FEL2013 - List of Authors (Raubenheimer, T.O.)

Paper

Title

Page

Multi-Objective Genetic Optimization for LCLS-II X-Ray FEL

12

L. Wang, T.O. Raubenheimer
SLAC, Menlo Park, California, USA

The Linac Coherent Light Source II (LCLS-II) will build on the success of the world's most powerful X-ray laser, the Linac Coherent Light Source (LCLS). It will add two new X-ray laser beams and room for additional new instruments, greatly increasing the number of experiments carried out each year. Multiple operation modes are proposed to accommodate a variety of user requirements. There are a large number of variables and objectives in the design. For each operation mode, Multi-Objective Genetic Algorithm (MOGA) is applied to optimize the machine parameters in order to minimize the jitters, energy spread, collective effects and emittance. The optimal designs for various operation modes are presented in this paper. The phase and voltage of the linac RF, R56 at the two bunch compressors are optimized. The CSR (coherent synchrotron radiation) can induce large emittance growth, which is minimized by optimizing the phase advance between the compressor and the bend section. The final emittance at the beginning of the undulator is just about 1um and even lower.

Slides MOOCNO02 [3.046 MB]

WEPSO10

Increased Stability Requirements for Seeded Beams at LCLS

518

F.-J. Decker, W.S. Colocho, Z. Huang, R.H. Iverson, A. Krasnykh, A.A. Lutman, M.N. Nguyen, T.O. Raubenheimer, M.C. Ross, J.L. Turner, L. Wang
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
Running the Linac Coherent Light Source (LCLS) with self-seeded photon beams requires better electron beam stability, especially in energy, to reduce the otherwise huge intensity variations of more than 100%. Code was written to identify and quantify the different jitter sources. Some improvements are being addressed, especially the stability of the modulator high voltage of some critical RF stations. Special setups like running the beam off crest in the last part of the linac can also be used to reduce the energy jitter. Even a slight dependence on the transverse position was observed. The intensity jitter distribution of a seeded beam is still more contained with peaks up too twice the average intensity, compared to the jitter distribution of a SASE beam going through a monochromator, which can have damaging spikes up to 5 times the average intensity.

WEPSO27

Recent LCLS Performance From 250 to 500 eV

554

R.H. Iverson, J. Arthur, U. Bergmann, C. Bostedt, J.D. Bozek, A. Brachmann, W.S. Colocho, F.-J. Decker, Y. Ding, Y. Feng, J.C. Frisch, J.N. Galayda, T. Galetto, Z. Huang, E.M. Kraft, J. Krzywinski, J.C. Liu, H. Loos, X.S. Mao, S.P. Moeller, H.-D. Nuhn, A.A. Prinz, D.F. Ratner, T.O. Raubenheimer, S.H. Rokni, W.F. Schlotter, P.M. Schuh, T.J. Smith, M. Stanek, P. Stefan, M.K. Sullivan, J.L. Turner, J.J. Turner, J.J. Welch, J. Wu, F. Zhou
SLAC, Menlo Park, California, USA
P. Emma
LBNL, Berkeley, California, USA
R. Soufli
LLNL, Livermore, California, USA

Funding: Work supported by US Department of Energy contract DE-AC02-76SF00515 and BES.
The Linac Coherent Light Source is an X-ray free-electron laser at the SLAC National Accelerator Laboratory. It produces coherent soft and hard X-rays with peak brightness nearly ten orders of magnitude beyond conventional synchrotron sources and a range of pulse durations from 500 to <10 fs. The facility has been operating at X-ray energy from 500 to 10,000eV. Users have expressed great interest in doing experiments with X-Rays near the carbon absorption edge at 284eV. We describe the operation and performance of the LCLS in the newly established regime between 250 and 500eV.
[1] Emma, P. et al., “First lasing and operation of an ˚angstrom-wavelength free-electron laser,” Nature Pho-
ton. 4(9), 641–647 (2010).

THOANO02

Experimental Demonstration of Echo-enabled Harmonic Generation at the 14th Harmonic

D. Xiang, M.P. Dunning, C. Hast, E. Hemsing, T.O. Raubenheimer, S.P. Weathersby
SLAC, Menlo Park, California, USA

Funding: Work supported by U.S. DOE under Contract No. DE-AC02-76SF00515.
Following the successful demonstration of echo-enabled harmonic generation [1] (EEHG [2]) with n=7 [3] at SLAC's NLCTA in 2011 [4], the beam line has been upgraded recently to benchmark EEHG theory at much higher harmonics. An optical parametric amplifier has been used to provide a seed with wavelength at 2.4 μm. Using an rf undulator as the radiator, coherent radiation at the 14th harmonic of the seed, i.e. with wavelength at 171 nm, has been generated using EEHG technique with a 120 MeV beam. We will present detailed experimental results on testing EEHG at n=14. Future plans in testing EEHG at n=30~75 in the coming year will be briefly discussed as well.
[1] G. Stupakov, PRL 102, 074801 (2009).
[2] D. Xiang and G. Stupakov, PRST-AB 12, 030702 (2009).
[3] D. Xiang et al., PRL 105, 114801 (2010).
[4] D. Xiang et al., PRL 108, 024802 (2012)

Slides THOANO02 [2.288 MB]

Paper	Title	Page
MOOCNO02	Multi-Objective Genetic Optimization for LCLS-II X-Ray FEL	12
	L. Wang, T.O. Raubenheimer SLAC, Menlo Park, California, USA
	The Linac Coherent Light Source II (LCLS-II) will build on the success of the world's most powerful X-ray laser, the Linac Coherent Light Source (LCLS). It will add two new X-ray laser beams and room for additional new instruments, greatly increasing the number of experiments carried out each year. Multiple operation modes are proposed to accommodate a variety of user requirements. There are a large number of variables and objectives in the design. For each operation mode, Multi-Objective Genetic Algorithm (MOGA) is applied to optimize the machine parameters in order to minimize the jitters, energy spread, collective effects and emittance. The optimal designs for various operation modes are presented in this paper. The phase and voltage of the linac RF, R56 at the two bunch compressors are optimized. The CSR (coherent synchrotron radiation) can induce large emittance growth, which is minimized by optimizing the phase advance between the compressor and the bend section. The final emittance at the beginning of the undulator is just about 1um and even lower.
	Slides MOOCNO02 [3.046 MB]

WEPSO10	Increased Stability Requirements for Seeded Beams at LCLS	518
	F.-J. Decker, W.S. Colocho, Z. Huang, R.H. Iverson, A. Krasnykh, A.A. Lutman, M.N. Nguyen, T.O. Raubenheimer, M.C. Ross, J.L. Turner, L. Wang SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515. Running the Linac Coherent Light Source (LCLS) with self-seeded photon beams requires better electron beam stability, especially in energy, to reduce the otherwise huge intensity variations of more than 100%. Code was written to identify and quantify the different jitter sources. Some improvements are being addressed, especially the stability of the modulator high voltage of some critical RF stations. Special setups like running the beam off crest in the last part of the linac can also be used to reduce the energy jitter. Even a slight dependence on the transverse position was observed. The intensity jitter distribution of a seeded beam is still more contained with peaks up too twice the average intensity, compared to the jitter distribution of a SASE beam going through a monochromator, which can have damaging spikes up to 5 times the average intensity.

WEPSO27	Recent LCLS Performance From 250 to 500 eV	554
	R.H. Iverson, J. Arthur, U. Bergmann, C. Bostedt, J.D. Bozek, A. Brachmann, W.S. Colocho, F.-J. Decker, Y. Ding, Y. Feng, J.C. Frisch, J.N. Galayda, T. Galetto, Z. Huang, E.M. Kraft, J. Krzywinski, J.C. Liu, H. Loos, X.S. Mao, S.P. Moeller, H.-D. Nuhn, A.A. Prinz, D.F. Ratner, T.O. Raubenheimer, S.H. Rokni, W.F. Schlotter, P.M. Schuh, T.J. Smith, M. Stanek, P. Stefan, M.K. Sullivan, J.L. Turner, J.J. Turner, J.J. Welch, J. Wu, F. Zhou SLAC, Menlo Park, California, USA P. Emma LBNL, Berkeley, California, USA R. Soufli LLNL, Livermore, California, USA
	Funding: Work supported by US Department of Energy contract DE-AC02-76SF00515 and BES. The Linac Coherent Light Source is an X-ray free-electron laser at the SLAC National Accelerator Laboratory. It produces coherent soft and hard X-rays with peak brightness nearly ten orders of magnitude beyond conventional synchrotron sources and a range of pulse durations from 500 to <10 fs. The facility has been operating at X-ray energy from 500 to 10,000eV. Users have expressed great interest in doing experiments with X-Rays near the carbon absorption edge at 284eV. We describe the operation and performance of the LCLS in the newly established regime between 250 and 500eV. [1] Emma, P. et al., “First lasing and operation of an ˚angstrom-wavelength free-electron laser,” Nature Pho- ton. 4(9), 641–647 (2010).

THOANO02	Experimental Demonstration of Echo-enabled Harmonic Generation at the 14th Harmonic
	D. Xiang, M.P. Dunning, C. Hast, E. Hemsing, T.O. Raubenheimer, S.P. Weathersby SLAC, Menlo Park, California, USA
	Funding: Work supported by U.S. DOE under Contract No. DE-AC02-76SF00515. Following the successful demonstration of echo-enabled harmonic generation [1] (EEHG [2]) with n=7 [3] at SLAC's NLCTA in 2011 [4], the beam line has been upgraded recently to benchmark EEHG theory at much higher harmonics. An optical parametric amplifier has been used to provide a seed with wavelength at 2.4 μm. Using an rf undulator as the radiator, coherent radiation at the 14th harmonic of the seed, i.e. with wavelength at 171 nm, has been generated using EEHG technique with a 120 MeV beam. We will present detailed experimental results on testing EEHG at n=14. Future plans in testing EEHG at n=30~75 in the coming year will be briefly discussed as well. [1] G. Stupakov, PRL 102, 074801 (2009). [2] D. Xiang and G. Stupakov, PRST-AB 12, 030702 (2009). [3] D. Xiang et al., PRL 105, 114801 (2010). [4] D. Xiang et al., PRL 108, 024802 (2012)
	Slides THOANO02 [2.288 MB]