IPAC2014 - List of Keywords (bunching)

Paper	Title	Other Keywords	Page
MOPRO003	Towards Stable Acceleration in Linacs	klystron, acceleration, electron, linac	65
	A. Dubrovskiy Private Address, Geneve, Switzerland
	Ultra-stable and -reproducible high-energy particle beams with short bunches are needed in novel linear accelerators and, in particular, in the Compact Linear Collider CLIC. A passive beam phase stabilization system based on a bunch compression with a negative transfer matrix element R56 and acceleration at a positive off-crest phase is proposed. The motivation and expected advantages of the proposed scheme are outlined.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO003
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRO015	Advances in Coherent Electron Cooling	electron, hadron, FEL, kicker	91
	V. Litvinenko, Y. Hao, Y.C. Jing, D. Kayran, G. Wang BNL, Upton, Long Island, New York, USA G.I. Bell, I.V. Pogorelov, B.T. Schwartz, A.V. Sobol, S.D. Webb Tech-X, Boulder, Colorado, USA D.L. Bruhwiler RadiaSoft LLC, Boulder, Colerado, USA A. Elizarov SUNY SB, Stony Brook, New York, USA D.F. Ratner SLAC, Menlo Park, California, USA O.A. Shevchenko BINP SB RAS, Novosibirsk, Russia
	This paper will be focused on advances and challenges in cooling of high-energy hadron – and potentially heavy lepton-beams. Such techniques are required to improve quality of hadron beams and for increasing the luminosity in hadron and electron-hadron colliders. In contrast with light leptons, which have very strong radiation damping via synchrotron radiation, the hadrons radiate very little (even in 7TeV LHC) and require additional cooling mechanism to control growth of their emittances. I will discuss the physics principles of revolutionary, but untested, technique: the coherent electron cooling (CeC). Further, current advances and novel CeC schemes will be presented as well as the status of preparation at Brookhaven National Laboratory for the CeC demonstration experiment.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO015
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPRO091	Fundamental Limits of Velocity Bunching of High-brightness Electron Beams	electron, emittance, cavity, gun	304
	A. Opanasenko, V.V. Mytrochenko NSC/KIPT, Kharkov, Ukraine V.A. Goryashko, V. Zhaunerchyk Uppsala University, Uppsala, Sweden P.M. Salen FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden
	The interest in superradiant THz sources based on the coherent transition, synchrotron or undulator radiation grows continuously and such sources require high-quality electron bunches with low emittance, high charge and sub-picosecond (sub-ps) duration. Since accelerator-based THz sources are usually driven by relatively low energy electron bunches of a few tens of MeV, space-charge makes bunch compression to sub-ps level very challenging. In the present work we investigate the feasibility of ballistic bunching down to sub-ps duration while preserving the transverse phase-space quality. We found that in order to compensate for the nonlinear dependency of the arrival time on the energy as well as bunch deformations induced by space-charge effects, one needs to apply a nonlinear energy chirp. This chirp permits to maximize the bunch compression and can be realized by exciting a cavity with higher harmonics of the fundamental frequency. Issues related to synchronizing the harmonics are discussed and the analytical analysis is complemented by simulations with PARMELA.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO091
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPME059	Design of a Multi-harmonic Buncher for LINCE	ion, rfq, operation, linac	508
	J. Labrador, C. Bonțoiu, J.A. Dueñas, I. Martel University of Huelva, Huelva, Spain M.A. Carrera, A. Garbayo AVS, Elgoibar, Spain A.C.C. Villari FRIB, East Lansing, Michigan, USA
	Funding: Work partially supported by the Spanish Government (MINECO-CDTI) under program FEDER INTERCONNECTA. Continuous beams delivered by the LINCE ECR ion source will be bunched by a multi-harmonic buncher consisting of two copper-made electrodes. Its numerical design is reported here along with electric and magnetic field maps. Multi-frequency operation is proven by tracking a continuous beam and optimizing the its longitudinal phase space bunching for various ion species under the influence of space charge effects. A thermo-mechanical study carried out in order to estimate the needed water flow through the electrodes is presented as well.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME059
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPME023	Overview of a muon capture section for muon accelerators	proton, target, cavity, solenoid	1398
	D. Stratakis, J.S. Berg, H. K. Sayed BNL, Upton, Long Island, New York, USA D.V. Neuffer, P. Snopok Fermilab, Batavia, Illinois, USA P. Snopok Illinois Institute of Technology, Chicago, Illinois, USA
	Funding: Work supported by Brookhaven Science Associates, LC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. We describe a muon capture section to manipulate the longitudinal and transverse phase-space so that to collect efficiently a muon beam produced from an intense proton source target. We show that this can be achieved by using a set of properly tuned rf cavities that captures the beam into string of bunches and aligns them into nearly equal central energies, and a solenoidal chicane that filters high momentum particles, followed by a proton absorber that reduces the energy of all particles. This work elucidates the key parameters that are needed for successful muon capture, such as the required rf frequencies, rf gradients and focusing field. We discuss the sensitivity in performance against the number of different rf frequencies and accelerating rf gradient.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME023
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPME055	Room-temperature Burst-mode GHz and THz Pulse-train Photoinjector	electron, laser, cathode, acceleration	1492
	F.H. Chao, C.H. Chen, K.Y. Huang, Y.-C. Huang, Y.C. Wang, M.H. Wu NTHU, Hsinchu, Taiwan P.J. Chou NSRRC, Hsinchu, Taiwan
	A photoinjector usually generates an electron pulse with few ps pulse duration repeating at 10-100 Hz. The low-pulse rate limits the data rate in a number of applications. Although high-repetition-rate operation is possible from a superconducting accelerator, the high cost and complexity of a superconducting system prevent it from being widely used. In this paper, we present our study toward a burst-mode GHz/THz pulse train photoinjector operating at room temperature. For the GHz operation mode, we self-develop a driver laser system, generating tens of laser pulses at 2.856 GHz in an adjustable 5-10 ns temporal envelope repeating at 10 Hz. Upon illuminating the photocathode with the driver laser, our S-band photoinjector (supported by Tsing Hua University, Beijing) is to generate a GHz electron pulse train with the same temporal structure as that of the driver laser pulses. For the THz operation mode, we illuminate the photocathode with two lasers, one being a typical UV gun-driver laser at 260 nm and the other being a mid-infrared laser at 100 THz. The UV laser induces photoemission and the infrared laser gates the emission current at 100 THz by virtue of the Schottky effect.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME055
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPME060	Simulation Analysis on Micro-Bunched Density Modulation from a Slit-Masked Chicane	simulation, electron, acceleration, dipole	1509
	Y.-M. Shin, P. Piot, C.R. Prokop Northern Illinois University, DeKalb, Illinois, USA D.R. Broemmelsiek, E.R. Harms, A.H. Lumpkin, J. Ruan, J.C.T. Thangaraj Fermilab, Batavia, Illinois, USA
	Funding: This work was supported by the DOE contract No. DEAC02-07CH11359 to the Fermi Research Alliance LLC. Pre-bunching a beam at a resonance condition with an accelerating structure vastly improves performance of beam-driven accelerators and undulators since it enhances a beam-wave coupling. We plan to test a slit-mask micro-buncher at the chicane of Fermilab-ASTA 50 MeV beamline in the effort of advanced accelerator research. With the chicane design parameters (bending angle (alpha) of 18 degree, R56 ~ - 0.18 m, and bending radius of ~ 0.78 m), analytic model showed that a slit-mask with W (period) = 900 um and a (aperture width) = 300 um (30 % transparency) generates 100 um spaced micro-bunches with 5 ~ 6 % correlated energy spread. Two kinds of combined beamline simulation, CST-PS+Impact-Z and Elegant+Shower, including space charge and CSR effects, showed that a 900 um spaced, 300 um wide slits placed in the middle of chicane splits 20 pC – 1 nC bunches into ~ 100 um spaced micro-bunches. It is possible that a further optimization of mask design creates sub-100 fs micro-bunches, which is currently under development. [1] NIM A 375, 597 (1996) [2] PRL 101, 054801 (2008) [3] Y.-E Sun, P. R. G. Piot, FEMILAB-CONF-08-408-APC * ASTA: Advanced Superconducting Test Accelerator
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME060
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRO008	Obtaining High Degree of Circular Polarization at X-ray FELs via a Reverse Undulator Taper	undulator, FEL, radiation, polarization	2870
	E. Schneidmiller, M.V. Yurkov DESY, Hamburg, Germany
	Baseline design of a typical X-ray FEL undulator assumes a planar configuration which results in a linear polarization of the FEL radiation. However, many experiments at X-ray FEL user facilities would profit from using a circularly polarized radiation. As a cheap upgrade one can consider an installation of a short helical (or cross-planar) afterburner, but then one should have an efficient method to suppress powerful linearly polarized background from the main undulator. In this paper we propose a new method for such a suppression: an application of the reverse taper in the main undulator. We discover that in a certain range of the taper strength, the density modulation (bunching) at saturation is practically the same as in the case of non-tapered undulator while the power of linearly polarized radiation is suppressed by orders of magnitude. Then strongly modulated electron beam radiates at full power in the afterburner. Considering SASE3 undulator of the European XFEL as a practical example, we demonstrate that soft X-ray radiation pulses with peak power in excess of 100 GW and an ultimately high degree of circular polarization can be produced. Phys. Rev. ST-AB 16(2013)110702
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO008
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRO029	A Front End for the CLARA FEL Test Facility at Daresbury Laboratory	linac, gun, dipole, emittance	2927
	P.H. Williams, D. Angal-Kalinin, J.A. Clarke, B.D. Fell, J.K. Jones, J.W. McKenzie, B.L. Militsyn STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
	The next step towards the full CLARA facility is installation of the CLARA front end to comprise a 2m S-band linac section after the photoinjector gun. This will be suitable for both the velocity bunching and standard booster modes of CLARA. An S-bend will also be installed to deflect the beam into the current VELA line, enabling delivery of higher energy beams to two existing user areas. The current photoinjector beam diagnostics section can then be used to test a High Repetition Rate electron gun currently under development. We describe the proposed CLARA front end design. We define two beam dynamics working points for CLARA, one working point for sending beam from the CLARA Front End to VELA, and one working point to feed an interim user station prior to CLARA full construction in the straight-on position.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO029
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRO038	Energy-Silenced HGHG	laser, FEL, electron, space-charge	2946
	E. Hemsing, G. Marcus, A. Marinelli SLAC, Menlo Park, California, USA D. Xiang Shanghai Jiao Tong University, Shanghai, People's Republic of China
	We study the effect of longitudinal space charge on the correlated energy spread of a relativistic beam that has been microbunched for the emission of high harmonic radiation. We show that, in the case of microbunching induced by a laser modulator followed by a dispersive chicane, longitudinal space charge forces can act to significantly reduce the induced energy spread of the beam without a reduction in the harmonic bunching content. This effect may significantly relax constraints on the harmonic number achievable in HGHG FELs, which are otherwise limited by the induced energy spread from the laser.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO038
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRO039	Model-independent Description of Shot-noise, Amplification and Saturation	FEL, electron, undulator, simulation	2949
	Y.C. Jing, V. Litvinenko, G. Wang BNL, Upton, Long Island, New York, USA V. Litvinenko Stony Brook University, Stony Brook, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. High-gain FEL is one of many electron-beam instabilities, which have a number of common features linking the shot noise, the amplification and the saturation. In this paper we present a new, model-independent description of the interplay between these effects and derivation of a simple formula determining the saturation and maximum attainable gain in such instabilities. Application of this model-independent formula to FEL is compared with FEL theory and simulations. We describe limitations resulting from these finding for FEL amplifiers used for seeded FELs and for Coherent electron Cooling.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO039
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPRO047	Linac Design for the Proposed NSRRC THz/VUV FEL Facility	electron, linac, optics, emittance	2971
	N.Y. Huang, W.K. Lau, A.P. Lee NSRRC, Hsinchu, Taiwan A. Chao, J. Wu SLAC, Menlo Park, California, USA C.H. Chen NTHU, Hsinchu, Taiwan
	A driver linac based on a photocathode RF gun injector system for a proposed free electron laser facility at National Synchrotron Radiation Research Center (NSRRC) in Taiwan is under study. This facility is designed to be operated in two modes, one for the VUV application and one for the THz application to fulfil the user needs. Generally the VUV radiation prefers a low emittance, high peak current beam free from collective instability during acceleration and magnetic pulse compression, whereas the THz radiation needs a moderate charge in hundred femtosecond bunch length free from space charge degradation in a transport line. In this paper, the schemes of bunch compression as well as the strategy to optimize and control of the beam quality will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO047
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME008	New Reference Design of the European ADS RFQ Accelerator for MYRRHA	rfq, emittance, simulation, operation	3223
	C. Zhang GSI, Darmstadt, Germany H. Podlech IAP, Frankfurt am Main, Germany
	For demonstrating the technical feasibility of nuclear waste transmutation in an Accelerator Driven System (ADS), the MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) proton driver is under intensive studies. Good performance of the 2 – 4 mA, 1.5MeV RFQ (Radio-Frequency Quadrupole), the start of the accelerator chain, is essential to the reliability of the whole facility, so it must be very well designed. On the basis of the first reference design, further improvements with respect to electrode aperture, emittance growths and output distributions have been performed. The simulation results of the new reference design are presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME008
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME009	Beam Dynamics for the FAIR Proton-Linac RFQ	rfq, linac, simulation, focusing	3226
	C. Zhang GSI, Darmstadt, Germany
	The FAIR (Facility for Antiproton and Ion Research) Proton-Linac (P-LINAC) will be started with a 325.224 MHz, 3 MeV Radio-Frequency Quadrupole (RFQ) accelerator. To ensure that a ≥35 mA beam can be injected into the downstream synchrotrons, the design beam intensity of this Proton-RFQ (P-RFQ) has been chosen as 70 mA. Based on the so-called NFSP (New Four-Section Procedure) method, two new beam dynamics designs with varying and constant transverse focusing strength, respectively, have been worked out to meet the latest design requirements using a compact structure. This paper presents the main design concepts and simulation results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME009
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME013	Field Optimized 4-rod RFQ Model	rfq, simulation, quadrupole, shielding	3238
	J.S. Schmidt, B. Koubek, A. Schempp IAP, Frankfurt am Main, Germany
	The performance of an RFQ in case of its beam quality and transmission is in the basis dependent on the conformity of the field distribution of the manufactured structure with the one of its particle dynamic design. In the last years studies have been performed on the influence of various elements of the 4-rod RFQ on its field distribution. In particular the tuning process of the 4-rod RFQ with its tuning plates has been optimized. These studies have been complemented with detailed simulations on the fringe fields at the end of the electrodes and the conformity of the fields along the structure as well as the influence of other tuning elements like the piston tuner. Based on the findings of this research a proposal for a field optimized 4-rod RFQ model has been developed and will be presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME013
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME051	Preparatory Investigations for a Low Frequency Prebuncher at ReA	rfq, linac, simulation, detector	3342
	D.M. Alt, J.F. Brandon, D. Leitner, D. Morris, M.J. Syphers, N.R. Usher, W. Wittmer NSCL, East Lansing, Michigan, USA
	The ReA reaccelerator facility at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) will provide a unique capability to study reactions with low-energy beams of rare isotopes. A beam from the coupled cyclotron facility is stopped in a gas stopping system, charge bred in an Electron Beam Ion Trap (EBIT), and then reaccelerated in a compact superconducting LINAC. At present the beam repetition rate at the ReA targets is the same as the LINAC RF frequency of 80.5 MHz. A lower frequency would be desirable for many types of experiments using time of flight data acquisitions. Studies were undertaken to investigate possible methods of reducing the beam frequency with minimal reduction in overall beam current. This paper reports the results of preliminary design studies of such a low frequency prebuncher designed to increase the pulse separation and minimize bunch lengths at the detector.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME051
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPME124	Spectral Analysis of Micro-Bunching Instabilities using Fast THz Detectors	detector, radiation, synchrotron, operation	3530
	J.L. Steinmann, E. Hertle, N. Hiller, V. Judin, A.-S. Müller, M. Schuh, P. Schönfeldt, P. Schütze KIT, Karlsruhe, Germany E. Bründermann Ruhr-Universität Bochum, Bochum, Germany
	Micro-bunching instabilities occur at synchrotron light sources when the particle density rises due to compression of the electron bunches. They lead to powerful bursts of coherent synchrotron radiation (CSR) in the THz range at the cost of very unstable intensity and spectral properties, highly fluctuating on a millisecond time scale. For interferometry this changing source demands a long averaging time to achieve a reasonably high signal-to-noise ratio or balancing by the use of an additional reference detector. In this study we present measurements taken by a Martin-Puplett-interferometer in the bursting regime with ultra-fast THz-detectors.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME124
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOPRO003

Towards Stable Acceleration in Linacs

klystron, acceleration, electron, linac

65

A. Dubrovskiy
Private Address, Geneve, Switzerland

Ultra-stable and -reproducible high-energy particle beams with short bunches are needed in novel linear accelerators and, in particular, in the Compact Linear Collider CLIC. A passive beam phase stabilization system based on a bunch compression with a negative transfer matrix element R56 and acceleration at a positive off-crest phase is proposed. The motivation and expected advantages of the proposed scheme are outlined.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO003

Export •

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

MOPRO015

Advances in Coherent Electron Cooling

electron, hadron, FEL, kicker

91

V. Litvinenko, Y. Hao, Y.C. Jing, D. Kayran, G. Wang
BNL, Upton, Long Island, New York, USA
G.I. Bell, I.V. Pogorelov, B.T. Schwartz, A.V. Sobol, S.D. Webb
Tech-X, Boulder, Colorado, USA
D.L. Bruhwiler
RadiaSoft LLC, Boulder, Colerado, USA
A. Elizarov
SUNY SB, Stony Brook, New York, USA
D.F. Ratner
SLAC, Menlo Park, California, USA
O.A. Shevchenko
BINP SB RAS, Novosibirsk, Russia

This paper will be focused on advances and challenges in cooling of high-energy hadron – and potentially heavy lepton-beams. Such techniques are required to improve quality of hadron beams and for increasing the luminosity in hadron and electron-hadron colliders. In contrast with light leptons, which have very strong radiation damping via synchrotron radiation, the hadrons radiate very little (even in 7TeV LHC) and require additional cooling mechanism to control growth of their emittances. I will discuss the physics principles of revolutionary, but untested, technique: the coherent electron cooling (CeC). Further, current advances and novel CeC schemes will be presented as well as the status of preparation at Brookhaven National Laboratory for the CeC demonstration experiment.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO015

Export •

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

MOPRO091

Fundamental Limits of Velocity Bunching of High-brightness Electron Beams

electron, emittance, cavity, gun

304

A. Opanasenko, V.V. Mytrochenko
NSC/KIPT, Kharkov, Ukraine
V.A. Goryashko, V. Zhaunerchyk
Uppsala University, Uppsala, Sweden
P.M. Salen
FYSIKUM, AlbaNova, Stockholm University, Stockholm, Sweden

The interest in superradiant THz sources based on the coherent transition, synchrotron or undulator radiation grows continuously and such sources require high-quality electron bunches with low emittance, high charge and sub-picosecond (sub-ps) duration. Since accelerator-based THz sources are usually driven by relatively low energy electron bunches of a few tens of MeV, space-charge makes bunch compression to sub-ps level very challenging. In the present work we investigate the feasibility of ballistic bunching down to sub-ps duration while preserving the transverse phase-space quality. We found that in order to compensate for the nonlinear dependency of the arrival time on the energy as well as bunch deformations induced by space-charge effects, one needs to apply a nonlinear energy chirp. This chirp permits to maximize the bunch compression and can be realized by exciting a cavity with higher harmonics of the fundamental frequency. Issues related to synchronizing the harmonics are discussed and the analytical analysis is complemented by simulations with PARMELA.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO091

Export •

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

MOPME059

Design of a Multi-harmonic Buncher for LINCE

ion, rfq, operation, linac

508

J. Labrador, C. Bonțoiu, J.A. Dueñas, I. Martel
University of Huelva, Huelva, Spain
M.A. Carrera, A. Garbayo
AVS, Elgoibar, Spain
A.C.C. Villari
FRIB, East Lansing, Michigan, USA

Funding: Work partially supported by the Spanish Government (MINECO-CDTI) under program FEDER INTERCONNECTA.
Continuous beams delivered by the LINCE ECR ion source will be bunched by a multi-harmonic buncher consisting of two copper-made electrodes. Its numerical design is reported here along with electric and magnetic field maps. Multi-frequency operation is proven by tracking a continuous beam and optimizing the its longitudinal phase space bunching for various ion species under the influence of space charge effects. A thermo-mechanical study carried out in order to estimate the needed water flow through the electrodes is presented as well.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME059

Export •

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

TUPME023

Overview of a muon capture section for muon accelerators

proton, target, cavity, solenoid

1398

D. Stratakis, J.S. Berg, H. K. Sayed
BNL, Upton, Long Island, New York, USA
D.V. Neuffer, P. Snopok
Fermilab, Batavia, Illinois, USA
P. Snopok
Illinois Institute of Technology, Chicago, Illinois, USA

Funding: Work supported by Brookhaven Science Associates, LC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
We describe a muon capture section to manipulate the longitudinal and transverse phase-space so that to collect efficiently a muon beam produced from an intense proton source target. We show that this can be achieved by using a set of properly tuned rf cavities that captures the beam into string of bunches and aligns them into nearly equal central energies, and a solenoidal chicane that filters high momentum particles, followed by a proton absorber that reduces the energy of all particles. This work elucidates the key parameters that are needed for successful muon capture, such as the required rf frequencies, rf gradients and focusing field. We discuss the sensitivity in performance against the number of different rf frequencies and accelerating rf gradient.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME023

Export •

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

TUPME055

Room-temperature Burst-mode GHz and THz Pulse-train Photoinjector

electron, laser, cathode, acceleration

1492

F.H. Chao, C.H. Chen, K.Y. Huang, Y.-C. Huang, Y.C. Wang, M.H. Wu
NTHU, Hsinchu, Taiwan
P.J. Chou
NSRRC, Hsinchu, Taiwan

A photoinjector usually generates an electron pulse with few ps pulse duration repeating at 10-100 Hz. The low-pulse rate limits the data rate in a number of applications. Although high-repetition-rate operation is possible from a superconducting accelerator, the high cost and complexity of a superconducting system prevent it from being widely used. In this paper, we present our study toward a burst-mode GHz/THz pulse train photoinjector operating at room temperature. For the GHz operation mode, we self-develop a driver laser system, generating tens of laser pulses at 2.856 GHz in an adjustable 5-10 ns temporal envelope repeating at 10 Hz. Upon illuminating the photocathode with the driver laser, our S-band photoinjector (supported by Tsing Hua University, Beijing) is to generate a GHz electron pulse train with the same temporal structure as that of the driver laser pulses. For the THz operation mode, we illuminate the photocathode with two lasers, one being a typical UV gun-driver laser at 260 nm and the other being a mid-infrared laser at 100 THz. The UV laser induces photoemission and the infrared laser gates the emission current at 100 THz by virtue of the Schottky effect.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME055

Export •

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

TUPME060

Simulation Analysis on Micro-Bunched Density Modulation from a Slit-Masked Chicane

simulation, electron, acceleration, dipole

1509

Y.-M. Shin, P. Piot, C.R. Prokop
Northern Illinois University, DeKalb, Illinois, USA
D.R. Broemmelsiek, E.R. Harms, A.H. Lumpkin, J. Ruan, J.C.T. Thangaraj
Fermilab, Batavia, Illinois, USA

Funding: This work was supported by the DOE contract No. DEAC02-07CH11359 to the Fermi Research Alliance LLC.
Pre-bunching a beam at a resonance condition with an accelerating structure vastly improves performance of beam-driven accelerators and undulators since it enhances a beam-wave coupling. We plan to test a slit-mask micro-buncher at the chicane of Fermilab-ASTA 50 MeV beamline in the effort of advanced accelerator research. With the chicane design parameters (bending angle (alpha) of 18 degree, R56 ~ - 0.18 m, and bending radius of ~ 0.78 m), analytic model showed that a slit-mask with W (period) = 900 um and a (aperture width) = 300 um (30 % transparency) generates 100 um spaced micro-bunches with 5 ~ 6 % correlated energy spread. Two kinds of combined beamline simulation, CST-PS+Impact-Z and Elegant+Shower, including space charge and CSR effects, showed that a 900 um spaced, 300 um wide slits placed in the middle of chicane splits 20 pC – 1 nC bunches into ~ 100 um spaced micro-bunches. It is possible that a further optimization of mask design creates sub-100 fs micro-bunches, which is currently under development.
*[1] NIM A 375, 597 (1996)
[2] PRL 101, 054801 (2008)
[3] Y.-E Sun, P. R. G. Piot, FEMILAB-CONF-08-408-APC
** ASTA: Advanced Superconducting Test Accelerator

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME060

Export •

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

THPRO008

Obtaining High Degree of Circular Polarization at X-ray FELs via a Reverse Undulator Taper

undulator, FEL, radiation, polarization

2870

E. Schneidmiller, M.V. Yurkov
DESY, Hamburg, Germany

Baseline design of a typical X-ray FEL undulator assumes a planar configuration which results in a linear polarization of the FEL radiation. However, many experiments at X-ray FEL user facilities would profit from using a circularly polarized radiation. As a cheap upgrade one can consider an installation of a short helical (or cross-planar) afterburner, but then one should have an efficient method to suppress powerful linearly polarized background from the main undulator. In this paper we propose a new method for such a suppression: an application of the reverse taper in the main undulator. We discover that in a certain range of the taper strength, the density modulation (bunching) at saturation is practically the same as in the case of non-tapered undulator while the power of linearly polarized radiation is suppressed by orders of magnitude. Then strongly modulated electron beam radiates at full power in the afterburner. Considering SASE3 undulator of the European XFEL as a practical example, we demonstrate that soft X-ray radiation pulses with peak power in excess of 100 GW and an ultimately high degree of circular polarization can be produced.
Phys. Rev. ST-AB 16(2013)110702

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO008

Export •

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

THPRO029

A Front End for the CLARA FEL Test Facility at Daresbury Laboratory

linac, gun, dipole, emittance

2927

P.H. Williams, D. Angal-Kalinin, J.A. Clarke, B.D. Fell, J.K. Jones, J.W. McKenzie, B.L. Militsyn
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom

The next step towards the full CLARA facility is installation of the CLARA front end to comprise a 2m S-band linac section after the photoinjector gun. This will be suitable for both the velocity bunching and standard booster modes of CLARA. An S-bend will also be installed to deflect the beam into the current VELA line, enabling delivery of higher energy beams to two existing user areas. The current photoinjector beam diagnostics section can then be used to test a High Repetition Rate electron gun currently under development. We describe the proposed CLARA front end design. We define two beam dynamics working points for CLARA, one working point for sending beam from the CLARA Front End to VELA, and one working point to feed an interim user station prior to CLARA full construction in the straight-on position.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO029

Export •

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

THPRO038

Energy-Silenced HGHG

laser, FEL, electron, space-charge

2946

E. Hemsing, G. Marcus, A. Marinelli
SLAC, Menlo Park, California, USA
D. Xiang
Shanghai Jiao Tong University, Shanghai, People's Republic of China

We study the effect of longitudinal space charge on the correlated energy spread of a relativistic beam that has been microbunched for the emission of high harmonic radiation. We show that, in the case of microbunching induced by a laser modulator followed by a dispersive chicane, longitudinal space charge forces can act to significantly reduce the induced energy spread of the beam without a reduction in the harmonic bunching content. This effect may significantly relax constraints on the harmonic number achievable in HGHG FELs, which are otherwise limited by the induced energy spread from the laser.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO038

Export •

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

THPRO039

Model-independent Description of Shot-noise, Amplification and Saturation

FEL, electron, undulator, simulation

2949

Y.C. Jing, V. Litvinenko, G. Wang
BNL, Upton, Long Island, New York, USA
V. Litvinenko
Stony Brook University, Stony Brook, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
High-gain FEL is one of many electron-beam instabilities, which have a number of common features linking the shot noise, the amplification and the saturation. In this paper we present a new, model-independent description of the interplay between these effects and derivation of a simple formula determining the saturation and maximum attainable gain in such instabilities. Application of this model-independent formula to FEL is compared with FEL theory and simulations. We describe limitations resulting from these finding for FEL amplifiers used for seeded FELs and for Coherent electron Cooling.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO039

Export •

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

THPRO047

Linac Design for the Proposed NSRRC THz/VUV FEL Facility

electron, linac, optics, emittance

2971

N.Y. Huang, W.K. Lau, A.P. Lee
NSRRC, Hsinchu, Taiwan
A. Chao, J. Wu
SLAC, Menlo Park, California, USA
C.H. Chen
NTHU, Hsinchu, Taiwan

A driver linac based on a photocathode RF gun injector system for a proposed free electron laser facility at National Synchrotron Radiation Research Center (NSRRC) in Taiwan is under study. This facility is designed to be operated in two modes, one for the VUV application and one for the THz application to fulfil the user needs. Generally the VUV radiation prefers a low emittance, high peak current beam free from collective instability during acceleration and magnetic pulse compression, whereas the THz radiation needs a moderate charge in hundred femtosecond bunch length free from space charge degradation in a transport line. In this paper, the schemes of bunch compression as well as the strategy to optimize and control of the beam quality will be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO047

Export •

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

THPME008

New Reference Design of the European ADS RFQ Accelerator for MYRRHA

rfq, emittance, simulation, operation

3223

C. Zhang
GSI, Darmstadt, Germany
H. Podlech
IAP, Frankfurt am Main, Germany

For demonstrating the technical feasibility of nuclear waste transmutation in an Accelerator Driven System (ADS), the MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Applications) proton driver is under intensive studies. Good performance of the 2 – 4 mA, 1.5MeV RFQ (Radio-Frequency Quadrupole), the start of the accelerator chain, is essential to the reliability of the whole facility, so it must be very well designed. On the basis of the first reference design, further improvements with respect to electrode aperture, emittance growths and output distributions have been performed. The simulation results of the new reference design are presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME008

Export •

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

THPME009

Beam Dynamics for the FAIR Proton-Linac RFQ

rfq, linac, simulation, focusing

3226

C. Zhang
GSI, Darmstadt, Germany

The FAIR (Facility for Antiproton and Ion Research) Proton-Linac (P-LINAC) will be started with a 325.224 MHz, 3 MeV Radio-Frequency Quadrupole (RFQ) accelerator. To ensure that a ≥35 mA beam can be injected into the downstream synchrotrons, the design beam intensity of this Proton-RFQ (P-RFQ) has been chosen as 70 mA. Based on the so-called NFSP (New Four-Section Procedure) method, two new beam dynamics designs with varying and constant transverse focusing strength, respectively, have been worked out to meet the latest design requirements using a compact structure. This paper presents the main design concepts and simulation results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME009

Export •

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

THPME013

Field Optimized 4-rod RFQ Model

rfq, simulation, quadrupole, shielding

3238

J.S. Schmidt, B. Koubek, A. Schempp
IAP, Frankfurt am Main, Germany

The performance of an RFQ in case of its beam quality and transmission is in the basis dependent on the conformity of the field distribution of the manufactured structure with the one of its particle dynamic design. In the last years studies have been performed on the influence of various elements of the 4-rod RFQ on its field distribution. In particular the tuning process of the 4-rod RFQ with its tuning plates has been optimized. These studies have been complemented with detailed simulations on the fringe fields at the end of the electrodes and the conformity of the fields along the structure as well as the influence of other tuning elements like the piston tuner. Based on the findings of this research a proposal for a field optimized 4-rod RFQ model has been developed and will be presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME013

Export •

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

THPME051

Preparatory Investigations for a Low Frequency Prebuncher at ReA

rfq, linac, simulation, detector

3342

D.M. Alt, J.F. Brandon, D. Leitner, D. Morris, M.J. Syphers, N.R. Usher, W. Wittmer
NSCL, East Lansing, Michigan, USA

The ReA reaccelerator facility at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU) will provide a unique capability to study reactions with low-energy beams of rare isotopes. A beam from the coupled cyclotron facility is stopped in a gas stopping system, charge bred in an Electron Beam Ion Trap (EBIT), and then reaccelerated in a compact superconducting LINAC. At present the beam repetition rate at the ReA targets is the same as the LINAC RF frequency of 80.5 MHz. A lower frequency would be desirable for many types of experiments using time of flight data acquisitions. Studies were undertaken to investigate possible methods of reducing the beam frequency with minimal reduction in overall beam current. This paper reports the results of preliminary design studies of such a low frequency prebuncher designed to increase the pulse separation and minimize bunch lengths at the detector.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME051

Export •

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

THPME124

Spectral Analysis of Micro-Bunching Instabilities using Fast THz Detectors

detector, radiation, synchrotron, operation

3530

J.L. Steinmann, E. Hertle, N. Hiller, V. Judin, A.-S. Müller, M. Schuh, P. Schönfeldt, P. Schütze
KIT, Karlsruhe, Germany
E. Bründermann
Ruhr-Universität Bochum, Bochum, Germany

Micro-bunching instabilities occur at synchrotron light sources when the particle density rises due to compression of the electron bunches. They lead to powerful bursts of coherent synchrotron radiation (CSR) in the THz range at the cost of very unstable intensity and spectral properties, highly fluctuating on a millisecond time scale. For interferometry this changing source demands a long averaging time to achieve a reasonably high signal-to-noise ratio or balancing by the use of an additional reference detector. In this study we present measurements taken by a Martin-Puplett-interferometer in the bursting regime with ultra-fast THz-detectors.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME124

Export •

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