HB2018 - Classification: Beam Dynamics in Linacs

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MOP1WB01

500 MeV@ CW 5 mA Beam Dynamics for CIADS and Beam Commissioning of 25 MeV CW Proton Superconducting Linac

Y. He
IMP/CAS, Lanzhou, People's Republic of China

This talk is about 500 MeV@ CW 5 mA beam dynamics for CIADS and beam commissioning of 25 MeV CW proton superconducting linac.

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MOP1WB02

Understanding the Source and Impact of Errant Beam Loss in the Spallation Neutron Source (SNS) Super Conducting Linac (SCL)

48

C.C. Peters, D. Curry, G.D. Johns, T.B. Southern
ORNL RAD, Oak Ridge, Tennessee, USA
A.V. Aleksandrov, W. Blokland, B. Han, T.A. Justice, S.-H. Kim, M.A. Plum, A.P. Shishlo, M.P. Stockli, J.Y. Tang, R.F. Welton
ORNL, Oak Ridge, Tennessee, USA

Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05- 00OR22725 for the U.S. Department of Energy.
The Spallation Neutron Source (SNS) Linear Accelerator (Linac) delivers a high power proton beam (>1 MW) for neutron production with high neutron availability (>90%). For beam acceleration, the Linac has both normal and super conducting RF sections, with the Super Conducting Linac (SCL) portion providing the majority of beam acceleration (81 of 96 RF cavities are super conducting). Operationally, the goal is to achieve the highest possible beam energy by maximizing SCL cavity RF gradients, but not at the expense of cavity reliability. One mechanism that has negatively impacted both SCL cavity RF gradients and reliability is beam lost into the SCL due to malfunctions of upstream components. Understanding the sources and impacts of errant beam on SCL cavity performance will be discussed.

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MOP1WB03

Experimental Study of Beam Dynamics in the PIP-II MEBT Prototype

54

A.V. Shemyakin, J.-P. Carneiro, B.M. Hanna, V.A. Lebedev, L.R. Prost, A. Saini, V.E. Scarpine
Fermilab, Batavia, Illinois, USA
C.J. Richard
NSCL, East Lansing, Michigan, USA
V.L. Sista
BARC, Mumbai, India

Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics
The Proton Improvement Plan, Stage Two (PIP-II) is a program of upgrades proposed for the Fermilab injection complex, which central part is an 800-MeV, 2-mA CW SRF linac. A prototype of the PIP-II linac front end called PIP-II Injector Test (PIP2IT) is being built at Fermilab. As of now, a 15-mA DC, 30-keV H⁻ ion source, a 2 m-long Low Energy Beam Transport (LEBT), a 2.1-MeV CW RFQ, followed by a 10-m Medium Energy Beam Transport (MEBT) have been assembled and commissioned. The MEBT bunch-by-bunch chopping system and the requirement of a low uncontrolled beam loss put stringent limitations on the beam envelope and its variation. Measurements of transverse and longitudinal beam dynamics in the MEBT were performed in the range of 1-10 mA of the RFQ beam current. Almost all measurements are made with 10 μs beam pulses in order to avoid damage to the beam line. This report presents measurements of the transverse optics with differential trajectories, reconstruction of the beam envelope with scrapers and an Allison emittance scanner, as well as bunch length measurements with a Fast Faraday Cup.

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MOP2WB01

60 mA Beam Study in J-PARC Linac

60

Y. Liu
KEK/JAEA, Ibaraki-Ken, Japan
A. Miura
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
T. Miyao
KEK, Ibaraki, Japan
M. Otani, T. Shibata
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

Upgrade of Linac peak current from 50 mA to 60 mA is one of the keys to the next power upgrade in J-PARC. Beam studies with 60 mA were carried out in July and December, 2017, for the challenging issues such as investigation of beam property from the ion source, halo behavior throughout the LEBT, RFQ and MEBT1, emittance/Twiss measurement at MEBT1, beam emittance control, etc. Expected/unexpected problems, intermediate results and preparation for the next trials were introduced in this paper.

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MOP2WB02

Simulation and Measurement Campaigns for Characterization and Performance Improvement of the CERN Heavy Ion Linac3

64

G. Bellodi, S. Benedetti, D. Küchler, F.J.C. Wenander
CERN, Geneva, Switzerland
V. Toivanen
GANIL, Caen, France

In the framework of the LHC Injector Upgrade programme (LIU), several activities have been carried out to improve the GTS-LHC ion source and Linac3 performance (Linac3 providing the charged heavy ion beams for CERN exper-iments). A restudy of the beam dynamics and transport through the linac was initiated, through a campaign of systematic machine measurements and parallel beam simulations, generalising techniques developed for beam characterization during Linac4 commissioning. The work here presented will review the most relevant findings and lessons learnt in the process.

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MOP2WB03

Emittance Growth and Beam Losses in LANSCE Linear Accelerator

70

Y.K. Batygin, R.W. Garnett, L. Rybarcyk
LANL, Los Alamos, New Mexico, USA

Funding: Work supported by the United States Department of Energy, National Nuclear Security Agency, under contract DE-AC52-06NA25396.
The LANSCE Accelerator facility currently utilizes four 800 MeV H⁻ beams and one 100 MeV proton beam. Multi-beam operation requires careful control of accelerator tune to minimize beam losses. The most powerful 80 kW H⁻ beam is accumulated in the Proton Storage Ring and is extracted to the Lujan Neutron Scattering Center facility for production of moderated neutrons with meV-keV energy. Another H⁻ beam is delivered to the Weapon Neutron Research facility to create un-moderated neutrons in the keV - MeV energy range. The third H⁻ beam is shared between the Proton Radiography Facility and the Ultra-Cold Neutron facility. The 23 kW proton beam is used for isotope production in the fields of medicine, nuclear physics, national security, environmental science and industry. Minimization of beam losses in the linac is achieved due to careful tuning of the beam in each section of the accelerator facility, imposing restrictions on amplitudes and phases of RF sections, control of H⁻ beam stripping, and optimization of ion sources operation. This paper summarizes experimental results in accelerator operations and categorizes various sources of emittance growth and beam losses.

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MOP2WB04

The Beam Dynamics Design of CW RFQ for Chinese ADS

W.P. Dou, Y. He, H. Jia, S.H. Liu, C. Wang, Z.J. Wang
IMP/CAS, Lanzhou, People's Republic of China

A superconducting proton linear accelerator for Chinese ADS have been proposed by IMP CAS. The preliminary beam dynamics design is finished. The RFQ is designed to be operated at CW mode will accelerate 10 mA proton from 35 keV to 2.1 MeV. The acceleration rate of RFQ is 95.2% with the length of 4.5 meters. The 99.9 % longitudinal emittance at the RFQ exit is optimized to 4.98 pi.mm.mrad and 0.18 times of the longitudinal acceptance of downstream superconducting accelerator. These goals of RFQ beam dynamic studies usually are minimize the vane length, beam loss and emittance growth. But the 99.9 % longitudinal emittance of RFQ is proposed as the new and key optimization goal to reduce the possibility of downstream beam loss for the RFQ which is in the front of superconducting linear accelerator. The 99.9 % longitudinal emittance is optimised at the cost of RFQ transmission rate though three steps. First, the optimised longitudinal phase space is got by the long and stable shaper section. Second, Smaller longitudinal acceptance is adopted to make particle loss in low energy section. third, the shrink of longitudinal acceptance is optimised to get lower 99.9% longitudinal emittance.

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MOP2WB05

Analysis of Envelope Perturbations in High-Intensity Beams Using Generalized Courant-Snyder Formulation

M. Chung
UNIST, Ulsan, Republic of Korea
H. Qin
PPPL, Princeton, New Jersey, USA

Funding: This research was supported by the National Research Foundation of Korea (Grant No. NRF-2017M1A7A1A02016413).
Analysis of the small-amplitude perturbations around the matched beam envelope has been used as a basic theoretical framework to characterize the high-intensity beam transport. The beam stability properties in periodic quadrupole and solenoid channels have been analyzed by many authors in terms of that framework. In general, the linearized perturbed envelope equations are coupled. Therefore, application of the conventional Courant-Snyder theory to this problem has not been straightforward. In this work, we adopt the recently developed generalized Courant-Snyder formulation, and revisit the spectral and structural stability properties of the envelope perturbations. The generalized Courant-Snyder invariant of the envelope perturbations is identified, and its physical interpretation will be given. Since the generalized Courant-Snyder formulation can be easily extended to three-dimensional cases, we also investigate the three-dimensional envelope instability by means of the generalized Courant-Snyder formulation.
mchung@unist.ac.kr

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WEA1WB01

Beam Dynamics and Beam Commissioning of 10 MeV CW Proton Superconducting Linac Based on Spoke Cavities

F. Yan, D.J. Gong, W. Yao
IHEP, Beijing, People's Republic of China

For high intensity CW beam, beam loading effect is a major issue for the stability operation of the linac. The steady state and transient perturbations of the accelerating voltage by the beam current causes significant differences between the design lattice to the actual operated parameters for the SC cavities. The errors accumulated along the linac, lead to undesirable beam behaviour, and cause beam losses finally. In this paper the beam loading effects of the SC cavities for Injector-I have been analyzed for 10 mA proton beam and presented.

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WEA1WB02

Characterization of High Intensity Beams in Linacs

P.A.P. Nghiem, N. Chauvin
CEA/IRFU, Gif-sur-Yvette, France
L. Ducrot
CEA/DSM/IRFU, France
W. Simeoni
IF-UFRGS, Porto Alegre, Brazil
D. Uriot
IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France
M. Valette
CERN, Geneva, Switzerland

For high intensity linacs, beam particle distributions are in most cases far from Gaussian ones. Furthermore, the distribution shapes drastically differ from a linac to another and significantly change along a given linac. For those reasons, classical RMS parameters like beam envelope or emittance are no longer enough for characterizing the beam as soon as comparison or evolution of beam quality is in view. This paper presents three alternative ways to characterize more suitably a high intensity beam: 6D coordinates of the actual number of particles, projections of the distribution onto a few axes, RMS parameters of the core and of the halo separately. The advantages and drawbacks of each method are then discussed in terms of beam representativeness, data weight and physics insight.

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WEA2WB01

Beam Loss Mechanisms in Ion Linacs and Development of Beam Collimation System

T. Maruta, Z.Q. He, M. Ikegami, F. Marti, P.N. Ostroumov, J. Wei, Y. Yamazaki, Q. Zhao
FRIB, East Lansing, USA

Funding: Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
Machine errors and interaction of ion beam with the stripper are known sources of possible beam losses in ion linacs. Our studies show that contaminant ion beams extracted from Electron Cyclotron Resonance ion source and accelerated together with main beam thanks to similar charge-to-mass ratio can produce substantial losses after the stripping due to modified charge-to-mass ratio. The contaminant beams must be well separated and collimated at low energies to avoid losses in the high energy section of the linac. An additional mechanism for beam losses is charge-exchange reactions in the residual gas near the charge selection slits. A set of collimators have been developed to intercept both contaminant ions and main beam halo in the example of Facility for Rare Isotope Beams (FRIB).

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WEA2WB02

Recent Studies of Beam Physics for Ion Linacs

200

L. Groening, S. Appel, X. Du, P. Gerhard, M.T. Maier, A. Rubin, P. Scharrer, H. Vormann, C. Xiao
GSI, Darmstadt, Germany
M. Chung
UNIST, Ulsan, Republic of Korea
P. Scharrer
HIM, Mainz, Germany
P. Scharrer
Mainz University, Mainz, Germany

The UNIversal Linear ACcelerator (UNILAC) at GSI aims at provision of high brilliant ion beams, as it main purpose will be to serve as injector for the upcoming FAIR accelerator complex. The UNILAC injects into the subsequent synchrotron SIS18 applying horizontal multi-turn injection (MTI). Optimization of this process triggered intense theoretical and experimental studies of dynamics of transversely coupled beams. These activities comprise round-to-flat beam transformation, full 4d transverse beam diagnostics, optimization of the MTI parameters through generic algorithms, and extension of Busch's theorem to accelerated particle beams. Finally, recent advance in modeling time-transition-factors and its impact on improved linac performance will be presented as well as progress in the optimization of ion charge state stripping.

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WEA2WB03

HIAF Front End for Transmission and Acceleration of 30 pμA ²³⁸U³⁵⁺

Y. Yang
IMP/CAS, Lanzhou, People's Republic of China

High Intensity heavy ion Accelerator Facility (HIAF) in China is currently in the state of physics design. The HIAF front end will provide beams of ions with a mass up to uranium at a beam energy of 0.5 MeV/u. The required intensity of uranium beam is of 30 pμA and the charge state is 35+. This paper presents a design of HIAF front end, which includes three ECR ion sources, LEBT, RFQ and MEBT. Beam transmission and dynamics studies have been performed and will be described. These studies include beam extraction simulation from ECR ion source, space charge compensation in LEBT, LEBT beam dynamics with a achromatic system, beam collimation in LEBT, RFQ beam dynamics with pre-bencher. In addition, end-to-end beam simulations have also been carried out to evaluate the front end performance.

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WEP1WB01

Beam Dynamics of the ESS Linac

206

Y. Levinsen, R. De Prisco, M. Eshraqi, N. Milas, R. Miyamoto, D.C. Plostinar, A. Ponton
ESS, Lund, Sweden

The ESS linac will deliver an unprecedented 5 MW of average beam power when completed. Beyond the 90 MeV normal conducting front-end, the acceleration is performed using SC structures up to the design energy of 2 GeV. As the ESS will send the beam to a fixed tungsten target, the emittance is not as important a factor as in injectors. However, the losses have to be studied in detail, including not only the average operational loss required to be of less than 1 W/m, but also the accidental losses, losses due to failure and other potentially damaging losses. The commissioning of the ion source and LEBT starts this year and will continue with the RFQ next year. In this contribution we will discuss the beam dynamics aspects and challenges of the ESS linac.

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WEP1WB02

Beam Dynamics Simulation and Measurements for the IFMIF/EVEDA Project

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%).

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WEP1WB03

First Heavy Ion Beam Acceleration with a Superconducting Multi Gap CH-cavity

215

W.A. Barth, M. Heilmann, A. Rubin, A. Schnase, S. Yaramyshev
GSI, Darmstadt, Germany
K. Aulenbacher, W.A. Barth, F.D. Dziuba, V. Gettmann, T. Kürzeder, M. Miski-Oglu
HIM, Mainz, Germany
K. Aulenbacher
IKP, Mainz, Germany
M. Basten, M. Busch, H. Podlech, M. Schwarz
IAP, Frankfurt am Main, Germany

A newly developed superconducting 15-gap RF-cavity has been successfully tested at GSI Helmholtzzentrum für Schwerionenforschung. After a short commissioning and ramp up time of some days, a Crossbar H-cavity accelerated first time heavy ion beams with full transmission up to the design beam energy of 1.85 MeV/u. The design acceleration gain of 3.5 MV inside a length of less than 70 cm has been verified with heavy ion beam of up to 1.5 particle mueA. The measured beam parameters showed excellent beam quality, while a dedicated beam dynamics layout provides beam energy variation between 1.2 and 2.2 MeV/u. The beam commissioning is a milestone of the R&D work of Helmholtz Institute Mainz and GSI in collaboration with Goethe University Frankfurt towards a superconducting heavy ion continuous wave linear accelerator cw-Linac with variable beam energy. Further linac beam dynamics layout issues will be presented as well.

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WEP1WB04

Design of Linac-100 and Linac-30 for New Rare Isotope Facility Project DERICA at JINR

220

S.M. Polozov, V.S. Dyubkov, T. Kulevoy, Y. Lozeev, T.A. Lozeeva, A.V. Samoshin
MEPhI, Moscow, Russia
A.S. Fomichev, L.V. Grigorenko
JINR/FLNR, Moscow region, Russia
T. Kulevoy
ITEP, Moscow, Russia

DERICA (Dubna Electron-Radioactive Ion Collider fAcility) is the new ambitious project under development at JINR, Dubna *. DERICA is proposed as the next step in RIB facilities development. It is planned that in the DERICA project the RIBs produced by the Fragment Separator, are stopped in a gas cell, are accumulated in the ion trap and then are transferred to the ion trap/charge breeder, creating the highest possible charge state for the further effective acceleration (system {gas cell - ion trap - ion trap/charge breeder}). From the accelerator point of view DERICA will include the driver LINAC-100 of heavy ions with Z=5-92 (energy up to 100 MeV/u) with operating mode close to CW, the fragment separator, the re-accelerator LINAC-30 of secondary beams with energies in the range 5-30 MeV/u), the fast ramping ring (energy <300 AMeV), the collector ring and the electron storage ring. General DERICA concept and possible design of the LINAC-100 and LINAC-30 accelerators playing a key role in the project will presented in this report.
* A.S. Fomichev et al., Scientific program of DERICA prospective accelerator and storage ring facility for radioactive ion beam research, http://aculina.jinr.ru/pdf/DERICA/DERICA-for-ufn-8-en.pdf

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THP1WB01

Commissioning Status of Linear IFMIF Prototype Accelerator (LIPAc)

366

A. Kasugai, T. Akagi, T. Ebisawa, Y. Hirata, R. Ichimiya, K. Kondo, S. Maebara, K. Sakamoto, T. Shinya, M. Sugimoto
QST, Aomori, Japan
P. Abbon, N. Bazin, B. Bolzon, N. Chauvin, S. Chel, R. Gobin, J. Marroncle, B. Renard
CEA/DSM/IRFU, France
L. Antoniazzi, L. Bellan, D. Bortolato, M. Comunian, E. Fagotti, F. Grespan, M. Montis, A. Palmieri, A. Pisent
INFN/LNL, Legnaro (PD), Italy
P.-Y. Beauvais, H. Dzitko, D. Gex, A. Jokinen, G. Phillips
F4E, Germany
P. Cara, R. Heidinger, I. Moya
Fusion for Energy, Garching, Germany
D. Jiménez-Rey, I. Kirpitchev, J. Mollá, P. Méndez, I. Podadera, D. Regidor, M. Weber, C. de la Morena
CIEMAT, Madrid, Spain
J. Knaster, A. Marqueta, G. Pruneri, F. Scantamburlo
IFMIF/EVEDA, Rokkasho, Japan

The IFMIF project aiming at material tests for a future fusion DEMO reactor is under the EVEDA phase in the BA Agreement of fusion program between Japan and EU. As the accelerator activity, the installation and commissioning of the Linear IFMIF Prototype Accelerator (LIPAc) is at the second stage of demonstration of the feasibility of the low energy section of an IFMIF deuteron accelerator up to 9 MeV with a beam current of 125 mA, CW. The installation of injector, RFQ, MEBT, D-Plate and LPBD for LIPAc with 8 coaxial high-power transmission lines and RF power system was just done in 2017 at Rokkasho, Japan. After that, the RF conditioning of RFQ for beam commissioning is underway. The beam commissioning of RFQ with H⁺/D⁺ and the acceleration demonstration up to 5 MeV-125 mA-0.1% duty cycle with D⁺ will be done.

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THP1WB02

Beam Dynamics in Low Energy Beam Lines with Space Charge Compensation

N. Chauvin, N. Pichoff, D. Uriot
IRFU, CEA, University Paris-Saclay, Gif-sur-Yvette, France
A. Chancé
CEA/DRF/IRFU, Gif-sur-Yvette, France
F. Gérardin
CEA/IRFU, Gif-sur-Yvette, France

The study of the dynamics of low energy beam transport (LEBT) line is one of the major challenges in the high intensity hadron accelerators field. At low energy, the beam transport is dominated by the charge space field which in many cases can induce a halo formation, emittance growth and eventually beam losses. Moreover, beam dynamics in LEBT features a unique specificity: space charge compensation induced by ionisation of the residual gas by the propagating beam. In order to attempt to reach a better understanding of space charge compensation and particles dynamics in LEBTs, extensive numerical simulations using the PIC code Warp have been performed. Simulation results for light ions beams propagating in the LEBT of the IFMIF-LIPAc and MYRRHA accelerator will be presented and compared to experimental results.

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THP1WB03

Classification of Space-Charge Resonances and Instabilities

D. Jeon
IBS, Daejeon, Republic of Korea

There are two families of space charge mechanisms: space charge resonances and instabilities. For the same mechanism, there are many different names and they are used in an ambiguous way: resonances or single particle resonances or incoherent resonances, and instabilities or parametric resonances or coherent resonances. This talk will emphasize the fundamental difference between the two families of mechanisms and to suggest how to name them in a more consistent way.

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THP2WB01

Revisiting the Longitudinal 90 Degree Limit for Superconducting Linear Accelerators

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.

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THP2WB02

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

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

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THP2WB03

Influence of the Cavity Field Flatness and Effect of the Phase Reference Line Errors on the Beam Dynamics of the ESS Linac

377

R. De Prisco, R. Zeng
ESS, Lund, Sweden
K. Czuba, T.P. Leśniak, R. Papis, D. Sikora, M. Żukociński
Warsaw University of Technology, Institute of Electronic Systems, Warsaw, Poland

The particle longitudinal dynamics is affected by errors on the phase and amplitude of the electro-magnetic field in each cavity that cause emittance growth, beam degradation and losses. One of the causes of the phase error is the change of the ambient temperature in the LINAC tunnel, in the stub and in the klystron gallery that induces a phase drift of the signal travelling through the cables and radio frequency components. The field flatness error of each multiple cell cavity is caused by volume perturbation, cell to cell coupling, tuner penetration, etc.. In this paper it is studied the influences of these two types of errors on the beam dynamics and it is determined their tolerances such that the beam quality is kept within acceptable limits.

Slides THP2WB03 [1.556 MB]

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THP2WB04

Longitudinal Dynamics of Low Energy Superconducting Linac

383

Z. Li
SCU, Chengdu, People's Republic of China

Funding: funded by NSFC(11375122, 11511140277)
The superconducting linac is composed of short independent cavities, and the cavity occupies only a small portion (1/4 to 1/6) of the machine compared with the normal conducting one. When phase advance per period is greater than 60 degrees, the smooth approximation is no longer valid and the longitudinal motion has to be described by time dependent system. With the help of Poincare map, the single particle nonlinear time dependent longitudinal motion is investigated. The study shows that when phase advance per period is less than 60 degrees, the system can be well described by smooth approximation, that means there is a clear boundary (separatrix) between stable and unstable area; when phase advance is greater than 60 degrees, the system shows a quite different dynamic structures and the phase acceptance is decreased significantly compared with the smooth approximation theory predicated, especially when phase advance per period is greater than 90 degrees. The results show that even for low current ma-chine, the zero current phase advance should be kept less than 90 degrees to make sure there is no particle loss because of the shrink of the longitudinal acceptance.

Slides THP2WB04 [1.061 MB]

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THP2WB05

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

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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THP2WB06

The Beam Dynamics Design of HIAF Superconducting Injector

S.H. Liu, Y. He, Z.J. Wang
IMP/CAS, Lanzhou, People's Republic of China

A new heavy ion superconducting linac, named Super-Conducting Ion Linac(iLinac) has been proposed and designed in the Institute of Modern physics of China. As the injector of High intensity heavy Ion accelerator facility (HIAF), iLinac will accelerate the 1 mA 238U⁴⁵⁺ beam to 17 MeV/u. In this paper, we will focus on the physics design study together with the design principles and the simulation results with machine errors.

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