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ABSTRACT: The Orsay storage ring free-electron laser has been operated in the short–wave-length side (blue) of the visible spectral range from 4630 Å to 4860 Å. General conclusions on storage ring free-electron laser are derived after our successive operations of a tunable laser over almost the entire visible spectral range.
EPL (Europhysics Letters) 07/2007; 3(6):689. · 2.17 Impact Factor
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ABSTRACT: Due to its low gain, the Orsay storage ring free-electron laser necessitates the use of high reflectivity mirrors. Three techniques for measuring the mirror losses are presented, based on cavity decay time measurements using either an external laser, the synchrotron radiation stored in the cavity, or the free-electron laser itself. The high signal-to-noise ratio allowed the detection of loss variations as low as 10(-7)/sec(1/2). From these diagnostics three distinct processes of UV-induced degradation of TiO2/SiO2 dielectric mirrors were identified. One was a surface absorption of the upper SiO2-air interface; it was not affected by annealing. The other two corresponded to a volume absorption of the layers which completely recovered after annealing.
Applied Optics 10/1985; 24(17):2762-70. · 1.41 Impact Factor
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IEEE Journal of Quantum Electronics 08/1985; 21(7):805- 823. · 1.88 Impact Factor
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ABSTRACT: The optical klystron, previously successfully optimized for the realization of a FEL on the ACO storage ring at Orsay, has been used as a nonlinear medium for producing harmonics of an external 1.06 μm Nd:YAG laser focused into it. Detailed experimental data are reported. A comparison with theoretical calculations shows very good qualitative and quantitative agreement between the experimental data and the theory.
IEEE Journal of Quantum Electronics 08/1985; · 1.88 Impact Factor
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ABSTRACT: During the last few years, radiation emitted by relativistic electrons
has received much attention. Such emission is basically related to
synchrotron radiation in a dipole field, in an undulator, or from a free
electron laser (FEL). The FEL is a very promising source of coherent
radiation in the spectral range from the far IR to the VUV. The two
basic classes of FEL include the type operating in the 'collective'
regime involving the emission of radiation in the far IR, and a type
operating in the low density or 'Compton' regime involving emission at
short wavelengths (IR, visible, UV). The present paper is concerned with
an experiment regarding the second basic class of FEL. Experiments
performed with the aid of a storage ring FEL (SRFEL) are reviewed.
IEEE Journal of Quantum Electronics 06/1985; 21:805-823. · 1.88 Impact Factor
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D. Deacon, P. Elleaume,
M. Xie,
C. Bazin,
M. Bergher,
M. Billardon,
B. Girard,
J. Madey,
J. Ortega,
Y. Petroff,
K. Robinson,
M. Velghe
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ABSTRACT: We report the first measurement of the off-diagonal terms in the transverse gain matrix in a free electron laser. We show that the higher order transverse modes stimulated in the FEL interaction diminish in amplitude as the electron beam size is increased, that the far field and the near field effects of the excited modes are not equivalent, and that in this low divergence case, the mode mixing is insensitive to the resonance parameter. Remarkably close agreement is demonstrated with the theory [1]. The effects of a multiple mode input beam are also observed, and the theoretical expression is derived.
IEEE Journal of Quantum Electronics 04/1985; · 1.88 Impact Factor
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ABSTRACT: This paper summarizes the basic low-current, laser-induced bunch-lengthening measurements that have been made on the ACO Storage-Ring Free-Electron Laser (SRFEL). The measurements provide verification of both the functional dependence and absolute magnitude of SRFEL theoretical models. The method of measurement, which is is explained, exploits frequency-domain techniques and is capable of accuracies comparable to those of a streak camara. The measurements are in good agreement with existing SRFEL theory and provide an important base for future work.
Applied Physics B 12/1984; 36(1):41-52. · 2.19 Impact Factor
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ABSTRACT: To improve the gain in the Orsay storage ring Free Electron Laser (FEL) experiment, the 17 period permanent magnet undulator has been modified to form an optical klystron (OK). We report the measurement of spontaneous emission and the effects on it of energy spread and angular spread. Gain and laser induced bunch lengthening measurements with the OK are also reported and are in very good agreement with the FEL classical theory. The spontaneous emission spectrum which is easy to measure with good signal to noise ratio, turns out to be a very good diagnostic tool forenergy spread and angular spread measurements on storage rings. The factor of four increase in the small gain obtained by converting the undulator NOEL into an OK was the critical factor in the recent operation of the ACO storage ring laser above threshold.
Applied Physics B 07/1984; 34(4):207-219. · 2.19 Impact Factor
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ABSTRACT: We review the recent results obtained at Orsay on the first storage ring Free Electron Laser and on V.U.V. experiments. Some prospects to extend the F.E.L. spectral range toward the V.U.V. region are examined.
AIP Conference Proceedings. 06/1984; 118(1):96-102.
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ABSTRACT: We derive the most general equations of motion for the electrons and the electromagnetic field in a free-electron laser including the effects of diffraction and pulse propagation. The field evolution is expressed in terms of the amplitudes and phases of a complete set of transverse modes. The analytic solution is given in the small-signal regime, where the theory is shown to be in excellent agreement with a recent experiment at Orsay.
Applied Physics B 12/1983; 33(1):9-16. · 2.19 Impact Factor
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ABSTRACT: The principles underlying the operation of free-electron lasers are
reviewed, with attention given to resonance between the radiation field
and the electrons, spontaneous emission, and amplification processes.
Experimental results on free-electron lasers are presented, and
attention is given to free-electron lasers emitting in the infrared,
visible, and ultraviolet ranges.
NASA STI/Recon Technical Report A. 05/1983; 83:35725.
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ABSTRACT: We report the results of the first gain measurements on the free electron laser being assembled on the storage ring ACO. The largest measured peak gain, averaged over the laser mode, is ¿ = 4.3 à 10-4 per pass. No laser induced bunch lengthening is observed within the experimental accuracy of 50 psec under a laser intensity of 1.6 kw/cm2 and under the conditions of strong anomalous bunch lengthening (¿¿/¿¿(I=0)) = 6.8 - 4.2.
IEEE Transactions on Nuclear Science 07/1981; · 1.45 Impact Factor
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ABSTRACT: A modification of the operating point of the machine is reported. Smaller transverse sizes of the electron beam have been achieved producing a higher optical gain, and a laser tunability ranging from 5700 to 6400 Å. The dependence of the temporal and spectral structure of the laser beam versus detuning and Q-switch frequency is discussed.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 250:26-34. · 1.21 Impact Factor
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ABSTRACT: The main results obtained on the free electron laser and on optical harmonic generation with the storage ring ACO at Orsay in France are reviewed. A specific magnetic device, generally called an undulator, allows one to collect coherent light. In the free electron laser case, the undulator radiation is stored and amplified in an optical cavity. Tunable light was obtained in the visible range. For optical harmonic generation, external laser light is emitted in the undulator area, generating coherent harmonic radiation. Experimentally, 350, 177 and 107 nm wavelengths were obtained with a Nd-YAG laser. New experiments are planned with the Super-ACO storage ring, and preliminary experiments with the optical klystron are given.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
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ABSTRACT: The FEL installed on the storage ring ACO at Orsay has been operated down to a wavelength of 463 nm, at a ring energy of 200 MeV. This is probably the lowest wavelength attainable on ACO with dielectric mirrors because of the near-UV TiO2 broad absorption band. A careful analysis of the optical gain, taking into account the measured beam characteristics, shows a spectral dependence scaling as λ1,1, with a maximum at λ = 650 nm close to 0.4%. Therefore the ACO FEL may be tuned over almost the whole visible spectrum at the expense of time consuming mirror changes. Due to the poor transmission of these very high reflectivity mirrors the average extracted power is only a few mW throughout the visible region. However the maximum intracavity peak power (at low frequency Q-switching) reaches about 0.5 MW. The next step will be to test new coated mirrors in the near-UV spectral range.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
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ABSTRACT: Optimisation du champ magnétique d'un onduleur pour laser à électrons libres à partir de mesures magnétiques des aimants constituant l'onduleur. A magnetic study on 300 REC magnets allows us a magnetic field optimization of the undulator built with these magnets.
http://dx.doi.org/10.1051/jphyscol:1984164.
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ABSTRACT: Un onduleur à aimants permanents a été construit et installé sur l'anneau de stockage ACO. La conception de cet onduleur, l'émission spontanée et le gain du système sont présentés ici, ainsi que l'allongement du paquet d'électron dû à un laser extérieur se propageant dans l'onduleur. Une cavité optique a également été construite et installée sur l'anneau. Les performances et les problèmes de dégradation des miroirs qui la composent sont discutés. On reporte également l'observation de l'amplification de l'émission spontanée stockée dans la cavité. Enfin, les premiers résultats obtenus sur l'émission spontanée de l'onduleur transformé en "Klystron Optique" sont détaillés et interprétés. A permanent magnet undulator has been built and installed on the ACO Storage Ring. The undulator design, the spontaneous emission and gain of the system, as well as the laser induced bunch lengthening of the electron bunch, are presented. A low-loss optical cavity has been also recently built and operated on the ring. Its performance and the degradation problems of the mirrors are discussed. Amplification of the spontaneous emission stored in the optical cavity has been observed. Also, preliminary results on the operation of an optical klystron are reported and interpreted.
http://dx.doi.org/10.1051/jphyscol:1983103.
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ABSTRACT: The optical klystron previously successfully optimized for the realization of an FEL on the ACO storage ring has been used as a non-linear medium aimed at producing harmonics of an external laser. For the first time we have demonstrated experimentally this effect by looking at the third harmonic of a 1.06 μm Nd:YAG laser focused into it. An enhancement of 102 to 103 of the spontaneous emission at 355 nm has been recorded.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
