Spatio-temporal dynamics of a nanosecond pulsed microwave plasma ignited by time reversal
Résumé
In the present paper, the first spatio temporal characterization of a time reversal microwave plasma generated in argon is provided using imaging. This novel source allows to ignite a plasma at a desired location in a reverberant cavity by focusing the electromagnetic energy in time and space. An important feature is the possibility to control the plasma position only by changing the input microwave waveform. The source is operated in a repetitive pulsed mode with very low duty cycle (typically 5×10−2 %). Nanosecond pulses have rise time lower than one nanosecond. The generated plasmas have typical sizes in the millimeter range and are observed for dozens of nanoseconds. The plasma behavior is investigated for different pressures and repetition frequencies. A strong dependence is observed between each discharge pulse suggesting the existence of an important memory effect. The latter is probably due to argon metastable atoms and/or residual charges remaining in the post-discharge and allowing the next breakdown to occur at a moderate electric field.
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