FEL2011 - List of Keywords (resonance)

Paper	Title	Other Keywords	Page
MOPB28	Gas-filled Cell as a Narrow Bandwidth Bandpass Filter in the VUV Wavelength Range	radiation, FEL, photon, simulation	73
	G. Geloni European XFEL GmbH, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	We propose a method for spectrally filtering radiation in the VUV wavelength range by means of a monochromator constituted by a cell filled with a resonantly absorbing rare gas. Around particular wavelengths, the gas exhibits narrow-bandwidth absorbing resonances following the Fano profile. Within the photon energy range 60-65 eV, the correlation index of the Fano profiles for the photo-ionization spectra in He is equal to unity, meaning that the minimum of the cross-section is exactly zero. For sufficiently large column density in the gas cell, the spectrum of the incoming radiation will be attenuated by the background cross-section of many orders of magnitude, except for those wavelengths close to the point where the cross-section is zero. Remarkable advantages of a gas monochromator based on this principle are simplicity, efficiency and narrow-bandwidth. A gas monochromator installed in the experimental hall of a VUV SASE FEL facility would enable the delivery of a single-mode VUV laser beam. The design is identical to that of existing gas attenuator systems for VUV or X-ray FELs. We present feasibility study and exemplifications for the FLASH facility in the VUV regime.

MOPB31	Self-seeding Scheme with Gas Monochromator for Narrow-Bandwidth Soft X-Ray	undulator, radiation, electron, FEL	85
	G. Geloni European XFEL GmbH, Hamburg, Germany V. Kocharyan, E. Saldin DESY, Hamburg, Germany
	We propose an extension of our recently-proposed single-crystal self-seeding scheme to the soft X-ray range using a cell filled with resonantly absorbing gas as monochromator. The transmittance spectrum in the gas exhibits an absorbing resonance with narrow bandwidth. Then, similarly to the hard X-ray case, the temporal waveform of the transmitted radiation pulse is characterized by a long monochromatic wake, whose power is much larger than the equivalent shot noise power in the electron bunch. The monochromatic wake of the radiation pulse is combined with the delayed electron bunch and amplified in the second undulator. The proposed setup is extremely simple, and composed of as few as two simple elements: a gas cell, to be filled with noble gas, and a short magnetic chicane. The installation of the magnetic chicane does not perturb the undulator focusing system and does not interfere with the baseline mode of operation.

MOPC04	The Effects of Jitters on Coherent X-ray Radiation Using a Modulation Compression Scheme	radiation, laser, electron, FEL	103
	J. Qiang LBNL, Berkeley, California, USA J. Wu SLAC, Menlo Park, California, USA
	Modulation compression scheme based on a chirped beam, laser modulator and laser chirper, and two bunch compressors was proposed recently to generate coherent multi-color atto-second X-ray radiation [1]. In this paper, we will present studies of effects of the initial longitudinal beam chirp jitter, time synchronization jitter between the electron beam and the laser chirper, and the laser chirper amplitude jitter on the final coherent X-ray radiation. [1]Ji Qiang and Juhao Wu, “Generation multi-color attosecond X-ray radiation through modulation compression,” arXiv:1102.4806v1.

MOPC27	Small Signal Gain for Two Stream FEL	electron, FEL, wiggler, free-electron-laser	141
	A. Raghavi PNUM, Mashhad, Iran N. Mahdizadeh Islamic Azad University, Sabzevar Branch, Sabzevar, Iran
	The problem of wave-particle interaction in the small signal gain regime for the tow-stream free electron laser is considered using a relativistic moving frame. The equation of motion in this frame is solved by means of a non-relativistic Hamiltonian. Small signal gain (SSG) for the laser is derived in both moving and laboratory frames.

WEPB16	Study for Evaluation of Undulator Magnetic Field Using Vibrating Wire Method	undulator, electron, radiation, damping	413
	Y. Tanaka Tohoku University, School of Science, Sendai, Japan H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, T. Muto, K. Nanbu Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
	A test accelerator for a terahertz source project (t-ACTS) has been progressed at the Electron Light Science Centre, Tohoku University, in which a generation of intense coherent terahertz radiation from the very short electron bunch will be demonstrated. A narrow-band coherent terahertz radiation using an undulator has been considered to be implemented. We have constructed a planer undulator that is basically a Halbach type composed of permanent magnet blocks. The period length of the undulator and the number of periods are 100 mm and 25, respectively. The vibrating wire method is studied to measure the periodic magnetic field of the undulator. A thin copper-beryllium wire is placed on beam axis in the undulator, and an AC current flow is applied in the wire. By measuring amplitudes and phases of standing waves excited on the wire by the Lorentz force between AC current and magnetic field, we can reconstruct the magnetic field distribution along the wire. We discuss relations between reproducibility of the undulator field and the mode harmonics number used for the reconstruction. The results of preliminary measurement using the vibrating wire will be shown in this conference.

Paper

Title

Other Keywords

Page

MOPB28

Gas-filled Cell as a Narrow Bandwidth Bandpass Filter in the VUV Wavelength Range

radiation, FEL, photon, simulation

73

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

We propose a method for spectrally filtering radiation in the VUV wavelength range by means of a monochromator constituted by a cell filled with a resonantly absorbing rare gas. Around particular wavelengths, the gas exhibits narrow-bandwidth absorbing resonances following the Fano profile. Within the photon energy range 60-65 eV, the correlation index of the Fano profiles for the photo-ionization spectra in He is equal to unity, meaning that the minimum of the cross-section is exactly zero. For sufficiently large column density in the gas cell, the spectrum of the incoming radiation will be attenuated by the background cross-section of many orders of magnitude, except for those wavelengths close to the point where the cross-section is zero. Remarkable advantages of a gas monochromator based on this principle are simplicity, efficiency and narrow-bandwidth. A gas monochromator installed in the experimental hall of a VUV SASE FEL facility would enable the delivery of a single-mode VUV laser beam. The design is identical to that of existing gas attenuator systems for VUV or X-ray FELs. We present feasibility study and exemplifications for the FLASH facility in the VUV regime.

MOPB31

Self-seeding Scheme with Gas Monochromator for Narrow-Bandwidth Soft X-Ray

undulator, radiation, electron, FEL

85

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

We propose an extension of our recently-proposed single-crystal self-seeding scheme to the soft X-ray range using a cell filled with resonantly absorbing gas as monochromator. The transmittance spectrum in the gas exhibits an absorbing resonance with narrow bandwidth. Then, similarly to the hard X-ray case, the temporal waveform of the transmitted radiation pulse is characterized by a long monochromatic wake, whose power is much larger than the equivalent shot noise power in the electron bunch. The monochromatic wake of the radiation pulse is combined with the delayed electron bunch and amplified in the second undulator. The proposed setup is extremely simple, and composed of as few as two simple elements: a gas cell, to be filled with noble gas, and a short magnetic chicane. The installation of the magnetic chicane does not perturb the undulator focusing system and does not interfere with the baseline mode of operation.

MOPC04

The Effects of Jitters on Coherent X-ray Radiation Using a Modulation Compression Scheme

radiation, laser, electron, FEL

103

J. Qiang
LBNL, Berkeley, California, USA
J. Wu
SLAC, Menlo Park, California, USA

Modulation compression scheme based on a chirped beam, laser modulator and laser chirper, and two bunch compressors was proposed recently to generate coherent multi-color atto-second X-ray radiation [1]. In this paper, we will present studies of effects of the initial longitudinal beam chirp jitter, time synchronization jitter between the electron beam and the laser chirper, and the laser chirper amplitude jitter on the final coherent X-ray radiation.
[1]Ji Qiang and Juhao Wu, “Generation multi-color attosecond X-ray radiation through modulation compression,” arXiv:1102.4806v1.

MOPC27

Small Signal Gain for Two Stream FEL

electron, FEL, wiggler, free-electron-laser

141

A. Raghavi
PNUM, Mashhad, Iran
N. Mahdizadeh
Islamic Azad University, Sabzevar Branch, Sabzevar, Iran

The problem of wave-particle interaction in the small signal gain regime for the tow-stream free electron laser is considered using a relativistic moving frame. The equation of motion in this frame is solved by means of a non-relativistic Hamiltonian. Small signal gain (SSG) for the laser is derived in both moving and laboratory frames.

WEPB16

Study for Evaluation of Undulator Magnetic Field Using Vibrating Wire Method

undulator, electron, radiation, damping

413

Y. Tanaka
Tohoku University, School of Science, Sendai, Japan
H. Hama, F. Hinode, S. Kashiwagi, M. Kawai, X. Li, T. Muto, K. Nanbu
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan

A test accelerator for a terahertz source project (t-ACTS) has been progressed at the Electron Light Science Centre, Tohoku University, in which a generation of intense coherent terahertz radiation from the very short electron bunch will be demonstrated. A narrow-band coherent terahertz radiation using an undulator has been considered to be implemented. We have constructed a planer undulator that is basically a Halbach type composed of permanent magnet blocks. The period length of the undulator and the number of periods are 100 mm and 25, respectively. The vibrating wire method is studied to measure the periodic magnetic field of the undulator. A thin copper-beryllium wire is placed on beam axis in the undulator, and an AC current flow is applied in the wire. By measuring amplitudes and phases of standing waves excited on the wire by the Lorentz force between AC current and magnetic field, we can reconstruct the magnetic field distribution along the wire. We discuss relations between reproducibility of the undulator field and the mode harmonics number used for the reconstruction. The results of preliminary measurement using the vibrating wire will be shown in this conference.