IPAC2017 - List of Keywords (bunching)

Paper	Title	Other Keywords	Page
MOOCA1	High Efficiency Klystrons Using the COM Bunching Technique	klystron, electron, cavity, simulation	37
	D.A. Constable Lancaster University, Lancaster, United Kingdom A.Yu. Baikov Moscow University of Finance & Law, Moscow, Russia G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R.D. Kowalczyk L-3, Williamsport, Pennsylvania, USA I. Syratchev CERN, Geneva, Switzerland
	Future large-scale particle accelerators, for example, the Future Circular Collider (FCC), the Compact Linear Collider (CLIC) and the International Linear Collider (ILC), will require significant RF drive power on the order of 100 MW. Thus, an RF source with high efficiency is preferable to minimise the overall power required. Klystrons represent an attractive RF source, with the current state of the art operating at efficiencies of up to 70%. Such devices feature monotonic bunching, where at the output cavity, a number of electrons will not be in the main bunch, and instead will be present in the anti-bunch, and therefore not contributing to the output power. Therefore, novel bunching methods, such as the Core Oscillation Method (COM), are worthy of investigation. By allowing the core of the electron beam to bunch and de-bunch between successive cavities, the number of electrons contained in the final bunch can increase, and therefore improve the efficiency of the device. Numerical simulation of klystrons featuring COM will be presented, with efficiencies of up to 85% being predicted thus far.
	Slides MOOCA1 [12.765 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOOCA1
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TUPAB077	A Combined THz/X-ray Source Based on Brake-applied Velocity Bunching and Magnetic Compression	electron, radiation, emittance, laser	1500
	R. Huang, Z.G. He, Q.K. Jia, B. Li, W.W. Li, L. Wang, S.C. Zhang USTC/NSRL, Hefei, Anhui, People's Republic of China
	Funding: Work supported by Chinese Universities Scientific Fund under Contracts WK2310000063 and WK2310000047 Ultrashort electron beam can be realized by the process of velocity bunching and magnetic compression. Velocity bunching technique is able to compress the bunch at relatively low energy, which presents peculiar challenges when approaching a very high current and a low transverse emittance in photoinjectors. A brake-applied velocity bunching scheme was proposed, so that the transverse emittance of the beam could be almost compensated even if the compression factor was extremely high. By adding a magnetic compressor, one could obtain a shorter beam and achieve the coherent synchrotron radiation in THz range. Meanwhile, when making the final compressed beam collide with the laser, one could acquire high energy X-ray pulses. This opens the possibility for some interesting combinations of pump-and-probe experiments.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB077
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TUPAB082	Research of L-Band Disk-Loaded Waveguides Travelling Wave Accelerating Structures for a High Power Linac	cavity, electron, network, impedance	1506
	Y.M. Zhang USTC, SNST, Anhui, People's Republic of China Y.J. Pei, L.S. Sheng, Y. Song USTC/NSRL, Hefei, Anhui, People's Republic of China
	L-band Electron Accelerator is widely used for industrial irradiation. This paper describes a constant-impedance, disk-loaded structure operating on the 2Pi/3 mode. The design details of L-band travelling wave accelerating structures are presented. All RF parameters in metal disk-loaded waveguides and fields were calculated. The SUPERFISH code was used to design the bunching and accelerating cavities. At the same time, we also calculated the beam dynamics. Some model cavities have been fabricated and experimental studies were carried on. In this study, some valuable results were obtained, which can provide a beneficial datum for the design and manufacture of L-band travelling-wave accelerating structures of 50MeV LINAC.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB082
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WEPAB015	Parameter Optimization for Operation of sFLASH With Echo-Enabled Harmonic Generation	FEL, laser, electron, operation	2592
	J. Bödewadt, R.W. Aßmann, C. Lechner DESY, Hamburg, Germany W. Hillert, T. Plath, J. Roßbach University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany S. Khan, N.M. Lockmann DELTA, Dortmund, Germany
	The free-electron laser facility FLASH has a dedicated experimental setup for external FEL seeding applications for the XUV and soft x-ray spectral range. Recently the setup is operated as high-gain harmonic generation FEL. Furthermore, it also allows the operation of echo-enabled harmonic generation (EEHG). A versatile laser injection system allows operation with seed wavelength in the infra-red, visible, and ultra-violet. Here, we present the parameter optimization for operating the seeding setup with EEHG. First experimental tests are planned in the first half of 2017.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB015
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WEPAB089	Design Study for the Generation of Few-Cycle FEL Pulses Using Mode-Locked Afterburner Scheme at Clara	FEL, laser, simulation, radiation	2783
	C.L. Shurvinton, D.J. Dunning, N. Thompson STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	Ultrashort pulse operation in FELs is a highly desirable capability for imaging matter on ultrafast timescales. This paper presents a design study for a proof-Âof-Âprinciple demonstration of the mode-locked afterburner (ML-AB) scheme on the FEL test facility CLARA. A start-to-end simulation has been constructed using the time-Âdependent three-Âdimensional FEL code GENESIS 1.3 to evaluate the performance of the scheme. The ability to produce pulses of several femtoseconds in duration with peak powers of the order of 100 MW at 100 nm wavelength is predicted.Â Such pulses have duration of 2 fs (6 optical cycles), a factor of ~5 shorter than the FEL cooperation length. Potential routes for further optimisation and alternative operating modes are explored.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB089
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WEPAB122	Experimental Demonstration of Ballistic Bunching with Dielectric-Lined Waveguides at Pitz	electron, experiment, linac, wakefield	2857
	F. Lemery University of Hamburg, Hamburg, Germany G.A. Amatuni, B. Grigoryan CANDLE, Yerevan, Armenia P. Boonpornprasert, Y. Chen, J.D. Good, M. Krasilnikov, O. Lishilin, G. Loisch, S. Philipp, H.J. Qian, Y. Renier, F. Stephan DESY Zeuthen, Zeuthen, Germany P. Piot Fermilab, Batavia, Illinois, USA P. Piot Northern Illinois University, DeKalb, Illinois, USA
	We report on the experimental demonstration of ballistic bunching of photoinjected, nC-scale electron bunches at the PITZ facility. In the experiment, electron bunches emanating from the photocathode were directly focused into a mm-scale dielectric-lined waveguide. The wakefield excited by the bunch acts back onto itself, leading to an energy modulation, which at a relatively low energy of 6~MeV, is converted into a density modulation before entering the linac ∼ 1~m downstream. We discuss the basic theory, experimental layout and results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB122
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WEPIK113	Entrance and Exit CSR Impedance for Non-Ultrarelativistic Beam	impedance, wakefield, dipole, FEL	3214
	R. Li JLab, Newport News, Virginia, USA C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
	Funding: Work supported by the Department of Energy, Laboratory Directed Research and Development Funding, under Contract No. DE-AC05-06OR23177 For a high-brightness electron beam being transported through beamlines involving bending systems, the coherent synchrotron radiation (CSR) and longitudinal space charge (LSC) interaction could often cause microbunching instability. The semi-analytical Vlasov solver for microbunching gain* depends on the impedances for the relevant collective effects. The existing results for CSR impedances are usually obtained for the ultrarelativistic limit. To extend the microbunching analysis to cases of low energies, such as the case of an ERL merger, or to density modulations at extremely small wavelength, it is necessary to extend the impedance analysis to the non-ultrarelativistic regime. In this study, we present the impedance analysis for the transient CSR interaction in the non-ultrarelativistic regime, for transients including both entrance to and exit from a magnetic dipole. These impedance results will be compared to their ultra-relativistic counterparts, and the corresponding wakefield obtained from the impedance for low-energy beams will be compared with the existing results of transient CSR wakefield for general beam energies. C.-Y. Tsai et al., Proc. of IPAC'15, 596 (2015). C. Mitchell et al ., Proc. of IPAC'13, 1832 (2014). * E. L. Saldin et al ., Nucl. Instrum. Meth. A 398, 373 (1997).
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WEPVA003	Designing a Dielectric Laser Accelerator on a Chip	laser, acceleration, electron, synchrotron	3250
	U. Niedermayer, O. Boine-Frankenheim, T. Egenolf TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: This work is funded by the Gordon and Betty Moore Foundation (Grant GBMF4744 to Stanford) and the German Federal Ministry of Science and Education (Grant FKZ:05K16RDB). Dielectric Laser Acceleration (DLA) achieves gradients of more than 1GeV/m, which are among the highest in non-plasma accelerators. The long-term goal of the ACHIP collaboration* is to provide relativistic (>1 MeV) electrons by means of a laser driven microchip accelerator. Examples of slightly resonant dielectric structures showing gradients in the range of 70% of the incident laser field (1 GV/m) for electrons with β=0.32 and 200% for β=0.91 are presented. We demonstrate the bunching and acceleration of low energy electrons in dedicated ballistic buncher and velocity matched grating structures. However, the design gradient of 500 MeV/m leads to rapid defocusing. Therefore we present a scheme to bunch the beam in stages, which does not only reduce the energy spread, but also the transverse defocusing. The designs are made with a dedicated homemade 6D particle tracking code. * https://achip.stanford.edu
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA003
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THOBA1	Studies of the Micro-Bunching Instability in Multi-Bunch Operation at the ANKA Storage Ring	synchrotron, photon, radiation, storage-ring	3645
	M. Brosi, E. Blomley, E. Bründermann, M. Caselle, B. Kehrer, A. Kopmann, A.-S. Müller, L. Rota, M. Schedler, M. Schuh, M. Schwarz, P. Schönfeldt, J.L. Steinmann, M. Weber KIT, Eggenstein-Leopoldshafen, Germany
	Funding: Supported by the German Federal Ministry of Education and Research (05K13VKA & 05K16VKA), the Helmholtz Association (VH-NG-320) and the Helmholtz International Research School for Teratronics (HIRST) The test facility and synchrotron light source ANKA at the Karlsruhe Institute of Technology (KIT) operates in the energy range from 0.5 to 2.5 GeV and can generate brilliant coherent synchrotron radiation (CSR) in the THz range employing a dedicated bunch length-reducing optic at 1.3 GeV beam energy. The high degree of spatial compression leads to complex longitudinal dynamics and to time evolving sub-structures in the longitudinal phase space of the electron bunches. The results of the micro-bunching instability are time-dependent fluctuations and strong bursts in the radiated THz power. To study these fluctuations in the emitted THz radiation simultaneously for each individual bunch in a multi-bunch environment, fast THz detectors are combined with KAPTURE, the dedicated KArlsruhe Pulse Taking and Ultrafast Readout Electronics system, developed at KIT. In this contribution we present measurements conducted to study possible multi-bunch effects on the characteristic bursting behavior of the micro-bunch instability.
	Slides THOBA1 [12.910 MB]
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THPAB001	Microbunching Instability as a Caustic Phenomenon	electron, radiation, linac, synchrotron	3676
	T.K. Charles, D.M. Paganin Monash University, Faculty of Science, Clayton, Victoria, Australia M.J. Boland The University of Melbourne, Melbourne, Victoria, Australia M.J. Boland, R.T. Dowd SLSA, Clayton, Australia
	Microbunching instability if left alone, threatens to degrade the beam quality of high brightness electron beams in Free Electron Lasers. Recently, caustic formation in electron trajectories was identified as a mechanism describing current modulations in accelerated particle beams. Here we consider CSR-induced microbunching as a caustic phenomenon. This analysis reports on the influence of longitudinal dispersion, R56, on the microbunching process, as well as elucidating the influence of the second and third order longitudinal dispersion values, T566 and U5666.
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THPAB014	An Adaptive Mesh-Based Method for the Efficient Simulation of LSC-Driven Microbunching Gain in FEL Applications	electron, FEL, acceleration, simulation	3720
	Ph. Amstutz University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany M. Vogt DESY, Hamburg, Germany
	Electron beams with high peak current as they are required for the operation of free-electron lasers (FELs) are often generated by means of a series of magnetic bunch compressors. In conjunction with a collective coherent force, e.g. longitudinal space-charge (LSC), bunch compressors can possibly cause a wavelength dependent amplification of initial density inhomogeneities, potentially to an extent detrimental to the operation of the FEL. A common model, consisting of LSC, acceleration (kicks), and magnetic chicanes (drift-type maps), is governed by a time-discrete Vlasov-Poisson system. Such systems have been successfully simulated using mesh based representations of the phase space density (PSD) and the method of characteristics for the update step. However, for the irregular and exotic PSDs, prevalent in FEL applications, a homogeneous high resolution discretization on a naive rectangular mesh can be prohibitively wasteful. Here we present an approach based on adaptive tree refinement that addresses the complexity of the PSDs and allows for the efficient simulation of LSC-driven micro-bunching in FELs.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB014
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THPIK056	Design of a C-Band High-Efficiency Multi-Beam Klystron	klystron, electron, cavity, simulation	4221
	Z.N. Liu, H.B. Chen, M.M. Peng, J. Shi TUB, Beijing, People's Republic of China
	A multi-beam klystron at 5.712GHz has been designed with efficiency of more than 80%. It can generate a pulse with output power of about 3MW and a pulse length of 5 us. Space charge effect and large signal theory, which both increase the accuracy theoretically, are considered in the simulation. A series of parameters of cavities are given after optimizing, including the frequency, R/Q, Q0 and Qe. This paper describes the beam dynamics design of the klystron as well as a preliminary machenical design.
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THPVA121	Focusing and Bunching of Ion Beam in Axial Injection Channel of IPHC Cyclotron TR24	ion, cyclotron, focusing, solenoid	4733
	N.Yu. Kazarinov, I.A. Ivanenko JINR, Dubna, Moscow Region, Russia T. Adam, F.R. Osswald, E.K. Traykov IPHC, Strasbourg Cedex 2, France
	The CYRCé cyclotron (CYclotron pour la ReCherche et l'Enseignement) is used at IPHC (Institut Pluridisciplinaire Hubert Curien) for the production of radio-isotopes for diagnostics, medical treatments and fundamental research in radiobiology. The TR24 cyclotron produced and commercialized by ACSI (Canada) delivers a 16-25 MeV proton beam with intensity from few nA up to 500 mcA. The solenoidal focusing instead of existing quadrupole one is proposed in this report. The changing of the focusing elements will give the better beam matching with the acceptance of the spiral inflector of the cyclotron. The parameters of the focusing solenoid is found. Additionally, the main parameters of the bunching system are evaluated in the presence of the beam space charge. This system consists of the buncher installed in the axial injection beam line of the cyclotron. The using of the greedless multi harmonic buncher may increase the accelerated beam current and will give the opportunity to a new proton beam applications.
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Paper

Title

Other Keywords

Page

MOOCA1

High Efficiency Klystrons Using the COM Bunching Technique

klystron, electron, cavity, simulation

37

D.A. Constable
Lancaster University, Lancaster, United Kingdom
A.Yu. Baikov
Moscow University of Finance & Law, Moscow, Russia
G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R.D. Kowalczyk
L-3, Williamsport, Pennsylvania, USA
I. Syratchev
CERN, Geneva, Switzerland

Future large-scale particle accelerators, for example, the Future Circular Collider (FCC), the Compact Linear Collider (CLIC) and the International Linear Collider (ILC), will require significant RF drive power on the order of 100 MW. Thus, an RF source with high efficiency is preferable to minimise the overall power required. Klystrons represent an attractive RF source, with the current state of the art operating at efficiencies of up to 70%. Such devices feature monotonic bunching, where at the output cavity, a number of electrons will not be in the main bunch, and instead will be present in the anti-bunch, and therefore not contributing to the output power. Therefore, novel bunching methods, such as the Core Oscillation Method (COM), are worthy of investigation. By allowing the core of the electron beam to bunch and de-bunch between successive cavities, the number of electrons contained in the final bunch can increase, and therefore improve the efficiency of the device. Numerical simulation of klystrons featuring COM will be presented, with efficiencies of up to 85% being predicted thus far.

Slides MOOCA1 [12.765 MB]

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TUPAB077

A Combined THz/X-ray Source Based on Brake-applied Velocity Bunching and Magnetic Compression

electron, radiation, emittance, laser

1500

R. Huang, Z.G. He, Q.K. Jia, B. Li, W.W. Li, L. Wang, S.C. Zhang
USTC/NSRL, Hefei, Anhui, People's Republic of China

Funding: Work supported by Chinese Universities Scientific Fund under Contracts WK2310000063 and WK2310000047
Ultrashort electron beam can be realized by the process of velocity bunching and magnetic compression. Velocity bunching technique is able to compress the bunch at relatively low energy, which presents peculiar challenges when approaching a very high current and a low transverse emittance in photoinjectors. A brake-applied velocity bunching scheme was proposed, so that the transverse emittance of the beam could be almost compensated even if the compression factor was extremely high. By adding a magnetic compressor, one could obtain a shorter beam and achieve the coherent synchrotron radiation in THz range. Meanwhile, when making the final compressed beam collide with the laser, one could acquire high energy X-ray pulses. This opens the possibility for some interesting combinations of pump-and-probe experiments.

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TUPAB082

Research of L-Band Disk-Loaded Waveguides Travelling Wave Accelerating Structures for a High Power Linac

cavity, electron, network, impedance

1506

Y.M. Zhang
USTC, SNST, Anhui, People's Republic of China
Y.J. Pei, L.S. Sheng, Y. Song
USTC/NSRL, Hefei, Anhui, People's Republic of China

L-band Electron Accelerator is widely used for industrial irradiation. This paper describes a constant-impedance, disk-loaded structure operating on the 2Pi/3 mode. The design details of L-band travelling wave accelerating structures are presented. All RF parameters in metal disk-loaded waveguides and fields were calculated. The SUPERFISH code was used to design the bunching and accelerating cavities. At the same time, we also calculated the beam dynamics. Some model cavities have been fabricated and experimental studies were carried on. In this study, some valuable results were obtained, which can provide a beneficial datum for the design and manufacture of L-band travelling-wave accelerating structures of 50MeV LINAC.

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WEPAB015

Parameter Optimization for Operation of sFLASH With Echo-Enabled Harmonic Generation

FEL, laser, electron, operation

2592

J. Bödewadt, R.W. Aßmann, C. Lechner
DESY, Hamburg, Germany
W. Hillert, T. Plath, J. Roßbach
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Khan, N.M. Lockmann
DELTA, Dortmund, Germany

The free-electron laser facility FLASH has a dedicated experimental setup for external FEL seeding applications for the XUV and soft x-ray spectral range. Recently the setup is operated as high-gain harmonic generation FEL. Furthermore, it also allows the operation of echo-enabled harmonic generation (EEHG). A versatile laser injection system allows operation with seed wavelength in the infra-red, visible, and ultra-violet. Here, we present the parameter optimization for operating the seeding setup with EEHG. First experimental tests are planned in the first half of 2017.

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WEPAB089

Design Study for the Generation of Few-Cycle FEL Pulses Using Mode-Locked Afterburner Scheme at Clara

FEL, laser, simulation, radiation

2783

C.L. Shurvinton, D.J. Dunning, N. Thompson
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

Ultrashort pulse operation in FELs is a highly desirable capability for imaging matter on ultrafast timescales. This paper presents a design study for a proof-Âof-Âprinciple demonstration of the mode-locked afterburner (ML-AB) scheme on the FEL test facility CLARA. A start-to-end simulation has been constructed using the time-Âdependent three-Âdimensional FEL code GENESIS 1.3 to evaluate the performance of the scheme. The ability to produce pulses of several femtoseconds in duration with peak powers of the order of 100 MW at 100 nm wavelength is predicted.Â Such pulses have duration of 2 fs (6 optical cycles), a factor of ~5 shorter than the FEL cooperation length. Potential routes for further optimisation and alternative operating modes are explored.

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WEPAB122

Experimental Demonstration of Ballistic Bunching with Dielectric-Lined Waveguides at Pitz

electron, experiment, linac, wakefield

2857

F. Lemery
University of Hamburg, Hamburg, Germany
G.A. Amatuni, B. Grigoryan
CANDLE, Yerevan, Armenia
P. Boonpornprasert, Y. Chen, J.D. Good, M. Krasilnikov, O. Lishilin, G. Loisch, S. Philipp, H.J. Qian, Y. Renier, F. Stephan
DESY Zeuthen, Zeuthen, Germany
P. Piot
Fermilab, Batavia, Illinois, USA
P. Piot
Northern Illinois University, DeKalb, Illinois, USA

We report on the experimental demonstration of ballistic bunching of photoinjected, nC-scale electron bunches at the PITZ facility. In the experiment, electron bunches emanating from the photocathode were directly focused into a mm-scale dielectric-lined waveguide. The wakefield excited by the bunch acts back onto itself, leading to an energy modulation, which at a relatively low energy of 6~MeV, is converted into a density modulation before entering the linac ∼ 1~m downstream. We discuss the basic theory, experimental layout and results.

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WEPIK113

Entrance and Exit CSR Impedance for Non-Ultrarelativistic Beam

impedance, wakefield, dipole, FEL

3214

R. Li
JLab, Newport News, Virginia, USA
C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA

Funding: Work supported by the Department of Energy, Laboratory Directed Research and Development Funding, under Contract No. DE-AC05-06OR23177
For a high-brightness electron beam being transported through beamlines involving bending systems, the coherent synchrotron radiation (CSR) and longitudinal space charge (LSC) interaction could often cause microbunching instability. The semi-analytical Vlasov solver for microbunching gain* depends on the impedances for the relevant collective effects. The existing results for CSR impedances are usually obtained for the ultrarelativistic limit. To extend the microbunching analysis to cases of low energies, such as the case of an ERL merger, or to density modulations at extremely small wavelength, it is necessary to extend the impedance analysis to the non-ultrarelativistic regime. In this study, we present the impedance analysis for the transient CSR interaction in the non-ultrarelativistic regime, for transients including both entrance to and exit from a magnetic dipole. These impedance results will be compared to their ultra-relativistic counterparts**, and the corresponding wakefield obtained from the impedance for low-energy beams will be compared with the existing results of transient CSR wakefield for general beam energies***.
* C.-Y. Tsai et al., Proc. of IPAC'15, 596 (2015).
** C. Mitchell et al ., Proc. of IPAC'13, 1832 (2014).
*** E. L. Saldin et al ., Nucl. Instrum. Meth. A 398, 373 (1997).

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WEPVA003

Designing a Dielectric Laser Accelerator on a Chip

laser, acceleration, electron, synchrotron

3250

U. Niedermayer, O. Boine-Frankenheim, T. Egenolf
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: This work is funded by the Gordon and Betty Moore Foundation (Grant GBMF4744 to Stanford) and the German Federal Ministry of Science and Education (Grant FKZ:05K16RDB).
Dielectric Laser Acceleration (DLA) achieves gradients of more than 1GeV/m, which are among the highest in non-plasma accelerators. The long-term goal of the ACHIP collaboration* is to provide relativistic (>1 MeV) electrons by means of a laser driven microchip accelerator. Examples of slightly resonant dielectric structures showing gradients in the range of 70% of the incident laser field (1 GV/m) for electrons with β=0.32 and 200% for β=0.91 are presented. We demonstrate the bunching and acceleration of low energy electrons in dedicated ballistic buncher and velocity matched grating structures. However, the design gradient of 500 MeV/m leads to rapid defocusing. Therefore we present a scheme to bunch the beam in stages, which does not only reduce the energy spread, but also the transverse defocusing. The designs are made with a dedicated homemade 6D particle tracking code.
* https://achip.stanford.edu

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THOBA1

Studies of the Micro-Bunching Instability in Multi-Bunch Operation at the ANKA Storage Ring

synchrotron, photon, radiation, storage-ring

3645

M. Brosi, E. Blomley, E. Bründermann, M. Caselle, B. Kehrer, A. Kopmann, A.-S. Müller, L. Rota, M. Schedler, M. Schuh, M. Schwarz, P. Schönfeldt, J.L. Steinmann, M. Weber
KIT, Eggenstein-Leopoldshafen, Germany

Funding: Supported by the German Federal Ministry of Education and Research (05K13VKA & 05K16VKA), the Helmholtz Association (VH-NG-320) and the Helmholtz International Research School for Teratronics (HIRST)
The test facility and synchrotron light source ANKA at the Karlsruhe Institute of Technology (KIT) operates in the energy range from 0.5 to 2.5 GeV and can generate brilliant coherent synchrotron radiation (CSR) in the THz range employing a dedicated bunch length-reducing optic at 1.3 GeV beam energy. The high degree of spatial compression leads to complex longitudinal dynamics and to time evolving sub-structures in the longitudinal phase space of the electron bunches. The results of the micro-bunching instability are time-dependent fluctuations and strong bursts in the radiated THz power. To study these fluctuations in the emitted THz radiation simultaneously for each individual bunch in a multi-bunch environment, fast THz detectors are combined with KAPTURE, the dedicated KArlsruhe Pulse Taking and Ultrafast Readout Electronics system, developed at KIT. In this contribution we present measurements conducted to study possible multi-bunch effects on the characteristic bursting behavior of the micro-bunch instability.

Slides THOBA1 [12.910 MB]

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THPAB001

Microbunching Instability as a Caustic Phenomenon

electron, radiation, linac, synchrotron

3676

T.K. Charles, D.M. Paganin
Monash University, Faculty of Science, Clayton, Victoria, Australia
M.J. Boland
The University of Melbourne, Melbourne, Victoria, Australia
M.J. Boland, R.T. Dowd
SLSA, Clayton, Australia

Microbunching instability if left alone, threatens to degrade the beam quality of high brightness electron beams in Free Electron Lasers. Recently, caustic formation in electron trajectories was identified as a mechanism describing current modulations in accelerated particle beams. Here we consider CSR-induced microbunching as a caustic phenomenon. This analysis reports on the influence of longitudinal dispersion, R56, on the microbunching process, as well as elucidating the influence of the second and third order longitudinal dispersion values, T566 and U5666.

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THPAB014

An Adaptive Mesh-Based Method for the Efficient Simulation of LSC-Driven Microbunching Gain in FEL Applications

electron, FEL, acceleration, simulation

3720

Ph. Amstutz
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
M. Vogt
DESY, Hamburg, Germany

Electron beams with high peak current as they are required for the operation of free-electron lasers (FELs) are often generated by means of a series of magnetic bunch compressors. In conjunction with a collective coherent force, e.g. longitudinal space-charge (LSC), bunch compressors can possibly cause a wavelength dependent amplification of initial density inhomogeneities, potentially to an extent detrimental to the operation of the FEL. A common model, consisting of LSC, acceleration (kicks), and magnetic chicanes (drift-type maps), is governed by a time-discrete Vlasov-Poisson system. Such systems have been successfully simulated using mesh based representations of the phase space density (PSD) and the method of characteristics for the update step. However, for the irregular and exotic PSDs, prevalent in FEL applications, a homogeneous high resolution discretization on a naive rectangular mesh can be prohibitively wasteful. Here we present an approach based on adaptive tree refinement that addresses the complexity of the PSDs and allows for the efficient simulation of LSC-driven micro-bunching in FELs.

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THPIK056

Design of a C-Band High-Efficiency Multi-Beam Klystron

klystron, electron, cavity, simulation

4221

Z.N. Liu, H.B. Chen, M.M. Peng, J. Shi
TUB, Beijing, People's Republic of China

A multi-beam klystron at 5.712GHz has been designed with efficiency of more than 80%. It can generate a pulse with output power of about 3MW and a pulse length of 5 us. Space charge effect and large signal theory, which both increase the accuracy theoretically, are considered in the simulation. A series of parameters of cavities are given after optimizing, including the frequency, R/Q, Q0 and Qe. This paper describes the beam dynamics design of the klystron as well as a preliminary machenical design.

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THPVA121

Focusing and Bunching of Ion Beam in Axial Injection Channel of IPHC Cyclotron TR24

ion, cyclotron, focusing, solenoid

4733

N.Yu. Kazarinov, I.A. Ivanenko
JINR, Dubna, Moscow Region, Russia
T. Adam, F.R. Osswald, E.K. Traykov
IPHC, Strasbourg Cedex 2, France

The CYRCé cyclotron (CYclotron pour la ReCherche et l'Enseignement) is used at IPHC (Institut Pluridisciplinaire Hubert Curien) for the production of radio-isotopes for diagnostics, medical treatments and fundamental research in radiobiology. The TR24 cyclotron produced and commercialized by ACSI (Canada) delivers a 16-25 MeV proton beam with intensity from few nA up to 500 mcA. The solenoidal focusing instead of existing quadrupole one is proposed in this report. The changing of the focusing elements will give the better beam matching with the acceptance of the spiral inflector of the cyclotron. The parameters of the focusing solenoid is found. Additionally, the main parameters of the bunching system are evaluated in the presence of the beam space charge. This system consists of the buncher installed in the axial injection beam line of the cyclotron. The using of the greedless multi harmonic buncher may increase the accelerated beam current and will give the opportunity to a new proton beam applications.

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