FEL2013 - List of Keywords (focusing)

Paper	Title	Other Keywords	Page
MOPSO57	Measurement of Wigner Distribution Function for Beam Characterization of FELs	laser, free-electron-laser, electron, FEL	92
	T. Mey, K. Mann, B. Schäfer LLG, Goettingen, Germany B. Keitel, S. Kreis, M. Kuhlmann, E. Plönjes, K.I. Tiedtke DESY, Hamburg, Germany
	Free-electron lasers deliver VUV and soft x-ray pulses with the highest brilliance available and high spatial coherence. Users of such facilities have high demands on phase and coherence properties of the beam, for instance when working with coherent diffractive imaging (CDI). To gain highly resolved spatial coherence information, we have performed a caustic scan at BL2 of FLASH using the ellipsoidal beam line focusing mirror and a movable XUV sensitive CCD detector. This measurement allows for retrieving the Wigner distribution function, being the two-dimensional Fourier transform of the mutual intensity of the beam. Computing the reconstruction on a four-dimensional grid, this yields the Wigner distribution which describes the beam propagation completely. Hence, we are able to provide comprehensive information about spatial coherence properties of the FLASH beam including the mutual coherence function and the global degree of coherence. Additionally, we derive the beam propagation parameters such as Rayleigh length, waist diameter and the beam quality factor M².

TUPSO46	Analysis and Measurement of Focusing Effects in a Traveling Wave Linear Accelerator	quadrupole, acceleration, electron, simulation	329
	H. Maesaka, T. Asaka, H. Ego, T. Hara, T. Inagaki, Y. Otake, T. Sakurai, H. Tanaka, K. Togawa RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
	We propose a further precise model of the transverse dynamics in a traveling wave linear accelerator (TWA) and report experimental results to demonstrate the validity of the model. In SACLA, the beam orbit is calculated by using a transfer matrix based on the transverse dynamics model of each component and the matrix is utilized for orbit stabilization, beam envelop matching etc. For the TWA part, a transfer matrix including an emittance damping effect and an edge focusing effect [] is employed. However, the beam orbit measured by rf cavity beam position monitors (RF-BPM) [] did not agree with the calculated orbit, especially for the off-crest acceleration part. Therefore, focusing effects in a TWA structure were analyzed by using a 3-dimensional rf simulation code. The analysis indicated that the transverse dynamics model of the TWA should include an additional quadrupole edge focusing effect. The amount of the additional focusing effect of the TWA was measured in SACLA and the rf simulation result was confirmed to be consistent with the measurement. After the modification of the transverse dynamics model, the beam orbit measured by RF-BPM agrees with the calculation. T. Hara et al., Nucl. Instrum. Methods A 624, 65 (2010). ** H. Maesaka et al., Nucl. Instrum. Methods A 696, 66 (2012).

TUPSO54	Undulators for Free Electron Lasers	undulator, electron, insertion, insertion-device	351
	C.W. Ostenfeld, M. Pedersen Danfysik A/S, Taastrup, Denmark
	Danfysik has produced insertion devices for the FEL community for almost 10 years. In this poster, we describe two recent undulator deliveries: a 2.8 m long undulator for the FELIX free electron laser, and a 4.5 m device for the FLARE project, both at Radboud University in Nijmegen, in the Netherlands. The device for FELIX is a 2.8 m PPM device, with a peak field of 0.483 T, and a minimum gap of 22 mm. The device for FLARE, is a 4.5 m hybrid device, with special poles, which allow for double focusing. For both devices, we describe the magnetic modelling, and the magnetic performance.

TUPSO62	Status of the Planar Undulator Applied in HUST THz-FEL Oscillator	undulator, FEL, radiation, electron	372
	B. Qin, X. Lei, K.F. Liu, X. Liu, P. Tan, Y.Q. Xiong, J. Yang, L. Yang HUST, Wuhan, People's Republic of China Y.B. Wang Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China
	To fulfill the physical requirement of a 50-100 um Free Electron Laser (FEL) oscillator, design considerations of a planar undulator are described. Some technical issues, including the tolerances study, the beam match, the field measurement setup and the influence on the magnetic field by the waveguide are discussed as well.

TUPSO77	Analytical and Numerical Analysis of Electron Trajectories in a 3-D Undulator Magnetic Field	undulator, electron, radiation, simulation	406
	N.V. Smolyakov, S.I. Tomin NRC, Moscow, Russia G. Geloni XFEL. EU, Hamburg, Germany
	In this contribution we present an analysis of electron trajectories in the three dimensional magnetic field from a planar undulator. The electron trajectory is influenced by the focusing properties of the undulator field. These focusing properties should be taken into account in simulations of spontaneous radiation, which constitutes the background signal of the FEL. The ideal magnetic field of an undulator can be described, in agreement with Maxwell equations, by a sinusoidal vertical magnetic field on the undulator axis, and by horizontal and longitudinal field components that appear out of axis. Exploiting this description for the ideal case, the differential equations of motion were solved by means of a perturbation theory approach, and the corresponding expressions for the electrons velocities and trajectories are derived. A computer code was also written, which relies on the Runge-Kutta algorithm. The analytical and numerical methods could then be compared, showing a good agreement.

Paper

Title

Other Keywords

Page

MOPSO57

Measurement of Wigner Distribution Function for Beam Characterization of FELs

laser, free-electron-laser, electron, FEL

92

T. Mey, K. Mann, B. Schäfer
LLG, Goettingen, Germany
B. Keitel, S. Kreis, M. Kuhlmann, E. Plönjes, K.I. Tiedtke
DESY, Hamburg, Germany

Free-electron lasers deliver VUV and soft x-ray pulses with the highest brilliance available and high spatial coherence. Users of such facilities have high demands on phase and coherence properties of the beam, for instance when working with coherent diffractive imaging (CDI). To gain highly resolved spatial coherence information, we have performed a caustic scan at BL2 of FLASH using the ellipsoidal beam line focusing mirror and a movable XUV sensitive CCD detector. This measurement allows for retrieving the Wigner distribution function, being the two-dimensional Fourier transform of the mutual intensity of the beam. Computing the reconstruction on a four-dimensional grid, this yields the Wigner distribution which describes the beam propagation completely. Hence, we are able to provide comprehensive information about spatial coherence properties of the FLASH beam including the mutual coherence function and the global degree of coherence. Additionally, we derive the beam propagation parameters such as Rayleigh length, waist diameter and the beam quality factor M².

TUPSO46

Analysis and Measurement of Focusing Effects in a Traveling Wave Linear Accelerator

quadrupole, acceleration, electron, simulation

329

H. Maesaka, T. Asaka, H. Ego, T. Hara, T. Inagaki, Y. Otake, T. Sakurai, H. Tanaka, K. Togawa
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan

We propose a further precise model of the transverse dynamics in a traveling wave linear accelerator (TWA) and report experimental results to demonstrate the validity of the model. In SACLA, the beam orbit is calculated by using a transfer matrix based on the transverse dynamics model of each component and the matrix is utilized for orbit stabilization, beam envelop matching etc. For the TWA part, a transfer matrix including an emittance damping effect and an edge focusing effect [*] is employed. However, the beam orbit measured by rf cavity beam position monitors (RF-BPM) [**] did not agree with the calculated orbit, especially for the off-crest acceleration part. Therefore, focusing effects in a TWA structure were analyzed by using a 3-dimensional rf simulation code. The analysis indicated that the transverse dynamics model of the TWA should include an additional quadrupole edge focusing effect. The amount of the additional focusing effect of the TWA was measured in SACLA and the rf simulation result was confirmed to be consistent with the measurement. After the modification of the transverse dynamics model, the beam orbit measured by RF-BPM agrees with the calculation.
* T. Hara et al., Nucl. Instrum. Methods A 624, 65 (2010).
** H. Maesaka et al., Nucl. Instrum. Methods A 696, 66 (2012).

TUPSO54

Undulators for Free Electron Lasers

undulator, electron, insertion, insertion-device

351

C.W. Ostenfeld, M. Pedersen
Danfysik A/S, Taastrup, Denmark

Danfysik has produced insertion devices for the FEL community for almost 10 years. In this poster, we describe two recent undulator deliveries: a 2.8 m long undulator for the FELIX free electron laser, and a 4.5 m device for the FLARE project, both at Radboud University in Nijmegen, in the Netherlands. The device for FELIX is a 2.8 m PPM device, with a peak field of 0.483 T, and a minimum gap of 22 mm. The device for FLARE, is a 4.5 m hybrid device, with special poles, which allow for double focusing. For both devices, we describe the magnetic modelling, and the magnetic performance.

TUPSO62

Status of the Planar Undulator Applied in HUST THz-FEL Oscillator

undulator, FEL, radiation, electron

372

B. Qin, X. Lei, K.F. Liu, X. Liu, P. Tan, Y.Q. Xiong, J. Yang, L. Yang
HUST, Wuhan, People's Republic of China
Y.B. Wang
Huazhong University of Science and Technology, State Key Laboratory of Advanced Electromagnetic Engineering and Technology,, Hubei, People's Republic of China

To fulfill the physical requirement of a 50-100 um Free Electron Laser (FEL) oscillator, design considerations of a planar undulator are described. Some technical issues, including the tolerances study, the beam match, the field measurement setup and the influence on the magnetic field by the waveguide are discussed as well.

TUPSO77

Analytical and Numerical Analysis of Electron Trajectories in a 3-D Undulator Magnetic Field

undulator, electron, radiation, simulation

406

N.V. Smolyakov, S.I. Tomin
NRC, Moscow, Russia
G. Geloni
XFEL. EU, Hamburg, Germany

In this contribution we present an analysis of electron trajectories in the three dimensional magnetic field from a planar undulator. The electron trajectory is influenced by the focusing properties of the undulator field. These focusing properties should be taken into account in simulations of spontaneous radiation, which constitutes the background signal of the FEL. The ideal magnetic field of an undulator can be described, in agreement with Maxwell equations, by a sinusoidal vertical magnetic field on the undulator axis, and by horizontal and longitudinal field components that appear out of axis. Exploiting this description for the ideal case, the differential equations of motion were solved by means of a perturbation theory approach, and the corresponding expressions for the electrons velocities and trajectories are derived. A computer code was also written, which relies on the Runge-Kutta algorithm. The analytical and numerical methods could then be compared, showing a good agreement.