IPAC2016 - List of Authors (Kim, K.-J.)

Paper	Title	Page
MOPOW039	An Oscillator Configuration for Full Realization of Hard X-ray Free Electron Laser	801
	K.-J. Kim, T. Kolodziej, R.R. Lindberg, D. Shu, Yu. Shvyd'ko, S. Stoupin ANL, Argonne, Ilinois, USA V.D. Blank, S. Terentiev TISNCM, Troitsk, Russia Y. Ding, W.M. Fawley, J.B. Hastings, Z. Huang, J. Krzywinski, G. Marcus, T.J. Maxwell SLAC, Menlo Park, California, USA N.A. Medvedev CFEL, Hamburg, Germany W. Qin PKU, Beijing, People's Republic of China J. Zemella DESY, Hamburg, Germany
	Funding: Work at ANL supported under US Department of Energy contract DE-AC02-76SF00515 and at SLAC by the U.S. Department of Energy, Office of Science, under Contract No. DE-ACO2-O6CH11357 An X-ray free electron laser can be built in an oscillator (XFELO) configuration by employing an X-ray cavity with Bragg mirrors such as diamond. An XFELO at the 5th harmonic frequency may be implemented at the LCLS II using its 4 GeV superconducting linac. The XFELO will provide stable, coherent, high-spectral-purity hard x-rays. In addition, portions of its output may be enhanced by the LCLS amplifier for stable pulses of ultrashort duration determined by the electron bunch length. Much progress has been made recently on the feasibility of an XFELO: Analytical and numerical methods have been developed to compute the performance of a harmonic XFELO. The energy spread requirement over a sufficient length of the bunch can be met by temporal shaping of the photo-cathode drive laser. Experiments at the APS have shown that Be-compound refractive lenses are suitable for a low-loss focusing and that the synthetic diamond crystals can withstand the intense x-ray exposure, in accord with estimates based on molecular dynamics considerations. A strain-free mounting of thin diamond crystal (< 100 microns) can be realized by shaping a thick diamond into a blind alley*. R. R. Lindberg et al., PRSTAB 1010701 (2011) W. Qin et al., this conference * N. Medvedev et al., Phys. Rev. B 88, 224304 (2013) **** S. Terentyev, private communication
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW039
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TUOBB01	Demonstration of Current Profile Shaping using Double Dog-Leg Emittance Exchange Beam Line at Argonne Wakefield Accelerator	1065
	G. Ha, M.-H. Cho, W. Namkung POSTECH, Pohang, Kyungbuk, Republic of Korea M.E. Conde, D.S. Doran, W. Gai, G. Ha, K.-J. Kim, W. Liu, J.G. Power, Y.-E. Sun, C. Whiteford, E.E. Wisniewski, A. Zholents ANL, Argonne, Illinois, USA C.-J. Jing Euclid TechLabs, LLC, Solon, Ohio, USA P. Piot Fermilab, Batavia, Illinois, USA
	Emittance exchange (EEX) based longitudinal current profile shaping is the one of the promising current profile shaping technique. This method can generate high quality arbitrary current profiles under the ideal conditions. The double dog-leg EEX beam line was recently installed at the Argonne Wakefield Accelerator (AWA) to explore the shaping capability and confirm the quality of this method. To demonstrate the arbitrary current profile generation, several different transverse masks are applied to generate different final current profiles. The phase space slopes and the charge of incoming beam are varied to observe and suppress the aberrations on the ideal profile. We present current profile shaping results, aberrations on the shaped profile, and its suppression.
	Slides TUOBB01 [5.032 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOBB01
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TUPMY031	Estimation and Suppression of Aberrations in Emittance Exchange based Current Profile Shaping	1615
	G. Ha, M.-H. Cho, W. Namkung POSTECH, Pohang, Kyungbuk, Republic of Korea W. Gai, G. Ha, K.-J. Kim, J.G. Power ANL, Argonne, Illinois, USA
	The longitudinal current profile manipulation has been explored for many applications including THz radiation, FEL and advanced acceleration schemes. Especially, collinear dielectric wakefield accelerations require a microbunch shaping for a high transformer ratio. We have studied aberrations from the emittance exchange based current profile shaping to preserve the high transformer ratio. All second order aberration terms in the double dog-leg emittance exchange beam line are discovered. Aberration patterns from each aberration sources like second order terms, space-charge, and CSR and their effect on the transformer ratio are estimated analytically. These aberration sources and corresponding patterns are confirmed using a particle tracking code GPT. Simple methods to suppress each aberration will be presented too. All calculation in this work is done with a double dog-leg emittance exchange beam line.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY031
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WEPOY019	Beam Optimization Study for an X-ray FEL Oscillator at the LCLS-II	3020
	W. Qin, S. Huang, K.X. Liu PKU, Beijing, People's Republic of China K.L.F. Bane, Y. Ding, Z. Huang, T.J. Maxwell SLAC, Menlo Park, California, USA K.-J. Kim, R.R. Lindberg ANL, Argonne, Ilinois, USA
	The 4 GeV LCLS-II superconducting linac with high repetition beam rate enables the possibility to drive an X-Ray FEL oscillator at harmonic frequencies . Compared to the regular LCLS-II machine setup, the oscillator mode requires a much longer bunch length with a relatively lower current. Also a flat longitudinal phase space distribution is critical to maintain the FEL gain since the X-ray cavity has extremely narrow bandwidth. In this paper, we study the longitudinal phase space optimization including shaping the initial beam from the injector and optimizing the bunch compressor and dechirper parameters. We obtain a bunch with a flat energy chirp over 400 fs in the core part with current above 100 A. The optimization was based on LiTrack and Elegant simulations using LCLS-II beam parameters. T. J. Maxwell et al., Feasibility study for an X-ray FEL oscillator at the LCLS-II, IPAC15, TUPMA028.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY019
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Paper

Title

Page

An Oscillator Configuration for Full Realization of Hard X-ray Free Electron Laser

801

K.-J. Kim, T. Kolodziej, R.R. Lindberg, D. Shu, Yu. Shvyd'ko, S. Stoupin
ANL, Argonne, Ilinois, USA
V.D. Blank, S. Terentiev
TISNCM, Troitsk, Russia
Y. Ding, W.M. Fawley, J.B. Hastings, Z. Huang, J. Krzywinski, G. Marcus, T.J. Maxwell
SLAC, Menlo Park, California, USA
N.A. Medvedev
CFEL, Hamburg, Germany
W. Qin
PKU, Beijing, People's Republic of China
J. Zemella
DESY, Hamburg, Germany

Funding: Work at ANL supported under US Department of Energy contract DE-AC02-76SF00515 and at SLAC by the U.S. Department of Energy, Office of Science, under Contract No. DE-ACO2-O6CH11357
An X-ray free electron laser can be built in an oscillator (XFELO) configuration by employing an X-ray cavity with Bragg mirrors such as diamond*. An XFELO at the 5th harmonic frequency may be implemented at the LCLS II using its 4 GeV superconducting linac. The XFELO will provide stable, coherent, high-spectral-purity hard x-rays. In addition, portions of its output may be enhanced by the LCLS amplifier for stable pulses of ultrashort duration determined by the electron bunch length. Much progress has been made recently on the feasibility of an XFELO: Analytical and numerical methods have been developed to compute the performance of a harmonic XFELO. The energy spread requirement over a sufficient length of the bunch can be met by temporal shaping of the photo-cathode drive laser**. Experiments at the APS have shown that Be-compound refractive lenses are suitable for a low-loss focusing and that the synthetic diamond crystals can withstand the intense x-ray exposure, in accord with estimates based on molecular dynamics considerations***. A strain-free mounting of thin diamond crystal (< 100 microns) can be realized by shaping a thick diamond into a blind alley****.
* R. R. Lindberg et al., PRSTAB 1010701 (2011)
** W. Qin et al., this conference
*** N. Medvedev et al., Phys. Rev. B 88, 224304 (2013)
**** S. Terentyev, private communication

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW039

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TUOBB01

Demonstration of Current Profile Shaping using Double Dog-Leg Emittance Exchange Beam Line at Argonne Wakefield Accelerator

1065

G. Ha, M.-H. Cho, W. Namkung
POSTECH, Pohang, Kyungbuk, Republic of Korea
M.E. Conde, D.S. Doran, W. Gai, G. Ha, K.-J. Kim, W. Liu, J.G. Power, Y.-E. Sun, C. Whiteford, E.E. Wisniewski, A. Zholents
ANL, Argonne, Illinois, USA
C.-J. Jing
Euclid TechLabs, LLC, Solon, Ohio, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Emittance exchange (EEX) based longitudinal current profile shaping is the one of the promising current profile shaping technique. This method can generate high quality arbitrary current profiles under the ideal conditions. The double dog-leg EEX beam line was recently installed at the Argonne Wakefield Accelerator (AWA) to explore the shaping capability and confirm the quality of this method. To demonstrate the arbitrary current profile generation, several different transverse masks are applied to generate different final current profiles. The phase space slopes and the charge of incoming beam are varied to observe and suppress the aberrations on the ideal profile. We present current profile shaping results, aberrations on the shaped profile, and its suppression.

Slides TUOBB01 [5.032 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUOBB01

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TUPMY031

Estimation and Suppression of Aberrations in Emittance Exchange based Current Profile Shaping

1615

G. Ha, M.-H. Cho, W. Namkung
POSTECH, Pohang, Kyungbuk, Republic of Korea
W. Gai, G. Ha, K.-J. Kim, J.G. Power
ANL, Argonne, Illinois, USA

The longitudinal current profile manipulation has been explored for many applications including THz radiation, FEL and advanced acceleration schemes. Especially, collinear dielectric wakefield accelerations require a microbunch shaping for a high transformer ratio. We have studied aberrations from the emittance exchange based current profile shaping to preserve the high transformer ratio. All second order aberration terms in the double dog-leg emittance exchange beam line are discovered. Aberration patterns from each aberration sources like second order terms, space-charge, and CSR and their effect on the transformer ratio are estimated analytically. These aberration sources and corresponding patterns are confirmed using a particle tracking code GPT. Simple methods to suppress each aberration will be presented too. All calculation in this work is done with a double dog-leg emittance exchange beam line.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPMY031

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WEPOY019

Beam Optimization Study for an X-ray FEL Oscillator at the LCLS-II

3020

W. Qin, S. Huang, K.X. Liu
PKU, Beijing, People's Republic of China
K.L.F. Bane, Y. Ding, Z. Huang, T.J. Maxwell
SLAC, Menlo Park, California, USA
K.-J. Kim, R.R. Lindberg
ANL, Argonne, Ilinois, USA

The 4 GeV LCLS-II superconducting linac with high repetition beam rate enables the possibility to drive an X-Ray FEL oscillator at harmonic frequencies *. Compared to the regular LCLS-II machine setup, the oscillator mode requires a much longer bunch length with a relatively lower current. Also a flat longitudinal phase space distribution is critical to maintain the FEL gain since the X-ray cavity has extremely narrow bandwidth. In this paper, we study the longitudinal phase space optimization including shaping the initial beam from the injector and optimizing the bunch compressor and dechirper parameters. We obtain a bunch with a flat energy chirp over 400 fs in the core part with current above 100 A. The optimization was based on LiTrack and Elegant simulations using LCLS-II beam parameters.
* T. J. Maxwell et al., Feasibility study for an X-ray FEL oscillator at the LCLS-II, IPAC15, TUPMA028.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY019

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