IPAC2017 - List of Authors (Wang, S.)

Paper	Title	Page
WEPIK109	Experimental Study of Vertical-Longitudinal Coupling Induced by Wakefields at CesrTA	3200
	S. Wang, J.D. Perrin, S. Poprocki, D. L. Rubin Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work supported by NSF PHY-1416318, PHYS-1068662 Transverse vertical wakefields can cause vertical beam size growth in accelerators. Here we report recent measurements and simulations of wakefields from movable scrapers at the CesrTA. The charge dependent vertical beam size growth was observed while a single scraper was inserted through the top of the chamber. No change in the beam size was observed with top and bottom scrapers inserted symmetrically. The apparent growth in the vertical beam size was due in large part to the y-z coupling (vertical crabbing) induced by the monopole wake of the asymmetric scraper configuration. We explored this y-z coupling by varying vertical betatron phase advance between the vertical beam size monitor and the scrapers. In addition, we found that existing residual, current independent y-z coupling could be compensated by the scraper wake. Predictions of a tracking simulation are in good agreement with the measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK109
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WEPIK110	Resistive Wall Instability and Impedance Studies of Narrow Undulator Chamber in CHESS-U	3204
	S. Wang, M.G. Billing, S. Poprocki, D. L. Rubin, D. Sagan Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work supported by NSF DMR-0936384 and NSF DMR-1332208 In a major upgrade of the Cornell Electron Storage Ring (CESR) one sextant of ring will be replaced with double bend achromats (DBAs) and undulator straights for x-ray users. The resistive wall impedance from the narrow gap (4.5 mm) undulator chambers (5 m per straight) may limit total beam. Here we report recent results of modelling and calculation of multibunch instabilities due to the impedance of chamber walls and transition tapers. The short range wakefields and resistive wall impedance are modelled and incorporated in a tracking simulation. The coupled-bunch growth rate found with the tracking study is in good agreement with the analytic approximation. We find that the resistive wall instability can be readily damped by our existing bunch-by-bunch feedback system.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK110
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THPVA034	Comparison of the Coupling of Dipole Motion From Bunch to Bunch in an Electron Beam Caused by Electron Clouds at CesrTA Due to Variations in Bunch Length and Chromaticity	4509
	M.G. Billing, L.Y. Bartnik, J.A. Crittenden, M.J. Forster, N.T. Rider, J.P. Shanks, M.B. Spiegel, S. Wang Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA R. Holtzapple CalPoly, San Luis Obispo, California, USA E.C. Runburg University of Notre Dame, Indiana, USA
	Earlier experiments at the Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) have probed the interaction of the electron cloud (EC) with a 2.1 GeV stored positron beam. Since a very low EC density is expected with the electron bunches, these results characterize the dependence of beam-vacuum chamber impedance interactions, which are common to both positron and electron beams. The experiments were performed on a 30-bunch electron train with a 14 ns spacing, at a fixed current of 0.75mA/bunch, at two different vertical chromaticity settings and for four different bunch lengths (or synchrotron tunes.) The beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using: 20 turn-by-turn beam position monitors in CESR to measure the correlated bunch-by-bunch dipole motion and an x-ray beam size monitor to record the bunch-by-bunch, turn-by-turn vertical size of each bunch within the trains. In this paper we report on the analysis of the observations from these experiments and compare them with effects of the EC on the positron beam's dipole motion and coupling of the motion from each bunch to its succeeding bunches.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA034
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THPVA035	Dependence of the Coupling of Dipole Motion From Bunch to Bunch Caused by Electron Clouds at CesrTA Due to Variations in Bunch Length and Chromaticity	4512
	M.G. Billing, L.Y. Bartnik, J.A. Crittenden, M.J. Forster, N.T. Rider, J.P. Shanks, M.B. Spiegel, S. Wang Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA R. Holtzapple CalPoly, San Luis Obispo, California, USA E.C. Runburg University of Notre Dame, Indiana, USA
	The Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) has conducted experiments to probe the interaction of the electron cloud (EC) with a 2.1 GeV stored positron beam. These experiments investigate the dependence of beam'electron cloud interactions vs. bunch length (or synchrotron tune) at two values of the vertical chromaticity. The experiments utilized a 30-bunch positron train with a 14 ns spacing, at a fixed current of 0.75mA/bunch. The beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using: 20 turn-by-turn beam position monitors in CESR to measure the correlated bunch-by-bunch dipole motion and an x-ray beam size monitor to record the bunch-by-bunch, turn-by-turn vertical size of each bunch within the trains. In this paper we report on the observations from these experiments and a more detailed analysis for the coupling of dipole motion via the EC from each bunch to succeeding bunches in the train.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA035
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Paper

Title

Page

Experimental Study of Vertical-Longitudinal Coupling Induced by Wakefields at CesrTA

3200

S. Wang, J.D. Perrin, S. Poprocki, D. L. Rubin
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by NSF PHY-1416318, PHYS-1068662
Transverse vertical wakefields can cause vertical beam size growth in accelerators. Here we report recent measurements and simulations of wakefields from movable scrapers at the CesrTA. The charge dependent vertical beam size growth was observed while a single scraper was inserted through the top of the chamber. No change in the beam size was observed with top and bottom scrapers inserted symmetrically. The apparent growth in the vertical beam size was due in large part to the y-z coupling (vertical crabbing) induced by the monopole wake of the asymmetric scraper configuration. We explored this y-z coupling by varying vertical betatron phase advance between the vertical beam size monitor and the scrapers. In addition, we found that existing residual, current independent y-z coupling could be compensated by the scraper wake. Predictions of a tracking simulation are in good agreement with the measurements.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK109

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WEPIK110

Resistive Wall Instability and Impedance Studies of Narrow Undulator Chamber in CHESS-U

3204

S. Wang, M.G. Billing, S. Poprocki, D. L. Rubin, D. Sagan
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by NSF DMR-0936384 and NSF DMR-1332208
In a major upgrade of the Cornell Electron Storage Ring (CESR) one sextant of ring will be replaced with double bend achromats (DBAs) and undulator straights for x-ray users. The resistive wall impedance from the narrow gap (4.5 mm) undulator chambers (5 m per straight) may limit total beam. Here we report recent results of modelling and calculation of multibunch instabilities due to the impedance of chamber walls and transition tapers. The short range wakefields and resistive wall impedance are modelled and incorporated in a tracking simulation. The coupled-bunch growth rate found with the tracking study is in good agreement with the analytic approximation. We find that the resistive wall instability can be readily damped by our existing bunch-by-bunch feedback system.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK110

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

THPVA034

Comparison of the Coupling of Dipole Motion From Bunch to Bunch in an Electron Beam Caused by Electron Clouds at CesrTA Due to Variations in Bunch Length and Chromaticity

4509

M.G. Billing, L.Y. Bartnik, J.A. Crittenden, M.J. Forster, N.T. Rider, J.P. Shanks, M.B. Spiegel, S. Wang
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
R. Holtzapple
CalPoly, San Luis Obispo, California, USA
E.C. Runburg
University of Notre Dame, Indiana, USA

Earlier experiments at the Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) have probed the interaction of the electron cloud (EC) with a 2.1 GeV stored positron beam. Since a very low EC density is expected with the electron bunches, these results characterize the dependence of beam-vacuum chamber impedance interactions, which are common to both positron and electron beams. The experiments were performed on a 30-bunch electron train with a 14 ns spacing, at a fixed current of 0.75mA/bunch, at two different vertical chromaticity settings and for four different bunch lengths (or synchrotron tunes.) The beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using: 20 turn-by-turn beam position monitors in CESR to measure the correlated bunch-by-bunch dipole motion and an x-ray beam size monitor to record the bunch-by-bunch, turn-by-turn vertical size of each bunch within the trains. In this paper we report on the analysis of the observations from these experiments and compare them with effects of the EC on the positron beam's dipole motion and coupling of the motion from each bunch to its succeeding bunches.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA034

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

THPVA035

Dependence of the Coupling of Dipole Motion From Bunch to Bunch Caused by Electron Clouds at CesrTA Due to Variations in Bunch Length and Chromaticity

4512

M.G. Billing, L.Y. Bartnik, J.A. Crittenden, M.J. Forster, N.T. Rider, J.P. Shanks, M.B. Spiegel, S. Wang
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
R. Holtzapple
CalPoly, San Luis Obispo, California, USA
E.C. Runburg
University of Notre Dame, Indiana, USA

The Cornell Electron-Positron Storage Ring Test Accelerator (CesrTA) has conducted experiments to probe the interaction of the electron cloud (EC) with a 2.1 GeV stored positron beam. These experiments investigate the dependence of beam'electron cloud interactions vs. bunch length (or synchrotron tune) at two values of the vertical chromaticity. The experiments utilized a 30-bunch positron train with a 14 ns spacing, at a fixed current of 0.75mA/bunch. The beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using: 20 turn-by-turn beam position monitors in CESR to measure the correlated bunch-by-bunch dipole motion and an x-ray beam size monitor to record the bunch-by-bunch, turn-by-turn vertical size of each bunch within the trains. In this paper we report on the observations from these experiments and a more detailed analysis for the coupling of dipole motion via the EC from each bunch to succeeding bunches in the train.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA035

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