IPAC2018 - List of Authors (Kang, H.-S.)

Paper	Title	Page
MOZGBD4	Toward 10 fs Timing Stability of PAL-XFEL
	C.-K. Min, I. Eom, J. Hu, S.H. Jung, H.-S. Kang, S.H. Kim, H.-S. Lee, S.S. Park PAL, Pohang, Kyungbuk, Republic of Korea
	PAL-XFEL demonstrates 20 fs jitter in e-bunch arrival time at the end of undulators and its pump-probe system, which is extremely useful for maintaining high stability of machine and time-resolved experiments with high time resolution. Our low phase noise timing system and high stability high power RF system enable this low jitter. Our measurement shows 10 fs jitter of e-bunch arrival time at the injector and it increased ~20 fs due to e-bunch energy variation. The possibility of improving the final jitter is described based on the optimization of bunch compressors and longitudinal feedback.
	Slides MOZGBD4 [14.381 MB]
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WEPAL070	HLS System to Measure the Location Changes in Real Time of PAL-XFEL Devices	2345
	H. J. Choi, J.H. Han, H.-S. Kang, S.H. Kim, H.-G. Lee, S.B. Lee PAL, Pohang, Kyungbuk, Republic of Korea
	All components of PAL-XFEL (Pohang Accelerator Laboratory's X-ray free-electron laser) were completely installed in December 2015, and Hard X-ray 0.1nm lasing achieved through its beam commissioning test and machine study on March 16, 2017. The beam line users has been performing various tests including pump-probe X-ray scattering, time-resolved x-ray liquidography, etc in the hard x-ray beam line since March 22. The energy and flux of x-ray photon beam generated from XFEL and synchronization timing should be stable to ensure successful time-resolved tests. Several parts that comprise the large scientific equipment should be installed and operated at precise three-dimensional location coordinates X, Y, and Z through survey and alignment to ensure their optimal performance. As time goes by, however, the ground goes through uplift and subsidence, which consequently changes the coordinates of installed components and leads to alignment errors ΔX, ΔY, and ΔZ. As a result, the system parameters change, and the performance of the large scientific equipment deteriorates accordingly. Measuring the change in locations of systems comprising the large scientific equipment in real time would make it possible to predict alignment errors, locate any region with greater changes, realign components in the region fast, and shorten the time of survey and alignment. For this purpose, a HLS's (hydrostatic leveling sensor) with 0.2um of resolution are installed and operated in a waterpipe of total length 1km in the PAL-XFEL building. This paper is designed to introduce the operating principle of the HLS, the installation and operation of the HLS system, and how to utilize the HLS system in order to ensure beam stabilization.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL070
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THPMK033	PAL-XFEL Linac RF System Status	4369
	H.-S. Lee, Heo, J.Y. Heo, J.H. Hong, H.-S. Kang, K.H. Kim, S.H. Kim, D.H. Na, S.S. Park, Y.J. Park PAL, Pohang, Kyungbuk, Republic of Korea
	Funding: Ministry of Science and ICT The PAL-XFEL Linear Accelerator began user support in March 2017 after one year of RF conditioning in 2016. The energy jitter was 0.013% when operating the H-X linear accelerator with 46 modulators, Klystron, LLRF, SSA and vacuum system at 6.838 GeV energy during user support period. So far, we have replaced four klystrons and 10 thyratron switches. We also measured the influence of temperature changes of RF components according to repetition rates of the machine. We will report on the measurement results of this operating experience and performance.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK033
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THPMK052	Numerical Simulation of Phase-Shift Method for Fel Power Enhancement in PAL-XFEL	4402
	C.-Y. Tsai, J. Wu, C. Yang, G. Zhou SLAC, Menlo Park, California, USA H.-S. Kang PAL, Pohang, Kyungbuk, Republic of Korea M. Yoon POSTECH, Pohang, Kyungbuk, Republic of Korea G. Zhou IHEP, Beijing, People's Republic of China
	Funding: The work was supported by the US Department of Energy (DOE) under contract DE- AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164. Recently the phase jump method for efficiency enhancement in free-electron laser (FEL) was proposed. One of the unique features of PAL-XFEL with phase shifters may be taken for the experimental demonstration of this phase jump scheme. In this paper we numerically investigate the scheme using the three-dimensional numerical simulation code GENESIS. The physical parameters are based on hard x-ray line of PAL-XFEL*. The preliminary simulation results indicate that this potential phase jump scheme can enhance at least one order of magnitude of FEL power performance. Combination of this scheme with undulator tapering is also discussed in this paper. A. Mak, F. Curbis, and S. Werin, PRAB 20, 060703 (2017) S. Rieche, NIMA 429(1):243-248 (1999) *I. S. Ko et al., Appl. Sci. 2017, 7, 479 (2017)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK052
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Paper

Title

Page

MOZGBD4

Toward 10 fs Timing Stability of PAL-XFEL

C.-K. Min, I. Eom, J. Hu, S.H. Jung, H.-S. Kang, S.H. Kim, H.-S. Lee, S.S. Park
PAL, Pohang, Kyungbuk, Republic of Korea

PAL-XFEL demonstrates 20 fs jitter in e-bunch arrival time at the end of undulators and its pump-probe system, which is extremely useful for maintaining high stability of machine and time-resolved experiments with high time resolution. Our low phase noise timing system and high stability high power RF system enable this low jitter. Our measurement shows 10 fs jitter of e-bunch arrival time at the injector and it increased ~20 fs due to e-bunch energy variation. The possibility of improving the final jitter is described based on the optimization of bunch compressors and longitudinal feedback.

Slides MOZGBD4 [14.381 MB]

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WEPAL070

HLS System to Measure the Location Changes in Real Time of PAL-XFEL Devices

2345

H. J. Choi, J.H. Han, H.-S. Kang, S.H. Kim, H.-G. Lee, S.B. Lee
PAL, Pohang, Kyungbuk, Republic of Korea

All components of PAL-XFEL (Pohang Accelerator Laboratory's X-ray free-electron laser) were completely installed in December 2015, and Hard X-ray 0.1nm lasing achieved through its beam commissioning test and machine study on March 16, 2017. The beam line users has been performing various tests including pump-probe X-ray scattering, time-resolved x-ray liquidography, etc in the hard x-ray beam line since March 22. The energy and flux of x-ray photon beam generated from XFEL and synchronization timing should be stable to ensure successful time-resolved tests. Several parts that comprise the large scientific equipment should be installed and operated at precise three-dimensional location coordinates X, Y, and Z through survey and alignment to ensure their optimal performance. As time goes by, however, the ground goes through uplift and subsidence, which consequently changes the coordinates of installed components and leads to alignment errors ΔX, ΔY, and ΔZ. As a result, the system parameters change, and the performance of the large scientific equipment deteriorates accordingly. Measuring the change in locations of systems comprising the large scientific equipment in real time would make it possible to predict alignment errors, locate any region with greater changes, realign components in the region fast, and shorten the time of survey and alignment. For this purpose, a HLS's (hydrostatic leveling sensor) with 0.2um of resolution are installed and operated in a waterpipe of total length 1km in the PAL-XFEL building. This paper is designed to introduce the operating principle of the HLS, the installation and operation of the HLS system, and how to utilize the HLS system in order to ensure beam stabilization.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-WEPAL070

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THPMK033

PAL-XFEL Linac RF System Status

4369

H.-S. Lee, Heo, J.Y. Heo, J.H. Hong, H.-S. Kang, K.H. Kim, S.H. Kim, D.H. Na, S.S. Park, Y.J. Park
PAL, Pohang, Kyungbuk, Republic of Korea

Funding: Ministry of Science and ICT
The PAL-XFEL Linear Accelerator began user support in March 2017 after one year of RF conditioning in 2016. The energy jitter was 0.013% when operating the H-X linear accelerator with 46 modulators, Klystron, LLRF, SSA and vacuum system at 6.838 GeV energy during user support period. So far, we have replaced four klystrons and 10 thyratron switches. We also measured the influence of temperature changes of RF components according to repetition rates of the machine. We will report on the measurement results of this operating experience and performance.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK033

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THPMK052

Numerical Simulation of Phase-Shift Method for Fel Power Enhancement in PAL-XFEL

4402

C.-Y. Tsai, J. Wu, C. Yang, G. Zhou
SLAC, Menlo Park, California, USA
H.-S. Kang
PAL, Pohang, Kyungbuk, Republic of Korea
M. Yoon
POSTECH, Pohang, Kyungbuk, Republic of Korea
G. Zhou
IHEP, Beijing, People's Republic of China

Funding: The work was supported by the US Department of Energy (DOE) under contract DE- AC02-76SF00515 and the US DOE Office of Science Early Career Research Program grant FWP-2013-SLAC-100164.
Recently the phase jump method for efficiency enhancement in free-electron laser (FEL) was proposed*. One of the unique features of PAL-XFEL with phase shifters may be taken for the experimental demonstration of this phase jump scheme. In this paper we numerically investigate the scheme using the three-dimensional numerical simulation code GENESIS**. The physical parameters are based on hard x-ray line of PAL-XFEL***. The preliminary simulation results indicate that this potential phase jump scheme can enhance at least one order of magnitude of FEL power performance. Combination of this scheme with undulator tapering is also discussed in this paper.
*A. Mak, F. Curbis, and S. Werin, PRAB 20, 060703 (2017)
**S. Rieche, NIMA 429(1):243-248 (1999)
***I. S. Ko et al., Appl. Sci. 2017, 7, 479 (2017)

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK052

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