IPAC2014 - Classification: 05 Beam Dynamics and Electromagnetic Fields / D03 High Intensity in Circular Machines - Incoherent Instabilities, Space Charge, Halos, Cooling

Paper	Title	Page
MOZA01	Ultralow Emittance Beam Production based on Doppler Laser Cooling and Coupling Resonance	28
	A. Noda, M. Nakao NIRS, Chiba-shi, Japan M. Grieser MPI-K, Heidelberg, Germany Z.Q. He FRIB, East Lansing, Michigan, USA Z.Q. He TUB, Beijing, People's Republic of China K. Jimbo Kyoto University, Kyoto, Japan H. Okamoto, K. Osaki HU/AdSM, Higashi-Hiroshima, Japan A.V. Smirnov JINR, Dubna, Moscow Region, Russia H. Souda Gunma University, Heavy-Ion Medical Research Center, Maebashi-Gunma, Japan H. Tongu Kyoto ICR, Uji, Kyoto, Japan Y. Yuri JAEA/TARRI, Gunma-ken, Japan
	Funding: Work supported by Advanced Compact Accelerator Development project by MEXT of Japan. It is also supported by GCOE project at Kyoto University, “The next generation of Physics-Spun from Universality" Doppler laser cooling has been applied to low-energy (40 keV) Mg ions together with the resonant coupling method* at the S-LSR at ICR, Kyoto University,. The S-LSR storage ring has a high super periodicity of 6, which is preferable from the beam dynamical point of view. At S-LSR one dimensional ordering of proton beam was already realized for the first time*. Active three dimensional laser cooling has been experimentally demonstrated for ions with un-negligible velocity (v/c=0.0019, where c is the light velocity) for the first time. Utilizing the above mentioned characteristics of S-LSR, an approach to realize ultralow emittances has been pursuit. To suppress heating effects, due to intra-beam scattering, the circulating ion beam intensity was reduced by scraping and beam emittances of 1.3·10^-11 pi m·rad and 8.5·10^-12 pi m·rad (normalized) have been realized for the horizontal and vertical directions, respectively with the 40 keV Mg ion beam at a beam intensity of ~10⁴, which is the lowest emittance ever attained by laser cooling. From MD computer simulations, it is predicted that reduction of the ion number to about 10³ is needed to realize a crystalline string. H. Okamoto, A.M. Sessler, D. Moehl, Phys. Rev. Lett. 72, 397 (1994). ** T. Shirai et. al., Phys. Rev. Lett. 98, 204801 (2007).
	Slides MOZA01 [13.336 MB]
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TUPME084	On the Frequency Choice for the eRHIC SRF Linac	1547
	S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, V. Ptitsyn, W. Xu BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, V. Ptitsyn Stony Brook University, Stony Brook, USA
	Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE. eRHIC is a future electron-hadron collider proposed at BNL. It will collide high-intensity hadron beams from one of the existing rings of RHIC with a 50-mA electron beam from a multi-pass 10-GeV superconducting RF (SRF) Energy Recovery Linac (ERL). A novel approach to the multi-pass ERL utilizing a non-scaling FFAG was recently proposed. It has many advantages over the previous designs including significant cost savings. The current design has 11 passes in two FFAG rings. To mitigate various beam dynamics effects, it was proposed to lower RF frequency of the SRF linac from 704 MHz used in the previous design. In this paper we consider different effects driving the frequency choice of the SRF ERL and present our arguments for choosing lower RF frequency.
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TUPRI016	First Studies on Ion Effects in the Accelerator ELSA	1585
	D. Sauerland, W. Hillert, M.T. Switka ELSA, Bonn, Germany A. Markoviḱ, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany A. Meseck HZB, Berlin, Germany
	Funding: BMBF (Federal Ministry of Education and Research) In the ELSA stretcher ring electrons are accelerated by a fast energy ramp of 6 GeV/s to a beam energy of 3.2 GeV. The high energetic electrons ionize the residual gas molecules in the beam pipe by collisions or synchrotron radiation. The generated ions in turn accumulate inside the beam potential, causing several undesired effects such as tune shifts and beam instabilities. These effects are studied experimentally at ELSA using its full diagnostic capabilities. Both tune shifts due to beam neutralization and transversal beam-ion instabilities can be determined from the beam spectrum. Additionally the beam's transfer function can be measured using a broadband transversal kicker. In the stretcher ring at a beam energy of 1.2 GeV, a periodic beam blow-up was detected in the horizontal plane. Additional measurements of the transversal beam spectrum and ns-time resolution observations with a streak camera identified this blow-up as a coherent dipole oscillation of the beam. This horizontal instability is presumably caused by trapped ions, as there is a strong correlation with the high voltage-bias of the clearing electrodes.
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TUPRI017	Artificial Collisions, Entropy and Emittance Growth in Computer Simulations of Intense Beams	1588
	O. Boine-Frankenheim, I. Hofmann, J. Struckmeier GSI, Darmstadt, Germany
	During particle tracking with self-consistent space charge artificial collision between the macro-particles lead to diffusion-like, numerical effects. The artificial collisions generate a stochastic noise spectrum. As a consequence the entropy and the emittance of the particle beam can growth along periodic focusing structures. The growth rates depend on the number of simulation macro-particles and on the space charge tune shifts. For long-term tracking studies the numerical diffusion can lead to incorrect beam loss predictions. In our study we present analytical prediction for the numerical friction and diffusion in 2D and 3D simulations. For simple focusing structures with derive a relation between the friction coefficient and the entropy growth. The scaling of the friction coefficient with the macro-particle number and the space charge tune shift is obtained from 2D and 3D simulations and compared to the analytic predictions.
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TUPRI018	Transition Energy Crossing in the Future FAIR SIS-100 for Proton Operation	1591
	S. Aumon, D. Ondreka, S. Sorge GSI, Darmstadt, Germany K. Groß TEMF, TU Darmstadt, Darmstadt, Germany
	The FAIR project foresees to deliver an intense single bunch beam with 2·10¹³ protons of 50ns duration to the experiments. Besides the original γ_t-shift scenario, an alternative RF proton cycle has been recently studied: the transition energy is crossed with possibly a gamma transition jump. The flexibility of the lattice allowing to change the value of γ_t, a transition crossing has been considered for two possible energies. This challenging scenario is limited by several constraints such as space charge, a small momentum acceptance and by the required RF manipulations aiming to produce the final single bunch beam in the future SIS-100. This paper focuses on how the high intensity beam would suffer of the mismatch in bunch length at transition and new sets of beam parameter are defined for the proton beam. The jump quadrupole system is also presented. The applicability of the foreseen longitudinal feedback system to cure quadrupolar oscillations is also discussed in this paper.
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TUPRI019	Incoherent and Coherent Effects of Space Charge Limited Electron Clouds	1594
	F.B. Petrov, O. Boine-Frankenheim, O.S. Haas TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: Work is supported by the BMBF under contract 05H12RD7. Recent studies show that the space charge limited (saturated) electron cloud generated by relativistic bunches has strongly inhomogeneous distribution. In particular, a dense electron sheath is formed near the pipe wall. This feature modifies the stopping powers and the microwave transmission compared with the uniform cloud case. In this paper we investigate further the influence of the space charge limited electron cloud on relativistic bunches. In particular, we focus on the incoherent tune spread and compare the results with the homogeneous cloud case. We derive analytical expressions governing the pinch dynamics of the saturated cloud in round geometry. The contribution of the electron cloud sheath to the wake fields is investigated as well. Findings of the analytical theory are then successfully compared with numerical particle-in-cell simulations.
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TUPRI020	Study of Electron Cloud Effects in SuperKEKB	1597
	K. Ohmi, D. Zhou KEK, Ibaraki, Japan
	In SuperKEKB, high beta section exists in the interaction region. Fast head-tail instability and incoherent emittance growth due to electron cloud are enhanced in the high beta section. Especially high beta sections are located every betatron phase advance pi. Nonlinear force due to electron cloud is coherently accumulated. Incoherent eminence growth dominates.
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TUPRI023	Simulation of Debunching for Slow Extraction in J-PARC MR	1606
	M. Yamamoto, M. Nomura, T. Shimada, F. Tamura JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, K. Takata, M. Toda, M. Yoshii KEK, Ibaraki, Japan A. Schnase GSI, Darmstadt, Germany
	The J-PARC MR delivers a proton beam for nuclear physics experiments with slow extraction. The beam is debunched at flat top to obtain a coasting beam by turning off the rf voltage. The controlled emittance blow-up before the flat top has been investigated to mitigate the microwave instability. Beam loading effect can disturb the uniformity of the debunching at the flat top. We describe the results of the particle tracking simulation whole acceleration cycle including the controlled emittance blow-up and the beam loading effect.
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TUPRI024	Simulation of Space Charge Dynamics on HPC	1609
	N.V. Kulabukhova, S.N. Andrianov St. Petersburg State University, St. Petersburg, Russia A. Bogdanov, A. Degtyarev Saint Petersburg State University, Saint Petersburg, Russia
	To represent the space charge forces of beam a software based on analytical models for space charge distributions was developed. Special algorithm for predictor-corrector method for beam map evaluation scheme including the space charge forces were used. This method allows us to evaluate the map along the reference trajectory and to analyze beam envelope dynamics. In three dimensional models the number of computing resources we use is significant. For this purpose graphical processors are used. This software is a part of Virtual Accelerator concept which is considered as a set of services and tools of modeling beam dynamics in accelerators on distributed computing resources.
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TUPRI025	Interplay of Touschek Scattering, Intrabeam Scattering, and RF Cavities in Ultralow-emittance Storage Rings	1612
	S.C. Leemann MAX-lab, Lund, Sweden
	When it goes into operation in 2016, the MAX IV 3 GeV storage ring will be the first ultralow-emittance storage ring based on a multibend achromat lattice. These lattices make use of a large number of weak bending magnets which considerably reduces the amount of power radiated in the dipoles in comparison to power radiated from insertion devices. Therefore parameters such as emittance, energy spread, and radiated power are no longer constant during a typical user shift. Since the charge per bunch is usually high, intrabeam scattering (IBS) becomes very strong creating a dependence of emittance on stored current. Since the bunch length can vary as insertion device gaps change, the emittance blow-up from IBS is not constant either. Therefore, the emittance, bunch length, and hence the resulting Touschek lifetime have to be calculated in a self-consistent fashion taking into account the bare lattice, RF cavity settings, bunch charge, and gap settings. This paper demonstrates the intricate interplay between transverse emittance (insertion devices, emittance coupling), longitudinal emittance (tuning of main cavities as well as harmonic Landau cavities), and choice of stored current.
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TUPRI027	Detailed Magnetic Model Simulations of the H⁻ Injection Chicane Magnets for the CERN PS Booster Upgrade, including Eddy Currents, and Influence on Beam Dynamics	1618
	E. Benedetto, B. Balhan, J. Borburgh, C. Carli, V. Forte, M. Martini CERN, Geneva, Switzerland V. Forte Université Blaise Pascal, Clermont-Ferrand, France
	The CERN PS Booster will be upgraded with an H⁻ injection system. The chicane magnets for the injection bump ramp-down in 5 ms and generate eddy currents in the inconel vacuum chamber which perturb the homogeneity of the magnetic field. The multipolar field components are extracted from 3D OPERA simulations and are included in the lattice model. The beta-beating correction is computed all along the ramp and complete tracking simulations including space-charge are performed to evaluate the impact of these perturbations and their correction.
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TUPRI029	The CERN PS Booster Space Charge Simulations with a Realistic Model for Alignment and Field Errors	1624
	V. Forte, E. Benedetto, M. McAteer CERN, Geneva, Switzerland
	The CERN PS Booster is one of the machines of the LHC injector chain which will be upgraded within the LIU (LHC Injectors upgrade) project. The injection energy of the PSB will be increased to 160MeV in order to mitigate direct space charge effects, considered to be the main performance limitation, thus allowing to double the brightness for the LHC beams. In order to better predict the gain to be expected, space charge simulations are being carried out. Efforts to establish a realistic modeling of field and alignment errors aim at extending the basic model of the machine towards a more realistic one. Simulations of beam dynamics with strong direct space charge and realistic errors are presented and analysed in this paper.
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TUPRI030	Beam Coupling Impedance of the New Beam Screen of the LHC Injection Kicker Magnets	1627
	H.A. Day, M.J. Barnes, F. Caspers, E. Métral, B. Salvant, J.A. Uythoven CERN, Geneva, Switzerland
	The LHC injection kicker magnets experienced significant beam induced heating of the ferrite yoke, with high intensity beam circulating for many hours, during operation of the LHC in 2011 and 2012. The causes of this beam coupling impedance were studied in depth and an improved beam screen implemented to reduce the impedance. Results of measurements and simulations of the new beam screen design are presented in this paper: these are used to predict power loss and temperature of the ferrite yoke for operation after long shutdown 1 and for proposed HL-LHC operational parameters.
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TUPRI031	A Precise Beam Dynamics Model of the PSI Injector 2 to Estimate the Intensity Limit	1630
SUSPSNE058	use link to see paper's listing under its alternate paper code
	A.M. Kolano, R.J. Barlow University of Huddersfield, Huddersfield, United Kingdom A. Adelmann, C. Baumgarten PSI, Villigen PSI, Switzerland
	We describe a precise beam dynamics model of the production set up of the Injector 2 Cyclotron at the Paul Scherrer Institut (PSI). Injector 2 is a 72 MeV separate-sector cyclotron producing a high intensity proton beam up to 2.7 mA CW, which is then injected into the 590 MeV Ring Cyclotron. The model includes space charge and is calculated for optimised matched initial conditions. It has been verified with measurements. Based on this model we estimate the limits to the intensity obtainable from Injector 2. The precise beam dynamics model is based on the OPAL (Object Oriented Parallel Accelerator Library) simulation code, a tool for charged-particle optics calculations in large accelerator structures and beam lines including 3D space charge.
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TUPRI034	Numerical Modeling for CesrTA Measurements of Electron Cloud Buildup in a Quadrupole Magnet	1632
	J.A. Crittenden, M.G. Billing, W. Hartung, C. Shill, J.P. Sikora, K.G. Sonnad Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work supported by the U.S. National Science Foundation contracts PHY-0734867, PHY-1002467, and the U.S. Department of Energy contract DE-FC02-08ER41538 We describe a numerical model for measurements of the formation of long-lived electron clouds in a quadrupole magnet in the CESR storage ring. The shielded stripline detector measures the electron flux incident on the vacuum chamber wall directly in front of one of the poles of the magnet. The model includes photo-electron production by synchrotron radiation, electrostatic forces from the bunched positron beam and the cloud, macroparticle tracking in the field of the quadrupole, secondary electron emission from the 9.5-cm-diameter cylindrical stainless steel beam-pipe and an analytic calculation of the transmission function of the holes in the vacuum chamber which allow cloud electrons to reach the stripline collector. These modeling studies provide a quantitative understanding of the trapping mechanism which results in cloud electrons surviving the 2.3-microsecond time interval prior to the return of a train of positron bunches. These studies have been performed in the context of the CESR Test Accelerator program, which aims to quantify and mitigate performance limitations on future low-emittance storage and damping rings.
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TUPRI035	Measurement of Beam Size in Intrabeam Scattering Dominated Beams at Various Energies at CesrTA	1635
	M. P. Ehrlichman, K.J. Blaser, A. Chatterjee, W. Hartung, B.K. Heltsley, D.P. Peterson, D. L. Rubin, D. Sagan, J.P. Shanks, S. Wang Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: This research was supported by NSF and DOE contracts PHY-0734867, PHY-1002467, PHYS-1068662, DE-FC02-08ER41538, DE-SC0006505. Recent reports from CesrTA have shown measurement and calculation of beam size versus current in CesrTA beams at 2.1 GeV. Here, the effect of changing the energy of IBS-dominated beams is reported. IBS growth rates have roughly a γ^-3 dependence. Measurements at 1.8, 2.1, 2.3, and 2.5 GeV are shown and compared with predictions from IBS theory.
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Paper

Title

Page

Ultralow Emittance Beam Production based on Doppler Laser Cooling and Coupling Resonance

28

A. Noda, M. Nakao
NIRS, Chiba-shi, Japan
M. Grieser
MPI-K, Heidelberg, Germany
Z.Q. He
FRIB, East Lansing, Michigan, USA
Z.Q. He
TUB, Beijing, People's Republic of China
K. Jimbo
Kyoto University, Kyoto, Japan
H. Okamoto, K. Osaki
HU/AdSM, Higashi-Hiroshima, Japan
A.V. Smirnov
JINR, Dubna, Moscow Region, Russia
H. Souda
Gunma University, Heavy-Ion Medical Research Center, Maebashi-Gunma, Japan
H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
Y. Yuri
JAEA/TARRI, Gunma-ken, Japan

Funding: Work supported by Advanced Compact Accelerator Development project by MEXT of Japan. It is also supported by GCOE project at Kyoto University, “The next generation of Physics-Spun from Universality"
Doppler laser cooling has been applied to low-energy (40 keV) Mg ions together with the resonant coupling method* at the S-LSR at ICR, Kyoto University,. The S-LSR storage ring has a high super periodicity of 6, which is preferable from the beam dynamical point of view. At S-LSR one dimensional ordering of proton beam was already realized for the first time**. Active three dimensional laser cooling has been experimentally demonstrated for ions with un-negligible velocity (v/c=0.0019, where c is the light velocity) for the first time. Utilizing the above mentioned characteristics of S-LSR, an approach to realize ultralow emittances has been pursuit. To suppress heating effects, due to intra-beam scattering, the circulating ion beam intensity was reduced by scraping and beam emittances of 1.3·10^-11 pi m·rad and 8.5·10^-12 pi m·rad (normalized) have been realized for the horizontal and vertical directions, respectively with the 40 keV Mg ion beam at a beam intensity of ~10⁴, which is the lowest emittance ever attained by laser cooling. From MD computer simulations, it is predicted that reduction of the ion number to about 10³ is needed to realize a crystalline string.
* H. Okamoto, A.M. Sessler, D. Moehl, Phys. Rev. Lett. 72, 397 (1994).
** T. Shirai et. al., Phys. Rev. Lett. 98, 204801 (2007).

Slides MOZA01 [13.336 MB]

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TUPME084

On the Frequency Choice for the eRHIC SRF Linac

1547

S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, V. Ptitsyn, W. Xu
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi, V. Litvinenko, V. Ptitsyn
Stony Brook University, Stony Brook, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
eRHIC is a future electron-hadron collider proposed at BNL. It will collide high-intensity hadron beams from one of the existing rings of RHIC with a 50-mA electron beam from a multi-pass 10-GeV superconducting RF (SRF) Energy Recovery Linac (ERL). A novel approach to the multi-pass ERL utilizing a non-scaling FFAG was recently proposed. It has many advantages over the previous designs including significant cost savings. The current design has 11 passes in two FFAG rings. To mitigate various beam dynamics effects, it was proposed to lower RF frequency of the SRF linac from 704 MHz used in the previous design. In this paper we consider different effects driving the frequency choice of the SRF ERL and present our arguments for choosing lower RF frequency.

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TUPRI016

First Studies on Ion Effects in the Accelerator ELSA

1585

D. Sauerland, W. Hillert, M.T. Switka
ELSA, Bonn, Germany
A. Markoviḱ, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
A. Meseck
HZB, Berlin, Germany

Funding: BMBF (Federal Ministry of Education and Research)
In the ELSA stretcher ring electrons are accelerated by a fast energy ramp of 6 GeV/s to a beam energy of 3.2 GeV. The high energetic electrons ionize the residual gas molecules in the beam pipe by collisions or synchrotron radiation. The generated ions in turn accumulate inside the beam potential, causing several undesired effects such as tune shifts and beam instabilities. These effects are studied experimentally at ELSA using its full diagnostic capabilities. Both tune shifts due to beam neutralization and transversal beam-ion instabilities can be determined from the beam spectrum. Additionally the beam's transfer function can be measured using a broadband transversal kicker. In the stretcher ring at a beam energy of 1.2 GeV, a periodic beam blow-up was detected in the horizontal plane. Additional measurements of the transversal beam spectrum and ns-time resolution observations with a streak camera identified this blow-up as a coherent dipole oscillation of the beam. This horizontal instability is presumably caused by trapped ions, as there is a strong correlation with the high voltage-bias of the clearing electrodes.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI016

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TUPRI017

Artificial Collisions, Entropy and Emittance Growth in Computer Simulations of Intense Beams

1588

O. Boine-Frankenheim, I. Hofmann, J. Struckmeier
GSI, Darmstadt, Germany

During particle tracking with self-consistent space charge artificial collision between the macro-particles lead to diffusion-like, numerical effects. The artificial collisions generate a stochastic noise spectrum. As a consequence the entropy and the emittance of the particle beam can growth along periodic focusing structures. The growth rates depend on the number of simulation macro-particles and on the space charge tune shifts. For long-term tracking studies the numerical diffusion can lead to incorrect beam loss predictions. In our study we present analytical prediction for the numerical friction and diffusion in 2D and 3D simulations. For simple focusing structures with derive a relation between the friction coefficient and the entropy growth. The scaling of the friction coefficient with the macro-particle number and the space charge tune shift is obtained from 2D and 3D simulations and compared to the analytic predictions.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI017

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TUPRI018

Transition Energy Crossing in the Future FAIR SIS-100 for Proton Operation

1591

S. Aumon, D. Ondreka, S. Sorge
GSI, Darmstadt, Germany
K. Groß
TEMF, TU Darmstadt, Darmstadt, Germany

The FAIR project foresees to deliver an intense single bunch beam with 2·10¹³ protons of 50ns duration to the experiments. Besides the original γ_t-shift scenario, an alternative RF proton cycle has been recently studied: the transition energy is crossed with possibly a gamma transition jump. The flexibility of the lattice allowing to change the value of γ_t, a transition crossing has been considered for two possible energies. This challenging scenario is limited by several constraints such as space charge, a small momentum acceptance and by the required RF manipulations aiming to produce the final single bunch beam in the future SIS-100. This paper focuses on how the high intensity beam would suffer of the mismatch in bunch length at transition and new sets of beam parameter are defined for the proton beam. The jump quadrupole system is also presented. The applicability of the foreseen longitudinal feedback system to cure quadrupolar oscillations is also discussed in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI018

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TUPRI019

Incoherent and Coherent Effects of Space Charge Limited Electron Clouds

1594

F.B. Petrov, O. Boine-Frankenheim, O.S. Haas
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: Work is supported by the BMBF under contract 05H12RD7.
Recent studies show that the space charge limited (saturated) electron cloud generated by relativistic bunches has strongly inhomogeneous distribution. In particular, a dense electron sheath is formed near the pipe wall. This feature modifies the stopping powers and the microwave transmission compared with the uniform cloud case. In this paper we investigate further the influence of the space charge limited electron cloud on relativistic bunches. In particular, we focus on the incoherent tune spread and compare the results with the homogeneous cloud case. We derive analytical expressions governing the pinch dynamics of the saturated cloud in round geometry. The contribution of the electron cloud sheath to the wake fields is investigated as well. Findings of the analytical theory are then successfully compared with numerical particle-in-cell simulations.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRI019

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TUPRI020

Study of Electron Cloud Effects in SuperKEKB

1597

K. Ohmi, D. Zhou
KEK, Ibaraki, Japan

In SuperKEKB, high beta section exists in the interaction region. Fast head-tail instability and incoherent emittance growth due to electron cloud are enhanced in the high beta section. Especially high beta sections are located every betatron phase advance pi. Nonlinear force due to electron cloud is coherently accumulated. Incoherent eminence growth dominates.

DOI •

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TUPRI023

Simulation of Debunching for Slow Extraction in J-PARC MR

1606

M. Yamamoto, M. Nomura, T. Shimada, F. Tamura
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, K. Takata, M. Toda, M. Yoshii
KEK, Ibaraki, Japan
A. Schnase
GSI, Darmstadt, Germany

The J-PARC MR delivers a proton beam for nuclear physics experiments with slow extraction. The beam is debunched at flat top to obtain a coasting beam by turning off the rf voltage. The controlled emittance blow-up before the flat top has been investigated to mitigate the microwave instability. Beam loading effect can disturb the uniformity of the debunching at the flat top. We describe the results of the particle tracking simulation whole acceleration cycle including the controlled emittance blow-up and the beam loading effect.

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TUPRI024

Simulation of Space Charge Dynamics on HPC

1609

N.V. Kulabukhova, S.N. Andrianov
St. Petersburg State University, St. Petersburg, Russia
A. Bogdanov, A. Degtyarev
Saint Petersburg State University, Saint Petersburg, Russia

To represent the space charge forces of beam a software based on analytical models for space charge distributions was developed. Special algorithm for predictor-corrector method for beam map evaluation scheme including the space charge forces were used. This method allows us to evaluate the map along the reference trajectory and to analyze beam envelope dynamics. In three dimensional models the number of computing resources we use is significant. For this purpose graphical processors are used. This software is a part of Virtual Accelerator concept which is considered as a set of services and tools of modeling beam dynamics in accelerators on distributed computing resources.

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TUPRI025

Interplay of Touschek Scattering, Intrabeam Scattering, and RF Cavities in Ultralow-emittance Storage Rings

1612

S.C. Leemann
MAX-lab, Lund, Sweden

When it goes into operation in 2016, the MAX IV 3 GeV storage ring will be the first ultralow-emittance storage ring based on a multibend achromat lattice. These lattices make use of a large number of weak bending magnets which considerably reduces the amount of power radiated in the dipoles in comparison to power radiated from insertion devices. Therefore parameters such as emittance, energy spread, and radiated power are no longer constant during a typical user shift. Since the charge per bunch is usually high, intrabeam scattering (IBS) becomes very strong creating a dependence of emittance on stored current. Since the bunch length can vary as insertion device gaps change, the emittance blow-up from IBS is not constant either. Therefore, the emittance, bunch length, and hence the resulting Touschek lifetime have to be calculated in a self-consistent fashion taking into account the bare lattice, RF cavity settings, bunch charge, and gap settings. This paper demonstrates the intricate interplay between transverse emittance (insertion devices, emittance coupling), longitudinal emittance (tuning of main cavities as well as harmonic Landau cavities), and choice of stored current.

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TUPRI027

Detailed Magnetic Model Simulations of the H⁻ Injection Chicane Magnets for the CERN PS Booster Upgrade, including Eddy Currents, and Influence on Beam Dynamics

1618

E. Benedetto, B. Balhan, J. Borburgh, C. Carli, V. Forte, M. Martini
CERN, Geneva, Switzerland
V. Forte
Université Blaise Pascal, Clermont-Ferrand, France

The CERN PS Booster will be upgraded with an H⁻ injection system. The chicane magnets for the injection bump ramp-down in 5 ms and generate eddy currents in the inconel vacuum chamber which perturb the homogeneity of the magnetic field. The multipolar field components are extracted from 3D OPERA simulations and are included in the lattice model. The beta-beating correction is computed all along the ramp and complete tracking simulations including space-charge are performed to evaluate the impact of these perturbations and their correction.

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TUPRI029

The CERN PS Booster Space Charge Simulations with a Realistic Model for Alignment and Field Errors

1624

V. Forte, E. Benedetto, M. McAteer
CERN, Geneva, Switzerland

The CERN PS Booster is one of the machines of the LHC injector chain which will be upgraded within the LIU (LHC Injectors upgrade) project. The injection energy of the PSB will be increased to 160MeV in order to mitigate direct space charge effects, considered to be the main performance limitation, thus allowing to double the brightness for the LHC beams. In order to better predict the gain to be expected, space charge simulations are being carried out. Efforts to establish a realistic modeling of field and alignment errors aim at extending the basic model of the machine towards a more realistic one. Simulations of beam dynamics with strong direct space charge and realistic errors are presented and analysed in this paper.

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TUPRI030

Beam Coupling Impedance of the New Beam Screen of the LHC Injection Kicker Magnets

1627

H.A. Day, M.J. Barnes, F. Caspers, E. Métral, B. Salvant, J.A. Uythoven
CERN, Geneva, Switzerland

The LHC injection kicker magnets experienced significant beam induced heating of the ferrite yoke, with high intensity beam circulating for many hours, during operation of the LHC in 2011 and 2012. The causes of this beam coupling impedance were studied in depth and an improved beam screen implemented to reduce the impedance. Results of measurements and simulations of the new beam screen design are presented in this paper: these are used to predict power loss and temperature of the ferrite yoke for operation after long shutdown 1 and for proposed HL-LHC operational parameters.

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TUPRI031

A Precise Beam Dynamics Model of the PSI Injector 2 to Estimate the Intensity Limit

1630

SUSPSNE058

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A.M. Kolano, R.J. Barlow
University of Huddersfield, Huddersfield, United Kingdom
A. Adelmann, C. Baumgarten
PSI, Villigen PSI, Switzerland

We describe a precise beam dynamics model of the production set up of the Injector 2 Cyclotron at the Paul Scherrer Institut (PSI). Injector 2 is a 72 MeV separate-sector cyclotron producing a high intensity proton beam up to 2.7 mA CW, which is then injected into the 590 MeV Ring Cyclotron. The model includes space charge and is calculated for optimised matched initial conditions. It has been verified with measurements. Based on this model we estimate the limits to the intensity obtainable from Injector 2. The precise beam dynamics model is based on the OPAL (Object Oriented Parallel Accelerator Library) simulation code, a tool for charged-particle optics calculations in large accelerator structures and beam lines including 3D space charge.

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TUPRI034

Numerical Modeling for CesrTA Measurements of Electron Cloud Buildup in a Quadrupole Magnet

1632

J.A. Crittenden, M.G. Billing, W. Hartung, C. Shill, J.P. Sikora, K.G. Sonnad
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by the U.S. National Science Foundation contracts PHY-0734867, PHY-1002467, and the U.S. Department of Energy contract DE-FC02-08ER41538
We describe a numerical model for measurements of the formation of long-lived electron clouds in a quadrupole magnet in the CESR storage ring. The shielded stripline detector measures the electron flux incident on the vacuum chamber wall directly in front of one of the poles of the magnet. The model includes photo-electron production by synchrotron radiation, electrostatic forces from the bunched positron beam and the cloud, macroparticle tracking in the field of the quadrupole, secondary electron emission from the 9.5-cm-diameter cylindrical stainless steel beam-pipe and an analytic calculation of the transmission function of the holes in the vacuum chamber which allow cloud electrons to reach the stripline collector. These modeling studies provide a quantitative understanding of the trapping mechanism which results in cloud electrons surviving the 2.3-microsecond time interval prior to the return of a train of positron bunches. These studies have been performed in the context of the CESR Test Accelerator program, which aims to quantify and mitigate performance limitations on future low-emittance storage and damping rings.

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TUPRI035

Measurement of Beam Size in Intrabeam Scattering Dominated Beams at Various Energies at CesrTA

1635

M. P. Ehrlichman, K.J. Blaser, A. Chatterjee, W. Hartung, B.K. Heltsley, D.P. Peterson, D. L. Rubin, D. Sagan, J.P. Shanks, S. Wang
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: This research was supported by NSF and DOE contracts PHY-0734867, PHY-1002467, PHYS-1068662, DE-FC02-08ER41538, DE-SC0006505.
Recent reports from CesrTA have shown measurement and calculation of beam size versus current in CesrTA beams at 2.1 GeV. Here, the effect of changing the energy of IBS-dominated beams is reported. IBS growth rates have roughly a γ^-3 dependence. Measurements at 1.8, 2.1, 2.3, and 2.5 GeV are shown and compared with predictions from IBS theory.

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