HB2018 - List of Keywords (space-charge)

Paper	Title	Other Keywords	Page
MOA1PL01	Challenges in Understanding Space Charge Dynamics	resonance, simulation, emittance, synchrotron	1
	H. Bartosik CERN, Geneva, Switzerland
	Space charge effects in high intensity and high brightness synchrotrons can lead to undesired beam emittance growth, beam halo formation and particle loss. A series of dedicated machine experiments has been performed over the past decade in order to study these effects in the particular regime of long-term beam storage (10⁵-10⁶ turns) as required for certain applications. This paper gives an overview of the present understanding of the underlying beam dynamics mechanisms. In particular it focuses on the space charge induced periodic resonance crossing, which has been identified as the main mechanism causing beam degradation in this regime. The challenges in further progressing with the understanding, the modelling and the mitigation of these space charge effects and the resulting beam degradation are discussed. Furthermore, an outlook for possible future directions of studies is presented.
	Slides MOA1PL01 [22.877 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOA1PL01
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MOA1PL02	Beam Dynamics Challenges for the LHC and Injector Upgrades	emittance, injection, brightness, impedance	8
	G. Rumolo CERN, Geneva, Switzerland
	The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) will rely on significantly higher bunch current and brightness to meet the future yearly integrated luminosity target. The implications are twofold. On one side, all the accelerators of the LHC injection chain will have to be upgraded to produce the desired beam parameters. For this purpose, the LHC Injectors Upgrade (LIU) program has been established to implement all the needed modifications for meeting the required beam specifications. These upgrades will lead to the lifting of the main intensity and brightness limitations in the injectors, linked to beam instabilities driven by impedance or electron cloud (e-cloud), and space charge. On the other side, the LHC will have to be able to swallow the new beam parameters. This will mainly require control of impedance driven instabilities and beam-beam effects, and e-cloud mitigation. In this paper, we will focus on proton beams by describing the identified performance limitations of the LHC and its injectors, as well as the actions envisioned to overcome them.
	Slides MOA1PL02 [13.138 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOA1PL02
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MOP1WA01	J-PARC RCS: Effects of Emittance Exchange on Injection Painting	emittance, operation, injection, betatron	20
	H. Hotchi JAEA/J-PARC, Tokai-mura, Japan
	The J-PARC RCS is a high-power rapid cycling synchrotron aiming for a 1-MW output beam power. This talk reports the recent progress of the J-PARC RCS beam commissioning and operation especially focusing on our efforts for beam dynamics issues that we faced during the process of the beam power ramp-up.
	Slides MOP1WA01 [4.081 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOP1WA01
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TUP1WA02	Fixed Field Accelerators and Space Charge Modeling	focusing, resonance, acceleration, synchrotron	158
	A. Adelmann PSI, Villigen PSI, Switzerland C.T. Rogers STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom S.L. Sheehy STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom
	The efforts of the Fixed Field Accelerators FFA (formerly known as FFAG accelerators) community to address the high intensity challenge are reviewed. Starting from analytic estimates and linear models for space charge computation, the current possibilities of precise 3D models for start to end modeling are discussed.
	Slides TUP1WA02 [9.488 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP1WA02
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WEP1WB02	Beam Dynamics Simulation and Measurements for the IFMIF/EVEDA Project	rfq, simulation, emittance, proton	210
	M. Comunian, L. Antoniazzi, A. Baldo, C. Baltador, L. Bellan, D. Bortolato, M. Cavenago, E. Fagotti, M.G. Giacchini, F. Grespan, M. Montis, A. Palmieri, A. Pisent, F. Scantamburlo INFN/LNL, Legnaro (PD), Italy L. Bellan Univ. degli Studi di Padova, Padova, Italy N. Chauvin IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France H. Dzitko F4E, Germany
	In the framework of IFMIF/EVEDA project the source and RFQ are ready to be tested with beam. In this article the beam dynamics simulation and the measurement performed in preparation of the first beam injection are presented. The installed line is composed by the proton and deuteron Source with the LEBT composed of two solenoids that inject in the 10 meters long RFQ, the MEBT, diagnostic plate and the beam dump. The line is prepared to be tested with protons of 8 mA in pulsed mode (up to 0.1%).
	Slides WEP1WB02 [10.303 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP1WB02
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WEA1WA01	Sum Resonances with Space Charge	resonance, coherent-effects, experiment, simulation	226
	G. Franchetti GSI, Darmstadt, Germany
	This presentation will discuss the extension of the theory of the sum resonances with space charge.
	Slides WEA1WA01 [5.267 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEA1WA01
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEA2WA01	High Intensity Effects of Fixed Target Beams in the CERN Injector Complex	impedance, simulation, proton, emittance	237
	E. Koukovini-Platia, H. Bartosik, M. Migliorati, G. Rumolo CERN, Geneva, Switzerland M. Migliorati INFN-Roma1, Rome, Italy M. Migliorati Sapienza University of Rome, Rome, Italy
	The current fixed target (FT) experiments at CERN are a complementary approach to the Large Hadron Collider (LHC) and play a crucial role in the investigation of fundamental questions in particle physics. Within the scope of the LHC Injectors Upgrade (LIU), aiming to improve the LHC beam production, the injector complex will be significantly upgraded during the second Long Shutdown (LS2). All non-LHC beams are expected to benefit from these upgrades. In this paper, we focus on the studies of the transverse instability in the Proton Synchrotron (PS), currently limiting the intensity of Time-Of-Flight (ToF) type beams, as well as the prediction of the impact of envisaged hardware modifications. A first discussion on the effect of space charge on the observed instability is also being presented.
	Slides WEA2WA01 [2.483 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEA2WA01
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WEA2WA04	Space-Charge Compensation Using Electron Columns at IOTA	electron, proton, simulation, plasma	247
	B.T. Freemire Northern Illinois University, DeKalb, Illinois, USA S. Chattopadhyay Northern Illinois Univerity, DeKalb, Illinois, USA M. Chung UNIST, Ulsan, Republic of Korea C.S. Park, V.D. Shiltsev, G. Stancari Fermilab, Batavia, Illinois, USA G. Penn LBNL, Berkeley, California, USA
	Funding: US Department of Energy contracts DE-AC02-07CH11359 and DE-AC02-05CH1123 and the GARD Program. Beam loss due to space charge is a major problem at current and future high intensity particle accelerators. The space charge force can be compensated for proton or ion beams by creating a column of electrons with a charge distribution matched to that of the beam, maintaining electron-proton stability. The column is created by the beam ionizing short sections of high pressure gas. The ionization electrons are then shaped appropriately using electric and magnetic fields. The Integrable Optics Test Accelerator (IOTA) at Fermilab is a test bed for beam loss and instability mitigation techniques. Simulations using the particle-in-cell code, Warp, have been made to track the evolution of both the electron column and the beam over multiple passes. A 2.5 MeV proton beamline is under construction at IOTA, to be used to study the effect of the electron column on a space charge dominated beam.
	Slides WEA2WA04 [8.501 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEA2WA04
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WEP2PO030	A 4D Emittance Measurement Device for the 870 keV HIPA Injection Line	cyclotron, simulation, proton, operation	329
	R. Dölling, M. Rohrer PSI, Villigen PSI, Switzerland
	A 4D emittance measurement device has recently been installed in PSI's high intensity proton accelerator (HIPA) after the acceleration tube of the Cockcroft-Walton pre-accelerator. A pinhole collimator is moved 2D transversally and at each collimator position, the resulting beamlet is downstream scanned 2D by vertically moving over it a horizontal linear array of small electrodes. The properties of this setup and the intended use are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO030
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THP2WB01	Revisiting the Longitudinal 90 Degree Limit for Superconducting Linear Accelerators	lattice, emittance, resonance, focusing	369
	I. Hofmann GSI, Darmstadt, Germany I. Hofmann TEMF, TU Darmstadt, Darmstadt, Germany
	In the design of high-intensity linear accelerators one of the generally adopted criteria is not to exceed a zero-current phase advance per focusing period of 90 degrees in order to avoid the space charge driven envelope instability, or a coinciding fourth order space charge resonance. Recently it was claimed that in certain structures, predominantly applicable to super-conducting linac lattices - such a constraint is not always necessary in the longitudinal plane (I. Hofmann and O. Boine-Frankenheim, Phys. Rev. Lett. 118, 2017). This applies primarily to such focusing structures, where the transverse focusing period only induces a weak space charge dependent modulation in the longitudinal plane, and a different periodicity is applicable to the longitudinal plane. Hence the longitudinal 90 degree stopband is practically absent, and phase advances significantly above 90 degrees should be possible in such structures, with a corresponding additional design freedom. As a consequence, we suggest that the 90 degree rule should no longer be taken as standard criterion in the longitudinal plane of linac design.
	Slides THP2WB01 [5.179 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THP2WB01
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THP2WB02	High-Intensity Beam Dynamics Simulation of the IFMIF-like Accelerators	simulation, emittance, beam-transport, rfq	373
	S.H. Moon, M. Chung UNIST, Ulsan, Republic of Korea
	Funding: This research was supported by the National Research Foundation of Korea (Grant No. NRF-2017M1A7A1A02016413). The IFMIF (International Fusion Material Irradiation Facility) project is being considered to build fusion material test facility. The IFMIF will use two accelerators to generate high energy neutrons. However, the IFMIF accelerators have been designed to have much higher beam power and beam current than the existing accelerators, so space charge effect is very strong. This raises big concerns about beam loss and beam transport stability, thus detailed high-intensity beam dynamics study of the IFMIF-like accelerators is indispensable. This research aims to perform source to target simulation of the IFMIF-like accelerator. The simulation has been carried out by two different kinds of simulation codes because the IFMIF accelerator has distinctive features. One is TRACEWIN simulation code which was used in IFMIF initial design. The other is WARP 3D PIC code which can precisely calculate space charge effects. This presentation will focus on beam simulations for LEBT, RFQ, and MEBT of the IFMIF accelerator
	Slides THP2WB02 [10.583 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THP2WB02
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THP2WB05	Halo Formation of the High Intensity Beams in a Periodic Solenoidal Fields	resonance, focusing, solenoid, lattice	387
	Y.L. Cheon, M. Chung UNIST, Ulsan, Republic of Korea
	Funding: This research was supported by the National Research Foundation of Korea (Grant No. NRF-2017M1A7A1A02016413). Transport of intense beams over long distances can be restricted by space-charge fields which force the trajectories of charged particles to deviate from the stable regions of propagation. The space-charge fields can be calculated from the density distribution of the beam particles, and Poisson's equation. As the space-charge term is put in the equations of motion, it affects the envelope equations and betatron wave number of a charged particle in the beam. Also, with different initial conditions of the beam particles, there can be perturbations on the matched beam envelopes which can generate a resonant interaction between the beam core and test particles. Unlike for the K-V beam, for nonuniform density beams such as Gaussian beams in the periodic quadrupole or solenoidal focusing fields, there exists higher order terms and non-periodic solutions of beam particle oscillations, which can generate halo regions and chaotic motions during the beam propagation. In this study, we have investigated the higher order resonances and non-periodic solutions of the Gaussian beam in the solenoidal focusing fields to understand halo formation mechanisms of the intense beams.
	Slides THP2WB05 [2.295 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THP2WB05
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THA1WE02	Requirements and Results for Quadrupole Mode Measurements	emittance, synchrotron, quadrupole, pick-up	393
	A. Oeftiger CERN, Geneva, Switzerland
	Funding: Research supported by the HL-LHC project. Direct space charge may be quantified, and hence the beam brightness observed, by measuring the quadrupolar beam modes in the CERN Proton Synchrotron (PS). The spectrum of the transverse beam size oscillations (i.e. the quadrupolar beam moment) contains valuable information: the betatron envelope modes and the coherent dispersive mode indicate optics mismatch, while their frequency shifts due to space charge allow a direct measurement thereof. To measure the quadrupolar beam moment we use the Base-Band Q-meter system of the PS which is based on a four electrode stripline pick-up. Past experiments with quadrupolar pick-ups often investigated coasting beams, where the coherent betatron and dispersion modes correspond to single peaks in the tune spectrum. In contrast, long bunched beams feature bands of betatron modes: the mode frequencies shift depending on the transverse space charge strength which varies with the local line charge density. By using the new transverse feedback in the PS as a quadrupolar RF exciter, we measured the quadrupolar beam transfer function. The beam response reveals the distinct band structure of the envelope modes as well as the coherent dispersive mode.
	Slides THA1WE02 [7.315 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THA1WE02
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THA2WE02	Application of Machine Learning for the IPM-Based Profile Reconstruction	electron, network, detector, simulation	410
	M. Sapinski, R. Singh, D.M. Vilsmeier GSI, Darmstadt, Germany J.W. Storey CERN, Geneva, Switzerland
	One of the most reliable devices to measure the transverse beam profile in hadron machines is Ionization Profile Monitor (IPM). This type of monitor can work in two modes: collecting electrons or ions. Typically, for lower intensity beams, the ions produced by ionization of the rest gas are extracted towards a position-sensitive detector. Ion trajectories follow the external electric field lines, however the field of the beam itself also affects their movement leading to a deformation of the observed beam profile. Correction methods for this case are known. For high brightness beams, IPM configuration in which electrons are measured, is typically used. In such mode, an external magnetic field is often applied in order to confine the transverse movement of electrons. However, for extreme beams, the distortion of the measured beam profile can still be present. The dynamics of electron movement is more complex than in case of ions, therefore the correction of the profile distortion is more difficult. Investigation of this problem using a dedicated simulation tool and machine learning algorithms lead to a beam profile correction methods for electron-collecting IPMs.
	Slides THA2WE02 [7.357 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THA2WE02
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Paper

Title

Other Keywords

Page

MOA1PL01

Challenges in Understanding Space Charge Dynamics

resonance, simulation, emittance, synchrotron

1

H. Bartosik
CERN, Geneva, Switzerland

Space charge effects in high intensity and high brightness synchrotrons can lead to undesired beam emittance growth, beam halo formation and particle loss. A series of dedicated machine experiments has been performed over the past decade in order to study these effects in the particular regime of long-term beam storage (10⁵-10⁶ turns) as required for certain applications. This paper gives an overview of the present understanding of the underlying beam dynamics mechanisms. In particular it focuses on the space charge induced periodic resonance crossing, which has been identified as the main mechanism causing beam degradation in this regime. The challenges in further progressing with the understanding, the modelling and the mitigation of these space charge effects and the resulting beam degradation are discussed. Furthermore, an outlook for possible future directions of studies is presented.

Slides MOA1PL01 [22.877 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOA1PL01

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MOA1PL02

Beam Dynamics Challenges for the LHC and Injector Upgrades

emittance, injection, brightness, impedance

8

G. Rumolo
CERN, Geneva, Switzerland

The High Luminosity upgrade of the Large Hadron Collider (HL-LHC) will rely on significantly higher bunch current and brightness to meet the future yearly integrated luminosity target. The implications are twofold. On one side, all the accelerators of the LHC injection chain will have to be upgraded to produce the desired beam parameters. For this purpose, the LHC Injectors Upgrade (LIU) program has been established to implement all the needed modifications for meeting the required beam specifications. These upgrades will lead to the lifting of the main intensity and brightness limitations in the injectors, linked to beam instabilities driven by impedance or electron cloud (e-cloud), and space charge. On the other side, the LHC will have to be able to swallow the new beam parameters. This will mainly require control of impedance driven instabilities and beam-beam effects, and e-cloud mitigation. In this paper, we will focus on proton beams by describing the identified performance limitations of the LHC and its injectors, as well as the actions envisioned to overcome them.

Slides MOA1PL02 [13.138 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOA1PL02

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MOP1WA01

J-PARC RCS: Effects of Emittance Exchange on Injection Painting

emittance, operation, injection, betatron

20

H. Hotchi
JAEA/J-PARC, Tokai-mura, Japan

The J-PARC RCS is a high-power rapid cycling synchrotron aiming for a 1-MW output beam power. This talk reports the recent progress of the J-PARC RCS beam commissioning and operation especially focusing on our efforts for beam dynamics issues that we faced during the process of the beam power ramp-up.

Slides MOP1WA01 [4.081 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-MOP1WA01

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TUP1WA02

Fixed Field Accelerators and Space Charge Modeling

focusing, resonance, acceleration, synchrotron

158

A. Adelmann
PSI, Villigen PSI, Switzerland
C.T. Rogers
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
S.L. Sheehy
STFC/RAL/ASTeC, Chilton, Didcot, Oxon, United Kingdom

The efforts of the Fixed Field Accelerators FFA (formerly known as FFAG accelerators) community to address the high intensity challenge are reviewed. Starting from analytic estimates and linear models for space charge computation, the current possibilities of precise 3D models for start to end modeling are discussed.

Slides TUP1WA02 [9.488 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-TUP1WA02

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WEP1WB02

Beam Dynamics Simulation and Measurements for the IFMIF/EVEDA Project

rfq, simulation, emittance, proton

210

M. Comunian, L. Antoniazzi, A. Baldo, C. Baltador, L. Bellan, D. Bortolato, M. Cavenago, E. Fagotti, M.G. Giacchini, F. Grespan, M. Montis, A. Palmieri, A. Pisent, F. Scantamburlo
INFN/LNL, Legnaro (PD), Italy
L. Bellan
Univ. degli Studi di Padova, Padova, Italy
N. Chauvin
IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France
H. Dzitko
F4E, Germany

In the framework of IFMIF/EVEDA project the source and RFQ are ready to be tested with beam. In this article the beam dynamics simulation and the measurement performed in preparation of the first beam injection are presented. The installed line is composed by the proton and deuteron Source with the LEBT composed of two solenoids that inject in the 10 meters long RFQ, the MEBT, diagnostic plate and the beam dump. The line is prepared to be tested with protons of 8 mA in pulsed mode (up to 0.1%).

Slides WEP1WB02 [10.303 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP1WB02

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WEA1WA01

Sum Resonances with Space Charge

resonance, coherent-effects, experiment, simulation

226

G. Franchetti
GSI, Darmstadt, Germany

This presentation will discuss the extension of the theory of the sum resonances with space charge.

Slides WEA1WA01 [5.267 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEA1WA01

Export •

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

WEA2WA01

High Intensity Effects of Fixed Target Beams in the CERN Injector Complex

impedance, simulation, proton, emittance

237

E. Koukovini-Platia, H. Bartosik, M. Migliorati, G. Rumolo
CERN, Geneva, Switzerland
M. Migliorati
INFN-Roma1, Rome, Italy
M. Migliorati
Sapienza University of Rome, Rome, Italy

The current fixed target (FT) experiments at CERN are a complementary approach to the Large Hadron Collider (LHC) and play a crucial role in the investigation of fundamental questions in particle physics. Within the scope of the LHC Injectors Upgrade (LIU), aiming to improve the LHC beam production, the injector complex will be significantly upgraded during the second Long Shutdown (LS2). All non-LHC beams are expected to benefit from these upgrades. In this paper, we focus on the studies of the transverse instability in the Proton Synchrotron (PS), currently limiting the intensity of Time-Of-Flight (ToF) type beams, as well as the prediction of the impact of envisaged hardware modifications. A first discussion on the effect of space charge on the observed instability is also being presented.

Slides WEA2WA01 [2.483 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEA2WA01

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WEA2WA04

Space-Charge Compensation Using Electron Columns at IOTA

electron, proton, simulation, plasma

247

B.T. Freemire
Northern Illinois University, DeKalb, Illinois, USA
S. Chattopadhyay
Northern Illinois Univerity, DeKalb, Illinois, USA
M. Chung
UNIST, Ulsan, Republic of Korea
C.S. Park, V.D. Shiltsev, G. Stancari
Fermilab, Batavia, Illinois, USA
G. Penn
LBNL, Berkeley, California, USA

Funding: US Department of Energy contracts DE-AC02-07CH11359 and DE-AC02-05CH1123 and the GARD Program.
Beam loss due to space charge is a major problem at current and future high intensity particle accelerators. The space charge force can be compensated for proton or ion beams by creating a column of electrons with a charge distribution matched to that of the beam, maintaining electron-proton stability. The column is created by the beam ionizing short sections of high pressure gas. The ionization electrons are then shaped appropriately using electric and magnetic fields. The Integrable Optics Test Accelerator (IOTA) at Fermilab is a test bed for beam loss and instability mitigation techniques. Simulations using the particle-in-cell code, Warp, have been made to track the evolution of both the electron column and the beam over multiple passes. A 2.5 MeV proton beamline is under construction at IOTA, to be used to study the effect of the electron column on a space charge dominated beam.

Slides WEA2WA04 [8.501 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEA2WA04

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WEP2PO030

A 4D Emittance Measurement Device for the 870 keV HIPA Injection Line

cyclotron, simulation, proton, operation

329

R. Dölling, M. Rohrer
PSI, Villigen PSI, Switzerland

A 4D emittance measurement device has recently been installed in PSI's high intensity proton accelerator (HIPA) after the acceleration tube of the Cockcroft-Walton pre-accelerator. A pinhole collimator is moved 2D transversally and at each collimator position, the resulting beamlet is downstream scanned 2D by vertically moving over it a horizontal linear array of small electrodes. The properties of this setup and the intended use are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-WEP2PO030

Export •

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

THP2WB01

Revisiting the Longitudinal 90 Degree Limit for Superconducting Linear Accelerators

lattice, emittance, resonance, focusing

369

I. Hofmann
GSI, Darmstadt, Germany
I. Hofmann
TEMF, TU Darmstadt, Darmstadt, Germany

In the design of high-intensity linear accelerators one of the generally adopted criteria is not to exceed a zero-current phase advance per focusing period of 90 degrees in order to avoid the space charge driven envelope instability, or a coinciding fourth order space charge resonance. Recently it was claimed that in certain structures, predominantly applicable to super-conducting linac lattices - such a constraint is not always necessary in the longitudinal plane (I. Hofmann and O. Boine-Frankenheim, Phys. Rev. Lett. 118, 2017). This applies primarily to such focusing structures, where the transverse focusing period only induces a weak space charge dependent modulation in the longitudinal plane, and a different periodicity is applicable to the longitudinal plane. Hence the longitudinal 90 degree stopband is practically absent, and phase advances significantly above 90 degrees should be possible in such structures, with a corresponding additional design freedom. As a consequence, we suggest that the 90 degree rule should no longer be taken as standard criterion in the longitudinal plane of linac design.

Slides THP2WB01 [5.179 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THP2WB01

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THP2WB02

High-Intensity Beam Dynamics Simulation of the IFMIF-like Accelerators

simulation, emittance, beam-transport, rfq

373

S.H. Moon, M. Chung
UNIST, Ulsan, Republic of Korea

Funding: This research was supported by the National Research Foundation of Korea (Grant No. NRF-2017M1A7A1A02016413).
The IFMIF (International Fusion Material Irradiation Facility) project is being considered to build fusion material test facility. The IFMIF will use two accelerators to generate high energy neutrons. However, the IFMIF accelerators have been designed to have much higher beam power and beam current than the existing accelerators, so space charge effect is very strong. This raises big concerns about beam loss and beam transport stability, thus detailed high-intensity beam dynamics study of the IFMIF-like accelerators is indispensable. This research aims to perform source to target simulation of the IFMIF-like accelerator. The simulation has been carried out by two different kinds of simulation codes because the IFMIF accelerator has distinctive features. One is TRACEWIN simulation code which was used in IFMIF initial design. The other is WARP 3D PIC code which can precisely calculate space charge effects. This presentation will focus on beam simulations for LEBT, RFQ, and MEBT of the IFMIF accelerator

Slides THP2WB02 [10.583 MB]

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THP2WB05

Halo Formation of the High Intensity Beams in a Periodic Solenoidal Fields

resonance, focusing, solenoid, lattice

387

Y.L. Cheon, M. Chung
UNIST, Ulsan, Republic of Korea

Funding: This research was supported by the National Research Foundation of Korea (Grant No. NRF-2017M1A7A1A02016413).
Transport of intense beams over long distances can be restricted by space-charge fields which force the trajectories of charged particles to deviate from the stable regions of propagation. The space-charge fields can be calculated from the density distribution of the beam particles, and Poisson's equation. As the space-charge term is put in the equations of motion, it affects the envelope equations and betatron wave number of a charged particle in the beam. Also, with different initial conditions of the beam particles, there can be perturbations on the matched beam envelopes which can generate a resonant interaction between the beam core and test particles. Unlike for the K-V beam, for nonuniform density beams such as Gaussian beams in the periodic quadrupole or solenoidal focusing fields, there exists higher order terms and non-periodic solutions of beam particle oscillations, which can generate halo regions and chaotic motions during the beam propagation. In this study, we have investigated the higher order resonances and non-periodic solutions of the Gaussian beam in the solenoidal focusing fields to understand halo formation mechanisms of the intense beams.

Slides THP2WB05 [2.295 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THP2WB05

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THA1WE02

Requirements and Results for Quadrupole Mode Measurements

emittance, synchrotron, quadrupole, pick-up

393

A. Oeftiger
CERN, Geneva, Switzerland

Funding: Research supported by the HL-LHC project.
Direct space charge may be quantified, and hence the beam brightness observed, by measuring the quadrupolar beam modes in the CERN Proton Synchrotron (PS). The spectrum of the transverse beam size oscillations (i.e. the quadrupolar beam moment) contains valuable information: the betatron envelope modes and the coherent dispersive mode indicate optics mismatch, while their frequency shifts due to space charge allow a direct measurement thereof. To measure the quadrupolar beam moment we use the Base-Band Q-meter system of the PS which is based on a four electrode stripline pick-up. Past experiments with quadrupolar pick-ups often investigated coasting beams, where the coherent betatron and dispersion modes correspond to single peaks in the tune spectrum. In contrast, long bunched beams feature bands of betatron modes: the mode frequencies shift depending on the transverse space charge strength which varies with the local line charge density. By using the new transverse feedback in the PS as a quadrupolar RF exciter, we measured the quadrupolar beam transfer function. The beam response reveals the distinct band structure of the envelope modes as well as the coherent dispersive mode.

Slides THA1WE02 [7.315 MB]

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THA2WE02

Application of Machine Learning for the IPM-Based Profile Reconstruction

electron, network, detector, simulation

410

M. Sapinski, R. Singh, D.M. Vilsmeier
GSI, Darmstadt, Germany
J.W. Storey
CERN, Geneva, Switzerland

One of the most reliable devices to measure the transverse beam profile in hadron machines is Ionization Profile Monitor (IPM). This type of monitor can work in two modes: collecting electrons or ions. Typically, for lower intensity beams, the ions produced by ionization of the rest gas are extracted towards a position-sensitive detector. Ion trajectories follow the external electric field lines, however the field of the beam itself also affects their movement leading to a deformation of the observed beam profile. Correction methods for this case are known. For high brightness beams, IPM configuration in which electrons are measured, is typically used. In such mode, an external magnetic field is often applied in order to confine the transverse movement of electrons. However, for extreme beams, the distortion of the measured beam profile can still be present. The dynamics of electron movement is more complex than in case of ions, therefore the correction of the profile distortion is more difficult. Investigation of this problem using a dedicated simulation tool and machine learning algorithms lead to a beam profile correction methods for electron-collecting IPMs.

Slides THA2WE02 [7.357 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-HB2018-THA2WE02

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