IPAC2014 - Classification: 05 Beam Dynamics and Electromagnetic Fields / D04 High Intensity in Linear Accelerators - Incoherent Instabilities, Space Charge, Halos, Cooling

Paper	Title	Page
MOZA02	Advanced RF Design and Tuning Methods of RFQ for High Intensity Proton Linacs	34
	A. France CEA/IRFU, Gif-sur-Yvette, France
	The injector of high intensity linacs includes a Radio Frequency Quadrupole (RFQ) which must sustain high surface fields and thermal effects while accelerating intense low energy beams. For this purpose, the modelisation, realisation and tuning of accurate field laws is mandatory to preserve beam emittances and minimize beam losses. This presentation reviews the progress of advanced methods for the RF design, RF measurements during fabrication and final tuning of RFQ for high intensity linacs. It reports the ongoing developments on the injectors of high intensity demonstrators and of the linacs under construction such as SPIRAL2, LINAC4 or IFMIF-EVEDA.
	Slides MOZA02 [2.026 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOZA02
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TUOAB03	Nonlinear Optics for Suppression of Halo Formation in Space Charge Dominated Beams	953
	Y.K. Batygin, A. Scheinker LANL, Los Alamos, New Mexico, USA C. Li IMP, Lanzhou, People's Republic of China
	Traditional accelerator designs utilize linear focusing elements (quadrupoles, solenoids) to provide stable particle motion. High – intensity rms - matched non - uniform beams are intrinsically mismatched with linear focusing structure. It results in space charge induced beam emittance growth and halo formation, which can be suppressed in a quadrupole channel with higher-order multipole field components. In this paper, overview of FODO quadrupole channels with arbitrary multipoles is given. Effective averaged potential is presented for the structure with periodic combination of multipole lenses and quadrupoles. Density of matched beam avoiding emittance growth and halo formation is derived. Performed analysis allows matching of realistic beam with the internal structure of the focusing field. Beam dynamics studies with suppressed halo are presented and discussed.
	Slides TUOAB03 [3.404 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUOAB03
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THPRO092	Stochastic Noise Effects in High Current PIC Simulation	3101
	I. Hofmann, O. Boine-Frankenheim TEMF, TU Darmstadt, Darmstadt, Germany O. Boine-Frankenheim, I. Hofmann GSI, Darmstadt, Germany
	The numerical noise inherent to particle-in-cell simulation of 3D high intensity bunched beams is studied with the TRACEWIN code and compared with the analytical model by Struckmeier (1994). The latter assumes the six-dimensional rms emittance or rms entropy growth can be related to Markov type stochastic processes due to temperature anisotropy and the artificial "collisions" caused by using macro-particles and calculating the space charge effect. Our entropy growth confirms the dependency on bunch temperature anisotropy as predicted by Struckmeier. However, we also find noise generation by the non-Liouvillean effect of the Poisson solver grid, which exists in periodic focusing systems even when local temperature anisotropy is absent - contrary to predictions by Struckmeier's model.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO092
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THPRO093	Low Emittance Electron Beam Transportation in Compact ERL Injector	3104
	T. Miyajima, K. Harada, Y. Honda, T. Kume, S. Nagahashi, N. Nakamura, T. Obina, S. Sakanaka, M. Shimada, R. Takai, T. Uchiyama, A. Ueda, M. Yamamoto KEK, Ibaraki, Japan R. Hajima, R. Nagai, N. Nishimori JAEA, Ibaraki-ken, Japan J.G. Hwang Kyungpook National University, Daegu, Republic of Korea
	For future light source based on Energy Recovery Linac (ERL), an injector, which consists of a photocathode DC gun and superconducting RF cavities, is a key part to generate a low emittance, short pulse and high bunch charge electron beam. In compact ERL (cERL) which is a test accelerator to develop key technologies for ERL, the generation of low emittance electron beam with 0.1 mm mrad normalized emittance and 390 keV beam energy from the photocathode DC gun, and the acceleration to 5.6 MeV by superconducting cavity, were demonstrated in the first beam commissioning. To keep the high quality in the beam transportation, understanding the beam optics, which is affected by not only the focusing effects due to the gun, solenoid magnets and RF cavities but also space charge effect, is required. In this presentation, we will show that how to measure and correct the focusing effect by experimental method. Using this method, we succeeded in correcting the analytical model to give the good agreement with the measured gun focusing for low charge beam. And, we will show the space charge effect for high bunch charge beam.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO093
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THPRO094	Large Scale Particle Tracking and the Application in the Simulation of the RFQ Accelerator	3107
	L. Du, Q.Z. Xing TUB, Beijing, People's Republic of China Y.K. Batygin LANL, Los Alamos, New Mexico, USA Y. He, L. Yang IMP, Lanzhou, People's Republic of China J. Xu, R. Zhao IS, Beijing, People's Republic of China
	Large scale particle tracking is important for the design and optimization of the Radio-frequency Quadrupole (RFQ) accelerator. In this paper, we present RFQ simulation results of new parallel software named LOCUS3D, which is developed at Institute of Software, Chinese Academy of Sciences. It is based on Particle-In-Cell method and calculates three-dimensional space charge field by an efficient parallel fast Fourier transform method. A RFQ accelerator in Tsinghua University is simulated by tracking 100 million macro particles. This RFQ is designed to accelerate protons from 50 keV to 3 MeV, with peak beam current of 50 mA. As large number of particles been simulated, more accurate and detailed information have been obtained.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO094
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THPRO096	Nonlinear Oscillations of a Sheet Electron Beam	3113
	H.Y. Barminova MEPhI, Moscow, Russia
	In collisionless approximation the nonlinear dynamics of continuous strong current intense electron beam is investigated. Nonlinear oscillations of the beam radius appear due to self-consistent nonlinear forces. To study these oscillations the model is used that automatically satisfy to Vlasov equation. The oscillations are described by means of Duffing equation. The equilibrium state is shown to exist. The solutions near the equilibrium state are analyzed. The asymptotic character of the solutions is found. Nonlinear beam transverse oscillations lead to filamentation and effective emittance growth. If particle energy dissipation is absent in the beam transportation channel the physical reason of the effective emittance growth is transfer of the part of the beam potential energy to kinetic energy of the particle transverse oscillations.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO096
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THPRO097	Space-charge Neutralization of 750-keV H⁻ Beam at LANSCE	3116
	Y.K. Batygin, C. Pillai, L. Rybarcyk LANL, Los Alamos, New Mexico, USA
	The injector part of Los Alamos Neutron Science Center (LANSCE) includes 750-keV H⁻ beam transport located upstream of the Drift Tube Linac. Space charge effects play an important role in the beam transport therein. A series of experiments were performed to determine the level of beam space charge neutralization, and time required for neutralization. Measurements performed at different places along the structure indicate significant variation of neutralized space charge beam dynamics along the beamline. Results of measurements were compared with numerical simulations using macroparticle method and envelope equations to determine values of the effective beam current after neutralization, and effective beam emittance, required for beam tuning.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO097
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THPME003	A Precise Determination of the Core-halo Limit	3208
	P.A.P. Nghiem, N. Chauvin, D. Uriot, M. Valette CEA/DSM/IRFU, France W. Simeoni IF-UFRGS, Porto Alegre, Brazil
	For high-intensity beams, the dynamics of the dense core is different from that of the much less dense halo. Relations between core emittance growth and halo generation are often studied, halo scraping often experienced and halo re-formation observed. For all that, a clear distinction between the core and the halo parts does not exist. This paper proposes a new method for precisely determining the core-halo limit applicable to any particle distribution type. Once this limit is known, the importance of the halo relative to the core can be precisely quantified. The core-halo limit determination may be easily extended to the nD phase space, allowing the definition of emittance and Twiss parameters for the core and the halo separately.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME003
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THPME009	Beam Dynamics for the FAIR Proton-Linac RFQ	3226
	C. Zhang GSI, Darmstadt, Germany
	The FAIR (Facility for Antiproton and Ion Research) Proton-Linac (P-LINAC) will be started with a 325.224 MHz, 3 MeV Radio-Frequency Quadrupole (RFQ) accelerator. To ensure that a ≥35 mA beam can be injected into the downstream synchrotrons, the design beam intensity of this Proton-RFQ (P-RFQ) has been chosen as 70 mA. Based on the so-called NFSP (New Four-Section Procedure) method, two new beam dynamics designs with varying and constant transverse focusing strength, respectively, have been worked out to meet the latest design requirements using a compact structure. This paper presents the main design concepts and simulation results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME009
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THPME057	Calculations of Halo in TraceWin Code	3361
	N. Pichoff, P.A.P. Nghiem, D. Uriot CEA/DSM/IRFU, France M. Valette CEA/IRFU, Gif-sur-Yvette, France
	The TraceWIN code is used to simulate the dynamics of the particles and to design linear particle accelerators. The growth of rms emittance along the accelerator is often used to estimate the quality of a design. For high beam powers, the aim is also to limit the production of halo in order to keep particle losses under a requested limit. We present in this article the different ways to quantify this halo in TraceWin.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME057
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THPRI065	Effects of Beam Loading and Higher-order Modes in RF Cavities for Muon Ionization Cooling	3921
	M. Chung, A.V. Tollestrup, K. Yonehara Fermilab, Batavia, Illinois, USA B.T. Freemire IIT, Chicago, Illinois, USA F. Marhauser Muons, Inc, Illinois, USA
	Envisioned muon ionization cooling channel is based on vaccum and/or gas-filled RF cavities of frequencies of 325 and 650 MHz. In particular, to meet the luminosity requirement for a muon collider, the muon beam intensity should be on the order of 10¹² muons per bunch. In this high beam intensity, transient beam loading can significantly reduce the accelerating gradients and deteriorate the beam quality. We estimate this beam loading effect using an equivalent circuit model. For gas-filled cavity case, the beam loading is compared with plasma loading. We also investigate the excitation of higher-order modes and their effects on the performance of the cavity.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI065
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Advanced RF Design and Tuning Methods of RFQ for High Intensity Proton Linacs

34

A. France
CEA/IRFU, Gif-sur-Yvette, France

The injector of high intensity linacs includes a Radio Frequency Quadrupole (RFQ) which must sustain high surface fields and thermal effects while accelerating intense low energy beams. For this purpose, the modelisation, realisation and tuning of accurate field laws is mandatory to preserve beam emittances and minimize beam losses. This presentation reviews the progress of advanced methods for the RF design, RF measurements during fabrication and final tuning of RFQ for high intensity linacs. It reports the ongoing developments on the injectors of high intensity demonstrators and of the linacs under construction such as SPIRAL2, LINAC4 or IFMIF-EVEDA.

Slides MOZA02 [2.026 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOZA02

Export •

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

TUOAB03

Nonlinear Optics for Suppression of Halo Formation in Space Charge Dominated Beams

953

Y.K. Batygin, A. Scheinker
LANL, Los Alamos, New Mexico, USA
C. Li
IMP, Lanzhou, People's Republic of China

Traditional accelerator designs utilize linear focusing elements (quadrupoles, solenoids) to provide stable particle motion. High – intensity rms - matched non - uniform beams are intrinsically mismatched with linear focusing structure. It results in space charge induced beam emittance growth and halo formation, which can be suppressed in a quadrupole channel with higher-order multipole field components. In this paper, overview of FODO quadrupole channels with arbitrary multipoles is given. Effective averaged potential is presented for the structure with periodic combination of multipole lenses and quadrupoles. Density of matched beam avoiding emittance growth and halo formation is derived. Performed analysis allows matching of realistic beam with the internal structure of the focusing field. Beam dynamics studies with suppressed halo are presented and discussed.

Slides TUOAB03 [3.404 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUOAB03

Export •

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

THPRO092

Stochastic Noise Effects in High Current PIC Simulation

3101

I. Hofmann, O. Boine-Frankenheim
TEMF, TU Darmstadt, Darmstadt, Germany
O. Boine-Frankenheim, I. Hofmann
GSI, Darmstadt, Germany

The numerical noise inherent to particle-in-cell simulation of 3D high intensity bunched beams is studied with the TRACEWIN code and compared with the analytical model by Struckmeier (1994). The latter assumes the six-dimensional rms emittance or rms entropy growth can be related to Markov type stochastic processes due to temperature anisotropy and the artificial "collisions" caused by using macro-particles and calculating the space charge effect. Our entropy growth confirms the dependency on bunch temperature anisotropy as predicted by Struckmeier. However, we also find noise generation by the non-Liouvillean effect of the Poisson solver grid, which exists in periodic focusing systems even when local temperature anisotropy is absent - contrary to predictions by Struckmeier's model.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO092

Export •

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

THPRO093

Low Emittance Electron Beam Transportation in Compact ERL Injector

3104

T. Miyajima, K. Harada, Y. Honda, T. Kume, S. Nagahashi, N. Nakamura, T. Obina, S. Sakanaka, M. Shimada, R. Takai, T. Uchiyama, A. Ueda, M. Yamamoto
KEK, Ibaraki, Japan
R. Hajima, R. Nagai, N. Nishimori
JAEA, Ibaraki-ken, Japan
J.G. Hwang
Kyungpook National University, Daegu, Republic of Korea

For future light source based on Energy Recovery Linac (ERL), an injector, which consists of a photocathode DC gun and superconducting RF cavities, is a key part to generate a low emittance, short pulse and high bunch charge electron beam. In compact ERL (cERL) which is a test accelerator to develop key technologies for ERL, the generation of low emittance electron beam with 0.1 mm mrad normalized emittance and 390 keV beam energy from the photocathode DC gun, and the acceleration to 5.6 MeV by superconducting cavity, were demonstrated in the first beam commissioning. To keep the high quality in the beam transportation, understanding the beam optics, which is affected by not only the focusing effects due to the gun, solenoid magnets and RF cavities but also space charge effect, is required. In this presentation, we will show that how to measure and correct the focusing effect by experimental method. Using this method, we succeeded in correcting the analytical model to give the good agreement with the measured gun focusing for low charge beam. And, we will show the space charge effect for high bunch charge beam.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO093

Export •

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

THPRO094

Large Scale Particle Tracking and the Application in the Simulation of the RFQ Accelerator

3107

L. Du, Q.Z. Xing
TUB, Beijing, People's Republic of China
Y.K. Batygin
LANL, Los Alamos, New Mexico, USA
Y. He, L. Yang
IMP, Lanzhou, People's Republic of China
J. Xu, R. Zhao
IS, Beijing, People's Republic of China

Large scale particle tracking is important for the design and optimization of the Radio-frequency Quadrupole (RFQ) accelerator. In this paper, we present RFQ simulation results of new parallel software named LOCUS3D, which is developed at Institute of Software, Chinese Academy of Sciences. It is based on Particle-In-Cell method and calculates three-dimensional space charge field by an efficient parallel fast Fourier transform method. A RFQ accelerator in Tsinghua University is simulated by tracking 100 million macro particles. This RFQ is designed to accelerate protons from 50 keV to 3 MeV, with peak beam current of 50 mA. As large number of particles been simulated, more accurate and detailed information have been obtained.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO094

Export •

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

THPRO096

Nonlinear Oscillations of a Sheet Electron Beam

3113

H.Y. Barminova
MEPhI, Moscow, Russia

In collisionless approximation the nonlinear dynamics of continuous strong current intense electron beam is investigated. Nonlinear oscillations of the beam radius appear due to self-consistent nonlinear forces. To study these oscillations the model is used that automatically satisfy to Vlasov equation. The oscillations are described by means of Duffing equation. The equilibrium state is shown to exist. The solutions near the equilibrium state are analyzed. The asymptotic character of the solutions is found. Nonlinear beam transverse oscillations lead to filamentation and effective emittance growth. If particle energy dissipation is absent in the beam transportation channel the physical reason of the effective emittance growth is transfer of the part of the beam potential energy to kinetic energy of the particle transverse oscillations.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO096

Export •

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

THPRO097

Space-charge Neutralization of 750-keV H⁻ Beam at LANSCE

3116

Y.K. Batygin, C. Pillai, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

The injector part of Los Alamos Neutron Science Center (LANSCE) includes 750-keV H⁻ beam transport located upstream of the Drift Tube Linac. Space charge effects play an important role in the beam transport therein. A series of experiments were performed to determine the level of beam space charge neutralization, and time required for neutralization. Measurements performed at different places along the structure indicate significant variation of neutralized space charge beam dynamics along the beamline. Results of measurements were compared with numerical simulations using macroparticle method and envelope equations to determine values of the effective beam current after neutralization, and effective beam emittance, required for beam tuning.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO097

Export •

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

THPME003

A Precise Determination of the Core-halo Limit

3208

P.A.P. Nghiem, N. Chauvin, D. Uriot, M. Valette
CEA/DSM/IRFU, France
W. Simeoni
IF-UFRGS, Porto Alegre, Brazil

For high-intensity beams, the dynamics of the dense core is different from that of the much less dense halo. Relations between core emittance growth and halo generation are often studied, halo scraping often experienced and halo re-formation observed. For all that, a clear distinction between the core and the halo parts does not exist. This paper proposes a new method for precisely determining the core-halo limit applicable to any particle distribution type. Once this limit is known, the importance of the halo relative to the core can be precisely quantified. The core-halo limit determination may be easily extended to the nD phase space, allowing the definition of emittance and Twiss parameters for the core and the halo separately.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME003

Export •

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

THPME009

Beam Dynamics for the FAIR Proton-Linac RFQ

3226

C. Zhang
GSI, Darmstadt, Germany

The FAIR (Facility for Antiproton and Ion Research) Proton-Linac (P-LINAC) will be started with a 325.224 MHz, 3 MeV Radio-Frequency Quadrupole (RFQ) accelerator. To ensure that a ≥35 mA beam can be injected into the downstream synchrotrons, the design beam intensity of this Proton-RFQ (P-RFQ) has been chosen as 70 mA. Based on the so-called NFSP (New Four-Section Procedure) method, two new beam dynamics designs with varying and constant transverse focusing strength, respectively, have been worked out to meet the latest design requirements using a compact structure. This paper presents the main design concepts and simulation results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME009

Export •

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

THPME057

Calculations of Halo in TraceWin Code

3361

N. Pichoff, P.A.P. Nghiem, D. Uriot
CEA/DSM/IRFU, France
M. Valette
CEA/IRFU, Gif-sur-Yvette, France

The TraceWIN code is used to simulate the dynamics of the particles and to design linear particle accelerators. The growth of rms emittance along the accelerator is often used to estimate the quality of a design. For high beam powers, the aim is also to limit the production of halo in order to keep particle losses under a requested limit. We present in this article the different ways to quantify this halo in TraceWin.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME057

Export •

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

THPRI065

Effects of Beam Loading and Higher-order Modes in RF Cavities for Muon Ionization Cooling

3921

M. Chung, A.V. Tollestrup, K. Yonehara
Fermilab, Batavia, Illinois, USA
B.T. Freemire
IIT, Chicago, Illinois, USA
F. Marhauser
Muons, Inc, Illinois, USA

Envisioned muon ionization cooling channel is based on vaccum and/or gas-filled RF cavities of frequencies of 325 and 650 MHz. In particular, to meet the luminosity requirement for a muon collider, the muon beam intensity should be on the order of 10¹² muons per bunch. In this high beam intensity, transient beam loading can significantly reduce the accelerating gradients and deteriorate the beam quality. We estimate this beam loading effect using an equivalent circuit model. For gas-filled cavity case, the beam loading is compared with plasma loading. We also investigate the excitation of higher-order modes and their effects on the performance of the cavity.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRI065

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