ICAP2018 - List of Keywords (dipole)

Paper	Title	Other Keywords	Page
SUPAG03	Challenges in Extracting Pseudo-Multipoles From Magnetic Measurements	multipole, induction, experiment, quadrupole	87
	S. Russenschuck, G. Caiafa, L. Fiscarelli, M. Liebsch, C. Petrone, P. Rogacki CERN, Geneva, Switzerland
	Extracting the coefficients of Fourier-Bessel series, known as pseudo-multipoles or generalized gradients, from magnetic measurements of accelerator magnets involves technical and mathematical challenges. First, a novel design of a short, rotating-coil magnetometer is required that does not intercept any axial field component of the magnet. Moreover, displacing short magnetometers, step-by-step along the magnet axis, yields a convolution of the local multipole field errors and the sensitivity (test function) of the induction coil. The deconvolution must then content with the low signal-to-noise ratio of the measurands, which are integrated voltages corresponding to spatial flux distributions. Finally, the compensation schemes, as implemented on long coils used for measuring the integrated field harmonics, cannot be applied to short magnetometers. All this requires careful design of experiment to derive the optimal length of the induction coil, the step size of the scan, and the highest order of pseudo-multipoles in the field reconstruction. This paper presents the theory of the measurement method, the data acquisition and deconvolution, and the design and production of a saddle-shaped, rotating-coil magnetometer.
	Slides SUPAG03 [4.548 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPAG03
About •	paper received ※ 18 October 2018 paper accepted ※ 27 January 2019 issue date ※ 26 January 2019
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TUPAF08	A Full Field-Map Modeling of Cornell-BNL CBETA 4-Pass Energy Recovery Linac	FFAG, linac, optics, simulation	186
	F. Méot, S.J. Brooks, D. Trbojevic, N. Tsoupas BNL, Upton, Long Island, New York, USA J.A. Crittenden Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy The Cornell-BNL Electron Test Accelerator (CBETA) is a four-pass, 150 MeV energy recovery linac (ERL), now in construction at Cornell. A single fixed-field alternating gradient (FFAG) beam line recirculates the four energies, 42, 78, 114 and 150 MeV. The return loop is comprised of 10⁷ quadrupole-doublet cells, built using Halbach permanent magnet technology. Spreader and combiner sections (4 independent beam lines each) connect the 36 MeV linac to the FFAG loop. We present here a start-to-end simulation of the 4-pass ERL, entirely, and exclusively, based on the use of magnetic field maps to model the magnets and correctors. There are paramount reasons for that and this is discussed, detailed outcomes are presented, together with comparisons with regular beam transport (mapping based) techniques.
	Slides TUPAF08 [2.568 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF08
About •	paper received ※ 23 October 2018 paper accepted ※ 07 December 2018 issue date ※ 26 January 2019
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TUPAG14	Constrained Multi-Objective Shape Optimization of Superconducting RF Cavities to Counteract Dangerous Higher Order Modes	cavity, HOM, impedance, superconducting-RF	293
	M. Kranjcevic, P. Arbenz ETH, Zurich, Switzerland A. Adelmann PSI, Villigen PSI, Switzerland S. Gorgi Zadeh, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
	High current storage rings, such as the Z operating mode of the FCC-ee, require superconducting radio frequency (RF) cavities that are optimized with respect to both the fundamental mode and the dangerous higher order modes. In order to optimize the shape of the RF cavity, a constrained multi-objective optimization problem is solved using a massively parallel implementation of an evolutionary algorithm. Additionally, a frequency-fixing scheme is employed to deal with the constraint on the frequency of the fundamental mode. Finally, the computed Pareto front approximation and an RF cavity shape with desired properties are shown.
	Slides TUPAG14 [3.001 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAG14
About •	paper received ※ 19 October 2018 paper accepted ※ 10 December 2018 issue date ※ 26 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAF01	A Compact Permanent Magnet Spectrometer for CILEX	electron, laser, permanent-magnet, simulation	320
	M. Khojoyan, A. Cauchois, J. Prudent, A. Specka LLR, Palaiseau, France
	Laser Wakefield acceleration experiments make exten- sive use of small permanent magnets or magnet assemblies for analyzing and focusing electron beams produced in plasma accelerators. Besides being compact, these magnets have to have a large angular acceptance for the divergent laser and electron beams which imposes constraint of the gap size. We will present the optimized design and charac- terization of a 100 mm long, 2.1 Tesla permanent magnet dipole. Furthermore, we will present the performance of such a magnet as a spectrometer in the CILEX/APOLLON 10PW laser facility in France.
	Slides WEPAF01 [6.898 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-WEPAF01
About •	paper received ※ 15 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPLG03	Theoretical and Computational Modeling of a Plasma Wakefield BBU Instability	plasma, wakefield, impedance, simulation	341
	S.D. Webb, D.L. Bruhwiler, N.M. Cook RadiaSoft LLC, Boulder, Colorado, USA A.V. Burov, V.A. Lebedev, S. Nagaitsev Fermilab, Batavia, Illinois, USA
	Funding: This work was supported in part by the Department of Energy, Office of Science, Office of High Energy Physics, under contract number DE-SC0018718. Plasma wakefield accelerators achieve accelerating gradients on the order of the wave-breaking limit, m c² k_p/e, so that higher accelerating gradients correspond to shorter plasma wavelengths. Small-scale accelerating structures, such as plasma and dielectric wakefields, are susceptible to the beam break-up instability (BBU), which can be understood from the Panofsky-Wenzel theorem: if the fundamental accelerating mode scales as b^-1 for a structure radius b, then the dipole mode must scale as b^-3, meaning that high accelerating gradients necessarily come with strong dipole wake fields. Because of this relationship, any plasma-accelerator-based future collider will require detailed study of the trade-offs between extracting the maximum energy from the driver and mitigating the beam break-up instability. Recent theoretical work* predicts the tradeoff between the witness bunch stability and the amount of energy that can be extracted from the drive bunch, a so-called efficiency-instability relation . We will discuss the beam break-up instability and the efficiency-instability relation and the theoretical assumptions made in reaching this conclusion. We will also present preliminary particle-in-cell simulations of a beam-driven plasma wakefield accelerator used to test the domain of validity for the assumptions made in this model. * V. Lebedev, A. Burov, and S. Nagaitsev, "Efficiency versus instability in plasma accelerators", Phys. Rev. Acc. Beams 20, 121301 (2017).
	Slides WEPLG03 [2.234 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-WEPLG03
About •	paper received ※ 01 November 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

SUPAG03

Challenges in Extracting Pseudo-Multipoles From Magnetic Measurements

multipole, induction, experiment, quadrupole

87

S. Russenschuck, G. Caiafa, L. Fiscarelli, M. Liebsch, C. Petrone, P. Rogacki
CERN, Geneva, Switzerland

Extracting the coefficients of Fourier-Bessel series, known as pseudo-multipoles or generalized gradients, from magnetic measurements of accelerator magnets involves technical and mathematical challenges. First, a novel design of a short, rotating-coil magnetometer is required that does not intercept any axial field component of the magnet. Moreover, displacing short magnetometers, step-by-step along the magnet axis, yields a convolution of the local multipole field errors and the sensitivity (test function) of the induction coil. The deconvolution must then content with the low signal-to-noise ratio of the measurands, which are integrated voltages corresponding to spatial flux distributions. Finally, the compensation schemes, as implemented on long coils used for measuring the integrated field harmonics, cannot be applied to short magnetometers. All this requires careful design of experiment to derive the optimal length of the induction coil, the step size of the scan, and the highest order of pseudo-multipoles in the field reconstruction. This paper presents the theory of the measurement method, the data acquisition and deconvolution, and the design and production of a saddle-shaped, rotating-coil magnetometer.

Slides SUPAG03 [4.548 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-SUPAG03

About •

paper received ※ 18 October 2018 paper accepted ※ 27 January 2019 issue date ※ 26 January 2019

Export •

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

TUPAF08

A Full Field-Map Modeling of Cornell-BNL CBETA 4-Pass Energy Recovery Linac

FFAG, linac, optics, simulation

186

F. Méot, S.J. Brooks, D. Trbojevic, N. Tsoupas
BNL, Upton, Long Island, New York, USA
J.A. Crittenden
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy
The Cornell-BNL Electron Test Accelerator (CBETA) is a four-pass, 150 MeV energy recovery linac (ERL), now in construction at Cornell. A single fixed-field alternating gradient (FFAG) beam line recirculates the four energies, 42, 78, 114 and 150 MeV. The return loop is comprised of 10⁷ quadrupole-doublet cells, built using Halbach permanent magnet technology. Spreader and combiner sections (4 independent beam lines each) connect the 36 MeV linac to the FFAG loop. We present here a start-to-end simulation of the 4-pass ERL, entirely, and exclusively, based on the use of magnetic field maps to model the magnets and correctors. There are paramount reasons for that and this is discussed, detailed outcomes are presented, together with comparisons with regular beam transport (mapping based) techniques.

Slides TUPAF08 [2.568 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAF08

About •

paper received ※ 23 October 2018 paper accepted ※ 07 December 2018 issue date ※ 26 January 2019

Export •

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

TUPAG14

Constrained Multi-Objective Shape Optimization of Superconducting RF Cavities to Counteract Dangerous Higher Order Modes

cavity, HOM, impedance, superconducting-RF

293

M. Kranjcevic, P. Arbenz
ETH, Zurich, Switzerland
A. Adelmann
PSI, Villigen PSI, Switzerland
S. Gorgi Zadeh, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany

High current storage rings, such as the Z operating mode of the FCC-ee, require superconducting radio frequency (RF) cavities that are optimized with respect to both the fundamental mode and the dangerous higher order modes. In order to optimize the shape of the RF cavity, a constrained multi-objective optimization problem is solved using a massively parallel implementation of an evolutionary algorithm. Additionally, a frequency-fixing scheme is employed to deal with the constraint on the frequency of the fundamental mode. Finally, the computed Pareto front approximation and an RF cavity shape with desired properties are shown.

Slides TUPAG14 [3.001 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-TUPAG14

About •

paper received ※ 19 October 2018 paper accepted ※ 10 December 2018 issue date ※ 26 January 2019

Export •

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

WEPAF01

A Compact Permanent Magnet Spectrometer for CILEX

electron, laser, permanent-magnet, simulation

320

M. Khojoyan, A. Cauchois, J. Prudent, A. Specka
LLR, Palaiseau, France

Laser Wakefield acceleration experiments make exten- sive use of small permanent magnets or magnet assemblies for analyzing and focusing electron beams produced in plasma accelerators. Besides being compact, these magnets have to have a large angular acceptance for the divergent laser and electron beams which imposes constraint of the gap size. We will present the optimized design and charac- terization of a 100 mm long, 2.1 Tesla permanent magnet dipole. Furthermore, we will present the performance of such a magnet as a spectrometer in the CILEX/APOLLON 10PW laser facility in France.

Slides WEPAF01 [6.898 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-WEPAF01

About •

paper received ※ 15 October 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019

Export •

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

WEPLG03

Theoretical and Computational Modeling of a Plasma Wakefield BBU Instability

plasma, wakefield, impedance, simulation

341

S.D. Webb, D.L. Bruhwiler, N.M. Cook
RadiaSoft LLC, Boulder, Colorado, USA
A.V. Burov, V.A. Lebedev, S. Nagaitsev
Fermilab, Batavia, Illinois, USA

Funding: This work was supported in part by the Department of Energy, Office of Science, Office of High Energy Physics, under contract number DE-SC0018718.
Plasma wakefield accelerators achieve accelerating gradients on the order of the wave-breaking limit, m c² k_p/e, so that higher accelerating gradients correspond to shorter plasma wavelengths. Small-scale accelerating structures, such as plasma and dielectric wakefields, are susceptible to the beam break-up instability (BBU), which can be understood from the Panofsky-Wenzel theorem: if the fundamental accelerating mode scales as b^-1 for a structure radius b, then the dipole mode must scale as b^-3, meaning that high accelerating gradients necessarily come with strong dipole wake fields. Because of this relationship, any plasma-accelerator-based future collider will require detailed study of the trade-offs between extracting the maximum energy from the driver and mitigating the beam break-up instability. Recent theoretical work* predicts the tradeoff between the witness bunch stability and the amount of energy that can be extracted from the drive bunch, a so-called efficiency-instability relation . We will discuss the beam break-up instability and the efficiency-instability relation and the theoretical assumptions made in reaching this conclusion. We will also present preliminary particle-in-cell simulations of a beam-driven plasma wakefield accelerator used to test the domain of validity for the assumptions made in this model.
* V. Lebedev, A. Burov, and S. Nagaitsev, "Efficiency versus
instability in plasma accelerators", Phys. Rev. Acc. Beams 20, 121301
(2017).

Slides WEPLG03 [2.234 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-ICAP2018-WEPLG03

About •

paper received ※ 01 November 2018 paper accepted ※ 28 January 2019 issue date ※ 26 January 2019

Export •

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