FEL2010 - List of Authors (Evain, C.)

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Evain, C.

Paper	Title	Page
TUPA04	Control of Instability Induced by a Detuning in FEL Oscillator	215
	C. Evain, M.-E. Couprie SOLEIL, Gif-sur-Yvette S. Bielawski, C. Szwaj PhLAM/CERCLA, Villeneuve d'Ascq Cedex M. Hosaka Nagoya University, Nagoya M. Katoh UVSOR, Okazaki A. Mochihashi JASRI/SPring-8, Hyogo-ken
	In FEL oscillator, a desynchronisation between the electron-bunch passage frequency and the repetition rate of the laser can lead to instability, characterised by erratic longitudinal shape of the emitted light pulses. We show that this instability can be controlled using a simple feedback system which consist in re-injecting in the cavity a part of the emitted light. Analytical, numerical and experimental studies on the UVSOR-II storage ring have been performed, and show that the energy needed to achieved the control can be extremely weak, in practical higher than the noise level[1]. We also show that another important parameter is the phase of the re-injected signal with respect to the light in the cavity. Depending of the value of this phase, we can observe a shift of the emitted light wavelength, which can go with a modulation of the laser pulse envelop. Both of this two phenomenas are quantitatively analysed. [1] C. Evain, C. Szwaj, S. Bielawski, M. Hosaka, A. Mochihashi, M. Katoh, and M.-E. Couprie, Phys. Rev. Lett. {10}2, 134501 (2009)

Paper

Title

Page

TUPA04

Control of Instability Induced by a Detuning in FEL Oscillator

215

C. Evain, M.-E. Couprie
SOLEIL, Gif-sur-Yvette
S. Bielawski, C. Szwaj
PhLAM/CERCLA, Villeneuve d'Ascq Cedex
M. Hosaka
Nagoya University, Nagoya
M. Katoh
UVSOR, Okazaki
A. Mochihashi
JASRI/SPring-8, Hyogo-ken

In FEL oscillator, a desynchronisation between the electron-bunch passage frequency and the repetition rate of the laser can lead to instability, characterised by erratic longitudinal shape of the emitted light pulses. We show that this instability can be controlled using a simple feedback system which consist in re-injecting in the cavity a part of the emitted light. Analytical, numerical and experimental studies on the UVSOR-II storage ring have been performed, and show that the energy needed to achieved the control can be extremely weak, in practical higher than the noise level[1]. We also show that another important parameter is the phase of the re-injected signal with respect to the light in the cavity. Depending of the value of this phase, we can observe a shift of the emitted light wavelength, which can go with a modulation of the laser pulse envelop. Both of this two phenomenas are quantitatively analysed.

[1] C. Evain, C. Szwaj, S. Bielawski, M. Hosaka, A. Mochihashi, M. Katoh, and M.-E. Couprie, Phys. Rev. Lett. {10}2, 134501 (2009)