FEL2011 - List of Keywords (wakefield)

Paper	Title	Other Keywords	Page
MOPB26	Self-seeded Operation of the LCLS Hard X-ray FEL in the Long-bunch Mode of Operation	undulator, electron, FEL, radiation	65
	G. Geloni European XFEL GmbH, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	Self-seeding options for the LCLS baseline were recently investigated using a scheme which relies on a single-crystal monochromator in Bragg-transmission geometry. The LCLS low-charge (0.02 nC) mode of operation was considered in order to demonstrate the feasibility of the proposed scheme. The wakefield effects from the linac and from the undulator vacuum chamber are much reduced at such low charge, and can be ignored. In this paper we extend our previous investigations to the case of the LCLS mode of operation with nominal charge. Based on the LCLS start-to-end simulation for an electron beam charge of 0.25 nC, and accounting for the wakefields from the undulator vacuum chamber we demonstrate that the same simplest self-seeding system (two undulators with a single-crystal monochromator in between) is appropriate not only for short (few femtosecond) bunches, but for longer bunches too.

TUOAI1	Hard X-ray Self-seeding for XFELs: Towards Coherent FEL Pulses	undulator, electron, radiation, FEL	148
	G. Geloni European XFEL GmbH, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	Start-up from shot noise limits the longitudinal coherence of typical SASE XFEL pulses. Self-seeding schemes provide an elegant solution to this problem. However, their applicability to the baseline of already working or designed XFELs is subject to constraints, including minimal changes to the baseline design and possibility to recover the baseline mode of operation. Here we discuss a recently proposed single-bunch self-seeding scheme for hard X-rays. The physical principles of this scheme can be extended to soft X-rays as well. The method is based on a particular kind of monochromator, which relies on the use of a single crystal in Bragg-transmission geometry. In its simplest configuration, the setup consists of an input undulator and an output undulator separated by such monochromator. Several, more advanced configurations can be considered. For example, for high repetition rates of the X-ray pulses, or when a high spectral purity of the output radiation is requested, the simplest two-undulator configuration is not optimal: three or more undulators separated by monochromators can then be used. Exemplifications, based on facilities working or under construction will be discussed.
	Slides TUOAI1 [2.818 MB]

TUPA19	Operation Modes and Longitudinal Layout for the SwissFEL Hard X-Ray Facility	photon, linac, FEL, undulator	235
	B. Beutner, S. Reiche Paul Scherrer Institut, Villigen, Switzerland
	The SwissFEL facility will produce coherent, ultrabright, and ultra-short photon pulses covering a wavelength range from 0.1 nm to 7 nm, requiring an emittance between 0.18 to 0.43 mm mrad at bunch charges between 10pC and 200pC. In nominal operation continous changes between these two bunch charges will be offered to the users in order to allow them an individual tradeoff between photon power and pulse length depending on thier requirements. The facility consists of an S-band rf-gun and booster and a C-band main linac, which accelerates the beam up to 5.8 GeV. Two compression chicanes will provide a nominal peak current of about 1-3 kA depending on the charge. In addition special operation setups for ultra short single mode photon pulses and large bandwidth will be availiable to users. In this paper different operation modes including nominal operation as well as special modes are presented and discussed in terms of photon performance and machine stability requiremnts.

WEPA16	Quasi-cw Normal Conducting Linac for Soft XFEL	linac, klystron, dipole, factory	359
	F. Wang, C. Adolphsen SLAC, Menlo Park, California, USA
	The CW operating soft XFELs have been proposed worldwide to serve large user community simultaneous. In principle, the superconducting linac technology is the only solution to realize such a cw light source. However, large amount of R&D efforts are still needed to build such a linac, which could delay such facility for a significant long period. Therefore, it will be very important to explore the other technology based such XFEL, like the normal conducting based quasi-cw (10s kHz) linac. With the initial study, it turns out that such a quasi-cw linac could be built with L-band (1.3 GHz) or X-band (11.4 GHz) technology. And the L-band devices for such a linac have been developed in the frame work of ILC.

THPB28	The High Power Test Model of C-band Accelerating Structure for Compact XFEL at SINAP	impedance, linac, target, factory	617
	W. Fang, Q. Gu, Z.T. Zhao SINAP, Shanghai, People's Republic of China D.C. Tong TUB, Beijing, People's Republic of China
	R&D of a C-band (5712 MHz) high gradient traveling-wave accelerating structure is being in progress at Shanghai Institute of Applied Physics (SINAP). Conceptual design of the accelerating structure has been accomplished, and verified by the cold test of the experimental model. Now the first prototype structure is ready for high RF power test and the optimization of a new operating mode is proposed for developing a robust high gradient C-band struture. In this paper, the results of the cold test of the first prototype structure and the optimization details are introduced.

Paper

Title

Other Keywords

Page

MOPB26

Self-seeded Operation of the LCLS Hard X-ray FEL in the Long-bunch Mode of Operation

undulator, electron, FEL, radiation

65

G. Geloni
European XFEL GmbH, Hamburg, Germany
V. Kocharyan, E. Saldin
DESY, Hamburg, Germany

Self-seeding options for the LCLS baseline were recently investigated using a scheme which relies on a single-crystal monochromator in Bragg-transmission geometry. The LCLS low-charge (0.02 nC) mode of operation was considered in order to demonstrate the feasibility of the proposed scheme. The wakefield effects from the linac and from the undulator vacuum chamber are much reduced at such low charge, and can be ignored. In this paper we extend our previous investigations to the case of the LCLS mode of operation with nominal charge. Based on the LCLS start-to-end simulation for an electron beam charge of 0.25 nC, and accounting for the wakefields from the undulator vacuum chamber we demonstrate that the same simplest self-seeding system (two undulators with a single-crystal monochromator in between) is appropriate not only for short (few femtosecond) bunches, but for longer bunches too.

TUOAI1

Hard X-ray Self-seeding for XFELs: Towards Coherent FEL Pulses

undulator, electron, radiation, FEL

148

G. Geloni
European XFEL GmbH, Hamburg, Germany
V. Kocharyan, E. Saldin
DESY, Hamburg, Germany

Start-up from shot noise limits the longitudinal coherence of typical SASE XFEL pulses. Self-seeding schemes provide an elegant solution to this problem. However, their applicability to the baseline of already working or designed XFELs is subject to constraints, including minimal changes to the baseline design and possibility to recover the baseline mode of operation. Here we discuss a recently proposed single-bunch self-seeding scheme for hard X-rays. The physical principles of this scheme can be extended to soft X-rays as well. The method is based on a particular kind of monochromator, which relies on the use of a single crystal in Bragg-transmission geometry. In its simplest configuration, the setup consists of an input undulator and an output undulator separated by such monochromator. Several, more advanced configurations can be considered. For example, for high repetition rates of the X-ray pulses, or when a high spectral purity of the output radiation is requested, the simplest two-undulator configuration is not optimal: three or more undulators separated by monochromators can then be used. Exemplifications, based on facilities working or under construction will be discussed.

Slides TUOAI1 [2.818 MB]

TUPA19

Operation Modes and Longitudinal Layout for the SwissFEL Hard X-Ray Facility

photon, linac, FEL, undulator

235

B. Beutner, S. Reiche
Paul Scherrer Institut, Villigen, Switzerland

The SwissFEL facility will produce coherent, ultrabright, and ultra-short photon pulses covering a wavelength range from 0.1 nm to 7 nm, requiring an emittance between 0.18 to 0.43 mm mrad at bunch charges between 10pC and 200pC. In nominal operation continous changes between these two bunch charges will be offered to the users in order to allow them an individual tradeoff between photon power and pulse length depending on thier requirements. The facility consists of an S-band rf-gun and booster and a C-band main linac, which accelerates the beam up to 5.8 GeV. Two compression chicanes will provide a nominal peak current of about 1-3 kA depending on the charge. In addition special operation setups for ultra short single mode photon pulses and large bandwidth will be availiable to users. In this paper different operation modes including nominal operation as well as special modes are presented and discussed in terms of photon performance and machine stability requiremnts.

WEPA16

Quasi-cw Normal Conducting Linac for Soft XFEL

linac, klystron, dipole, factory

359

F. Wang, C. Adolphsen
SLAC, Menlo Park, California, USA

The CW operating soft XFELs have been proposed worldwide to serve large user community simultaneous. In principle, the superconducting linac technology is the only solution to realize such a cw light source. However, large amount of R&D efforts are still needed to build such a linac, which could delay such facility for a significant long period. Therefore, it will be very important to explore the other technology based such XFEL, like the normal conducting based quasi-cw (10s kHz) linac. With the initial study, it turns out that such a quasi-cw linac could be built with L-band (1.3 GHz) or X-band (11.4 GHz) technology. And the L-band devices for such a linac have been developed in the frame work of ILC.

THPB28

The High Power Test Model of C-band Accelerating Structure for Compact XFEL at SINAP

impedance, linac, target, factory

617

W. Fang, Q. Gu, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
D.C. Tong
TUB, Beijing, People's Republic of China

R&D of a C-band (5712 MHz) high gradient traveling-wave accelerating structure is being in progress at Shanghai Institute of Applied Physics (SINAP). Conceptual design of the accelerating structure has been accomplished, and verified by the cold test of the experimental model. Now the first prototype structure is ready for high RF power test and the optimization of a new operating mode is proposed for developing a robust high gradient C-band struture. In this paper, the results of the cold test of the first prototype structure and the optimization details are introduced.