10 research outputs found
Relativistic ponderomotive force, uphill acceleration, and transition to chaos
Starting from a covariant cycle-averaged Lagrangian the relativistic
oscillation center equation of motion of a point charge is deduced and
analytical formulae for the ponderomotive force in a travelling wave of
arbitrary strength are presented. It is further shown that the ponderomotive
forces for transverse and longitudinal waves are different; in the latter,
uphill acceleration can occur. In a standing wave there exists a threshold
intensity above which, owing to transition to chaos, the secular motion can no
longer be described by a regular ponderomotive force.
PACS number(s): 52.20.Dq,05.45.+b,52.35.Mw,52.60.+hComment: 8 pages, RevTeX, 3 figures in PostScript, see also
http://www.physik.th-darmstadt.de/tqe
Microwave-induced control of Free Electron Laser radiation
The dynamical response of a relativistic bunch of electrons injected in a
planar magnetic undulator and interacting with a counterpropagating
electromagnetic wave is studied. We demonstrate a resonance condition for which
the free electron laser (FEL) dynamics is strongly influenced by the presence
of the external field. It opens up the possibility of control of short
wavelength FEL emission characteristics by changing the parameters of the
microwave field without requiring change in the undulator's geometry or
configuration. Numerical examples, assuming realistic parameter values
analogous to those of the TTF-FEL, currently under development at DESY, are
given for possible control of the amplitude or the polarization of the emitted
radiation.Comment: 14 pages, 5 figures, accepted for publication in Phys. Rev.
Thomson and Compton scattering with an intense laser pulse
Our paper concerns the scattering of intense laser radiation on free
electrons and it is focused on the relation between nonlinear Compton and
nonlinear Thomson scattering. The analysis is performed for a laser field
modeled by an ideal pulse with a finite duration, a fixed direction of
propagation and indefinitely extended in the plane perpendicular to it. We
derive the classical limit of the quantum spectral and angular distribution of
the emitted radiation, for an arbitrary polarization of the laser pulse. We
also rederive our result directly, in the framework of classical
electrodynamics, obtaining, at the same time, the distribution for the emitted
radiation with a well defined polarization. The results reduce to those
established by Krafft et al. [Phys. Rev. E 72, 056502 (2005)] in the particular
case of linear polarization of the pulse, orthogonal to the initial electron
momentum. Conditions in which the differences between classical and quantum
results are visible are discussed and illustrated by graphs
Collimated and Ultrafast X-Ray Beams from Laser-Plasma Interactions
International audienceWe show that different schemes can be now followed to produce collimated X-ray radiation using laser systems. By focusing intense femtosecond laser light onto a gas jet, electrons of the plasma can be manipulated to generate ultrafast (femtosecond) X-ray radiation in the forward direction along the laser axis. In this chapter we discuss nonlinear Thomson scattering, betatron emission and Compton scattering. In years to come, the rapid development of laser technology will provide more intense laser systems. We can expect to see the creation of bright X-ray beams with a high degree of collimation (< 1 mrad divergence), as well as even shorter pulse durations, down to attosecond time scales. Such sources will provide multidisciplinary scientific communities with unique tools to probe and excite matter
Tests of Classical and Quantum Electrodynamics with Intense Laser Fields
n this chapter classical and quantum electrodynamics in intense laser fields are discussed. We focus on the interaction of relativistic electrons with strong laser pulses. In particular, by analyzing the dynamics of this interaction, we show how the peak intensity of a strong laser pulse can be related to the spectrum of the radiation emitted by the electron during the interaction itself. The discussed method could be used to accurately measure high peak laser intensities exceeding 1020 W/cm2 up to about 1023 W/cm2 with theoretical envisaged accuracies of the order of 10 %. Furthermore, we investigate non-linear quantum effects originating from the interaction of an electron with its own electromagnetic field in the presence of an intense plane wave. These “radiative corrections” modify the electron wave-function in the plane wave. The self-interaction changes, amongst others, the dynamics of the electron’s spin in comparison with the prediction of the Dirac equation. We show that this effect can be measured, in principle, already at intensities of the order of 1022 W/cm