IPAC2019 - List of Authors (Smaluk, V.V.)

Paper	Title	Page
MOZZPLS1	eRHIC Design Overview	45
	C. Montag, G. Bassi, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, A. Blednykh, J.M. Brennan, S.J. Brooks, K.A. Brown, K.A. Drees, A.V. Fedotov, W. Fischer, D.M. Gassner, W. Guo, A. Hershcovitch, C. Hetzel, D. Holmes, H. Huang, W.A. Jackson, J. Kewisch, Y. Li, C. Liu, H. Lovelace III, Y. Luo, F. Méot, M.G. Minty, R.B. Palmer, B. Parker, S. Peggs, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, S. Seletskiy, V.V. Smaluk, K.S. Smith, S. Tepikian, P. Thieberger, D. Trbojevic, N. Tsoupas, S. Verdú-Andrés, W.-T. Weng, F.J. Willeke, H. Witte, Q. Wu, W. Xu, A. Zaltsman, W. Zhang BNL, Upton, Long Island, New York, USA E. Gianfelice-Wendt Fermilab, Batavia, Illinois, USA Y. Hao FRIB, East Lansing, Michigan, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The Electron-Ion Collider (EIC) is being envisioned as the next facility to be constructed by the DOE Nuclear Physics program. Brookhaven National Laboratory is proposing eRHIC, a facility based on the existing RHIC complex as a cost effective realization of the EIC project with a peak luminosity of 10³⁴ cm^-2 sec^-1. An electron storage ring with an energy range from 5 to 18 GeV will be added in the existing RHIC tunnel. A spin-transparent rapid-cycling synchrotron (RCS) will serve as a full-energy polarized electron injector. Recent design improvements include reduction of the IR magnet strengths to avoid the necessity for Nb₃Sn magnets, and a novel hadron injection scheme to maximize the integrated luminosity. We will provide an overview of this proposed project and present the current design status.
	Slides MOZZPLS1 [5.428 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOZZPLS1
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW115	A Cross-Cell Interleaved Nonlinear Lattice for Potential NSLS-II Upgrade	393
	Y. Li, A. He, B.N. Kosciuk, T.V. Shaftan, V.V. Smaluk BNL, Upton, Long Island, New York, USA Z.H. Bai, L. Wang USTC/NSRL, Hefei, Anhui, People’s Republic of China
	An interleaved sextupole scheme using cross-cell betatron phase cancellation technique is adopted as a candidate for the future NSLS-II upgrade lattice. The lattice uses as many NSLS-II installed magnets as possible, including 30 dipoles, to compose a triple bend achromat lattice. A 300 pm.rad horizontal beam emittance is achieved. The emittance can be further reduced to around 200 pm rad with damping wigglers. Various design concepts used in modern 4th-generation light sources, such as adopting longitudinal gradient dipoles and anti-bend scheme, are incorporated into the design as well. The betatron phase-advance between sextupoles is designed to have a cross-cell interleaving cancellation pattern in the transverse planes. The dynamic aperture is big enough for the conventional off-axis top-off injection. At the same time, a large energy acceptance looks promising to ensure a sufficiently long beam lifetime.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW115
About •	paper received ※ 12 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPGW122	Beam-based Measurement of Broadband Longitudinal Impedance at NSLS-II	400
	V.V. Smaluk, B. Bacha, G. Bassi, A. Blednykh BNL, Upton, Long Island, New York, USA
	Funding: Department of Energy Contract No. DE-SC0012704 Interaction of a particle beam with the vacuum chamber impedance is one of the main effects limiting the beam intensity in accelerators. Minimization of the impedance is an essential part of the vacuum chamber design for any new accelerator project. The impedance can be estimated experimentally by measuring beam dynamics effects caused by the beam-impedance interaction. Experience obtained at many accelerator facilities shows the beam-based measurements are often different from the pre-computed impedance budgets, the discrepancy of a factor of two or even more is not unusual. The measurements of broadband longitudinal impedance carried out at NSLS-II are discussed in comparison with the numerically simulated impedance budget.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW122
About •	paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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MOPGW125	Lossless Crossing of 1/2 Resonance Stopband by Synchrotron Oscillations	410
	G.M. Wang, Y. Li, J. Rose, T.V. Shaftan, V.V. Smaluk BNL, Upton, Long Island, New York, USA
	Funding: DOE under contract No.DE-AC02- 98CH10886 Modern high performance circular accelerators require sophisticated corrections of nonlinear lattices. The beam betatron tune footprint may cross many resonances, reducing dynamic aperture and causing particle loss. However, if particles cross a resonance reasonably fast, the beam deterioration may be minimized. In this paper, we present the experiments with the beam passing through a half-integer resonance stopband via chromatic tune modulation by exciting synchrotron oscillations. This is the first time that beam dynamics have been kept under precise control while the beam crosses a half-integer resonance. Our results convincingly demonstrate that particles can cross the half-integer resonance without being lost if the passage is reasonably fast and the resonance stopband is sufficiently narrow.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW125
About •	paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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MOPRB091	Combined Strong-Strong and Weak-Strong Beam-Beam Simulations for Crabbed Collision in eRHIC	788
	Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, Y. Hao, C. Montag, V. Ptitsyn, V.V. Smaluk, F.J. Willeke BNL, Upton, Long Island, New York, USA K. Ohmi KEK, Ibaraki, Japan J. Qiang LBNL, Berkeley, California, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In the eRHIC, to compensate the geometric luminosity loss, local crab cavities on both sides of the interaction points are to adopted. The previous strong-strong beam-beam simulations showed that the luminosity degradation depends on the crab cavity frequency, proton synchrotron tune, proton bunch length and so on. In this article, we apply a combined strong-strong and weak-strong beam-beam simulation to investigate the incoherent and coherent beam motions with crabbed collison, and to calculate more realistic beam emittance growth rates and luminosity degradation rate.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB091
About •	paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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TUPGW082	Impedance of the Flange Joints With the RF Contact Spring in NSLS-II	1597
	A. Blednykh, B. Bacha, G. Bassi, C. Hetzel, B.N. Kosciuk, T.V. Shaftan, V.V. Smaluk, G.M. Wang BNL, Upton, Long Island, New York, USA
	Funding: This work was supported by Department of Energy Contract No. DE-SC0012704 Since the beginning of the NSLS-II commissioning, temperature of the vacuum components has been moni-tored by the Resistance Temperature Detectors located predominantly outside of the vacuum enclosure and at-tached to the chamber body. 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 harmonic cavities. Effect of the RF shielded flanges on local heat and on the longitu-dinal beam dynamics is discussed in details.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW082
About •	paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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TUPRB105	Realizing Low-Emittance Lattice Solutions With Complex Bends	1906
	V.V. Smaluk, T.V. Shaftan BNL, Upton, Long Island, New York, USA
	Funding: Department of Energy Contract No. DE-SC0012704 A concept of new lattice element called "Complex Bend" is recently proposed at NSLS-II. Replacing the regular dipoles in the Double-Bend Achromat lattice by Complex Bends significantly reduces the beam emittance. The first attempt of lattice design for potential NSLS-II upgrade based on Complex Bend, is described. Compared with the current NSLS-II lattice, the new solution modifies only three of the six girders per cell. The linear optics has been matched keeping unchanged the lattice parameters at the straight sections, where the light-generating insertion devices are located. The Complex Bend gradient is limited by 250 T/m assuming possible use of permanent magnets. The lattice provides 65 pm emittance without damping wigglers, use of which results in further decrease of the emittance
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB105
About •	paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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WEYPLS1	Building the Impedance Model of a Real Machine	2249
	B. Salvant, D. Amorim, S.A. Antipov, S. Arsenyev, M.S. Beck, N. Biancacci, O.S. Brüning, J.V. Campelo, E. Carideo, F. Caspers, A. Farricker, A. Grudiev, T. Kaltenbacher, E. Koukovini-Platia, P. Kramer, A. Lasheen, M. Migliorati, N. Mounet, E. Métral, N. Nasr Esfahani, S. Persichelli, B.K. Popovic, T.L. Rijoff, G. Rumolo, E.N. Shaposhnikova, V.G. Vaccaro, C. Vollinger, N. Wang, C. Zannini, B. Zotter CERN, Meyrin, Switzerland D. Amorim Grenoble-INP Phelma, Grenoble, France T. Dalascu EPFL, Lausanne, Switzerland M. Migliorati Sapienza University of Rome, Rome, Italy R. Nagaoka SOLEIL, Gif-sur-Yvette, France V.V. Smaluk BNL, Upton, Long Island, New York, USA B. Spataro INFN/LNF, Frascati, Italy N. Wang IHEP, Beijing, People’s Republic of China S.M. White ESRF, Grenoble, France
	A reliable impedance model of a particle accelerator can be built by combining the beam coupling impedances of all the components. This is a necessary step to be able to evaluate the machine performance limitations, identify the main contributors in case an impedance reduction is required, and study the interaction with other mechanisms such as optics nonlinearities, transverse damper, noise, space charge, electron cloud, beam-beam (in a collider). The main phases to create a realistic impedance model, and verify it experimentally, will be reviewed, highlighting the main challenges. Some examples will be presented revealing the levels of precision of machine impedance models that have been achieved.
	Slides WEYPLS1 [5.648 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEYPLS1
About •	paper received ※ 10 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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WEPGW102	Investigation on Mysterious Long-Term Orbit Drift at NSLS-II	2728
	Y. Hidaka, W.X. Cheng, L. Doom, R.P. Fliller, G. Ganetis, J. Gosman, C. Hetzel, R.A. Hubbard, D. Padrazo Jr, B. Podobedov, J. Rose, T.V. Shaftan, S.K. Sharma, V.V. Smaluk, T. Tanabe, Y. Tian, G.M. Wang, C.H. Yu BNL, Upton, Long Island, New York, USA
	Funding: The study is supported by U.S. DOE under Contract No. DE-SC0012704. Over a few months in 2018, we observed occasional episodes of relatively quick accumulation of correction strengths for the fast correctors (used by the fast orbit feedback) near Cell 4 (C04) region at NSLS-II Storage Ring. We immediately started investigating the problem, but the cause remained unclear. However, after coming back from the Fall shutdown, we experienced even faster drifts, at a rate of as much as 10 urad per day in terms of orbit kick angle accumulation. The risk of damage on the ring vacuum chambers by the continuing orbit drift without explanation eventually forced us to take emergency study shifts and temporarily lock out the C04 IVU beamline. After extensive investigation by many subsystem experts in Accelerator Division, ruling out many suspicious sources one by one, we were finally able to conclude the cause to be the localized ground motion induced by large temperature jumps of the utility tunnel right underneath the C04 straight section. We report the details of this incident.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW102
About •	paper received ※ 19 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019
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WEPGW114	Interferometric Measurement of Bunch Length of a 3Mev Picocoulomb Electron Beam	2766
	X. Yang, M. Babzien, B. Bacha, G.L. Carr, W.X. Cheng, L. Doom, M.G. Fedurin, B.N. Kosciuk, J.J. Li, D. Padrazo Jr, T.V. Shaftan, V.V. Smaluk, C. Swinson, L.-H. Yu, Y. Zhu BNL, Upton, Long Island, New York, USA
	Funding: BNL LDRD We report the bunch length measurement of low-energy 3 MeV electron beams in picosecond regime with the charge from 1.0 to 14 pC. It is the first time that we demonstrate single-cycle nano-joule coherent terahertz (THz) radiation from 3MeV electron beam can be meas-ured via a far-infrared Michelson interferometer using a QOD. At this low energy range, when charge is about 1 pC, the signal from the conventional helium-cooled sili-con composite bolometer is too low. Compared to the bunch length measurement via the ultrafast-laser-pump and electron-beam-probe in the timescale 10^-14 to 10-12 s which is determined by the phase-transition dynamics in solids, the advantages are: there are no needs of pump laser and probe sample, greatly simplifying the experi-ment; the timing jitter between laser and electron beams contributes no error to the bunch length measurement; furthermore, the method can be extended to sub-picosecond regime enabling bunch length measurement in a much broader timescale 10-14 to 10-11 s for low-energy electron beams. In the current experiment the bunch length is limited to 1 ps only because the setup of driving laser to cathode with a large 70° incident angle, effective-ly lengthening the laser pulse to ≥1 ps.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW114
About •	paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019
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THPMP053	Tuning Quadrupoles for Brighter and Sharper Ultra-fast Electron Diffraction Imaging	3571
	X. Yang, L. Doom, M.G. Fedurin, Y. Hidaka, J.J. Li, D. Padrazo Jr, T.V. Shaftan, V.V. Smaluk, G.M. Wang, L.-H. Yu, Y. Zhu BNL, Upton, Long Island, New York, USA W. Wan ShanghaiTech University, Shanghai, People’s Republic of China
	Funding: BNL LDRD We report our proof-of-principle design and experi-mental commissioning of broadly tunable and low-cost transverse focusing lens system for MeV-energy electron beams at the ultra-fast electron diffraction (UED) beam-line of the Accelerator Test Facility II of BNL. We exper-imentally demonstrate the independent control over the size and divergence of the electron beam at the sample via tunable quadrupoles. By applying online optimiza-tion, we achieve minimum beam sizes 75 µm from 1 to 13 pC, two orders of magnitude higher charge density than previously achieved using conventional solenoid tech-nique. Finally, we experimentally demonstrate Bragg-diffraction image (BDI) with significant improvement up to 3 times brighter and 2 times sharper BDI peaks via the optimized quadrupoles, improvement larger with higher charge. The result could be crucial for the future single-shot ultra-fast electron microscope development.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP053
About •	paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019
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THPTS094	High Gradient Quadrupoles for Low Emittance Synchrtrons	4332
	S.K. Sharma, T.V. Shaftan, V.V. Smaluk, C.J. Spataro, T. Tanabe, G.M. Wang BNL, Upton, Long Island, New York, USA N.A. Mezentsev BINP SB RAS, Novosibirsk, Russia
	A new lattice design has been proposed recently based on a Complex-Bend concept [1,2] for low emittance syn-chrotrons. The dipoles of a standard DBA lattice are replaced in the Complex Bend by high-gradient (~ 450 T/m) quadrupoles interleaved between discrete dipoles. In another version of the Complex Bend [3] the high gradient quadrupoles are displaced transversely along the beam trajectory to generate the required dipole field. In the latter version the quadrupole strength is reduced to ~ 250 T/m for a lattice that will conform to the layout of the existing NSLS-II 3-GeV storage ring. In this paper we present conceptual designs of a Halbach permanent-magnet (PM) quadrupole, a hybrid PM quadrupole, and a superconducting quadrupole, that can produce the de-sired quadrupole strengths for the Complex Bend appli-cation. REFERENCES [1] T. Shaftan, V. Smaluk and G. Wang, ’The Concept of Com-plex Bend’, NSLS-II Tech note No. 276, Jan 2018. [2] G. Wang et al., ’Complex Bend: Strong-focusing magnet for low emittance synchrotrons’, Physical Review Accelerators and Beams, 21, 100703 (2018). [3] G. Wang et al., ’Complex Bend II’, paper submitted to Physi-cal Review Accelerators and Beams.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS094
About •	paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019
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Paper

Title

Page

eRHIC Design Overview

45

C. Montag, G. Bassi, J. Beebe-Wang, J.S. Berg, M. Blaskiewicz, A. Blednykh, J.M. Brennan, S.J. Brooks, K.A. Brown, K.A. Drees, A.V. Fedotov, W. Fischer, D.M. Gassner, W. Guo, A. Hershcovitch, C. Hetzel, D. Holmes, H. Huang, W.A. Jackson, J. Kewisch, Y. Li, C. Liu, H. Lovelace III, Y. Luo, F. Méot, M.G. Minty, R.B. Palmer, B. Parker, S. Peggs, V. Ptitsyn, V.H. Ranjbar, G. Robert-Demolaize, S. Seletskiy, V.V. Smaluk, K.S. Smith, S. Tepikian, P. Thieberger, D. Trbojevic, N. Tsoupas, S. Verdú-Andrés, W.-T. Weng, F.J. Willeke, H. Witte, Q. Wu, W. Xu, A. Zaltsman, W. Zhang
BNL, Upton, Long Island, New York, USA
E. Gianfelice-Wendt
Fermilab, Batavia, Illinois, USA
Y. Hao
FRIB, East Lansing, Michigan, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The Electron-Ion Collider (EIC) is being envisioned as the next facility to be constructed by the DOE Nuclear Physics program. Brookhaven National Laboratory is proposing eRHIC, a facility based on the existing RHIC complex as a cost effective realization of the EIC project with a peak luminosity of 10³⁴ cm^-2 sec^-1. An electron storage ring with an energy range from 5 to 18 GeV will be added in the existing RHIC tunnel. A spin-transparent rapid-cycling synchrotron (RCS) will serve as a full-energy polarized electron injector. Recent design improvements include reduction of the IR magnet strengths to avoid the necessity for Nb₃Sn magnets, and a novel hadron injection scheme to maximize the integrated luminosity. We will provide an overview of this proposed project and present the current design status.

Slides MOZZPLS1 [5.428 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOZZPLS1

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW115

A Cross-Cell Interleaved Nonlinear Lattice for Potential NSLS-II Upgrade

393

Y. Li, A. He, B.N. Kosciuk, T.V. Shaftan, V.V. Smaluk
BNL, Upton, Long Island, New York, USA
Z.H. Bai, L. Wang
USTC/NSRL, Hefei, Anhui, People’s Republic of China

An interleaved sextupole scheme using cross-cell betatron phase cancellation technique is adopted as a candidate for the future NSLS-II upgrade lattice. The lattice uses as many NSLS-II installed magnets as possible, including 30 dipoles, to compose a triple bend achromat lattice. A 300 pm.rad horizontal beam emittance is achieved. The emittance can be further reduced to around 200 pm rad with damping wigglers. Various design concepts used in modern 4th-generation light sources, such as adopting longitudinal gradient dipoles and anti-bend scheme, are incorporated into the design as well. The betatron phase-advance between sextupoles is designed to have a cross-cell interleaving cancellation pattern in the transverse planes. The dynamic aperture is big enough for the conventional off-axis top-off injection. At the same time, a large energy acceptance looks promising to ensure a sufficiently long beam lifetime.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW115

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paper received ※ 12 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPGW122

Beam-based Measurement of Broadband Longitudinal Impedance at NSLS-II

400

V.V. Smaluk, B. Bacha, G. Bassi, A. Blednykh
BNL, Upton, Long Island, New York, USA

Funding: Department of Energy Contract No. DE-SC0012704
Interaction of a particle beam with the vacuum chamber impedance is one of the main effects limiting the beam intensity in accelerators. Minimization of the impedance is an essential part of the vacuum chamber design for any new accelerator project. The impedance can be estimated experimentally by measuring beam dynamics effects caused by the beam-impedance interaction. Experience obtained at many accelerator facilities shows the beam-based measurements are often different from the pre-computed impedance budgets, the discrepancy of a factor of two or even more is not unusual. The measurements of broadband longitudinal impedance carried out at NSLS-II are discussed in comparison with the numerically simulated impedance budget.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW122

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paper received ※ 15 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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MOPGW125

Lossless Crossing of 1/2 Resonance Stopband by Synchrotron Oscillations

410

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

Funding: DOE under contract No.DE-AC02- 98CH10886
Modern high performance circular accelerators require sophisticated corrections of nonlinear lattices. The beam betatron tune footprint may cross many resonances, reducing dynamic aperture and causing particle loss. However, if particles cross a resonance reasonably fast, the beam deterioration may be minimized. In this paper, we present the experiments with the beam passing through a half-integer resonance stopband via chromatic tune modulation by exciting synchrotron oscillations. This is the first time that beam dynamics have been kept under precise control while the beam crosses a half-integer resonance. Our results convincingly demonstrate that particles can cross the half-integer resonance without being lost if the passage is reasonably fast and the resonance stopband is sufficiently narrow.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW125

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paper received ※ 13 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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MOPRB091

Combined Strong-Strong and Weak-Strong Beam-Beam Simulations for Crabbed Collision in eRHIC

788

Y. Luo, G. Bassi, M. Blaskiewicz, W. Fischer, Y. Hao, C. Montag, V. Ptitsyn, V.V. Smaluk, F.J. Willeke
BNL, Upton, Long Island, New York, USA
K. Ohmi
KEK, Ibaraki, Japan
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In the eRHIC, to compensate the geometric luminosity loss, local crab cavities on both sides of the interaction points are to adopted. The previous strong-strong beam-beam simulations showed that the luminosity degradation depends on the crab cavity frequency, proton synchrotron tune, proton bunch length and so on. In this article, we apply a combined strong-strong and weak-strong beam-beam simulation to investigate the incoherent and coherent beam motions with crabbed collison, and to calculate more realistic beam emittance growth rates and luminosity degradation rate.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB091

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paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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TUPGW082

Impedance of the Flange Joints With the RF Contact Spring in NSLS-II

1597

A. Blednykh, B. Bacha, G. Bassi, C. Hetzel, B.N. Kosciuk, T.V. Shaftan, V.V. Smaluk, G.M. Wang
BNL, Upton, Long Island, New York, USA

Funding: This work was supported by Department of Energy Contract No. DE-SC0012704
Since the beginning of the NSLS-II commissioning, temperature of the vacuum components has been moni-tored by the Resistance Temperature Detectors located predominantly outside of the vacuum enclosure and at-tached to the chamber body. 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 harmonic cavities. Effect of the RF shielded flanges on local heat and on the longitu-dinal beam dynamics is discussed in details.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW082

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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TUPRB105

Realizing Low-Emittance Lattice Solutions With Complex Bends

1906

V.V. Smaluk, T.V. Shaftan
BNL, Upton, Long Island, New York, USA

Funding: Department of Energy Contract No. DE-SC0012704
A concept of new lattice element called "Complex Bend" is recently proposed at NSLS-II. Replacing the regular dipoles in the Double-Bend Achromat lattice by Complex Bends significantly reduces the beam emittance. The first attempt of lattice design for potential NSLS-II upgrade based on Complex Bend, is described. Compared with the current NSLS-II lattice, the new solution modifies only three of the six girders per cell. The linear optics has been matched keeping unchanged the lattice parameters at the straight sections, where the light-generating insertion devices are located. The Complex Bend gradient is limited by 250 T/m assuming possible use of permanent magnets. The lattice provides 65 pm emittance without damping wigglers, use of which results in further decrease of the emittance

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPRB105

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paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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WEYPLS1

Building the Impedance Model of a Real Machine

2249

B. Salvant, D. Amorim, S.A. Antipov, S. Arsenyev, M.S. Beck, N. Biancacci, O.S. Brüning, J.V. Campelo, E. Carideo, F. Caspers, A. Farricker, A. Grudiev, T. Kaltenbacher, E. Koukovini-Platia, P. Kramer, A. Lasheen, M. Migliorati, N. Mounet, E. Métral, N. Nasr Esfahani, S. Persichelli, B.K. Popovic, T.L. Rijoff, G. Rumolo, E.N. Shaposhnikova, V.G. Vaccaro, C. Vollinger, N. Wang, C. Zannini, B. Zotter
CERN, Meyrin, Switzerland
D. Amorim
Grenoble-INP Phelma, Grenoble, France
T. Dalascu
EPFL, Lausanne, Switzerland
M. Migliorati
Sapienza University of Rome, Rome, Italy
R. Nagaoka
SOLEIL, Gif-sur-Yvette, France
V.V. Smaluk
BNL, Upton, Long Island, New York, USA
B. Spataro
INFN/LNF, Frascati, Italy
N. Wang
IHEP, Beijing, People’s Republic of China
S.M. White
ESRF, Grenoble, France

A reliable impedance model of a particle accelerator can be built by combining the beam coupling impedances of all the components. This is a necessary step to be able to evaluate the machine performance limitations, identify the main contributors in case an impedance reduction is required, and study the interaction with other mechanisms such as optics nonlinearities, transverse damper, noise, space charge, electron cloud, beam-beam (in a collider). The main phases to create a realistic impedance model, and verify it experimentally, will be reviewed, highlighting the main challenges. Some examples will be presented revealing the levels of precision of machine impedance models that have been achieved.

Slides WEYPLS1 [5.648 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEYPLS1

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paper received ※ 10 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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WEPGW102

Investigation on Mysterious Long-Term Orbit Drift at NSLS-II

2728

Y. Hidaka, W.X. Cheng, L. Doom, R.P. Fliller, G. Ganetis, J. Gosman, C. Hetzel, R.A. Hubbard, D. Padrazo Jr, B. Podobedov, J. Rose, T.V. Shaftan, S.K. Sharma, V.V. Smaluk, T. Tanabe, Y. Tian, G.M. Wang, C.H. Yu
BNL, Upton, Long Island, New York, USA

Funding: The study is supported by U.S. DOE under Contract No. DE-SC0012704.
Over a few months in 2018, we observed occasional episodes of relatively quick accumulation of correction strengths for the fast correctors (used by the fast orbit feedback) near Cell 4 (C04) region at NSLS-II Storage Ring. We immediately started investigating the problem, but the cause remained unclear. However, after coming back from the Fall shutdown, we experienced even faster drifts, at a rate of as much as 10 urad per day in terms of orbit kick angle accumulation. The risk of damage on the ring vacuum chambers by the continuing orbit drift without explanation eventually forced us to take emergency study shifts and temporarily lock out the C04 IVU beamline. After extensive investigation by many subsystem experts in Accelerator Division, ruling out many suspicious sources one by one, we were finally able to conclude the cause to be the localized ground motion induced by large temperature jumps of the utility tunnel right underneath the C04 straight section. We report the details of this incident.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW102

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paper received ※ 19 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019

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WEPGW114

Interferometric Measurement of Bunch Length of a 3Mev Picocoulomb Electron Beam

2766

X. Yang, M. Babzien, B. Bacha, G.L. Carr, W.X. Cheng, L. Doom, M.G. Fedurin, B.N. Kosciuk, J.J. Li, D. Padrazo Jr, T.V. Shaftan, V.V. Smaluk, C. Swinson, L.-H. Yu, Y. Zhu
BNL, Upton, Long Island, New York, USA

Funding: BNL LDRD
We report the bunch length measurement of low-energy 3 MeV electron beams in picosecond regime with the charge from 1.0 to 14 pC. It is the first time that we demonstrate single-cycle nano-joule coherent terahertz (THz) radiation from 3MeV electron beam can be meas-ured via a far-infrared Michelson interferometer using a QOD. At this low energy range, when charge is about 1 pC, the signal from the conventional helium-cooled sili-con composite bolometer is too low. Compared to the bunch length measurement via the ultrafast-laser-pump and electron-beam-probe in the timescale 10^-14 to 10-12 s which is determined by the phase-transition dynamics in solids, the advantages are: there are no needs of pump laser and probe sample, greatly simplifying the experi-ment; the timing jitter between laser and electron beams contributes no error to the bunch length measurement; furthermore, the method can be extended to sub-picosecond regime enabling bunch length measurement in a much broader timescale 10-14 to 10-11 s for low-energy electron beams. In the current experiment the bunch length is limited to 1 ps only because the setup of driving laser to cathode with a large 70° incident angle, effective-ly lengthening the laser pulse to ≥1 ps.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW114

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paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019

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THPMP053

Tuning Quadrupoles for Brighter and Sharper Ultra-fast Electron Diffraction Imaging

3571

X. Yang, L. Doom, M.G. Fedurin, Y. Hidaka, J.J. Li, D. Padrazo Jr, T.V. Shaftan, V.V. Smaluk, G.M. Wang, L.-H. Yu, Y. Zhu
BNL, Upton, Long Island, New York, USA
W. Wan
ShanghaiTech University, Shanghai, People’s Republic of China

Funding: BNL LDRD
We report our proof-of-principle design and experi-mental commissioning of broadly tunable and low-cost transverse focusing lens system for MeV-energy electron beams at the ultra-fast electron diffraction (UED) beam-line of the Accelerator Test Facility II of BNL. We exper-imentally demonstrate the independent control over the size and divergence of the electron beam at the sample via tunable quadrupoles. By applying online optimiza-tion, we achieve minimum beam sizes 75 µm from 1 to 13 pC, two orders of magnitude higher charge density than previously achieved using conventional solenoid tech-nique. Finally, we experimentally demonstrate Bragg-diffraction image (BDI) with significant improvement up to 3 times brighter and 2 times sharper BDI peaks via the optimized quadrupoles, improvement larger with higher charge. The result could be crucial for the future single-shot ultra-fast electron microscope development.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP053

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paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019

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THPTS094

High Gradient Quadrupoles for Low Emittance Synchrtrons

4332

S.K. Sharma, T.V. Shaftan, V.V. Smaluk, C.J. Spataro, T. Tanabe, G.M. Wang
BNL, Upton, Long Island, New York, USA
N.A. Mezentsev
BINP SB RAS, Novosibirsk, Russia

A new lattice design has been proposed recently based on a Complex-Bend concept [1,2] for low emittance syn-chrotrons. The dipoles of a standard DBA lattice are replaced in the Complex Bend by high-gradient (~ 450 T/m) quadrupoles interleaved between discrete dipoles. In another version of the Complex Bend [3] the high gradient quadrupoles are displaced transversely along the beam trajectory to generate the required dipole field. In the latter version the quadrupole strength is reduced to ~ 250 T/m for a lattice that will conform to the layout of the existing NSLS-II 3-GeV storage ring. In this paper we present conceptual designs of a Halbach permanent-magnet (PM) quadrupole, a hybrid PM quadrupole, and a superconducting quadrupole, that can produce the de-sired quadrupole strengths for the Complex Bend appli-cation. REFERENCES [1] T. Shaftan, V. Smaluk and G. Wang, ’The Concept of Com-plex Bend’, NSLS-II Tech note No. 276, Jan 2018. [2] G. Wang et al., ’Complex Bend: Strong-focusing magnet for low emittance synchrotrons’, Physical Review Accelerators and Beams, 21, 100703 (2018). [3] G. Wang et al., ’Complex Bend II’, paper submitted to Physi-cal Review Accelerators and Beams.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS094

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paper received ※ 15 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019

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