IPAC2021 - List of Authors (Li, W.)

Paper	Title	Page
TUPAB117	Eigenmode Decomposition for Free-Electron Lasers Using Bayesian Analysis	1666
	P. Liu, W. Li, Y.K. Wu, J. Yan FEL/Duke University, Durham, North Carolina, USA
	Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033. Laser beams from an optical cavity, such as free-electron laser (FEL) resonators, are typically a mixture of the cavity’s eigenmodes, such as the Hermite-Gaussian (HG) modes or Laguerre-Gaussian (LG) modes. Robust evaluation of the eigenmode spectrum of a multimode laser beam has various applications in laser development, research, and utilization. In this work, a general eigenmode decomposition method for a multimode laser beam has been developed based on Bayesian analysis. This problem is transformed into a linear system and then solved using a Gaussian probabilistic model. Using Bayesian analysis, prior knowledge about the mode content is further incorporated into the solution to improve the results for laser beams contaminated with complex disturbances. The decomposition of the beam image from the incoherent intensity addition of HG modes is discussed with different types of noise or disturbances. The simulation results have been used to show the robustness of this method. This method can be straightforwardly extended into other cases such as the wavefront decomposition into the coherent superposition of HG and LG modes.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB117
About •	paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 01 September 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPAB079	Design Study on Beam Size Measurement System Using SR Interferometry for Low Beam Current	3949
	W. Li, P. Liu, Y.K. Wu, J. Yan FEL/Duke University, Durham, North Carolina, USA
	Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033. To enable reliable measurements of the small vertical size of the electron beam in the Duke storage ring, a measurement system is being developed using synchrotron radiation interferometry (SRI). By relating the transverse beam size to the transverse spatial coherence of synchrotron radiation from a dipole magnet according to the Van Cittert-Zernike theorem, the transverse beam size can be inferred by recording and fitting the interference fringe as a function of the characteristic features of the interference filter used. In this paper, we describe the preliminary design of such a measurement system and present design considerations to make it possible to measure the electron beam vertical size for a wide range of electron beam energies and currents. Especially this system will be optimized to measure the electron beam size for low current operation down to 50 to 100~μA. This beam size measurement system will be used as an important beam diagnostic for the intrabeam scattering research at the Duke storage ring.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB079
About •	paper received ※ 27 May 2021 paper accepted ※ 12 July 2021 issue date ※ 28 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Eigenmode Decomposition for Free-Electron Lasers Using Bayesian Analysis

1666

P. Liu, W. Li, Y.K. Wu, J. Yan
FEL/Duke University, Durham, North Carolina, USA

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
Laser beams from an optical cavity, such as free-electron laser (FEL) resonators, are typically a mixture of the cavity’s eigenmodes, such as the Hermite-Gaussian (HG) modes or Laguerre-Gaussian (LG) modes. Robust evaluation of the eigenmode spectrum of a multimode laser beam has various applications in laser development, research, and utilization. In this work, a general eigenmode decomposition method for a multimode laser beam has been developed based on Bayesian analysis. This problem is transformed into a linear system and then solved using a Gaussian probabilistic model. Using Bayesian analysis, prior knowledge about the mode content is further incorporated into the solution to improve the results for laser beams contaminated with complex disturbances. The decomposition of the beam image from the incoherent intensity addition of HG modes is discussed with different types of noise or disturbances. The simulation results have been used to show the robustness of this method. This method can be straightforwardly extended into other cases such as the wavefront decomposition into the coherent superposition of HG and LG modes.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB117

About •

paper received ※ 18 May 2021 paper accepted ※ 15 June 2021 issue date ※ 01 September 2021

Export •

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

THPAB079

Design Study on Beam Size Measurement System Using SR Interferometry for Low Beam Current

3949

W. Li, P. Liu, Y.K. Wu, J. Yan
FEL/Duke University, Durham, North Carolina, USA

Funding: This work is supported in part by the US DOE grant no. DE-FG02-97ER41033.
To enable reliable measurements of the small vertical size of the electron beam in the Duke storage ring, a measurement system is being developed using synchrotron radiation interferometry (SRI). By relating the transverse beam size to the transverse spatial coherence of synchrotron radiation from a dipole magnet according to the Van Cittert-Zernike theorem, the transverse beam size can be inferred by recording and fitting the interference fringe as a function of the characteristic features of the interference filter used. In this paper, we describe the preliminary design of such a measurement system and present design considerations to make it possible to measure the electron beam vertical size for a wide range of electron beam energies and currents. Especially this system will be optimized to measure the electron beam size for low current operation down to 50 to 100~μA. This beam size measurement system will be used as an important beam diagnostic for the intrabeam scattering research at the Duke storage ring.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB079

About •

paper received ※ 27 May 2021 paper accepted ※ 12 July 2021 issue date ※ 28 August 2021

Export •

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