NAPAC2019 - List of Authors (Yao, C.)

Paper	Title	Page
MOPLM17	Longitudinal Impedance Modeling of APS Particle Accumulator Ring with CST	140
	C. Yao, J. Carvelli, K.C. Harkay, L.H. Morrison ANL, Lemont, Illinois, USA D. Hui University of Arizona, Tucson, Arizona, USA J.S. Wang Dassault Systems Simulia, Waltham, Massachusetts, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. The APS-U (APS upgrade) ring plans implement a "swap out" injection scheme, which requires a injected beam of 15.6 nC single-bunch beam. The Particle Accumulator Ring (PAR), originally designed for up to 6 nC charge, must be upgraded to provide 20 nC single bunch beam. Our studies have shown that bunch length of the PAR beam, typically 300 ps at lower charge, increases to 800 ps at high charge due to longitudinal instabilities, which causes low injection efficiency of the downstream Booster ring. We completed beam impedance of all the PAR vacuum components recently with CST wakefield solver. 3D CAD models are directly imported into CST and various techniques were explored to improve and verify the results. The results are also cross-checked with that from GdfidL and Echo simulation. We identified 23 bellow- and 24 non-bellow flanges that contribute to as much as 50% of the total loss factor. We are considering upgrade options to reduce over all beam loading and longitudinal impedance. Beam tracking simulation is in progress that including the longitudinal impedance results from the simulations. We report the results and methods of the CST impedance simulations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM17
About •	paper received ※ 22 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
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MOPLM21	Circuit Model Analysis for High Charge in the APS Particle Accumulator Ring	151
	K.C. Harkay, J.R. Calvey, J.C. Dooling, L. Emery, R.R. Lindberg, K.P. Wootton, C. Yao ANL, Lemont, Illinois, USA
	Funding: Work supported by U. S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source (APS) particle accumulator ring (PAR) was designed to accumulate linac pulses into a single bunch with a fundamental rf system, and longitudinally compress the beam with a harmonic rf system prior to injection into the booster. For APS Upgrade, the injectors will need to supply full-current bunch replacement with high single-bunch charge for swap-out in the new storage ring. Significant bunch lengthening, energy spread, and synchrotron sidebands are observed in PAR at high charge. Lower-charge dynamics are dominated by potential well distortion, while higher-charge dynamics appear to be dominated by microwave instability. Before a numerical impedance model was available, a simple circuit model was developed by fitting the measured bunch distributions to the Haissinski equation. Energy scaling was then used to predict the beam energy sufficient to raise the instability threshold to 18-20 nC. With the beam in a linear or nearly linear regime, higher harmonic radio frequency (rf) gap voltage can be used to reduce the bunch length at high charge and better match the booster acceptance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM21
About •	paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019
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TUPLE11	Proposed Enhanced Imaging Station in the 6-GeV Booster-to-Storage Ring Transport Line for APS Upgrade	583
	A.H. Lumpkin Fermilab, Batavia, Illinois, USA W. Berg, J.C. Dooling, K.P. Wootton, C. Yao ANL, Lemont, Illinois, USA
	Funding: This manuscript has been authored by FRA, LLC under Contract No.DE-AC02-07CH11359 with the U.S.DoE, Office of HEP. Work supported by U.S.DoE, Office of Science, under Contract No.DE-AC02-06CH11357. One of the challenges of the injector for the Advanced Photon Source Upgrade (APS-U) is the measurement and monitoring of the required high charge electron beam at 6 GeV between the Booster synchrotron and the storage ring in the transport line (BTS. In APS-U charges of up to 17 nC per micropulse are specified with a beam geometrical horizontal emittance of 60 nm rad. Vertical beam sizes at the imaging station of ~80 µm (σ) are expected so system resolutions of <30 µm are warranted. A phased approach to enhance the imaging station performance has been initiated. Recently, the 20-year-old Chromox screen oriented at 45 degrees to the beam was replaced by a 100-micron thick YAG:Ce screen which gave an improved screen resolution of <10 micron(σ. However, the optical magnification of the system still needs to be increased. In addition, the high areal charge densities are expected to exceed the scintillator mechanism’s saturation threshold so an optical transition radiation (OTR) screen will be added to the station for high-charge studies. A final phase would be the use of optical diffraction radiation (ODR) as a non-intercepting, beam-size monitor during top-up injections.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE11
About •	paper received ※ 22 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
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WEPLE05	Tracking With Space Harmonics in ELEGANT Code	892
	Y.P. Sun, C. Yao ANL, Lemont, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The elegant code has the capability of simulating particle motion in accelerating or deflecting RF cavities, with a simplified (or ideal) model of the electromagnetic fields. To improve the accuracy of RF cavity simulations, the ability to track with space harmonics has been added to the elegant code. The sum of all the space harmonics will mimic the real electromagnetic fields in the RF cavity. These space harmonics will be derived from electromagnetic fields simulation of the RF cavity. This method should be general, which can be applied to any RF cavity structure, including accelerating and deflecting cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE05
About •	paper received ※ 31 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Longitudinal Impedance Modeling of APS Particle Accumulator Ring with CST

140

C. Yao, J. Carvelli, K.C. Harkay, L.H. Morrison
ANL, Lemont, Illinois, USA
D. Hui
University of Arizona, Tucson, Arizona, USA
J.S. Wang
Dassault Systems Simulia, Waltham, Massachusetts, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The APS-U (APS upgrade) ring plans implement a "swap out" injection scheme, which requires a injected beam of 15.6 nC single-bunch beam. The Particle Accumulator Ring (PAR), originally designed for up to 6 nC charge, must be upgraded to provide 20 nC single bunch beam. Our studies have shown that bunch length of the PAR beam, typically 300 ps at lower charge, increases to 800 ps at high charge due to longitudinal instabilities, which causes low injection efficiency of the downstream Booster ring. We completed beam impedance of all the PAR vacuum components recently with CST wakefield solver. 3D CAD models are directly imported into CST and various techniques were explored to improve and verify the results. The results are also cross-checked with that from GdfidL and Echo simulation. We identified 23 bellow- and 24 non-bellow flanges that contribute to as much as 50% of the total loss factor. We are considering upgrade options to reduce over all beam loading and longitudinal impedance. Beam tracking simulation is in progress that including the longitudinal impedance results from the simulations. We report the results and methods of the CST impedance simulations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM17

About •

paper received ※ 22 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

Export •

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

MOPLM21

Circuit Model Analysis for High Charge in the APS Particle Accumulator Ring

151

K.C. Harkay, J.R. Calvey, J.C. Dooling, L. Emery, R.R. Lindberg, K.P. Wootton, C. Yao
ANL, Lemont, Illinois, USA

Funding: Work supported by U. S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) particle accumulator ring (PAR) was designed to accumulate linac pulses into a single bunch with a fundamental rf system, and longitudinally compress the beam with a harmonic rf system prior to injection into the booster. For APS Upgrade, the injectors will need to supply full-current bunch replacement with high single-bunch charge for swap-out in the new storage ring. Significant bunch lengthening, energy spread, and synchrotron sidebands are observed in PAR at high charge. Lower-charge dynamics are dominated by potential well distortion, while higher-charge dynamics appear to be dominated by microwave instability. Before a numerical impedance model was available, a simple circuit model was developed by fitting the measured bunch distributions to the Haissinski equation. Energy scaling was then used to predict the beam energy sufficient to raise the instability threshold to 18-20 nC. With the beam in a linear or nearly linear regime, higher harmonic radio frequency (rf) gap voltage can be used to reduce the bunch length at high charge and better match the booster acceptance.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM21

About •

paper received ※ 27 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019

Export •

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

TUPLE11

Proposed Enhanced Imaging Station in the 6-GeV Booster-to-Storage Ring Transport Line for APS Upgrade

583

A.H. Lumpkin
Fermilab, Batavia, Illinois, USA
W. Berg, J.C. Dooling, K.P. Wootton, C. Yao
ANL, Lemont, Illinois, USA

Funding: This manuscript has been authored by FRA, LLC under Contract No.DE-AC02-07CH11359 with the U.S.DoE, Office of HEP. Work supported by U.S.DoE, Office of Science, under Contract No.DE-AC02-06CH11357.
One of the challenges of the injector for the Advanced Photon Source Upgrade (APS-U) is the measurement and monitoring of the required high charge electron beam at 6 GeV between the Booster synchrotron and the storage ring in the transport line (BTS. In APS-U charges of up to 17 nC per micropulse are specified with a beam geometrical horizontal emittance of 60 nm rad. Vertical beam sizes at the imaging station of ~80 µm (σ) are expected so system resolutions of <30 µm are warranted. A phased approach to enhance the imaging station performance has been initiated. Recently, the 20-year-old Chromox screen oriented at 45 degrees to the beam was replaced by a 100-micron thick YAG:Ce screen which gave an improved screen resolution of <10 micron(σ. However, the optical magnification of the system still needs to be increased. In addition, the high areal charge densities are expected to exceed the scintillator mechanism’s saturation threshold so an optical transition radiation (OTR) screen will be added to the station for high-charge studies. A final phase would be the use of optical diffraction radiation (ODR) as a non-intercepting, beam-size monitor during top-up injections.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLE11

About •

paper received ※ 22 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

Export •

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

WEPLE05

Tracking With Space Harmonics in ELEGANT Code

892

Y.P. Sun, C. Yao
ANL, Lemont, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The elegant code has the capability of simulating particle motion in accelerating or deflecting RF cavities, with a simplified (or ideal) model of the electromagnetic fields. To improve the accuracy of RF cavity simulations, the ability to track with space harmonics has been added to the elegant code. The sum of all the space harmonics will mimic the real electromagnetic fields in the RF cavity. These space harmonics will be derived from electromagnetic fields simulation of the RF cavity. This method should be general, which can be applied to any RF cavity structure, including accelerating and deflecting cavities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLE05

About •

paper received ※ 31 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019

Export •

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