IPAC2012 - List of Keywords (bunching)

Paper	Title	Other Keywords	Page
MOPPD028	Observation of Longitudinal Space Charge Effects in the Injection Beam Line of NIRS-930 Cyclotron	cyclotron, space-charge, injection, simulation	427
	S. Hojo, A. Goto, T. Honma, K. Katagiri, A. Sugiura NIRS, Chiba-shi, Japan
	Dependence of bunching efficiencies on the position of a beam buncher was measured for the AVF cyclotron at the National Institute of Radiological Sciences (NIRS) for 30 MeV proton beams with intensities up to 100 microamperes at injection. The measurement was carried out for two positions: 1.53 m and 2.33 m upstream from the inflector. For the buncher position of 2.33 m the bunching efficiency decreased, as the beam intensity increased, to about half of that at low intensities, while for 1.5 m it was constant up to 100 microamperes. The intensity distributions of extracted beam with respect to the buncher phase were also measured for the two buncher positions. The dependence of bunch width on the beam intensity is discussed by comparing the data with one-dimensional simulations on longitudinal space charge effects.

MOPPD038	Simulation Study of Electron Response Amplification in Coherent Electron Cooling	electron, ion, FEL, undulator	448
	Y. Hao, V. Litvinenko BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In Coherent Electron Cooling (CEC), it is essential to study the amplification of electron response to a single ion in the FEL process, in order to proper align the electron beam and the ion beam in the kicker to maximize the cooling effect. In this paper, we use Genesis to simulate the amplified electron beam response of single ion in FEL amplification process, which acts as 'Green function' of the FEL amplifier.

MOPPP012	Experimental Observation of Energy Modulation in Electron Beams Passing through Terahertz Dielectric Wakefield Structures	wakefield, radiation, FEL, acceleration	595
	S.P. Antipov, C.-J. Jing, A. Kanareykin, P. Schoessow Euclid TechLabs, LLC, Solon, Ohio, USA M.G. Fedurin, K. Kusche, V. Yakimenko BNL, Upton, Long Island, New York, USA W. Gai, A. Zholents ANL, Argonne, USA B.C. Jiang SINAP, Shanghai, People's Republic of China
	Funding: DOE SBIR. We report observation of a strong wakefield induced energy modulation in an energy-chirped electron bunch passing through a terahertz dielectric-lined waveguide. This modulation can be effectively converted into a spatial modulation by means of a chicane, forming micro-bunches (density modulation) with a periodicity of 0.5 - 1 picosecond, hence capable of driving coherent THz radiation. The experimental results agree well with theoretical predictions.

TUEPPB004	A Longitudinal Beam Dynamics Code for Proton Synchrotron	cavity, simulation, space-charge, synchrotron	1119
	Y.S. Yuan, N. Wang, S. Wang, S.Y. Xu IHEP, Beijing, People's Republic of China
	The accelerator of China Spallation Neutron Source (CSNS) consists of an 80 MeV linac and a 1.6 GeV Rapid Cycling Synchrotron (RCS). Longitudinal beam dynamics study is one of the most important issues for RCS beam dynamics design. However, the existing codes cannot meet the requirement of longitudinal beam dynamics for CSNS/RCS. A new code has been developed for longitudinal beam dynamics design and simulation. The code can perform the voltage and phase curves design for non-sinusoidal magnetic field of dipole in an RCS cycle, with the fundamental RF mode and dual harmonic mode. The code can also be used for the beam simulation with longitudinal space charge effect, including the effects of higher order mode of RF cavities. By using the code, the longitudinal beam dynamics of CSNS/RCS was designed and optimized, and the simulation study with dual harmonics higher order modes of RF cavity was done, and the simulation results are presented.

TUEPPB010	Oscillator Seeding of a High Gain Harmonic Generation FEL in a Radiator-first Configuration	FEL, electron, radiation, laser	1137
	P.R. Gandhi, J.S. Wurtele UCB, Berkeley, California, USA G. Penn, M.W. Reinsch LBNL, Berkeley, California, USA
	A longitudinally coherent X-ray pulse from a high repetition rate free electron laser (FEL) is desired for a wide variety of experimental applications. However, generating such a pulse with a repetition rate greater than ~1 MHz is a significant challenge. The desired high rep rate sources, primarily high harmonic generation with intense lasers in gases or plasmas, do not exist now, and, for the multi-MHz bunch trains that superconducting accelerators can potentially produce, are likely not feasible with current technology. In this paper, we propose to place an oscillator downstream of a radiator. The oscillator generates radiation that is used as a seed for a high gain harmonic generation (HGHG) FEL which is upstream of the oscillator. For the first few pulses the oscillator builds up power and, until power is built up, the radiator has no HGHG seed. As power in the oscillator saturates, the HGHG is seeded and power is produced. The dynamics and stability of this radiator-first scheme is explored analytically and numerically. A single-pass map is derived using a semi-analytic model for FEL gain and saturation. Iteration of the map is shown to be in good agreement with simulations.

TUEPPB011	Echo Enabled High Mode Generation for X-ray FELs	laser, electron, FEL, free-electron-laser	1140
	E. Hemsing SLAC, Menlo Park, California, USA A. Marinelli UCLA, Los Angeles, California, USA
	Funding: Work supported by U.S. DOE under Contract Nos. DE-AC02-76SF00515 and DE-FG02-07ER46272. We describe a simple technique based on a modified echo-enabled harmonic generation (EEHG) scheme to manipulate the three-dimensional electron beam microbunching distribution in order to generate higher-order optical modes in an FEL. As with EEHG, the concept uses two modulators and two chicanes to produce microbunching. However, in one of the modulators, the resonant interaction with the laser has a well-defined transverse structure that becomes strongly correlated to the longitudinal microbunching distribution. Both high-harmonic frequencies and high transverse mode numbers can be generated through a transversely-dependent echo effect.

TUEPPB015	Generation of Narrow-Band Coherent Tunable Terahertz Radiation using a Laser-Modulated Electron Beam	laser, electron, radiation, undulator	1146
	M.P. Dunning, C. Hast, E. Hemsing, R.K. Jobe, D.J. McCormick, J. Nelson, T.O. Raubenheimer, K. Soong, Z.M. Szalata, D.R. Walz, S.P. Weathersby, D. Xiang SLAC, Menlo Park, California, USA
	Funding: Work supported by US DOE contract DE-AC02-76SF00515. The technical layout and initial results of an experiment to generate narrow-band, coherent, tunable terahertz (THz) radiation through the down-conversion of the frequency of optical lasers using a laser-modulated electron beam are described. In this experiment a 120 MeV electron beam is first energy modulated by two lasers with different wavelengths. After passing through a dispersive section, the energy modulation is converted into a density modulation at THz frequencies. This density-modulated beam will be used to generate narrow-band THz radiation using a coherent transition radiator inserted into the beam path. The central frequency of the THz radiation can be tuned by varying the wavelength of one of the two lasers or the energy chirp of the electron beam. The experiment is being performed at the NLCTA at SLAC, and will utilize the existing Echo-7 beamline, where echo-enabled harmonic generation (EEHG) was recently demonstrated.

TUPPC026	Design of Compact C-Band Standing-Wave Accelerating Structure Enhancing RF Phase Focusing	coupling, cavity, focusing, simulation	1221
	H.R. Yang, M.-H. Cho, J. Jang, S.H. Kim, W. Namkung, S.J. Park POSTECH, Pohang, Kyungbuk, Republic of Korea J.-S. Oh NFRI, Daejon, Republic of Korea
	Funding: Work supported by POSTECH Physics BK21 Program. We design a C-band standing-wave accelerating structure for an X-ray source of the imaging and medical applications. It is capable of producing 6-MeV, 100-mA pulsed electron beams which is focused by less than 1.5 mm without external magnets. As an RF source, we use peak 1.5-MW magnetron with duty factor of 0.08%. The accelerating structure is a bi-periodic and on-axis-coupled structure with a built-in bunching section, which consists 3 bunching cells, 13 normal cells and a coupler cell. It operated with π/2-mode standing-waves. The bunching section is designed to enhance the RF phase focusing in order to achieve 1.2-mm beam spot size. Each cavity is designed with the MWS code to maximize the effective shunt impedance within 3.5% inter-cell coupling. In this paper, we present design details of RF cavities and the beam dynamics simulation by the PARMELA code.

TUPPD055	Characterization of ps-spaced Comb Beams at SPARC	simulation, linac, radiation, laser	1527
	A. Mostacci URLS, Rome, Italy A. Bacci, A.R. Rossi Istituto Nazionale di Fisica Nucleare, Milano, Italy M. Bellaveglia, E. Chiadroni, G. Di Pirro, M. Ferrario, G. Gatti, C. Vaccarezza INFN/LNF, Frascati (Roma), Italy A. Cianchi Università di Roma II Tor Vergata, Roma, Italy C. Ronsivalle ENEA C.R. Frascati, Frascati (Roma), Italy
	SPARC in Frascati is a high brightness photo-injector used to explore advanced beam manipulation techniques. Sub-picosecond, high brightness electron bunch trains (the so called comb beam) can be generated illuminating the cathode of a RF photoinjector with a laser pulse train and via velocity bunching technique. In this paper different aspects of the physics of this advanced beam manipulation technique are discussed combining simulation and measurements. Beam dynamics numerical macroparticle simulations have been compared with the experimental results for model validation; they allow to gain insights on the beam evolution highlighting several aspects which can not be measured. In particular, we focus on the train evolution in the linac sections and in the dog-leg line up to the THz station and on the effective rms length of the single pulses within the train when it becomes shorter than the resolution.

TUPPP026	RF Rescue Option for TPS Linac	electron, linac, booster, injection	1668
	K.L. Tsai, H.-P. Chang, C.-T. Chen, C.-S. Fann, K.T. Hsu, S.Y. Hsu, K.-K. Lin, H.M. Shih NSRRC, Hsinchu, Taiwan K. Dunkel, C. Piel RI Research Instruments GmbH, Bergisch Gladbach, Germany
	The 150 MeV linac of Taiwan Photon Source was commissioned in June 2011. It consists of 90 keV electron source, bunching system and three S-band accelerating sections driven by three high-power klystrons. The rf system is equipped with rescue option such that the rf power from second klystron can be split and fed into both accelerating section 1 and 2. The rescue operation will be needed in the event of a failure occurred at the first klystron. In the report, the rescue capability will be illustrated and the test results will also be discussed.

TUPPP031	Modelling the Steady-state CSR Emission in Low Alpha Mode at the Diamond Storage Ring	wakefield, electron, impedance, factory	1677
	I.P.S. Martin, C.A. Thomas Diamond, Oxfordshire, United Kingdom R. Bartolini JAI, Oxford, United Kingdom
	The CSR emitted by short electron bunches can be of a stable or bursting nature, with transition between the two states characterised by a threshold current that depends on various machine parameters. Key to understanding this process is to develop an effective model that describes the way the electron bunch interacts with impedance sources such as the CSR wakefield and surrounding vacuum chamber. In this paper we present the latest results of modelling the equilibrium distribution calculated using the Haissinski equation driven by different impedance models. The bunch lengthening with current, bunch profiles and CSR form factors derived from this model are compared to measured data for both positive and negative momentum compaction factor. Comparisons of the measured bursting thresholds to theoretical predictions are also discussed.

TUPPP050	FEL Performances of the French LUNEX5 Project	FEL, laser, electron, undulator	1712
	C. Evain, S. Bielawski PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France C. Benabderrahmane, M.-E. Couprie, C. Evain, M. Labat, A. Loulergue SOLEIL, Gif-sur-Yvette, France G. Lambert, A. Lifschitz, V. Malka LOA, Palaiseau, France
	LUNEX5 is a french FEL test facility project based on two types of accelerators: a 400 MeV Conventional Linear Accelerator (CLA) and a Laser WakeField Accelerator (LWFA). The FEL performances will be presented at 20 nm and at 12 nm, wavelengths of interest for the pilot experiments. Results are obtained with GENESIS simulations in time-dependent mode. With the CLA, we compare different seeded schemes as EEHG scheme (Echo Enabled Harmonic Generation) or HGHG scheme (High Gain Harmonic Generation) using HHG source (High Harmonic in Gaz). In parallel, LWFA FEL performances will be presented as a function of the electron bunch characteristics, in particular the bunch length and the energy-spread. The transport of the LWFA output beams into undulators which is found to be a critical issue will be also discussed.

WEOBB01	Measurement of the Local Energy Spread of Electron Beam at SDUV-FEL	laser, electron, FEL, radiation	2143
	C. Feng, J.H. Chen, H.X. Deng, T. Lan, B. Liu, D. Wang, X. Wang, M. Zhang, T. Zhang, Z.T. Zhao SINAP, Shanghai, People's Republic of China
	The slice energy spread of electron beam is a very important parameter for high gain free electron lasers (FELs) especially the seeded FELs. Because of its extremely small value, highly accurate measurement of the slice energy spread is rather challenging. In this paper, we propose a novel method to accurately measure the slice energy spread based on the coherent harmonic generation (CHG) scheme. This method has been demonstrated on the Shanghai deep ultraviolent FEL (SDUV-FEL), and the results show that the slice energy spread is about only 1.2keV at the exit of the 136MeV linac when the bunch compressor is off, and this value change to about 2.6keV when the bunch compressor is on. * Chao Feng, et al, Phys. Rev. ST Accel. Beams 14, 090701 (2011)
	Slides WEOBB01 [3.309 MB]

THPPP080	Beam Halo Reduction in the J-PARC 3-GeV RCS	emittance, injection, extraction, linac	3918
	H. Hotchi, H. Harada, P.K. Saha, Y. Shobuda, F. Tamura, K. Yamamoto, M. Yamamoto, M. Yoshimoto JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan Y. Irie, T. Koseki, Y. Sato, M.J. Shirakata KEK, Ibaraki, Japan K. Satou J-PARC, KEK & JAEA, Ibaraki-ken, Japan
	The J-PARC RCS (3-GeV rapid cycling synchrotron) has two functions as a proton driver to the MLF (Materials and life science facility) and an injector to the MR (50-GeV main ring synchrotron). One of important issues in the current RCS bam tuning is to suppress the beam halo formation, which is essential especially to reduce the beam loss at the MR. In this paper, we present beam study results on the formation mechanism and reduction of the beam halo in the RCS.

Paper

Title

Other Keywords

Page

MOPPD028

Observation of Longitudinal Space Charge Effects in the Injection Beam Line of NIRS-930 Cyclotron

cyclotron, space-charge, injection, simulation

427

S. Hojo, A. Goto, T. Honma, K. Katagiri, A. Sugiura
NIRS, Chiba-shi, Japan

Dependence of bunching efficiencies on the position of a beam buncher was measured for the AVF cyclotron at the National Institute of Radiological Sciences (NIRS) for 30 MeV proton beams with intensities up to 100 microamperes at injection. The measurement was carried out for two positions: 1.53 m and 2.33 m upstream from the inflector. For the buncher position of 2.33 m the bunching efficiency decreased, as the beam intensity increased, to about half of that at low intensities, while for 1.5 m it was constant up to 100 microamperes. The intensity distributions of extracted beam with respect to the buncher phase were also measured for the two buncher positions. The dependence of bunch width on the beam intensity is discussed by comparing the data with one-dimensional simulations on longitudinal space charge effects.

MOPPD038

Simulation Study of Electron Response Amplification in Coherent Electron Cooling

electron, ion, FEL, undulator

448

Y. Hao, V. Litvinenko
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In Coherent Electron Cooling (CEC), it is essential to study the amplification of electron response to a single ion in the FEL process, in order to proper align the electron beam and the ion beam in the kicker to maximize the cooling effect. In this paper, we use Genesis to simulate the amplified electron beam response of single ion in FEL amplification process, which acts as 'Green function' of the FEL amplifier.

MOPPP012

Experimental Observation of Energy Modulation in Electron Beams Passing through Terahertz Dielectric Wakefield Structures

wakefield, radiation, FEL, acceleration

595

S.P. Antipov, C.-J. Jing, A. Kanareykin, P. Schoessow
Euclid TechLabs, LLC, Solon, Ohio, USA
M.G. Fedurin, K. Kusche, V. Yakimenko
BNL, Upton, Long Island, New York, USA
W. Gai, A. Zholents
ANL, Argonne, USA
B.C. Jiang
SINAP, Shanghai, People's Republic of China

Funding: DOE SBIR.
We report observation of a strong wakefield induced energy modulation in an energy-chirped electron bunch passing through a terahertz dielectric-lined waveguide. This modulation can be effectively converted into a spatial modulation by means of a chicane, forming micro-bunches (density modulation) with a periodicity of 0.5 - 1 picosecond, hence capable of driving coherent THz radiation. The experimental results agree well with theoretical predictions.

TUEPPB004

A Longitudinal Beam Dynamics Code for Proton Synchrotron

cavity, simulation, space-charge, synchrotron

1119

Y.S. Yuan, N. Wang, S. Wang, S.Y. Xu
IHEP, Beijing, People's Republic of China

The accelerator of China Spallation Neutron Source (CSNS) consists of an 80 MeV linac and a 1.6 GeV Rapid Cycling Synchrotron (RCS). Longitudinal beam dynamics study is one of the most important issues for RCS beam dynamics design. However, the existing codes cannot meet the requirement of longitudinal beam dynamics for CSNS/RCS. A new code has been developed for longitudinal beam dynamics design and simulation. The code can perform the voltage and phase curves design for non-sinusoidal magnetic field of dipole in an RCS cycle, with the fundamental RF mode and dual harmonic mode. The code can also be used for the beam simulation with longitudinal space charge effect, including the effects of higher order mode of RF cavities. By using the code, the longitudinal beam dynamics of CSNS/RCS was designed and optimized, and the simulation study with dual harmonics higher order modes of RF cavity was done, and the simulation results are presented.

TUEPPB010

Oscillator Seeding of a High Gain Harmonic Generation FEL in a Radiator-first Configuration

FEL, electron, radiation, laser

1137

P.R. Gandhi, J.S. Wurtele
UCB, Berkeley, California, USA
G. Penn, M.W. Reinsch
LBNL, Berkeley, California, USA

A longitudinally coherent X-ray pulse from a high repetition rate free electron laser (FEL) is desired for a wide variety of experimental applications. However, generating such a pulse with a repetition rate greater than ~1 MHz is a significant challenge. The desired high rep rate sources, primarily high harmonic generation with intense lasers in gases or plasmas, do not exist now, and, for the multi-MHz bunch trains that superconducting accelerators can potentially produce, are likely not feasible with current technology. In this paper, we propose to place an oscillator downstream of a radiator. The oscillator generates radiation that is used as a seed for a high gain harmonic generation (HGHG) FEL which is upstream of the oscillator. For the first few pulses the oscillator builds up power and, until power is built up, the radiator has no HGHG seed. As power in the oscillator saturates, the HGHG is seeded and power is produced. The dynamics and stability of this radiator-first scheme is explored analytically and numerically. A single-pass map is derived using a semi-analytic model for FEL gain and saturation. Iteration of the map is shown to be in good agreement with simulations.

TUEPPB011

Echo Enabled High Mode Generation for X-ray FELs

laser, electron, FEL, free-electron-laser

1140

E. Hemsing
SLAC, Menlo Park, California, USA
A. Marinelli
UCLA, Los Angeles, California, USA

Funding: Work supported by U.S. DOE under Contract Nos. DE-AC02-76SF00515 and DE-FG02-07ER46272.
We describe a simple technique based on a modified echo-enabled harmonic generation (EEHG) scheme to manipulate the three-dimensional electron beam microbunching distribution in order to generate higher-order optical modes in an FEL. As with EEHG, the concept uses two modulators and two chicanes to produce microbunching. However, in one of the modulators, the resonant interaction with the laser has a well-defined transverse structure that becomes strongly correlated to the longitudinal microbunching distribution. Both high-harmonic frequencies and high transverse mode numbers can be generated through a transversely-dependent echo effect.

TUEPPB015

Generation of Narrow-Band Coherent Tunable Terahertz Radiation using a Laser-Modulated Electron Beam

laser, electron, radiation, undulator

1146

M.P. Dunning, C. Hast, E. Hemsing, R.K. Jobe, D.J. McCormick, J. Nelson, T.O. Raubenheimer, K. Soong, Z.M. Szalata, D.R. Walz, S.P. Weathersby, D. Xiang
SLAC, Menlo Park, California, USA

Funding: Work supported by US DOE contract DE-AC02-76SF00515.
The technical layout and initial results of an experiment to generate narrow-band, coherent, tunable terahertz (THz) radiation through the down-conversion of the frequency of optical lasers using a laser-modulated electron beam are described. In this experiment a 120 MeV electron beam is first energy modulated by two lasers with different wavelengths. After passing through a dispersive section, the energy modulation is converted into a density modulation at THz frequencies. This density-modulated beam will be used to generate narrow-band THz radiation using a coherent transition radiator inserted into the beam path. The central frequency of the THz radiation can be tuned by varying the wavelength of one of the two lasers or the energy chirp of the electron beam. The experiment is being performed at the NLCTA at SLAC, and will utilize the existing Echo-7 beamline, where echo-enabled harmonic generation (EEHG) was recently demonstrated.

TUPPC026

Design of Compact C-Band Standing-Wave Accelerating Structure Enhancing RF Phase Focusing

coupling, cavity, focusing, simulation

1221

H.R. Yang, M.-H. Cho, J. Jang, S.H. Kim, W. Namkung, S.J. Park
POSTECH, Pohang, Kyungbuk, Republic of Korea
J.-S. Oh
NFRI, Daejon, Republic of Korea

Funding: Work supported by POSTECH Physics BK21 Program.
We design a C-band standing-wave accelerating structure for an X-ray source of the imaging and medical applications. It is capable of producing 6-MeV, 100-mA pulsed electron beams which is focused by less than 1.5 mm without external magnets. As an RF source, we use peak 1.5-MW magnetron with duty factor of 0.08%. The accelerating structure is a bi-periodic and on-axis-coupled structure with a built-in bunching section, which consists 3 bunching cells, 13 normal cells and a coupler cell. It operated with π/2-mode standing-waves. The bunching section is designed to enhance the RF phase focusing in order to achieve 1.2-mm beam spot size. Each cavity is designed with the MWS code to maximize the effective shunt impedance within 3.5% inter-cell coupling. In this paper, we present design details of RF cavities and the beam dynamics simulation by the PARMELA code.

TUPPD055

Characterization of ps-spaced Comb Beams at SPARC

simulation, linac, radiation, laser

1527

A. Mostacci
URLS, Rome, Italy
A. Bacci, A.R. Rossi
Istituto Nazionale di Fisica Nucleare, Milano, Italy
M. Bellaveglia, E. Chiadroni, G. Di Pirro, M. Ferrario, G. Gatti, C. Vaccarezza
INFN/LNF, Frascati (Roma), Italy
A. Cianchi
Università di Roma II Tor Vergata, Roma, Italy
C. Ronsivalle
ENEA C.R. Frascati, Frascati (Roma), Italy

SPARC in Frascati is a high brightness photo-injector used to explore advanced beam manipulation techniques. Sub-picosecond, high brightness electron bunch trains (the so called comb beam) can be generated illuminating the cathode of a RF photoinjector with a laser pulse train and via velocity bunching technique. In this paper different aspects of the physics of this advanced beam manipulation technique are discussed combining simulation and measurements. Beam dynamics numerical macroparticle simulations have been compared with the experimental results for model validation; they allow to gain insights on the beam evolution highlighting several aspects which can not be measured. In particular, we focus on the train evolution in the linac sections and in the dog-leg line up to the THz station and on the effective rms length of the single pulses within the train when it becomes shorter than the resolution.

TUPPP026

RF Rescue Option for TPS Linac

electron, linac, booster, injection

1668

K.L. Tsai, H.-P. Chang, C.-T. Chen, C.-S. Fann, K.T. Hsu, S.Y. Hsu, K.-K. Lin, H.M. Shih
NSRRC, Hsinchu, Taiwan
K. Dunkel, C. Piel
RI Research Instruments GmbH, Bergisch Gladbach, Germany

The 150 MeV linac of Taiwan Photon Source was commissioned in June 2011. It consists of 90 keV electron source, bunching system and three S-band accelerating sections driven by three high-power klystrons. The rf system is equipped with rescue option such that the rf power from second klystron can be split and fed into both accelerating section 1 and 2. The rescue operation will be needed in the event of a failure occurred at the first klystron. In the report, the rescue capability will be illustrated and the test results will also be discussed.

TUPPP031

Modelling the Steady-state CSR Emission in Low Alpha Mode at the Diamond Storage Ring

wakefield, electron, impedance, factory

1677

I.P.S. Martin, C.A. Thomas
Diamond, Oxfordshire, United Kingdom
R. Bartolini
JAI, Oxford, United Kingdom

The CSR emitted by short electron bunches can be of a stable or bursting nature, with transition between the two states characterised by a threshold current that depends on various machine parameters. Key to understanding this process is to develop an effective model that describes the way the electron bunch interacts with impedance sources such as the CSR wakefield and surrounding vacuum chamber. In this paper we present the latest results of modelling the equilibrium distribution calculated using the Haissinski equation driven by different impedance models. The bunch lengthening with current, bunch profiles and CSR form factors derived from this model are compared to measured data for both positive and negative momentum compaction factor. Comparisons of the measured bursting thresholds to theoretical predictions are also discussed.

TUPPP050

FEL Performances of the French LUNEX5 Project

FEL, laser, electron, undulator

1712

C. Evain, S. Bielawski
PhLAM/CERCLA, Villeneuve d'Ascq Cedex, France
C. Benabderrahmane, M.-E. Couprie, C. Evain, M. Labat, A. Loulergue
SOLEIL, Gif-sur-Yvette, France
G. Lambert, A. Lifschitz, V. Malka
LOA, Palaiseau, France

LUNEX5 is a french FEL test facility project based on two types of accelerators: a 400 MeV Conventional Linear Accelerator (CLA) and a Laser WakeField Accelerator (LWFA). The FEL performances will be presented at 20 nm and at 12 nm, wavelengths of interest for the pilot experiments. Results are obtained with GENESIS simulations in time-dependent mode. With the CLA, we compare different seeded schemes as EEHG scheme (Echo Enabled Harmonic Generation) or HGHG scheme (High Gain Harmonic Generation) using HHG source (High Harmonic in Gaz). In parallel, LWFA FEL performances will be presented as a function of the electron bunch characteristics, in particular the bunch length and the energy-spread. The transport of the LWFA output beams into undulators which is found to be a critical issue will be also discussed.

WEOBB01

Measurement of the Local Energy Spread of Electron Beam at SDUV-FEL

laser, electron, FEL, radiation

2143

C. Feng, J.H. Chen, H.X. Deng, T. Lan, B. Liu, D. Wang, X. Wang, M. Zhang, T. Zhang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China

The slice energy spread of electron beam is a very important parameter for high gain free electron lasers (FELs) especially the seeded FELs. Because of its extremely small value, highly accurate measurement of the slice energy spread is rather challenging. In this paper, we propose a novel method to accurately measure the slice energy spread based on the coherent harmonic generation (CHG) scheme. This method has been demonstrated on the Shanghai deep ultraviolent FEL (SDUV-FEL), and the results show that the slice energy spread is about only 1.2keV at the exit of the 136MeV linac when the bunch compressor is off, and this value change to about 2.6keV when the bunch compressor is on.
* Chao Feng, et al, Phys. Rev. ST Accel. Beams 14, 090701 (2011)

Slides WEOBB01 [3.309 MB]

THPPP080

Beam Halo Reduction in the J-PARC 3-GeV RCS

emittance, injection, extraction, linac

3918

H. Hotchi, H. Harada, P.K. Saha, Y. Shobuda, F. Tamura, K. Yamamoto, M. Yamamoto, M. Yoshimoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
Y. Irie, T. Koseki, Y. Sato, M.J. Shirakata
KEK, Ibaraki, Japan
K. Satou
J-PARC, KEK & JAEA, Ibaraki-ken, Japan

The J-PARC RCS (3-GeV rapid cycling synchrotron) has two functions as a proton driver to the MLF (Materials and life science facility) and an injector to the MR (50-GeV main ring synchrotron). One of important issues in the current RCS bam tuning is to suppress the beam halo formation, which is essential especially to reduce the beam loss at the MR. In this paper, we present beam study results on the formation mechanism and reduction of the beam halo in the RCS.