, which is the dominant limitation of beam lifetime. Touschek scattering strongly depends on momentum aperture. Understanding momentum aperture is extremely important. NSLS II storage ring RF system has the digital ramp control function, enabling rapid change of the cavity phase and amplitude. This makes the possibility to ping the beam in longitudinal phase space and directly measure the longitudinal acceptance, in contrast with traditional indirect way to understand it from other aspect of parameters. In this paper, we present the tool, longitudinal pinger, its application to characterize NSLS II longitudinal acceptance and localize the momentum aperture limit with SR BPMs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB155
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WEPIK122	Applying Square Matrix to Optimize Storage Ring Nonlinear Lattice	3241
	Y. Li, L. Yu BNL, Upton, Long Island, New York, USA
	Funding: Supported by US DOE Contract No. DE-AC02-98CH10886 and DE-SC0012704. A new method of using linear algebra technique to analyze periodical nonlinear beam dynamics is presented. For a given dynamical system, a square upper triangular transfer matrix is constructed out of a one turn Taylor transfer map. First we separate the matrix into different low dimensional invariant subspaces according to their eigenvalues. Then a stable Jordan transformation can be obtained on each subspace. The transformation provides an excellent action-angle approximation to the solution of the nonlinear dynamics. And the deviation of the new action from constancy provides a measure of the nonlinearity of the motions, which provides a novel method to optimize the nonlinear dynamic system. We applied this method to optimize various rings, such as NSLS-II, SPEAR3, and APS-U lattice, the promising dynamic aperture have been achieved from both tracking simulation and experimental measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK122
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Paper

Title

Page

Techniques for Transparent Lattice Measurement and Correction

483

W.X. Cheng, K. Ha, Y. Li
BNL, Upton, Long Island, New York, USA

Funding: Work supported by DOE contract No: DE-SC0012704
NSLS-II storage ring started top off operation since Oct 2015. It has been noticed during the user operation that machine lattice was affected by insertion devices (ID). The storage ring coupling, emittance and lifetime vary when ID gap changes. Lattice characterization was typically carried out with dedicated machine study time with low storage current. Due to collective effect, the lattice at high operation current is different. To characterize the machine lattice during normal user operation with little disturbance, a small portion of beam (~1%) filled in the ion gap can be excited by the bunch by bunch feedback system near betatron frequency. Recent development on BPM electronics enables the gate function to detect partial beam motion in the ring. With the gated BPM turn by turn data from excited bunches, storage ring lattice can be measured and corrected with the well-developed tools. We present in the paper preliminary test results with these tools to characterize the lattice and how it improves the machine performance during user operation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB151

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPAB155

Characterization of the Longitudinal Acceptance in a Storage Ring with RF Pinger

497

G.M. Wang, B. Holub, Y. Li, J. Rose, T.V. Shaftan
BNL, Upton, Long Island, New York, USA

In modern generation light sources, it is desired to have SR performance at high beam current, low horizontal emittance with small coupling, resulting in intense Touschek scattering, which is the dominant limitation of beam lifetime. Touschek scattering strongly depends on momentum aperture. Understanding momentum aperture is extremely important. NSLS II storage ring RF system has the digital ramp control function, enabling rapid change of the cavity phase and amplitude. This makes the possibility to ping the beam in longitudinal phase space and directly measure the longitudinal acceptance, in contrast with traditional indirect way to understand it from other aspect of parameters. In this paper, we present the tool, longitudinal pinger, its application to characterize NSLS II longitudinal acceptance and localize the momentum aperture limit with SR BPMs.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB155

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK122

Applying Square Matrix to Optimize Storage Ring Nonlinear Lattice

3241

Y. Li, L. Yu
BNL, Upton, Long Island, New York, USA

Funding: Supported by US DOE Contract No. DE-AC02-98CH10886 and DE-SC0012704.
A new method of using linear algebra technique to analyze periodical nonlinear beam dynamics is presented. For a given dynamical system, a square upper triangular transfer matrix is constructed out of a one turn Taylor transfer map. First we separate the matrix into different low dimensional invariant subspaces according to their eigenvalues. Then a stable Jordan transformation can be obtained on each subspace. The transformation provides an excellent action-angle approximation to the solution of the nonlinear dynamics. And the deviation of the new action from constancy provides a measure of the nonlinearity of the motions, which provides a novel method to optimize the nonlinear dynamic system. We applied this method to optimize various rings, such as NSLS-II, SPEAR3, and APS-U lattice, the promising dynamic aperture have been achieved from both tracking simulation and experimental measurements.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK122

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)