Cyclotrons2013 - List of Keywords (space-charge)

Paper	Title	Other Keywords	Page
MO4PB01	Experimental Study Towards High Beam Power FFAG	acceleration, injection, linac, cavity	111
	T. Uesugi Kyoto University, Research Reactor Institute, Osaka, Japan
	The FFAG complex at KURRI is not only the first proton FFAG accelerator facility for beam users but the one aiming to have high beam power. The talk will present various efforts to increase beam power for the last few years and systematic strategy in near future toward the space charge limit.
	Slides MO4PB01 [6.691 MB]

WE2PB01	Space Charge Limit in Separated Turn Cyclotrons	cyclotron, emittance, extraction, TRIUMF	305
	R.A. Baartman TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	A review will be given of the intensity limits of cyclotrons due to space charge, both longitudinal and transverse.
	Slides WE2PB01 [1.513 MB]

WE2PB02	Vlasov Equation Approach to Space Charge Effects in Isochronous Machines	simulation, cyclotron, betatron, plasma	310
	A.J. Cerfon, O. Bühler, J.V. Guadagni Courant Institute of Mathematical Sciences, New York University, New York, USA J.P. Freidberg, F.I. Parra Diaz MIT/PSFC, Cambridge, Massachusetts, USA
	Starting from the collisionless Vlasov equation, we derive two simple coupled two-dimensional fluid equations describing the radial-longitudinal beam vortex motion associated with space charge effects in isochronous cyclotrons. These equations show that the vortex motion can be intuitively understood as the nonlinear advection of the beam by the ExB velocity field, where E is the electric field due to the space charge and B is the applied magnetic field. This explains why elongated beams develop spiral halos while round beams are always stable. Solving the coupled equations numerically, we find good agreement between our model and 3-D Particle-In-Cell OPAL simulations. J.J. Yang, A.Adelmann, M. Humbel, M. Seidel, and T.J. Zhang, Physical Review Special Topics Accelerators and Beams 13, 062401 (2010)
	Slides WE2PB02 [1.166 MB]

WE2PB03	Transverse-Longitudinal Coupling by Space Charge in Cyclotrons	emittance, cyclotron, focusing, simulation	315
	C. Baumgarten PSI, Villigen PSI, Switzerland
	Based on a linear space charge model and on the results of PIC-simulations with OPAL, we analyze the conditions under which space charge forces support bunch compactness in high intensity cyclotrons and/or FFAGs. For this purpose we compare the simulated emittance increase and halo formation for different matched and mismatched particle distributions injected into a separate sector cyclotron with different phase curves.
	Slides WE2PB03 [3.187 MB]

WEPPT004	Feasibility Study of Intense Beam Matching at the Spiral Inflector Using Elliptical Solenoid	solenoid, emittance, focusing, injection	326
	A. Goswami, V.S. Pandit, P. Sing Babu VECC, Kolkata, India
	Simulation results on a spiral inflector for compact cyclotron, indicate that convergent phase ellipses with different orientations in x and y planes and a comparatively smaller width in the y plane gives better beam transmission through the inflector. In order to transform the axisymmetric beam to a non-axisymmetric beam for matching at the entrance of the inflector one needs either an elliptical solenoid or a quadrupole doublet. The injection system of 10MeV-5mA proton cyclotron being developed at VECC consists of a 2.45GHz (80keV) microwave ion source and two solenoids to transport and match the beam at the spiral inflector. Due to space constraint we have planned to use an elliptical solenoid just before the spiral inflector for transverse matching of the beam. In this work the beam optical properties of an elliptical solenoid have been studied, including the effect of space charge. An envelope model based on the canonical description of motion has been developed and utilized to study the feasibility of using an elliptical solenoid for transverse matching of a space charge dominated beam to the acceptance of a spiral inflector.

WEPPT018	Behavior of Space Charge Dominated Beam Envelope in Central Region of High Current Cyclotron	acceleration, simulation, injection, cyclotron	359
	R. Azizi, H. Afarideh, V. Afzalan AUT, Tehran, Iran J.-S. Chai, M. Ghergherehchi SKKU, Suwon, Republic of Korea
	In this paper the space charge effect in the two first turn after injection has been investigated. In order to determine beam envelopes, two corresponding equations were chosen. In addition, all steps of calculation were done by MATLAB program. It should be mentioned limiting current and also magnetic, electrical field and edge effect has been considered. As far as, the high current cyclotron with 0.8π mm mrad emittance has been studied and current alters till 10 mA.* *M. Reiser, Theory and Design of Charged Particle Beams (Wiley, New York, 1994), Chapters.3 and 4.

WEPPT019	Investigation on the Transverse Emittance Growth of Intense Beam during Bunching	bunching, emittance, simulation, solenoid	361
	P. Sing Babu, A. Goswami, V.S. Pandit VECC, Kolkata, India
	Bunchers are widely used in the injection system of cyclotrons to transform dc beam into a bunched beam in a desired phase width. In the case of low beam current, the longitudinal compression of beam has very little effect on the transverse dynamics. However in the case of high current bunching the increase of current in the specified bunch width as the beam advances affects the transverse behavior. A 2D particle-in-cell code has been developed to study the transverse dynamics during beam bunching in the injection system of 10MeV, 5mA compact proton cyclotron. We have used a linear increase of beam current in the specified bunch width from the buncher position to the time focus. In the PIC method this effect is introduced by reweighting the charge and mass of the macroparticles during the transport with longitudinal compression. The evolutions of beam envelope and emittance growth have been estimated for various initial particle distributions. It is observed that the rms beam size is independent of particular beam distribution whereas rms emittance grows with nonuniformity of the distribution and peaks near the time focus.

WEPPT031	High Intensity Beam Studies Using the KURRI FFAGs	scattering, emittance, synchrotron, injection	387
	S. Machida, C. Gabor, D.J. Kelliher, C.R. Prior, C.T. Rogers, S.L. Sheehy STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom Y. Ishi, J.-B. Lagrange, Y. Mori, T. Uesugi Kyoto University, Research Reactor Institute, Osaka, Japan
	Increasing the repetition rate of FFAG accelerators is one way of obtaining high average beam current. However, in order to achieve beam powers of up to 10 MW for applications like ADSR, the number of particles per bunch has to be approximately the same order in an FFAG as in a high power synchrotron. Collective effects such as space charge then become crucial issues. To understand high current beam behaviour in FFAGs, an international collaboration has been established to carry out an experimental programme using the FFAGs at Kyoto University's Research Reactor Institute, KURRI. The goal is to demonstrate acceleration of high bunch charge and identify the fundamental limitations. In this paper, we will show simulation results toward the first beam experiment which is planned for later in 2013.

WE3PB02	Improvement of the Current Stability from the TRIUMF Cyclotron	cyclotron, TRIUMF, injection, focusing	414
	T. Planche, R.A. Baartman, Y.-N. Rao TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	The ν_r=3/2 resonance, driven by the third harmonic of the magnetic gradient errors, causes modulation of the radial beam density in the TRIUMF cyclotron. Since extraction is by H^- stripping, this modulation induces unwanted fluctuations of the current split between the two high-energy beam lines. To compensate field imperfections, the cyclotron has sets of harmonic correction coils at different radii, each set constituted of 6 pairs of coils placed in a 6-fold symmetrical manner. The 6-fold symmetry of this layout cannot create a third harmonic of arbitrary phase, and so a single set of harmonic coils cannot provide a full correction of third harmonic errors driving the ν_r=3/2 resonance. However, the outermost two sets of harmonic correction coils are azimuthally displaced. We took advantage of it to achieve a full correction of the resonance. This greatly improved the beam current stability in the high-energy beam lines. To further improve the current stability in the high-energy beam lines, we implemented an active feedback system. This feedback system acts on the amplitude of the first harmonic Bz correction produced by outermost set of harmonic coils.
	Slides WE3PB02 [1.007 MB]

WE3PB03	Space Charge Compensation Measurements in the Injector Beam Lines of the NSCL Coupled Cyclotron Facility	ion, electron, ECRIS, cyclotron	417
	D. Winklehner, D.G. Cole, D. Leitner, G. Machicoane, L. Tobos NSCL, East Lansing, Michigan, USA
	Space charge compensation is a well-known phenomenon for high current injector beam lines. For beam lines using mostly magnetic focusing elements and for pressures above 10^-6 mbar, compensation (neutralization) up to 98% has been observed. However, due to the low pressures required for the efficient transport of high charge state ions, ion beams in ECR injector lines are typically only partly neutralized and space charge effects are present. With the dramatic performance increase of the next generation Electron Cyclotron Resonance Ion Sources (ECRIS) it is possible to extract tens of mA of beams from ECR plasmas. Realistic beam transport simulations are important to meet the acceptance criteria of subsequent accelerator systems and have to include non-linear effects from space charge, but also space charge compensation. In this contribution we report on measurements of space charge compensation in the ECRIS low energy beam lines of the Coupled Cyclotron Facility at NSCL using a retarding field analyzer. Results are discussed and compared to simulations.
	Slides WE3PB03 [8.833 MB]

Paper

Title

Other Keywords

Page

MO4PB01

Experimental Study Towards High Beam Power FFAG

acceleration, injection, linac, cavity

111

T. Uesugi
Kyoto University, Research Reactor Institute, Osaka, Japan

The FFAG complex at KURRI is not only the first proton FFAG accelerator facility for beam users but the one aiming to have high beam power. The talk will present various efforts to increase beam power for the last few years and systematic strategy in near future toward the space charge limit.

Slides MO4PB01 [6.691 MB]

WE2PB01

Space Charge Limit in Separated Turn Cyclotrons

cyclotron, emittance, extraction, TRIUMF

305

R.A. Baartman
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

A review will be given of the intensity limits of cyclotrons due to space charge, both longitudinal and transverse.

Slides WE2PB01 [1.513 MB]

WE2PB02

Vlasov Equation Approach to Space Charge Effects in Isochronous Machines

simulation, cyclotron, betatron, plasma

310

A.J. Cerfon, O. Bühler, J.V. Guadagni
Courant Institute of Mathematical Sciences, New York University, New York, USA
J.P. Freidberg, F.I. Parra Diaz
MIT/PSFC, Cambridge, Massachusetts, USA

Starting from the collisionless Vlasov equation, we derive two simple coupled two-dimensional fluid equations describing the radial-longitudinal beam vortex motion associated with space charge effects in isochronous cyclotrons. These equations show that the vortex motion can be intuitively understood as the nonlinear advection of the beam by the ExB velocity field, where E is the electric field due to the space charge and B is the applied magnetic field. This explains why elongated beams develop spiral halos while round beams are always stable. Solving the coupled equations numerically, we find good agreement between our model and 3-D Particle-In-Cell OPAL simulations*.
* J.J. Yang, A.Adelmann, M. Humbel, M. Seidel, and T.J. Zhang, Physical Review Special Topics Accelerators and Beams 13, 062401 (2010)

Slides WE2PB02 [1.166 MB]

WE2PB03

Transverse-Longitudinal Coupling by Space Charge in Cyclotrons

emittance, cyclotron, focusing, simulation

315

C. Baumgarten
PSI, Villigen PSI, Switzerland

Based on a linear space charge model and on the results of PIC-simulations with OPAL, we analyze the conditions under which space charge forces support bunch compactness in high intensity cyclotrons and/or FFAGs. For this purpose we compare the simulated emittance increase and halo formation for different matched and mismatched particle distributions injected into a separate sector cyclotron with different phase curves.

Slides WE2PB03 [3.187 MB]

WEPPT004

Feasibility Study of Intense Beam Matching at the Spiral Inflector Using Elliptical Solenoid

solenoid, emittance, focusing, injection

326

A. Goswami, V.S. Pandit, P. Sing Babu
VECC, Kolkata, India

Simulation results on a spiral inflector for compact cyclotron, indicate that convergent phase ellipses with different orientations in x and y planes and a comparatively smaller width in the y plane gives better beam transmission through the inflector. In order to transform the axisymmetric beam to a non-axisymmetric beam for matching at the entrance of the inflector one needs either an elliptical solenoid or a quadrupole doublet. The injection system of 10MeV-5mA proton cyclotron being developed at VECC consists of a 2.45GHz (80keV) microwave ion source and two solenoids to transport and match the beam at the spiral inflector. Due to space constraint we have planned to use an elliptical solenoid just before the spiral inflector for transverse matching of the beam. In this work the beam optical properties of an elliptical solenoid have been studied, including the effect of space charge. An envelope model based on the canonical description of motion has been developed and utilized to study the feasibility of using an elliptical solenoid for transverse matching of a space charge dominated beam to the acceptance of a spiral inflector.

WEPPT018

Behavior of Space Charge Dominated Beam Envelope in Central Region of High Current Cyclotron

acceleration, simulation, injection, cyclotron

359

R. Azizi, H. Afarideh, V. Afzalan
AUT, Tehran, Iran
J.-S. Chai, M. Ghergherehchi
SKKU, Suwon, Republic of Korea

In this paper the space charge effect in the two first turn after injection has been investigated. In order to determine beam envelopes, two corresponding equations were chosen. In addition, all steps of calculation were done by MATLAB program. It should be mentioned limiting current and also magnetic, electrical field and edge effect has been considered. As far as, the high current cyclotron with 0.8π mm mrad emittance has been studied and current alters till 10 mA.*
*M. Reiser, Theory and Design of Charged Particle Beams (Wiley, New York, 1994), Chapters.3 and 4.

WEPPT019

Investigation on the Transverse Emittance Growth of Intense Beam during Bunching

bunching, emittance, simulation, solenoid

361

P. Sing Babu, A. Goswami, V.S. Pandit
VECC, Kolkata, India

Bunchers are widely used in the injection system of cyclotrons to transform dc beam into a bunched beam in a desired phase width. In the case of low beam current, the longitudinal compression of beam has very little effect on the transverse dynamics. However in the case of high current bunching the increase of current in the specified bunch width as the beam advances affects the transverse behavior. A 2D particle-in-cell code has been developed to study the transverse dynamics during beam bunching in the injection system of 10MeV, 5mA compact proton cyclotron. We have used a linear increase of beam current in the specified bunch width from the buncher position to the time focus. In the PIC method this effect is introduced by reweighting the charge and mass of the macroparticles during the transport with longitudinal compression. The evolutions of beam envelope and emittance growth have been estimated for various initial particle distributions. It is observed that the rms beam size is independent of particular beam distribution whereas rms emittance grows with nonuniformity of the distribution and peaks near the time focus.

WEPPT031

High Intensity Beam Studies Using the KURRI FFAGs

scattering, emittance, synchrotron, injection

387

S. Machida, C. Gabor, D.J. Kelliher, C.R. Prior, C.T. Rogers, S.L. Sheehy
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
Y. Ishi, J.-B. Lagrange, Y. Mori, T. Uesugi
Kyoto University, Research Reactor Institute, Osaka, Japan

Increasing the repetition rate of FFAG accelerators is one way of obtaining high average beam current. However, in order to achieve beam powers of up to 10 MW for applications like ADSR, the number of particles per bunch has to be approximately the same order in an FFAG as in a high power synchrotron. Collective effects such as space charge then become crucial issues. To understand high current beam behaviour in FFAGs, an international collaboration has been established to carry out an experimental programme using the FFAGs at Kyoto University's Research Reactor Institute, KURRI. The goal is to demonstrate acceleration of high bunch charge and identify the fundamental limitations. In this paper, we will show simulation results toward the first beam experiment which is planned for later in 2013.

WE3PB02

Improvement of the Current Stability from the TRIUMF Cyclotron

cyclotron, TRIUMF, injection, focusing

414

T. Planche, R.A. Baartman, Y.-N. Rao
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

The ν_r=3/2 resonance, driven by the third harmonic of the magnetic gradient errors, causes modulation of the radial beam density in the TRIUMF cyclotron. Since extraction is by H^- stripping, this modulation induces unwanted fluctuations of the current split between the two high-energy beam lines. To compensate field imperfections, the cyclotron has sets of harmonic correction coils at different radii, each set constituted of 6 pairs of coils placed in a 6-fold symmetrical manner. The 6-fold symmetry of this layout cannot create a third harmonic of arbitrary phase, and so a single set of harmonic coils cannot provide a full correction of third harmonic errors driving the ν_r=3/2 resonance. However, the outermost two sets of harmonic correction coils are azimuthally displaced. We took advantage of it to achieve a full correction of the resonance. This greatly improved the beam current stability in the high-energy beam lines. To further improve the current stability in the high-energy beam lines, we implemented an active feedback system. This feedback system acts on the amplitude of the first harmonic Bz correction produced by outermost set of harmonic coils.

Slides WE3PB02 [1.007 MB]

WE3PB03

Space Charge Compensation Measurements in the Injector Beam Lines of the NSCL Coupled Cyclotron Facility

ion, electron, ECRIS, cyclotron

417

D. Winklehner, D.G. Cole, D. Leitner, G. Machicoane, L. Tobos
NSCL, East Lansing, Michigan, USA

Space charge compensation is a well-known phenomenon for high current injector beam lines. For beam lines using mostly magnetic focusing elements and for pressures above 10^-6 mbar, compensation (neutralization) up to 98% has been observed. However, due to the low pressures required for the efficient transport of high charge state ions, ion beams in ECR injector lines are typically only partly neutralized and space charge effects are present. With the dramatic performance increase of the next generation Electron Cyclotron Resonance Ion Sources (ECRIS) it is possible to extract tens of mA of beams from ECR plasmas. Realistic beam transport simulations are important to meet the acceptance criteria of subsequent accelerator systems and have to include non-linear effects from space charge, but also space charge compensation. In this contribution we report on measurements of space charge compensation in the ECRIS low energy beam lines of the Coupled Cyclotron Facility at NSCL using a retarding field analyzer. Results are discussed and compared to simulations.

Slides WE3PB03 [8.833 MB]