IPAC2012 - List of Authors (Wu, J.)

Paper

Title

Page

Resistive Wall Heating of the Undulator in High Repetition Rate FELs

652

J. Qiang, J.N. Corlett, P. Emma
LBNL, Berkeley, California, USA
J. Wu
SLAC, Menlo Park, California, USA

Funding: Work supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
In next generation high repetition rate FELs, beam energy loss due to resistive wall wakefields will produce significant amount of heat. The heat load for a superconducting undulator (operating at low temperature), must be removed and will be expensive to remove. In this paper, we study this effect in an undulator proposed for a Next Generation Light Source (NGLS) at LBNL. We benchmark our calculations with measurements at the LCLS and carry out detailed parameter studies using beam from a start-to-end simulation. Our preliminary results suggest that the heat load in the undulator is about 2 W/m with an aperture size of 6 mm for nominal NGLS design parameters.

TUPPC048

Online Physics Model Platform

1275

P. Chu, Y. Zhang
FRIB, East Lansing, Michigan, USA
C. Benatti, V. Vuppala
NSCL, East Lansing, Michigan, USA
D. Dohan, G. Shen
BNL, Upton, Long Island, New York, USA
J. Wu
SLAC, Menlo Park, California, USA

Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661
For a complex accelerator such as the Facility for Rare Isotope Beams (FRIB), a transfer matrix based online model might not be sufficient for the entire machine. On the other hand, if introducing another modelling tools, physics applications have to be rewritten for all modelling tools. A platform which can host multiple modelling tools would be ideal for such scenario. Furthermore, the model platform along with infrastructure support can be used not only for online applications but also for offline purposes with multi-particle tracking simulation. In order to achieve such a platform, a set of common physics data structures has to be set. XAL's accelerator hierarchy based data structure is a good choice as the common structure for various models. Application Programming Interface (API) for physics applications should also be defined within a model data provider. A preliminary platform design and prototype is discussed.

TUPPP082

Optimization of a Terawatt Free Electron Laser

1780

J. Wu, X. Huang, Y. Jiao, A.U. Mandlekar, T.O. Raubenheimer, S. Spampinati, G. Yu
SLAC, Menlo Park, California, USA
P. Chu
FRIB, East Lansing, Michigan, USA
J. Qiang
LBNL, Berkeley, California, USA

Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515.
There is great interest in generating a terawatt (TW) hard X-ray free electron laser (FEL) that will enable coherent diffraction imaging of complex molecules like proteins and probe fundamental high-field physics. A feasibility study of producing such pulses was carried out em- ploying a configuration beginning with an SASE amplifier, followed by a "self-seeding" crystal monochromator, and finishing with a long tapered undulator. The undulator tapering profile, the phase advance in the undulator break sections, the quadrupole focusing strength, etc. are parameters to be optimized. A genetic algorithm (GA) is adopted for this multi-dimensional optimization. Concrete examples are given for LCLS/LCLS-II systems.

TUPPP083

Multi-Dimensional Optimization of a Tapered Free Electron Laser

1783

Y. Jiao, J. Wu
SLAC, Menlo Park, California, USA
Q. Qin
IHEP, Beijing, People's Republic of China

Energy extraction efficiency of a free electron laser (FEL) can be increased when the undulator is tapered. In this paper, we report a multi-dimensional optimizer to maximize the radiation power in a tapered FEL by searching for an optimal taper profile as well as a reasonable variation in electron beam radius. Applications of the proposed multi-dimensional optimization to the terawatt-level, tapered FELs with LCLS-like electron beam parameters are presented, and the proposed optimization scheme is compared with the GINGER’s self-design taper algorithm. At the end, the dependence of the available maximum radiation power on various parameters of the initial electron beam, the initial radiation field and the undulator system is summarized.

TUPPP084

Efficiency Enhancement in a Tapered Free Electron Laser by Varying the Electron Beam Radius

1786

Y. Jiao, J. Wu
SLAC, Menlo Park, California, USA
Q. Qin
IHEP, Beijing, People's Republic of China

Energy extraction efficiency of a free electron laser (FEL) can be increased when the undulator is tapered. An in-depth understanding of the tapering-related physics is required to explore the full potential of a tapered FEL, not only by tapering the undulator parameters in longitudinal dimension, but also optimizing the transverse effects. Based on the modified 1D FEL model and time-steady numerical simulations, we study the contribution of the variation in electron beam radius and the related transverse effects. Taking a terawatt-level, 120-m tapered FEL as example, we demonstrate that a reasonably varied, instead of a constant, electron beam radius along the undulator helps to improve the optical guiding and thus the radiation output.

WEYB02

Hard X-ray Self-seeding at the Linac Coherent Light Source

P. Emma, J.W. Amann, F.-J. Decker, Y.T. Ding, Y. Feng, J.C. Frisch, D. Fritz, J.B. Hastings, Z. Huang, J. Krzywinski, H. Loos, A.A. Lutman, H.-D. Nuhn, D.F. Ratner, J.A. Rzepiela, S. Spampinati, D.R. Walz, J.J. Welch, J. Wu, D. Zhu
SLAC, Menlo Park, California, USA
W. Berg, R.R. Lindberg, D. Shu, Yu. Shvyd'ko, S. Stoupin, E. Trakhtenberg, A. Zholents
ANL, Argonne, USA
V.D. Blank, S. Terentiev
TISNCM, Troitsk, Russia

Funding: Work supported by US Department of Energy, contract number DE-AC02-76SF00515.
We report on experimental results of FEL self-seeding with Angstrom wavelengths at the Linac Coherent Light Source (LCLS) at SLAC. The scheme, suggested at DESY*, replaces the 16th 4-m long undulator segment (out of 33 total) with a weak magnetic chicane and a diamond-based monochromator in Bragg transmission geometry. The monochromatized SASE FEL pulse from the first half of the undulator line then seeds the second half. This demonstration of hard x-ray self-seeding is shown to narrow the FEL bandwidth by a factor 40-50, allows longitudinally coherent x-ray pulses near the Fourier-transform limit, and may eventually allow an increases in peak brightness by 1-2 orders of magnitude after applying an aggressive undulator field taper.
* G. Geloni, V. Kocharyan, E. Saldin, DESY 10-133, Aug. 2010.

Slides WEYB02 [5.946 MB]

Paper	Title	Page
MOPPP040	Resistive Wall Heating of the Undulator in High Repetition Rate FELs	652
	J. Qiang, J.N. Corlett, P. Emma LBNL, Berkeley, California, USA J. Wu SLAC, Menlo Park, California, USA
	Funding: Work supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. In next generation high repetition rate FELs, beam energy loss due to resistive wall wakefields will produce significant amount of heat. The heat load for a superconducting undulator (operating at low temperature), must be removed and will be expensive to remove. In this paper, we study this effect in an undulator proposed for a Next Generation Light Source (NGLS) at LBNL. We benchmark our calculations with measurements at the LCLS and carry out detailed parameter studies using beam from a start-to-end simulation. Our preliminary results suggest that the heat load in the undulator is about 2 W/m with an aperture size of 6 mm for nominal NGLS design parameters.

TUPPC048	Online Physics Model Platform	1275
	P. Chu, Y. Zhang FRIB, East Lansing, Michigan, USA C. Benatti, V. Vuppala NSCL, East Lansing, Michigan, USA D. Dohan, G. Shen BNL, Upton, Long Island, New York, USA J. Wu SLAC, Menlo Park, California, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 For a complex accelerator such as the Facility for Rare Isotope Beams (FRIB), a transfer matrix based online model might not be sufficient for the entire machine. On the other hand, if introducing another modelling tools, physics applications have to be rewritten for all modelling tools. A platform which can host multiple modelling tools would be ideal for such scenario. Furthermore, the model platform along with infrastructure support can be used not only for online applications but also for offline purposes with multi-particle tracking simulation. In order to achieve such a platform, a set of common physics data structures has to be set. XAL's accelerator hierarchy based data structure is a good choice as the common structure for various models. Application Programming Interface (API) for physics applications should also be defined within a model data provider. A preliminary platform design and prototype is discussed.

TUPPP082	Optimization of a Terawatt Free Electron Laser	1780
	J. Wu, X. Huang, Y. Jiao, A.U. Mandlekar, T.O. Raubenheimer, S. Spampinati, G. Yu SLAC, Menlo Park, California, USA P. Chu FRIB, East Lansing, Michigan, USA J. Qiang LBNL, Berkeley, California, USA
	Funding: Work supported by U.S. Department of Energy, Office of Basic Energy Sciences, under Contract DE-AC02-76SF00515. There is great interest in generating a terawatt (TW) hard X-ray free electron laser (FEL) that will enable coherent diffraction imaging of complex molecules like proteins and probe fundamental high-field physics. A feasibility study of producing such pulses was carried out em- ploying a configuration beginning with an SASE amplifier, followed by a "self-seeding" crystal monochromator, and finishing with a long tapered undulator. The undulator tapering profile, the phase advance in the undulator break sections, the quadrupole focusing strength, etc. are parameters to be optimized. A genetic algorithm (GA) is adopted for this multi-dimensional optimization. Concrete examples are given for LCLS/LCLS-II systems.

TUPPP083	Multi-Dimensional Optimization of a Tapered Free Electron Laser	1783
	Y. Jiao, J. Wu SLAC, Menlo Park, California, USA Q. Qin IHEP, Beijing, People's Republic of China
	Energy extraction efficiency of a free electron laser (FEL) can be increased when the undulator is tapered. In this paper, we report a multi-dimensional optimizer to maximize the radiation power in a tapered FEL by searching for an optimal taper profile as well as a reasonable variation in electron beam radius. Applications of the proposed multi-dimensional optimization to the terawatt-level, tapered FELs with LCLS-like electron beam parameters are presented, and the proposed optimization scheme is compared with the GINGER’s self-design taper algorithm. At the end, the dependence of the available maximum radiation power on various parameters of the initial electron beam, the initial radiation field and the undulator system is summarized.

TUPPP084	Efficiency Enhancement in a Tapered Free Electron Laser by Varying the Electron Beam Radius	1786
	Y. Jiao, J. Wu SLAC, Menlo Park, California, USA Q. Qin IHEP, Beijing, People's Republic of China
	Energy extraction efficiency of a free electron laser (FEL) can be increased when the undulator is tapered. An in-depth understanding of the tapering-related physics is required to explore the full potential of a tapered FEL, not only by tapering the undulator parameters in longitudinal dimension, but also optimizing the transverse effects. Based on the modified 1D FEL model and time-steady numerical simulations, we study the contribution of the variation in electron beam radius and the related transverse effects. Taking a terawatt-level, 120-m tapered FEL as example, we demonstrate that a reasonably varied, instead of a constant, electron beam radius along the undulator helps to improve the optical guiding and thus the radiation output.

WEYB02	Hard X-ray Self-seeding at the Linac Coherent Light Source
	P. Emma, J.W. Amann, F.-J. Decker, Y.T. Ding, Y. Feng, J.C. Frisch, D. Fritz, J.B. Hastings, Z. Huang, J. Krzywinski, H. Loos, A.A. Lutman, H.-D. Nuhn, D.F. Ratner, J.A. Rzepiela, S. Spampinati, D.R. Walz, J.J. Welch, J. Wu, D. Zhu SLAC, Menlo Park, California, USA W. Berg, R.R. Lindberg, D. Shu, Yu. Shvyd'ko, S. Stoupin, E. Trakhtenberg, A. Zholents ANL, Argonne, USA V.D. Blank, S. Terentiev TISNCM, Troitsk, Russia
	Funding: Work supported by US Department of Energy, contract number DE-AC02-76SF00515. We report on experimental results of FEL self-seeding with Angstrom wavelengths at the Linac Coherent Light Source (LCLS) at SLAC. The scheme, suggested at DESY, replaces the 16th 4-m long undulator segment (out of 33 total) with a weak magnetic chicane and a diamond-based monochromator in Bragg transmission geometry. The monochromatized SASE FEL pulse from the first half of the undulator line then seeds the second half. This demonstration of hard x-ray self-seeding is shown to narrow the FEL bandwidth by a factor 40-50, allows longitudinally coherent x-ray pulses near the Fourier-transform limit, and may eventually allow an increases in peak brightness by 1-2 orders of magnitude after applying an aggressive undulator field taper. G. Geloni, V. Kocharyan, E. Saldin, DESY 10-133, Aug. 2010.
	Slides WEYB02 [5.946 MB]