Forward THz radiation emission by femtosecond filamentation in gases: theory and experiment

International audienceA transition–Cherenkov electromagnetic emission by a femtosecond laser pulse propagating in a self-induced plasma channel in air has been very recently proposed as mechanism for production of terahertz (THz) radiation in the forward direction. In this paper, we study in detail the theory of the transition–Cherenkov process. The theoretical model is developed and compared with recent experimental results for several gases

High current permanent discharges in air induced by femtosecond laser filamentation

International audienceFilaments created in air by an intense femtosecond laser pulse in the presence of an electric field generate a highly conductive permanent plasma column

Radiofrequency conical emission from femtosecond filaments in air

International audienceWe show that the broadband conical emission associated with filaments in air extends down to the radiofrequency region. This rf emission which originates from the longitudinal oscillation of charged ions formed during filamentation is strongly enhanced by the presence of a longitudinal static electric field

Revival of femtosecond laser plasma filaments in air by a nanosecond laser

International audienceShort lived plasma channels generated through filamentation of femtosecond laser pulses in air can be revived after several milliseconds by a delayed nanosecond pulse. Electrons initially ionized from oxygen molecules and subsequently captured by neutral oxygen molecules provide the long-lived reservoir of low affinity allowing this process. A Bessel-like nanosecond-duration laser beam can easily detach these weakly bound electrons and multiply them in an avalanche process. We have experimentally demonstrated such revivals over a channel length of 50 cm by focusing the nanosecond laser with an axicon

Machbarkeitstudie für einen industriellen supraleitenden Table Top Elektronenbeschleuniger

At the Forschungszentrum Rossendorf the build-up of the superconducting 1.3 GHz accelerator ELBE is still in progress. Furthermore a new sc photo injector (SRF gun) is under development, which should accelerate electrons up to 10 MeV at 1.3 GHz frequency. The use of electron accelerators is also more and more interesting for applications where the destructive potential of the electrons are used like sterilization of medical waste and medical products, food irradiation or decontamination of sewage. For these processes a high power is required to achieve a high product throughput in a plant. The aim is therefore to use beam powers of around 100 kW or more. Since the applications of electron accelerators in industrial environments are steadily increasing one can speculate about transferring the above named state of the arte technology to industrial electron accelerators. At the FZR a feasibility study of such a table top electron accelerator (TTE) has been performed to investigate its technical limits and marketabilitys

An advanced pattern-matching method taking into account the uncertainty in meaning

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Fuzzy pattern matching

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Accès linguistique associatif à une base de données

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