FEL2017 - List of Authors (Yang, B.)

Paper	Title	Page
MOP018	Distributed Self-Seeding Scheme for LCLS-II	68
	C. Yang, Y. Feng, T.O. Raubenheimer, C.-Y. Tsai, J. Wu, M. Yoon, G. Zhou SLAC, Menlo Park, California, USA B. Yang University of Texas at Arlington, Arlington, USA
	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. Self-seeding is a successful approach for generating high-brightness x-ray free electron laser (XFEL). A single-crystal monochromator in-between the undulator sections to generate a coherent seed is adopted in LCLS. However, for a high-repetition rate machine like LCLS-II, the crystal monochromator in current setup cannot sustain the high average power; hence a distributed self-seeding scheme utilizing multi-stages is necessary. Based on the criteria set on the crystal, the maximum allowed x-ray energy deposited in the crystal will determine the machine configuration for such a distributed self-seeding scheme. In this paper, a distributed self-seeding configuration is optimized for LCLS-II type projects in the hard x-ray FEL energy regime. The study is carried out based on numerical simulation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP018
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOP019	Transient Thermal Stress Wave Analysis of a Thin Diamond Crystal Under Laser Heat Load	72
	J. Wu SLAC, Menlo Park, California, USA B. Yang University of Texas at Arlington, Arlington, USA
	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. When a laser pulse impinges on a thin crystal, energy is deposited resulting in an instantaneous temperature surge in the local volume and emission of stress waves. In the present work, we perform a transient thermal stress wave analysis of a diamond layer 200 μm thick in the low energy deposition per pulse regime. The layer thickness and laser spot size are comparable. The analysis reveals the characteristic non-planar stress wave propagation. The stress wave emission lasts by hundreds of nanoseconds, at a time scale relevant to the high-repetition-rate FELs at the megahertz range. The kinetic energy converted from the thermal strain energy is calculated, which may be important to estimate the vibrational amplitude of the thin crystal when excited under repeated heat loads. The transient heat transfer plays an important role in draining the mechanical energy during the dynamic wave emission process.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP057	Measurement of Short-Wavelength High-Gain FEL Temporal Coherence Length by a Phase Shifter	344
	G. Zhou IHEP, Beijing, People's Republic of China W. Liu USTC/NSRL, Hefei, Anhui, People's Republic of China W. Qin, T.O. Raubenheimer, J. Wu, C. Yang SLAC, Menlo Park, California, USA C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA B. Yang University of Texas at Arlington, Arlington, USA M. Yoon POSTECH, Pohang, Kyungbuk, Republic of Korea
	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. Short-wavelength high-gain free-electron lasers (FELs) are now well established as a source of ultra-fast, ultra-brightness, longitudinally partial coherent light. Since coherence is one of the fundamental properties of light source, so continual effort is devoted to high-gain free-electron laser coherence measurements. In this work, we propose a possible approach, employing a phase shifter to induce electron beam delay to measure the temporal coherence length. Simple analysis, numerical simulation and preliminary experimental results are presented. This approach can be robust and independent of frequency.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP057
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP058	Slippage-Enhanced SASE FEL	348
	J. Wu, A. Brachmann, K. Fang, A. Marinelli, C. Pellegrini, T.O. Raubenheimer, C.-Y. Tsai, C. Yang, M. Yoon, G. Zhou SLAC, Menlo Park, California, USA H.-S. Kang, G. Kim, I.H. Nam PAL, Pohang, Republic of Korea B. Yang University of Texas at Arlington, Arlington, USA
	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. High-brightness XFEL is demanding for many users, in particular for certain types of imaging applications. Seeded FELs including self-seeding XFELs were successfully demonstrated. Alternative approaches by enhancing slippage between the x-ray pulse and the electron bunch were also demonstrated. This class of Slippage-enhanced SASE (SeSASE) schemes can be unique for FEL spectral range between 1.5 keV to 4 keV where neither grating-based soft x-ray self-seeding nor crystal-based hard x-ray self-seeding can easily access. SeSASE can provide high-brightness XFEL for high repetition rate machines not suffering from heat load on the crystal monochromator. We report start-to-end simulation results for LCLS-II project and PAL-XFEL project with study on tolerance. Performance comparison between SaSASE FEL and self-seeding FEL in the overlapping frequency range is also presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP058
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEP061	Thermal Stress Analysis of a Thin Diamond Crystal Under Repeated Free Electron Laser Heat Load	539
	J. Wu SLAC, Menlo Park, California, USA B. Yang University of Texas at Arlington, Arlington, USA
	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. Thin crystals are used in many important optical elements, such as monochromator and spectrometer, in XFELs. To function properly, they must survive the ever-increasing heat load under repeated pulses. Here, we conduct a thermal stress analysis to examine the crystal lattice distortion due to the thermal load under various rep rates from 0.1 to 1 MHz. The thermal field is obtained by solving the transient heat transfer equations. The temperature-dependent material properties are used. It is shown that for pulse adsorption energy around tens of microjoule over a spot size of 10 micrometer, the thermal response of diamond is sensitive to rep rate. The thermal strain components are very different in the in- and out-of-plane directions, due to different constraint conditions. It suggests complicated strain effects in the Bragg and Laue diffraction cases.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP061
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Distributed Self-Seeding Scheme for LCLS-II

68

C. Yang, Y. Feng, T.O. Raubenheimer, C.-Y. Tsai, J. Wu, M. Yoon, G. Zhou
SLAC, Menlo Park, California, USA
B. Yang
University of Texas at Arlington, Arlington, USA

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.
Self-seeding is a successful approach for generating high-brightness x-ray free electron laser (XFEL). A single-crystal monochromator in-between the undulator sections to generate a coherent seed is adopted in LCLS. However, for a high-repetition rate machine like LCLS-II, the crystal monochromator in current setup cannot sustain the high average power; hence a distributed self-seeding scheme utilizing multi-stages is necessary. Based on the criteria set on the crystal, the maximum allowed x-ray energy deposited in the crystal will determine the machine configuration for such a distributed self-seeding scheme. In this paper, a distributed self-seeding configuration is optimized for LCLS-II type projects in the hard x-ray FEL energy regime. The study is carried out based on numerical simulation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP018

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOP019

Transient Thermal Stress Wave Analysis of a Thin Diamond Crystal Under Laser Heat Load

72

J. Wu
SLAC, Menlo Park, California, USA
B. Yang
University of Texas at Arlington, Arlington, USA

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.
When a laser pulse impinges on a thin crystal, energy is deposited resulting in an instantaneous temperature surge in the local volume and emission of stress waves. In the present work, we perform a transient thermal stress wave analysis of a diamond layer 200 μm thick in the low energy deposition per pulse regime. The layer thickness and laser spot size are comparable. The analysis reveals the characteristic non-planar stress wave propagation. The stress wave emission lasts by hundreds of nanoseconds, at a time scale relevant to the high-repetition-rate FELs at the megahertz range. The kinetic energy converted from the thermal strain energy is calculated, which may be important to estimate the vibrational amplitude of the thin crystal when excited under repeated heat loads. The transient heat transfer plays an important role in draining the mechanical energy during the dynamic wave emission process.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP019

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP057

Measurement of Short-Wavelength High-Gain FEL Temporal Coherence Length by a Phase Shifter

344

G. Zhou
IHEP, Beijing, People's Republic of China
W. Liu
USTC/NSRL, Hefei, Anhui, People's Republic of China
W. Qin, T.O. Raubenheimer, J. Wu, C. Yang
SLAC, Menlo Park, California, USA
C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
B. Yang
University of Texas at Arlington, Arlington, USA
M. Yoon
POSTECH, Pohang, Kyungbuk, Republic of Korea

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.
Short-wavelength high-gain free-electron lasers (FELs) are now well established as a source of ultra-fast, ultra-brightness, longitudinally partial coherent light. Since coherence is one of the fundamental properties of light source, so continual effort is devoted to high-gain free-electron laser coherence measurements. In this work, we propose a possible approach, employing a phase shifter to induce electron beam delay to measure the temporal coherence length. Simple analysis, numerical simulation and preliminary experimental results are presented. This approach can be robust and independent of frequency.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP057

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP058

Slippage-Enhanced SASE FEL

348

J. Wu, A. Brachmann, K. Fang, A. Marinelli, C. Pellegrini, T.O. Raubenheimer, C.-Y. Tsai, C. Yang, M. Yoon, G. Zhou
SLAC, Menlo Park, California, USA
H.-S. Kang, G. Kim, I.H. Nam
PAL, Pohang, Republic of Korea
B. Yang
University of Texas at Arlington, Arlington, USA

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.
High-brightness XFEL is demanding for many users, in particular for certain types of imaging applications. Seeded FELs including self-seeding XFELs were successfully demonstrated. Alternative approaches by enhancing slippage between the x-ray pulse and the electron bunch were also demonstrated. This class of Slippage-enhanced SASE (SeSASE) schemes can be unique for FEL spectral range between 1.5 keV to 4 keV where neither grating-based soft x-ray self-seeding nor crystal-based hard x-ray self-seeding can easily access. SeSASE can provide high-brightness XFEL for high repetition rate machines not suffering from heat load on the crystal monochromator. We report start-to-end simulation results for LCLS-II project and PAL-XFEL project with study on tolerance. Performance comparison between SaSASE FEL and self-seeding FEL in the overlapping frequency range is also presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP058

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEP061

Thermal Stress Analysis of a Thin Diamond Crystal Under Repeated Free Electron Laser Heat Load

539

J. Wu
SLAC, Menlo Park, California, USA
B. Yang
University of Texas at Arlington, Arlington, USA

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.
Thin crystals are used in many important optical elements, such as monochromator and spectrometer, in XFELs. To function properly, they must survive the ever-increasing heat load under repeated pulses. Here, we conduct a thermal stress analysis to examine the crystal lattice distortion due to the thermal load under various rep rates from 0.1 to 1 MHz. The thermal field is obtained by solving the transient heat transfer equations. The temperature-dependent material properties are used. It is shown that for pulse adsorption energy around tens of microjoule over a spot size of 10 micrometer, the thermal response of diamond is sensitive to rep rate. The thermal strain components are very different in the in- and out-of-plane directions, due to different constraint conditions. It suggests complicated strain effects in the Bragg and Laue diffraction cases.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP061

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)