NAPAC2019 - List of Keywords (impedance)

Paper	Title	Other Keywords	Page
MOZBA6	The Broad-Band Impedance Budget of the Accumulator Ring in the ALS-U Project	wakefield, simulation, cavity, vacuum	74
	D. Wang, S. De Santis, D. Li, T.H. Luo, M. Venturini LBNL, Berkeley, California, USA K.L.F. Bane SLAC, Menlo Park, California, USA
	Design work is underway for the upgrade of the Advanced Light Source (ALS-U) to a diffraction-limited soft x-rays radiation source. It consists of an accumulator and a storage ring. In both rings, coupling-impedance driven instabilities need careful evaluation to ensure meeting the machine high-performance goals. This paper presents the impedance budget of the accumulator ring both longitudinally and transversely. The budget includes the resistive wall impedance as well as the geometric impedance from the main vacuum components. Our calculations primarily rely on electromagnetic simulations with the CST code; when possible validation has been sought against analytical modeling, typically in the low-frequency limit, and good agreement generally found. Collective-instability current thresholds are also discussed.
	Slides MOZBA6 [8.926 MB]
	Poster MOZBA6 [3.542 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA6
About •	paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPLM17	Longitudinal Impedance Modeling of APS Particle Accumulator Ring with CST	simulation, kicker, cavity, vacuum	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)

MOPLM20	Impedance Considerations for the APS Upgrade	photon, vacuum, cavity, simulation	147
	R.R. Lindberg ANL, Lemont, Illinois, USA A. Blednykh BNL, Upton, New York, USA
	Funding: Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 The APS-Upgrade is targeting a 42 pm lattice that requires strong magnets and small vacuum chambers. Hence, impedance is of significant concern. We overview recent progress on identifying and modelling vacuum components that are important sources of impedance in the ring, including photon absorbers, BPMs, and flange joints. We also show how these impact collective dynamics in the APS-U lattice.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM20
About •	paper received ※ 27 August 2019 paper accepted ※ 01 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	injection, booster, synchrotron, photon	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)

TUPLM36	Temperature Measurements of the NSLS-II Vacuum Components	vacuum, experiment, cavity, detector	443
	A. Blednykh, G. Bassi, C. Hetzel, B.N. Kosciuk, D. Padrazo Jr, T.V. Shaftan, V.V. Smaluk, G.M. Wang BNL, Upton, New York, USA
	This paper is dedicated to the analysis of our recent experience from ramp-up of operating current at NSLS-II from 25 mA at the end of commissioning in 2014 to 475 mA achieved in studies today. To approach the design level of the ring intensity we had to solve major problems in overheating of the chamber components. Since the beginning of the NSLS-II commissioning, the temperature of the vacuum components has been monitored by the Resistance Temperature Detectors located predominantly outside of the vacuum chamber and attached to the chamber body. A couple of vacuum components were designed with the possibility for internal temperature measurements under the vacuum as diagnostic assemblies. Temperature map helps us to control overheating of the vacuum components around the ring especially during the current ramp-up. The average current of 475mA has been achieved with two main 500MHz RF cavities and w/o any harmonic cavities. In this paper we discuss the heating results for a 15ps bunch length (at low current) of the following vacuum components: Large Aperture BPM, Small Aperture BPM, Bellows, Flanges, Ceramics Chambers and Stripline Kickers.
	Poster TUPLM36 [3.696 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM36
About •	paper received ※ 28 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)

TUPLS07	Helical Transmission Line Test Stand for Non-Relativistic BPM Calibration	simulation, network, resonance, linac	463
	C.J. Richard NSCL, East Lansing, Michigan, USA S.M. Lidia FRIB, East Lansing, Michigan, USA
	Measurements of non-relativistic beams by coupling to the fields are affected by the properties of the non-relativistic fields. The authors propose calibrating for these effects with a test stand using a helical line which can propagate pulses at low velocities. Presented are simulations of a helical transmission line for such a test stand which propagates pulses at 0.033c. A description of the helix geometry used to reduce dispersion is given as well as the geometry of the input network.
	Poster TUPLS07 [3.469 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLS07
About •	paper received ※ 27 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)

TUPLH07	High-Gradient Short Pulse Accelerating Structures	electron, experiment, wakefield, acceleration	500
	S.V. Kuzikov, S.P. Antipov, E. Gomez Euclid TechLabs, LLC, Solon, Ohio, USA A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia
	High gradients are necessary for lots of applications of electron accelerators. As the maximum gradient is limited by effects of RF breakdown, we present a development of an electron accelerating structure operating with a short multi-megawatt RF pulse. The structure exploits an idea to decrease the breakdown probability due to RF pulse length reduction. This concept requires to distribute RF power so that all accelerating cells are fed independently each other. This implies waveguide net system which allows to delay and to distribute properly RF radiation along the structure keeping synchronism of particles and waves. We have designed an X-band pi-mode structure including the RF design, optimization, and engineering. The structure will be tested as an RF power extractor at the Argonne Wakefield Accelerator Facility for two-beam acceleration experiments. In this regime we anticipate to obtain 10 ns, gigawatt power level RF pulses generated by train consisted of eight 25-50 nC relativistic bunches.
	Poster TUPLH07 [0.999 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH07
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)

TUPLH20	Commissioning of the CESR Upgrade for CHESS-U	MMI, HOM, wiggler, storage-ring	522
	J.P. Shanks, G.W. Codner, M.J. Forster, D.L. Rubin, S. Wang, L. Ying Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Funding for the CHESS-U upgrade provided by New York State Capital Grant #AA737 / CFA #53676 The Cornell Electron Storage Ring (CESR) was upgraded in the second half of 2018 to become a dedicated synchrotron light source, CHESS-U. The upgrade is by far the largest modification to CESR in its 40-year history, replacing one-sixth of the storage ring with six new double-bend achromats, increasing beam energy from 5.3 GeV to 6.0 GeV, and switching from two counter-rotating beams to a single on-axis positron beam. The new achromats include combined-function dipoles, a first in CESR, and reduce the horizontal emittance by a factor of four. Eight compact narrow-gap undulators (4.6mm vacuum chamber aperture) and one high-energy 24-pole wiggler feed a total of six new and five existing x-ray end stations from a single positron beam. Commissioning of CHESS-U took place in the first half of 2019. We report on the methods and results of beam commissioning, including initial beam accumulation, optics correction, characterization, and commissioning of compact permanent-magnet insertion devices.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH20
About •	paper received ※ 26 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)

WEPLM04	Precision Cavity Higher-Order Mode Tuning Scheme for Stabilizing the Stored Beam in the Advanced Photon Source Upgrade	cavity, HOM, damping, resonance	670
	L. Emery, P.S. Kallakuri, U. Wienands ANL, Lemont, Illinois, USA D. Teytelman Dimtel, Redwood City, California, 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 Advanced Photon Source Upgrade will suffer longitudinal multi-bunch instability because of the presence of several monopole higher-order mode (HOMs) of the 12 352-MHz rf cavities. Even with a feedback system, it would be good to mitigate any driving terms with conventional means such as tuning HOM frequencies with temperature. However the latter is problematic because there will be 90 or so HOMs that are potentially harmful. A scheme is developed, utilizing the measured spectrum of HOMs, to find the best temperature setting for each cavity. We present measurements of 30 or so HOMs, and a thermal model of HOM frequencies using cavity wall power and cooling water temperature as inputs to maintain the optimum tuning condition with sufficient accuracy. The newly acquired Dimtel iGp12 processor box is central to the HOM frequency measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM04
About •	paper received ※ 29 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)

WEPLH16	Tolerances on Energy Deviation in Microbunched Electron Cooling	electron, plasma, hadron, kicker	837
	P. Baxevanis, G. Stupakov SLAC, Menlo Park, California, USA
	The performance of microbunched electron cooling (MBEC)* is highly dependent on the quality of the hadron and cooler electron beams. As a result, understanding the influence of beam imperfections is very important from the point of view of determining the tolerances of MBEC. In this work, we incorporate a non-zero average energy offset into our 1D formalism (,), which allows us to study the impact of effects such as correlated energy spread (chirp). In particular, we use our analytical theory to calculate the cooling rate loss due to the electron beam chirp and discuss ways to minimize the influence of this effect on MBEC. D. Ratner, Phys. Rev. Lett. 111, 084802 (2013). G. Stupakov, Phys. Rev. AB, 21, 114402 (2018). * G. Stupakov and P. Baxevanis, Phys. Rev. AB, 22, 034401 (2019).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH16
About •	paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOZBA6

The Broad-Band Impedance Budget of the Accumulator Ring in the ALS-U Project

wakefield, simulation, cavity, vacuum

74

D. Wang, S. De Santis, D. Li, T.H. Luo, M. Venturini
LBNL, Berkeley, California, USA
K.L.F. Bane
SLAC, Menlo Park, California, USA

Design work is underway for the upgrade of the Advanced Light Source (ALS-U) to a diffraction-limited soft x-rays radiation source. It consists of an accumulator and a storage ring. In both rings, coupling-impedance driven instabilities need careful evaluation to ensure meeting the machine high-performance goals. This paper presents the impedance budget of the accumulator ring both longitudinally and transversely. The budget includes the resistive wall impedance as well as the geometric impedance from the main vacuum components. Our calculations primarily rely on electromagnetic simulations with the CST code; when possible validation has been sought against analytical modeling, typically in the low-frequency limit, and good agreement generally found. Collective-instability current thresholds are also discussed.

Slides MOZBA6 [8.926 MB]

Poster MOZBA6 [3.542 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOZBA6

About •

paper received ※ 27 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019

Export •

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

MOPLM17

Longitudinal Impedance Modeling of APS Particle Accumulator Ring with CST

simulation, kicker, cavity, vacuum

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)

MOPLM20

Impedance Considerations for the APS Upgrade

photon, vacuum, cavity, simulation

147

R.R. Lindberg
ANL, Lemont, Illinois, USA
A. Blednykh
BNL, Upton, New York, USA

Funding: Supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
The APS-Upgrade is targeting a 42 pm lattice that requires strong magnets and small vacuum chambers. Hence, impedance is of significant concern. We overview recent progress on identifying and modelling vacuum components that are important sources of impedance in the ring, including photon absorbers, BPMs, and flange joints. We also show how these impact collective dynamics in the APS-U lattice.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOPLM20

About •

paper received ※ 27 August 2019 paper accepted ※ 01 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

injection, booster, synchrotron, photon

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)

TUPLM36

Temperature Measurements of the NSLS-II Vacuum Components

vacuum, experiment, cavity, detector

443

A. Blednykh, G. Bassi, C. Hetzel, B.N. Kosciuk, D. Padrazo Jr, T.V. Shaftan, V.V. Smaluk, G.M. Wang
BNL, Upton, New York, USA

This paper is dedicated to the analysis of our recent experience from ramp-up of operating current at NSLS-II from 25 mA at the end of commissioning in 2014 to 475 mA achieved in studies today. To approach the design level of the ring intensity we had to solve major problems in overheating of the chamber components. Since the beginning of the NSLS-II commissioning, the temperature of the vacuum components has been monitored by the Resistance Temperature Detectors located predominantly outside of the vacuum chamber and attached to the chamber body. A couple of vacuum components were designed with the possibility for internal temperature measurements under the vacuum as diagnostic assemblies. Temperature map helps us to control overheating of the vacuum components around the ring especially during the current ramp-up. The average current of 475mA has been achieved with two main 500MHz RF cavities and w/o any harmonic cavities. In this paper we discuss the heating results for a 15ps bunch length (at low current) of the following vacuum components: Large Aperture BPM, Small Aperture BPM, Bellows, Flanges, Ceramics Chambers and Stripline Kickers.

Poster TUPLM36 [3.696 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM36

About •

paper received ※ 28 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

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

TUPLS07

Helical Transmission Line Test Stand for Non-Relativistic BPM Calibration

simulation, network, resonance, linac

463

C.J. Richard
NSCL, East Lansing, Michigan, USA
S.M. Lidia
FRIB, East Lansing, Michigan, USA

Measurements of non-relativistic beams by coupling to the fields are affected by the properties of the non-relativistic fields. The authors propose calibrating for these effects with a test stand using a helical line which can propagate pulses at low velocities. Presented are simulations of a helical transmission line for such a test stand which propagates pulses at 0.033c. A description of the helix geometry used to reduce dispersion is given as well as the geometry of the input network.

Poster TUPLS07 [3.469 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLS07

About •

paper received ※ 27 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)

TUPLH07

High-Gradient Short Pulse Accelerating Structures

electron, experiment, wakefield, acceleration

500

S.V. Kuzikov, S.P. Antipov, E. Gomez
Euclid TechLabs, LLC, Solon, Ohio, USA
A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia

High gradients are necessary for lots of applications of electron accelerators. As the maximum gradient is limited by effects of RF breakdown, we present a development of an electron accelerating structure operating with a short multi-megawatt RF pulse. The structure exploits an idea to decrease the breakdown probability due to RF pulse length reduction. This concept requires to distribute RF power so that all accelerating cells are fed independently each other. This implies waveguide net system which allows to delay and to distribute properly RF radiation along the structure keeping synchronism of particles and waves. We have designed an X-band pi-mode structure including the RF design, optimization, and engineering. The structure will be tested as an RF power extractor at the Argonne Wakefield Accelerator Facility for two-beam acceleration experiments. In this regime we anticipate to obtain 10 ns, gigawatt power level RF pulses generated by train consisted of eight 25-50 nC relativistic bunches.

Poster TUPLH07 [0.999 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH07

About •

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

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

TUPLH20

Commissioning of the CESR Upgrade for CHESS-U

MMI, HOM, wiggler, storage-ring

522

J.P. Shanks, G.W. Codner, M.J. Forster, D.L. Rubin, S. Wang, L. Ying
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Funding for the CHESS-U upgrade provided by New York State Capital Grant #AA737 / CFA #53676
The Cornell Electron Storage Ring (CESR) was upgraded in the second half of 2018 to become a dedicated synchrotron light source, CHESS-U. The upgrade is by far the largest modification to CESR in its 40-year history, replacing one-sixth of the storage ring with six new double-bend achromats, increasing beam energy from 5.3 GeV to 6.0 GeV, and switching from two counter-rotating beams to a single on-axis positron beam. The new achromats include combined-function dipoles, a first in CESR, and reduce the horizontal emittance by a factor of four. Eight compact narrow-gap undulators (4.6mm vacuum chamber aperture) and one high-energy 24-pole wiggler feed a total of six new and five existing x-ray end stations from a single positron beam. Commissioning of CHESS-U took place in the first half of 2019. We report on the methods and results of beam commissioning, including initial beam accumulation, optics correction, characterization, and commissioning of compact permanent-magnet insertion devices.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH20

About •

paper received ※ 26 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)

WEPLM04

Precision Cavity Higher-Order Mode Tuning Scheme for Stabilizing the Stored Beam in the Advanced Photon Source Upgrade

cavity, HOM, damping, resonance

670

L. Emery, P.S. Kallakuri, U. Wienands
ANL, Lemont, Illinois, USA
D. Teytelman
Dimtel, Redwood City, California, 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 Advanced Photon Source Upgrade will suffer longitudinal multi-bunch instability because of the presence of several monopole higher-order mode (HOMs) of the 12 352-MHz rf cavities. Even with a feedback system, it would be good to mitigate any driving terms with conventional means such as tuning HOM frequencies with temperature. However the latter is problematic because there will be 90 or so HOMs that are potentially harmful. A scheme is developed, utilizing the measured spectrum of HOMs, to find the best temperature setting for each cavity. We present measurements of 30 or so HOMs, and a thermal model of HOM frequencies using cavity wall power and cooling water temperature as inputs to maintain the optimum tuning condition with sufficient accuracy. The newly acquired Dimtel iGp12 processor box is central to the HOM frequency measurements.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM04

About •

paper received ※ 29 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)

WEPLH16

Tolerances on Energy Deviation in Microbunched Electron Cooling

electron, plasma, hadron, kicker

837

P. Baxevanis, G. Stupakov
SLAC, Menlo Park, California, USA

The performance of microbunched electron cooling (MBEC)* is highly dependent on the quality of the hadron and cooler electron beams. As a result, understanding the influence of beam imperfections is very important from the point of view of determining the tolerances of MBEC. In this work, we incorporate a non-zero average energy offset into our 1D formalism (**,***), which allows us to study the impact of effects such as correlated energy spread (chirp). In particular, we use our analytical theory to calculate the cooling rate loss due to the electron beam chirp and discuss ways to minimize the influence of this effect on MBEC.
* D. Ratner, Phys. Rev. Lett. 111, 084802 (2013).
** G. Stupakov, Phys. Rev. AB, 21, 114402 (2018).
*** G. Stupakov and P. Baxevanis, Phys. Rev. AB, 22, 034401 (2019).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLH16

About •

paper received ※ 28 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019

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