FEL2014 - List of Keywords (space-charge)

Paper	Title	Other Keywords	Page
THP008	Evolution of a Warm Bunched Electron Beam in a Free Drift Region	electron, plasma, FEL, bunching	692
	B. Maly, A. Friedman Ariel University, Ariel, Israel
	The state of the art of FELs development at present is "Table-Top X Ray Free Electron Lasers". Almost any such scheme involves a pre-bunched electron beam. In this paper we will analyze the evolution and "survivability" of bunching introduced into the beam in the free drift region prior to the wiggler. We examined analytically the first order degradation in beam bunching due to space charge effect. It will be shown that there is a limited interaction region, characterized by an exponential decay of the bunching factor, having a length inversely proportional to the square of the electron beam normalized temperature, followed by a stable bunch region. We will present examples of the effect for several schemes of X Ray and Tera Hertz FELs considered or being constructed presently.

THP019	Higher-Order Moment Models of Longitudinal Pulse Shape Evolution in Photoinjectors	wakefield, FEL, cavity, electron	722
	C.E. Mitchell, D. Filippetto, R. Huang, C. F. Papadopoulos, H.J. Qian, J. Qiang, F. Sannibale, M. Venturini LBNL, Berkeley, California, USA
	The presence of longitudinal asymmetry, sometimes in the form of a one-sided tail, in the current profile emerging from low-energy photoinjectors can strongly impact the beam quality downstream of the compression system of the FEL beam delivery system. To understand the origin of this feature, an approximate model for the evolution of higher-order beam moments is developed in the presence of nonlinear kinematic effects and longitudinal space-charge. This model is applied to investigate the evolution of beam skewness for injector systems with parameters similar to the APEX Injector under investigation at Lawrence Berkeley National Laboratory.

THP032	Effects of Potential Energy Spread on Particle Dynamics in Magnetic Bending Systems	transverse-dynamics, optics, electron, simulation	779
	R. Li JLab, Newport News, Virginia, USA
	Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Understanding CSR effects for the generation and transport of high brightness electron beams is crucial for designs of modern FELs. Most studies of CSR effects focus on the impacts of the longitudinal CSR wakefield. In this study, we investigate the impact of the initial retarded potential energy of particles, due to bunch collective interaction, on the transverse dynamics of particles on a curved orbit. It is shown that as part of the remnants of the CSR cancellation effect when both the longitudinal and transverse CSR fores are taken into account, this initial potential energy at the entrance of a bending system acts as a pseudo kinetic energy, or pseudo energy in short, because its effect on particle optics through dispersion and momentum compaction is indistinguishable from effect of the usual kinetic energy offset from the design energy. Our estimation indicates that the resulting effect of pseudo energy spread can be measurable only when the peak current of the bunch is high enough such that the slice pseudo energy spread is appreciable compared to the slice kinetic energy spread. The implication of this study on simulations and experiments of CSR effects will be discussed.

THP035	Relativistic Effects in Micro-bunching	bunching, electron, plasma, dipole	790
	V. Litvinenko Stony Brook University, Stony Brook, USA G. Wang BNL, Upton, Long Island, New York, USA
	In this paper we present our theoretical studies of limits on bunching using magnetic systems. We discuss the connection of this limit with plasma oscillations in electron beams and present simple formulae for an additional limit of micro-bunching amplification.

THP036	Benchmark and Simulation Design of a Low Energy Bunch Compressor	gun, simulation, electron, focusing	795
	A. He, F.J. Willeke, L. Yang, L.-H. Yu BNL, Upton, Long Island, New York, USA J. Qiang LBNL, Berkeley, California, USA
	In the electron beam slicing method, a low energy bunch with very short and focused beam size is required to interact with the storage ring bunch. We have designed a low energy bunch compressor with BNL photocathode electron RF-gun by applying simulation code PARMELA. In this paper, in order to increase the repetition rate of the electron beam slicing system, we change the compressor’s RF gun from BNL RF-gun to LBNL’s VHF gun and redesign the compressor by applying IMPACT-T with both space charge effects and CSR effects considered. The benchmark between PARMELA and IMPACT-T has produced excellent agreement. The comparison of the CSR effects also shows the bunch can be compressed and focused to our desired size after optimization using code IMPACT-T with CSR effects turned on. The new compressor with high repetition rate still works in space charge dominated domain and the bunch with a negative energy chirp at the entrance of the chicane is compressed by a chicane with positive R56. After the optimization, we have achieved a low energy bunch with the 128 fs RMS bunch length, 42 μm and 25 μm RMS beam size in the vertical and horizontal directions respectively, at 22 MeV with 200 pC charge.

Paper

Title

Other Keywords

Page

THP008

Evolution of a Warm Bunched Electron Beam in a Free Drift Region

electron, plasma, FEL, bunching

692

B. Maly, A. Friedman
Ariel University, Ariel, Israel

The state of the art of FELs development at present is "Table-Top X Ray Free Electron Lasers". Almost any such scheme involves a pre-bunched electron beam. In this paper we will analyze the evolution and "survivability" of bunching introduced into the beam in the free drift region prior to the wiggler. We examined analytically the first order degradation in beam bunching due to space charge effect. It will be shown that there is a limited interaction region, characterized by an exponential decay of the bunching factor, having a length inversely proportional to the square of the electron beam normalized temperature, followed by a stable bunch region. We will present examples of the effect for several schemes of X Ray and Tera Hertz FELs considered or being constructed presently.

THP019

Higher-Order Moment Models of Longitudinal Pulse Shape Evolution in Photoinjectors

wakefield, FEL, cavity, electron

722

C.E. Mitchell, D. Filippetto, R. Huang, C. F. Papadopoulos, H.J. Qian, J. Qiang, F. Sannibale, M. Venturini
LBNL, Berkeley, California, USA

The presence of longitudinal asymmetry, sometimes in the form of a one-sided tail, in the current profile emerging from low-energy photoinjectors can strongly impact the beam quality downstream of the compression system of the FEL beam delivery system. To understand the origin of this feature, an approximate model for the evolution of higher-order beam moments is developed in the presence of nonlinear kinematic effects and longitudinal space-charge. This model is applied to investigate the evolution of beam skewness for injector systems with parameters similar to the APEX Injector under investigation at Lawrence Berkeley National Laboratory.

THP032

Effects of Potential Energy Spread on Particle Dynamics in Magnetic Bending Systems

transverse-dynamics, optics, electron, simulation

779

R. Li
JLab, Newport News, Virginia, USA

Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Understanding CSR effects for the generation and transport of high brightness electron beams is crucial for designs of modern FELs. Most studies of CSR effects focus on the impacts of the longitudinal CSR wakefield. In this study, we investigate the impact of the initial retarded potential energy of particles, due to bunch collective interaction, on the transverse dynamics of particles on a curved orbit. It is shown that as part of the remnants of the CSR cancellation effect when both the longitudinal and transverse CSR fores are taken into account, this initial potential energy at the entrance of a bending system acts as a pseudo kinetic energy, or pseudo energy in short, because its effect on particle optics through dispersion and momentum compaction is indistinguishable from effect of the usual kinetic energy offset from the design energy. Our estimation indicates that the resulting effect of pseudo energy spread can be measurable only when the peak current of the bunch is high enough such that the slice pseudo energy spread is appreciable compared to the slice kinetic energy spread. The implication of this study on simulations and experiments of CSR effects will be discussed.

THP035

Relativistic Effects in Micro-bunching

bunching, electron, plasma, dipole

790

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

In this paper we present our theoretical studies of limits on bunching using magnetic systems. We discuss the connection of this limit with plasma oscillations in electron beams and present simple formulae for an additional limit of micro-bunching amplification.

THP036

Benchmark and Simulation Design of a Low Energy Bunch Compressor

gun, simulation, electron, focusing

795

A. He, F.J. Willeke, L. Yang, L.-H. Yu
BNL, Upton, Long Island, New York, USA
J. Qiang
LBNL, Berkeley, California, USA

In the electron beam slicing method, a low energy bunch with very short and focused beam size is required to interact with the storage ring bunch. We have designed a low energy bunch compressor with BNL photocathode electron RF-gun by applying simulation code PARMELA. In this paper, in order to increase the repetition rate of the electron beam slicing system, we change the compressor’s RF gun from BNL RF-gun to LBNL’s VHF gun and redesign the compressor by applying IMPACT-T with both space charge effects and CSR effects considered. The benchmark between PARMELA and IMPACT-T has produced excellent agreement. The comparison of the CSR effects also shows the bunch can be compressed and focused to our desired size after optimization using code IMPACT-T with CSR effects turned on. The new compressor with high repetition rate still works in space charge dominated domain and the bunch with a negative energy chirp at the entrance of the chicane is compressed by a chicane with positive R56. After the optimization, we have achieved a low energy bunch with the 128 fs RMS bunch length, 42 μm and 25 μm RMS beam size in the vertical and horizontal directions respectively, at 22 MeV with 200 pC charge.