The possibility of laser spark initiation of microwave discharge in quiescent air under the atmospheric pressure has been investigated. Laser spark is created by impulse Ruby laser (6943 A, 0.22 J pulse energy and 25 ns-pulse duration) in focal point of short-focus lens (12 mm). This point is placed in the vicinity of the main maximum of MW-field in the focal area of parabolic mirror. The X-range impulse MW generator with output power 180 kW and pulse duration 1,2 μs via radiating system illuminates the focal area. Digital synchronous Schlieren system is used for visualisation of shock wave structures, exciting by laser spark and initiated MW discharge. The time delays between laser impulse, MW impulse and impulse of Schlieren registration (0,5 μs) are managing by the CAMAC system. Luminosity of discharges is measured by fast PMT (time resolution better than 30 ns). The range of time-shifts between laser spark and MW pulse 15-210 μs is investigated. Our results show that semi-self-maintained MW discharge can arise during the time window, corresponding to decaying phase of laser-induced plasma. Contribution of MW energy in plasma luminosity has distinct maximum under the Laser-MW delays 80-110 μs, duration of this discharge is defined by MW impulse. For the Laser-MW delay 85 μs the series of shock-wave pictures is recorded. They clearly show the weak quasi-spherical shock wave structure originating due to MW energy contribution. Thus, the first important step for MW discharge position control by laser-ignited spark is made, in spite the results of this work have a preliminary character. The developing technique may become a promising way for creating of spatially compact MW discharges with predictable shape and position for plasmadynamic applications.
|Number of pages||7|
|State||Published - 1 Jul 2004|
|Event||42nd AIAA Aerospace Sciences Meeting and Exhibit - Reno, NV, United States|
Duration: 5 Jan 2004 → 8 Jan 2004
|Conference||42nd AIAA Aerospace Sciences Meeting and Exhibit|
|Period||5/01/04 → 8/01/04|
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