FEL2019 - List of Keywords (alignment)

Paper	Title	Other Keywords	Page
TUP027	Modelling Crystal Misaligments for the X-ray FEL Oscillator	FEL, cavity, undulator, simulation	110
	R.R. Lindberg ANL, Lemont, Illinois, USA
	Funding: Work supported by U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357. The X-ray FEL oscillator has the potential to be a revolutionary new light source providing unprecedented stability in a narrow bandwidth [1]. However, a detailed understanding of cavity tolerance and stability has only begun, and there are presently no suitable simulation tools. To address this issue, we have developed a fast FEL oscillator code that discretizes the field using a Gauss-Hermite mode expansion of the oscillator cavity. Errors in crystal alignment result in a mixing of the modes that is easily modeled with a loss and coupling matrix. We show first results from our code, including the effects of static and time-varying crystal misalignments. [1] K.-J. Kim, Y. Shvyd’ko, and S. Reiche, PRL 100 244802 (2008)
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP027
About •	paper received ※ 20 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WED01	Experience with Short-Period, Small Gap Undulators at the SwissFEL Aramis Beamline	undulator, photon, FEL, electron	564
	T. Schmidt, M. Aiba, A.D. Alarcon, C. Arrell, S. Bettoni, M. Calvi, A. Cassar, E. Ferrari, R. Follath, R. Ganter, N. Hiller, P.N. Juranič, C. Kittel, F. Löhl, E. Prat, S. Reiche, T. Schietinger, D. Voulot, U.H. Wagner PSI, Villigen PSI, Switzerland N.J. Sammut University of Malta, Faculty of Engineering, Msida, Malta
	The SwissFEL Aramis beamline provides hard X-ray FEL radiation down to 1 Angström with 5.8 GeV and short period, 15 mm, in-vacuum undulators (U15). To reach the maximum designed K-value of 1.8 the U15s have to be operated with vacuum gaps down to 3.0 mm. The thirteen-undulator modules are 4 m long and each of them is equipped with a pair of permanent magnet quadrupoles at the two ends, aligned magnetically to the undulator axis. Optical systems and dedicated photon diagnostics are used to check the alignment and improve the K-value calibration. In this talk the main steps of the undulator commissioning will be recalled and a systematic comparison between the magnetic results and the electron and photon based measurements will be reported to highlight achievements and open issues.
	Slides WED01 [13.825 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WED01
About •	paper received ※ 28 August 2019 paper accepted ※ 06 November 2019 issue date ※ 05 November 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THP002	Beam Based Alignment in all Undulator Beamlines at European XFEL	FEL, undulator, quadrupole, electron	592
	M. Scholz, W. Decking DESY, Hamburg, Germany Y. Li EuXFEL, Hamburg, Germany
	The Free Electron Laser European XFEL aims at delivering X-rays from 0.25 keV up to 25 keV out of three SASE undulators. A good overlap of photon and electron beams is indispensable to obtain good lasing performance, especially for the higher photon energies. Thus the quadrupole magnets in the undulators must be aligned as good as possible on a straight line. This can only be realized with a beam based alignment procedure. In this paper we will report on the method that was performed at the European XFEL. We will also discuss our results.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP002
About •	paper received ※ 20 August 2019 paper accepted ※ 12 September 2019 issue date ※ 05 November 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THP068	LCLS-II Extruded Aluminum Undulator Vacuum Chambers — New Approaches to an Improved Aperture Surface Finish	undulator, vacuum, electron, FEL	719
	G.E. Wiemerslage, P.K. Den Hartog, J. Qian, M. White ANL, Lemont, Illinois, USA
	Funding: Work at Argonne National Laboratory is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract # DE-AC02-06CH11357. The Linac Coherent Light Source, (LCLS) the world’s first x-ray free electron laser (FEL) became operational in 2009. The Advanced Photon Source contributed to the original project by designing and building the undulator line. Two slightly different variations of these chambers were required for LCLS-II: one for a soft X-ray (SXR) undulator line, and one for a hard X-ray (HXR) undulator line. Because of the extremely short electron bunch length, a key physics requirement was to achieve the best possible surface finish within the chamber aperture. Improvements to our earlier fabrication methods allowed us to meet the critical surface roughness finish defined by RF impedance requirements. We were able to improve the surface finish from an average of 812 nm rms to 238 nm rms. The average longitudinal surface roughness slope of all chambers was to be less than 20 mrad. We achieved an average longitudinal surface roughness slope of 8.5 mrad with no chamber exceeding 20 mrad. In the end, sixty-four undulator vacuum chambers and alignment systems were delivered to SLAC for the LCLS-II Upgrade project. Here we will report on the process improvements for the fabrication of these chambers.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP068
About •	paper received ※ 16 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

TUP027

Modelling Crystal Misaligments for the X-ray FEL Oscillator

FEL, cavity, undulator, simulation

110

R.R. Lindberg
ANL, Lemont, Illinois, USA

Funding: Work supported by U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357.
The X-ray FEL oscillator has the potential to be a revolutionary new light source providing unprecedented stability in a narrow bandwidth [1]. However, a detailed understanding of cavity tolerance and stability has only begun, and there are presently no suitable simulation tools. To address this issue, we have developed a fast FEL oscillator code that discretizes the field using a Gauss-Hermite mode expansion of the oscillator cavity. Errors in crystal alignment result in a mixing of the modes that is easily modeled with a loss and coupling matrix. We show first results from our code, including the effects of static and time-varying crystal misalignments.
[1] K.-J. Kim, Y. Shvyd’ko, and S. Reiche, PRL 100 244802 (2008)

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-TUP027

About •

paper received ※ 20 August 2019 paper accepted ※ 25 August 2019 issue date ※ 05 November 2019

Export •

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

WED01

Experience with Short-Period, Small Gap Undulators at the SwissFEL Aramis Beamline

undulator, photon, FEL, electron

564

T. Schmidt, M. Aiba, A.D. Alarcon, C. Arrell, S. Bettoni, M. Calvi, A. Cassar, E. Ferrari, R. Follath, R. Ganter, N. Hiller, P.N. Juranič, C. Kittel, F. Löhl, E. Prat, S. Reiche, T. Schietinger, D. Voulot, U.H. Wagner
PSI, Villigen PSI, Switzerland
N.J. Sammut
University of Malta, Faculty of Engineering, Msida, Malta

The SwissFEL Aramis beamline provides hard X-ray FEL radiation down to 1 Angström with 5.8 GeV and short period, 15 mm, in-vacuum undulators (U15). To reach the maximum designed K-value of 1.8 the U15s have to be operated with vacuum gaps down to 3.0 mm. The thirteen-undulator modules are 4 m long and each of them is equipped with a pair of permanent magnet quadrupoles at the two ends, aligned magnetically to the undulator axis. Optical systems and dedicated photon diagnostics are used to check the alignment and improve the K-value calibration. In this talk the main steps of the undulator commissioning will be recalled and a systematic comparison between the magnetic results and the electron and photon based measurements will be reported to highlight achievements and open issues.

Slides WED01 [13.825 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-WED01

About •

paper received ※ 28 August 2019 paper accepted ※ 06 November 2019 issue date ※ 05 November 2019

Export •

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

THP002

Beam Based Alignment in all Undulator Beamlines at European XFEL

FEL, undulator, quadrupole, electron

592

M. Scholz, W. Decking
DESY, Hamburg, Germany
Y. Li
EuXFEL, Hamburg, Germany

The Free Electron Laser European XFEL aims at delivering X-rays from 0.25 keV up to 25 keV out of three SASE undulators. A good overlap of photon and electron beams is indispensable to obtain good lasing performance, especially for the higher photon energies. Thus the quadrupole magnets in the undulators must be aligned as good as possible on a straight line. This can only be realized with a beam based alignment procedure. In this paper we will report on the method that was performed at the European XFEL. We will also discuss our results.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP002

About •

paper received ※ 20 August 2019 paper accepted ※ 12 September 2019 issue date ※ 05 November 2019

Export •

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

THP068

LCLS-II Extruded Aluminum Undulator Vacuum Chambers — New Approaches to an Improved Aperture Surface Finish

undulator, vacuum, electron, FEL

719

G.E. Wiemerslage, P.K. Den Hartog, J. Qian, M. White
ANL, Lemont, Illinois, USA

Funding: Work at Argonne National Laboratory is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under contract # DE-AC02-06CH11357.
The Linac Coherent Light Source, (LCLS) the world’s first x-ray free electron laser (FEL) became operational in 2009. The Advanced Photon Source contributed to the original project by designing and building the undulator line. Two slightly different variations of these chambers were required for LCLS-II: one for a soft X-ray (SXR) undulator line, and one for a hard X-ray (HXR) undulator line. Because of the extremely short electron bunch length, a key physics requirement was to achieve the best possible surface finish within the chamber aperture. Improvements to our earlier fabrication methods allowed us to meet the critical surface roughness finish defined by RF impedance requirements. We were able to improve the surface finish from an average of 812 nm rms to 238 nm rms. The average longitudinal surface roughness slope of all chambers was to be less than 20 mrad. We achieved an average longitudinal surface roughness slope of 8.5 mrad with no chamber exceeding 20 mrad. In the end, sixty-four undulator vacuum chambers and alignment systems were delivered to SLAC for the LCLS-II Upgrade project. Here we will report on the process improvements for the fabrication of these chambers.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2019-THP068

About •

paper received ※ 16 August 2019 paper accepted ※ 27 August 2019 issue date ※ 05 November 2019

Export •

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