HB2012 - List of Keywords (coupling)

Paper	Title	Other Keywords	Page
MOP206	Numerical Calculation of Beam Coupling Impedances for the SIS-100 Synchrotron for FAIR	impedance, kicker, space-charge, synchrotron	54
	U. Niedermayer, O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany
	The transverse impedance of kicker magnets is considered to be one of the main beam instability sources in the projected SIS-100 at FAIR and also in the SPS at CERN. The longitudinal impedance can contribute to the heat load, which is especially a concern in the cold sections of SIS-100 and LHC. In the high frequency range, time domain codes are commercially available to calculate the impedance but they become inapplicable at medium and low frequencies. We present the ongoing work of developing a Finite Integration (FIT) solver in frequency domain which is based on the Parallel and Extensible Toolkit for Scientific computing (PETSc) framework in C++. The code is applied to an inductive insert used to compensate the longitudinal space charge impedance in low energy machines. Another application focuses on the impedance contribution of a ferrite kicker with inductively coupled pulse forming network (PFN) and frequency dependent complex material permeability. In future we plan to confirm our simulations with dedicated wire or coil bench measurements.

MOP207	Planning for Experimental Demonstration of Transverse Emittance Transfer at the GSI UNILAC through Eigen-emittance Shaping	emittance, quadrupole, simulation, scattering	57
	C. Xiao, O.K. Kester IAP, Frankfurt am Main, Germany L. Groening GSI, Darmstadt, Germany
	The minimum transverse emittances achievable in a beam line are determined by the two transverse eigen-emittances of the beam. For vanishing interplane correlations they are equal to the well-know rms-emittances. Eigen-emittances are constants of motion for all symplectic beam line elements, i.e. (even tilted) linear elements. To allow for rms-emittance transfer, the eigen-emittances must be changed by applying a non-symplectic action to the beam, preferably preserving the 4d-rms-emittance. This contribution will introduce the concept for eigen-emittance shaping and rms-emittance transfer at an ion linac. A path towards the experimental demonstration of the concept at the GSI UNILAC is presented.

MOP262	Observations of Space Charge Effects in the Spallation Neutron Source Accumulator Ring	simulation, space-charge, accumulation, target	223
	R.E. Potts ORNL RAD, Oak Ridge, Tennessee, USA S.M. Cousineau, J.A. Holmes ORNL, Oak Ridge, Tennessee, USA
	Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. The Spallation Neutron Source accumulator ring was designed to allow independent control of the transverse beam distribution in each plane. However, at high beam intensities, nonlinear space charge forces can strongly influence the final beam distribution and compromise our ability to independently control the transverse distributions. In this study we investigate the evolution of the beam at intensities of up to ~8x10¹³ ppp through both simulation and experiment. Specifically, we analyze the evolution of the beam distribution for beams with different transverse aspect ratios and tune splits. We present preliminary results of simulations of our experiments.

TUO3A01	Dynamical Aspects of Emittance Coupling in Intense Beams	emittance, resonance, linac, simulation	240
	I. Hofmann GSI, Darmstadt, Germany I. Hofmann HIJ, Jena, Germany
	In this paper we study in an idealized lattice model the dynamical behavior of non-equipartitioned beams and of approach to equipartition. It is shown that emittance transfer depends on times scales of tune change, but also the direction of crossing the stopbands of space charge resonances. This provides additional information to support the stability charts suggested previously as design tool for high current linacs.
	Slides TUO3A01 [4.897 MB]

TUO3A03	Equipartition, Reality or Swindle?	resonance, linac, emittance, space-charge	250
	J.-M. Lagniel GANIL, Caen, France
	By way of introduction to a general discussion on space-charge induced energy equipartition (EQP), the following questions will be tackled: Why the formula presently used to define EQP is wrong? Why energy exchanges can occur although the EQP rule is respected? Why safe tunings can be find although the EQP rule is not respected? Why EQP is a swindle for a large majority of our accelerated beams? Why LINAC designers nevertheless like to use the EQP rule?
	Slides TUO3A03 [1.537 MB]

WEO1A01	Impedance Studies of 2D Azimuthally Symmetric Devices of Finite Length	impedance, resonance, simulation, cavity	344
	N. Biancacci, E. Métral, B. Salvant CERN, Geneva, Switzerland N. Biancacci Rome University La Sapienza, Roma, Italy M. Migliorati, L. Palumbo URLS, Rome, Italy V.G. Vaccaro Naples University Federico II, Mathematical, Physical and Natural Sciences Faculty, Napoli, Italy
	In circular accelerators, the beam quality can be strongly affected by the self-induced electromagnetic fields excited by the beam in the passage through the elements of the accelerator. The beam coupling impedance quantifies this interaction and allows predicting the stability of the dynamics of high intensity, high brilliance beams. The coupling impedance can be evaluated with finite element methods or using analytical methods, such as Field Matching or Mode Matching. In this paper we present an application of the Mode Matching technique for an azimuthally uniform structure of finite length: a cylindrical cavity loaded with a toroidal slab of lossy dielectric, connected with cylindrical beam pipes. In order to take into account the finite length of the structure, with respect to the infinite length approximation, we decompose the fields in the cavity into a set of orthonormal modes. We obtain a complete set of equations using the magnetic field matching and the non-uniform convergence of the electric field on the cavity boundaries. We present benchmarks done with CST Particle Studio simulations and existing analytical formulas, pointing out the effect of finite length and non-relativistic beta.
	Slides WEO1A01 [6.689 MB]

THO1B03	Measurement of Optics Errors and Space Charge Effects	space-charge, optics, sextupole, betatron	517
	K. Ohmi, Y. Sato, J. Takano KEK, Ibaraki, Japan S. Hatakeyama JAEA/J-PARC, Tokai-mura, Japan
	Beta function and x-y coupling are measured using turn-by-turn monitor system in J-PARC MR. Errors of the optics parameters induce to undesirable resonances due to lattice nonlinear magnets and space charge force. We estimate the resonance strength and the degradation of emittance growth and beam loss.
	Slides THO1B03 [2.240 MB]

Paper

Title

Other Keywords

Page

MOP206

Numerical Calculation of Beam Coupling Impedances for the SIS-100 Synchrotron for FAIR

impedance, kicker, space-charge, synchrotron

54

U. Niedermayer, O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany

The transverse impedance of kicker magnets is considered to be one of the main beam instability sources in the projected SIS-100 at FAIR and also in the SPS at CERN. The longitudinal impedance can contribute to the heat load, which is especially a concern in the cold sections of SIS-100 and LHC. In the high frequency range, time domain codes are commercially available to calculate the impedance but they become inapplicable at medium and low frequencies. We present the ongoing work of developing a Finite Integration (FIT) solver in frequency domain which is based on the Parallel and Extensible Toolkit for Scientific computing (PETSc) framework in C++. The code is applied to an inductive insert used to compensate the longitudinal space charge impedance in low energy machines. Another application focuses on the impedance contribution of a ferrite kicker with inductively coupled pulse forming network (PFN) and frequency dependent complex material permeability. In future we plan to confirm our simulations with dedicated wire or coil bench measurements.

MOP207

Planning for Experimental Demonstration of Transverse Emittance Transfer at the GSI UNILAC through Eigen-emittance Shaping

emittance, quadrupole, simulation, scattering

57

C. Xiao, O.K. Kester
IAP, Frankfurt am Main, Germany
L. Groening
GSI, Darmstadt, Germany

The minimum transverse emittances achievable in a beam line are determined by the two transverse eigen-emittances of the beam. For vanishing interplane correlations they are equal to the well-know rms-emittances. Eigen-emittances are constants of motion for all symplectic beam line elements, i.e. (even tilted) linear elements. To allow for rms-emittance transfer, the eigen-emittances must be changed by applying a non-symplectic action to the beam, preferably preserving the 4d-rms-emittance. This contribution will introduce the concept for eigen-emittance shaping and rms-emittance transfer at an ion linac. A path towards the experimental demonstration of the concept at the GSI UNILAC is presented.

MOP262

Observations of Space Charge Effects in the Spallation Neutron Source Accumulator Ring

simulation, space-charge, accumulation, target

223

R.E. Potts
ORNL RAD, Oak Ridge, Tennessee, USA
S.M. Cousineau, J.A. Holmes
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
The Spallation Neutron Source accumulator ring was designed to allow independent control of the transverse beam distribution in each plane. However, at high beam intensities, nonlinear space charge forces can strongly influence the final beam distribution and compromise our ability to independently control the transverse distributions. In this study we investigate the evolution of the beam at intensities of up to ~8x10¹³ ppp through both simulation and experiment. Specifically, we analyze the evolution of the beam distribution for beams with different transverse aspect ratios and tune splits. We present preliminary results of simulations of our experiments.

TUO3A01

Dynamical Aspects of Emittance Coupling in Intense Beams

emittance, resonance, linac, simulation

240

I. Hofmann
GSI, Darmstadt, Germany
I. Hofmann
HIJ, Jena, Germany

In this paper we study in an idealized lattice model the dynamical behavior of non-equipartitioned beams and of approach to equipartition. It is shown that emittance transfer depends on times scales of tune change, but also the direction of crossing the stopbands of space charge resonances. This provides additional information to support the stability charts suggested previously as design tool for high current linacs.

Slides TUO3A01 [4.897 MB]

TUO3A03

Equipartition, Reality or Swindle?

resonance, linac, emittance, space-charge

250

J.-M. Lagniel
GANIL, Caen, France

By way of introduction to a general discussion on space-charge induced energy equipartition (EQP), the following questions will be tackled: Why the formula presently used to define EQP is wrong? Why energy exchanges can occur although the EQP rule is respected? Why safe tunings can be find although the EQP rule is not respected? Why EQP is a swindle for a large majority of our accelerated beams? Why LINAC designers nevertheless like to use the EQP rule?

Slides TUO3A03 [1.537 MB]

WEO1A01

Impedance Studies of 2D Azimuthally Symmetric Devices of Finite Length

impedance, resonance, simulation, cavity

344

N. Biancacci, E. Métral, B. Salvant
CERN, Geneva, Switzerland
N. Biancacci
Rome University La Sapienza, Roma, Italy
M. Migliorati, L. Palumbo
URLS, Rome, Italy
V.G. Vaccaro
Naples University Federico II, Mathematical, Physical and Natural Sciences Faculty, Napoli, Italy

In circular accelerators, the beam quality can be strongly affected by the self-induced electromagnetic fields excited by the beam in the passage through the elements of the accelerator. The beam coupling impedance quantifies this interaction and allows predicting the stability of the dynamics of high intensity, high brilliance beams. The coupling impedance can be evaluated with finite element methods or using analytical methods, such as Field Matching or Mode Matching. In this paper we present an application of the Mode Matching technique for an azimuthally uniform structure of finite length: a cylindrical cavity loaded with a toroidal slab of lossy dielectric, connected with cylindrical beam pipes. In order to take into account the finite length of the structure, with respect to the infinite length approximation, we decompose the fields in the cavity into a set of orthonormal modes. We obtain a complete set of equations using the magnetic field matching and the non-uniform convergence of the electric field on the cavity boundaries. We present benchmarks done with CST Particle Studio simulations and existing analytical formulas, pointing out the effect of finite length and non-relativistic beta.

Slides WEO1A01 [6.689 MB]

THO1B03

Measurement of Optics Errors and Space Charge Effects

space-charge, optics, sextupole, betatron

517

K. Ohmi, Y. Sato, J. Takano
KEK, Ibaraki, Japan
S. Hatakeyama
JAEA/J-PARC, Tokai-mura, Japan

Beta function and x-y coupling are measured using turn-by-turn monitor system in J-PARC MR. Errors of the optics parameters induce to undesirable resonances due to lattice nonlinear magnets and space charge force. We estimate the resonance strength and the degradation of emittance growth and beam loss.

Slides THO1B03 [2.240 MB]