FEL2014 - List of Authors (Fang, K.)

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.

TUP029

iSASE Study

442

K. Fang
Indiana University, Bloomington, Indiana, USA
S.D. Chen
NCTU, Hsinchu, Taiwan
S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA
C. Emma, C. Pellegrini
UCLA, Los Angeles, California, USA
S. Reiche
PSI, Villigen PSI, Switzerland

Improved Self Amplified Spontaneous Emission (iSASE) is a scheme that reduces FEL bandwidth by increasing phase slippage between the electron bunch and radiation field. This is achieved by repeatedly delaying electrons using phase shifters between undulator sections. Genesis code is modified to facilitate this simulation. With this simulation code, the iSASE bandwidth reduction mechanism is studied in detail. A Temporal correlation function is introduced to describe the similarity between the new grown field from bunching factor and the amplified shifted field. This correlation function indicates the efficiency of iSASE process.

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.

MOC03

Radiation Properties of Tapered Hard X-ray Free Electron Lasers

300

C. Emma, C. Pellegrini
UCLA, Los Angeles, California, USA
S.D. Chen
NCTU, Hsinchu, Taiwan
K. Fang, C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA
S. Serkez
DESY, Hamburg, Germany

We perform an analysis of the transverse coherence of the radiation from a TW level tapered hard X-ray Free Electron Laser (FEL). The radiation properties of the FEL are studied for a Gaussian, parabolic and uniform transverse electron beam density profile in a 200-m undulator at a resonant wavelength of 1.5 Angstrom. Simulations performed using the 3-D FEL particle code GENESIS show that diffraction of the radiation occurs due to a reduction in optical guiding in the tapered section of the undulator. This results in an increasing transverse coherence for all three transverse electron beam profiles. We determine that for each case considered the radiation coherence area is much larger than the electron beam spot size, making X-ray diffraction experiments possible for TW X-ray FELs.

Slides MOC03 [3.797 MB]

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.

TUP029

iSASE Study

442

K. Fang
Indiana University, Bloomington, Indiana, USA
S.D. Chen
NCTU, Hsinchu, Taiwan
S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu
SLAC, Menlo Park, California, USA
C. Emma, C. Pellegrini
UCLA, Los Angeles, California, USA
S. Reiche
PSI, Villigen PSI, Switzerland

Improved Self Amplified Spontaneous Emission (iSASE) is a scheme that reduces FEL bandwidth by increasing phase slippage between the electron bunch and radiation field. This is achieved by repeatedly delaying electrons using phase shifters between undulator sections. Genesis code is modified to facilitate this simulation. With this simulation code, the iSASE bandwidth reduction mechanism is studied in detail. A Temporal correlation function is introduced to describe the similarity between the new grown field from bunching factor and the amplified shifted field. This correlation function indicates the efficiency of iSASE process.

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
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.

TUP029	iSASE Study	442
	K. Fang Indiana University, Bloomington, Indiana, USA S.D. Chen NCTU, Hsinchu, Taiwan S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA C. Emma, C. Pellegrini UCLA, Los Angeles, California, USA S. Reiche PSI, Villigen PSI, Switzerland
	Improved Self Amplified Spontaneous Emission (iSASE) is a scheme that reduces FEL bandwidth by increasing phase slippage between the electron bunch and radiation field. This is achieved by repeatedly delaying electrons using phase shifters between undulator sections. Genesis code is modified to facilitate this simulation. With this simulation code, the iSASE bandwidth reduction mechanism is studied in detail. A Temporal correlation function is introduced to describe the similarity between the new grown field from bunching factor and the amplified shifted field. This correlation function indicates the efficiency of iSASE process.

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.

MOC03	Radiation Properties of Tapered Hard X-ray Free Electron Lasers	300
	C. Emma, C. Pellegrini UCLA, Los Angeles, California, USA S.D. Chen NCTU, Hsinchu, Taiwan K. Fang, C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA S. Serkez DESY, Hamburg, Germany
	We perform an analysis of the transverse coherence of the radiation from a TW level tapered hard X-ray Free Electron Laser (FEL). The radiation properties of the FEL are studied for a Gaussian, parabolic and uniform transverse electron beam density profile in a 200-m undulator at a resonant wavelength of 1.5 Angstrom. Simulations performed using the 3-D FEL particle code GENESIS show that diffraction of the radiation occurs due to a reduction in optical guiding in the tapered section of the undulator. This results in an increasing transverse coherence for all three transverse electron beam profiles. We determine that for each case considered the radiation coherence area is much larger than the electron beam spot size, making X-ray diffraction experiments possible for TW X-ray FELs.
	Slides MOC03 [3.797 MB]

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.

TUP029	iSASE Study	442
	K. Fang Indiana University, Bloomington, Indiana, USA S.D. Chen NCTU, Hsinchu, Taiwan S.D. Chen, K. Fang, X. Huang, C. Pellegrini, J. Wu SLAC, Menlo Park, California, USA C. Emma, C. Pellegrini UCLA, Los Angeles, California, USA S. Reiche PSI, Villigen PSI, Switzerland
	Improved Self Amplified Spontaneous Emission (iSASE) is a scheme that reduces FEL bandwidth by increasing phase slippage between the electron bunch and radiation field. This is achieved by repeatedly delaying electrons using phase shifters between undulator sections. Genesis code is modified to facilitate this simulation. With this simulation code, the iSASE bandwidth reduction mechanism is studied in detail. A Temporal correlation function is introduced to describe the similarity between the new grown field from bunching factor and the amplified shifted field. This correlation function indicates the efficiency of iSASE process.

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.