FEL2014 - List of Authors (Hwang, C.-S.)

Paper	Title	Page
MOP045	Phase Shifter Design for iSASE	123
	S.D. Chen, K. Fang, H.-D. Nuhn, C. Pellegrini, J. Wu, L. Zhu SLAC, Menlo Park, California, USA S.D. Chen, C.-S. Hwang NCTU, Hsinchu, Taiwan K. Fang Indiana University, Bloomington, Indiana, USA C.-S. Hwang NSRRC, Hsinchu, Taiwan
	A phase shifter to generate an additional phase advance of the spontaneous light versus the electron beam was de- signed for the iSASE scheme. The iSASE mechanism is for reducing the bandwidth further from SASE FEL process. A large phase advance about 1600*2Pi as the FEL operating at wavelength 0.8 nm was needed according to the simulation of iSASE process. Since the iSASE is thought to implement into LCLS II project, the space limitation causing by LCLS II should be considered when designing the phase shifter. An optimized three-pole electric phase shifter with 7.3 mm gap has the center field of 1.8 T . The vanadium steel was considered as pole material and the magnet physical length is 260 mm, meanwhile the water-cooling type copper coil was adopted. The temperature increment, force analysis, low field operation mode concept, and preliminary tolerance study were discussed.

TUP028	Mode Contents Analysis of a Tapered Free Electron Laser	437
	S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA S.D. Chen, C.-S. Hwang NCTU, Hsinchu, Taiwan C. Emma, C. Pellegrini UCLA, Los Angeles, California, USA K. Fang, S.-Y. Lee Indiana University, Bloomington, Indiana, USA C.-S. Hwang NSRRC, Hsinchu, Taiwan S. Serkez DESY, Hamburg, Germany
	For the ultimate use for the scientific experiments, the free electron laser (FEL) will propagate for long distance, much longer than the Rayleigh range, after exiting the undu- lator. To characterize the FEL for this purpose, we study the electromagnetic field mode components of the FEL photon beam. With the mode decomposition, the transverse coher- ence can be analyzed all along. The FEL here in this paper is a highly tapered one evolving through the exponential growth and then the post-saturation taper. Modes contents are analyzed for electron bunch with three different types of transverse distribution: flattop, Gaussian, and parabolic. The tapered FEL simulation is performed with Genesis code. The FEL photon beam transverse electric field is decom- posed with Gaussian-Laguerre polynomials. The evolutions of spot size, source location, and the portion of the power in the fundamental mode are discussed here. The approach can be applicable to various kind scheme of FEL.

TUP028	Mode Contents Analysis of a Tapered Free Electron Laser	437
	S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA S.D. Chen, C.-S. Hwang NCTU, Hsinchu, Taiwan C. Emma, C. Pellegrini UCLA, Los Angeles, California, USA K. Fang, S.-Y. Lee Indiana University, Bloomington, Indiana, USA C.-S. Hwang NSRRC, Hsinchu, Taiwan S. Serkez DESY, Hamburg, Germany
	For the ultimate use for the scientific experiments, the free electron laser (FEL) will propagate for long distance, much longer than the Rayleigh range, after exiting the undu- lator. To characterize the FEL for this purpose, we study the electromagnetic field mode components of the FEL photon beam. With the mode decomposition, the transverse coher- ence can be analyzed all along. The FEL here in this paper is a highly tapered one evolving through the exponential growth and then the post-saturation taper. Modes contents are analyzed for electron bunch with three different types of transverse distribution: flattop, Gaussian, and parabolic. The tapered FEL simulation is performed with Genesis code. The FEL photon beam transverse electric field is decom- posed with Gaussian-Laguerre polynomials. The evolutions of spot size, source location, and the portion of the power in the fundamental mode are discussed here. The approach can be applicable to various kind scheme of FEL.

TUP030	Mode Component Evolution and Coherence Analysis in Terawatt Tapered FEL	446
	K. Fang, S.D. Chen, X. Huang, C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA S.D. Chen NCTU, Hsinchu, Taiwan C. Emma, C. Pellegrini UCLA, Los Angeles, California, USA K. Fang Indiana University, Bloomington, Indiana, USA C.-S. Hwang NSRRC, Hsinchu, Taiwan S. Serkez DESY, Hamburg, Germany
	A fast and robust algorithm is developed to decompose FEL radiation field transverse distribution into a set of orthonormal basis. Laguerre Gaussian and Hermite Gaussian can be used in the analysis. The information of mode components strength and Gaussian beam parameters allows users in downstream better utilize FEL. With this method, physics of mode components evolution from starting stage, to linear regime and post saturation are studied with detail. With these decomposed modes, correlation function can be computed with less complexity. Eigenmodes of the FEL system can be solved using this method.

Paper

Title

Page

Phase Shifter Design for iSASE

123

S.D. Chen, K. Fang, H.-D. Nuhn, C. Pellegrini, J. Wu, L. Zhu
SLAC, Menlo Park, California, USA
S.D. Chen, C.-S. Hwang
NCTU, Hsinchu, Taiwan
K. Fang
Indiana University, Bloomington, Indiana, USA
C.-S. Hwang
NSRRC, Hsinchu, Taiwan

A phase shifter to generate an additional phase advance of the spontaneous light versus the electron beam was de- signed for the iSASE scheme. The iSASE mechanism is for reducing the bandwidth further from SASE FEL process. A large phase advance about 1600*2Pi as the FEL operating at wavelength 0.8 nm was needed according to the simulation of iSASE process. Since the iSASE is thought to implement into LCLS II project, the space limitation causing by LCLS II should be considered when designing the phase shifter. An optimized three-pole electric phase shifter with 7.3 mm gap has the center field of 1.8 T . The vanadium steel was considered as pole material and the magnet physical length is 260 mm, meanwhile the water-cooling type copper coil was adopted. The temperature increment, force analysis, low field operation mode concept, and preliminary tolerance study were discussed.

TUP028

Mode Contents Analysis of a Tapered Free Electron Laser

437

S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA
S.D. Chen, C.-S. Hwang
NCTU, Hsinchu, Taiwan
C. Emma, C. Pellegrini
UCLA, Los Angeles, California, USA
K. Fang, S.-Y. Lee
Indiana University, Bloomington, Indiana, USA
C.-S. Hwang
NSRRC, Hsinchu, Taiwan
S. Serkez
DESY, Hamburg, Germany

For the ultimate use for the scientific experiments, the free electron laser (FEL) will propagate for long distance, much longer than the Rayleigh range, after exiting the undu- lator. To characterize the FEL for this purpose, we study the electromagnetic field mode components of the FEL photon beam. With the mode decomposition, the transverse coher- ence can be analyzed all along. The FEL here in this paper is a highly tapered one evolving through the exponential growth and then the post-saturation taper. Modes contents are analyzed for electron bunch with three different types of transverse distribution: flattop, Gaussian, and parabolic. The tapered FEL simulation is performed with Genesis code. The FEL photon beam transverse electric field is decom- posed with Gaussian-Laguerre polynomials. The evolutions of spot size, source location, and the portion of the power in the fundamental mode are discussed here. The approach can be applicable to various kind scheme of FEL.

TUP028

Mode Contents Analysis of a Tapered Free Electron Laser

437

S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA
S.D. Chen, C.-S. Hwang
NCTU, Hsinchu, Taiwan
C. Emma, C. Pellegrini
UCLA, Los Angeles, California, USA
K. Fang, S.-Y. Lee
Indiana University, Bloomington, Indiana, USA
C.-S. Hwang
NSRRC, Hsinchu, Taiwan
S. Serkez
DESY, Hamburg, Germany

For the ultimate use for the scientific experiments, the free electron laser (FEL) will propagate for long distance, much longer than the Rayleigh range, after exiting the undu- lator. To characterize the FEL for this purpose, we study the electromagnetic field mode components of the FEL photon beam. With the mode decomposition, the transverse coher- ence can be analyzed all along. The FEL here in this paper is a highly tapered one evolving through the exponential growth and then the post-saturation taper. Modes contents are analyzed for electron bunch with three different types of transverse distribution: flattop, Gaussian, and parabolic. The tapered FEL simulation is performed with Genesis code. The FEL photon beam transverse electric field is decom- posed with Gaussian-Laguerre polynomials. The evolutions of spot size, source location, and the portion of the power in the fundamental mode are discussed here. The approach can be applicable to various kind scheme of FEL.

TUP030

Mode Component Evolution and Coherence Analysis in Terawatt Tapered FEL

446

K. Fang, S.D. Chen, X. Huang, C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA
S.D. Chen
NCTU, Hsinchu, Taiwan
C. Emma, C. Pellegrini
UCLA, Los Angeles, California, USA
K. Fang
Indiana University, Bloomington, Indiana, USA
C.-S. Hwang
NSRRC, Hsinchu, Taiwan
S. Serkez
DESY, Hamburg, Germany

A fast and robust algorithm is developed to decompose FEL radiation field transverse distribution into a set of orthonormal basis. Laguerre Gaussian and Hermite Gaussian can be used in the analysis. The information of mode components strength and Gaussian beam parameters allows users in downstream better utilize FEL. With this method, physics of mode components evolution from starting stage, to linear regime and post saturation are studied with detail. With these decomposed modes, correlation function can be computed with less complexity. Eigenmodes of the FEL system can be solved using this method.