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1 Interaction of a 2.45GHz wave with a plasma filament driven by femtosecond laser in atmospheric air Interaction of a 2.45GHz wave with a plasma filament.

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Presentation on theme: "1 Interaction of a 2.45GHz wave with a plasma filament driven by femtosecond laser in atmospheric air Interaction of a 2.45GHz wave with a plasma filament."— Presentation transcript:

1 1 Interaction of a 2.45GHz wave with a plasma filament driven by femtosecond laser in atmospheric air Interaction of a 2.45GHz wave with a plasma filament driven by femtosecond laser in atmospheric air Yves-Bernard André Bernard Prade (André Mysyrowicz’s group) Jean Larour Copenhagen, DK 7-8 April rd Panel Business Meeting Week AVT 190 final year

2 2 Objectives  Coupling a HF wave with a laser filament  Injecting µ-wave energy into the filamentary plasma  Depositing into the plasma an energy much higher than the laser pulse one  The whole in a fast pulsed regime

3 3 Recall of the principles  Plasma sustained by surface waves traveling at the edge of the plasma and releasing energy inside the evanescence length  Surfatron® applicator  Proven on large bore (1cm to 1’’) tube for gas flow  liter.mn -1  Dependent on long-life (µs) of ionizable excited species

4 4 CST Microwave Studio® simulation 1212  =1  =5- 10 Excitation of the rumbatron : capacitive or inductive (at 2,4GHz or in X band) Materials : perfect metal, sapphire, ceramics Plasma : coaxial tubes with complex permittivities (Drude model)  ’  –  p       ’’ = (  p        p  = n e   m e    plasma frequency Modelling the coupling cavity

5 5 CST Microwave Studio® simulation E field distribution (instantaneous)

6 6 CST Microwave Studio® simulation Low coupling

7 7 CST Microwave Studio® simulation poor coupling

8 8 CST Microwave Studio® simulation Tendency to a weak coupling with reduced diameter Not favoured by a unique filament (diam 100µm) Not favoured by a very short lifetime filament (1ns) Possibly favoured by a bundle of 100 – 400 filaments (within diam. 4mm)  Exploring the option of a filament close to the launching zone

9 Surfatron® device coaxial cable Movable capacitive antenna Gas inlet Plunger Steel knife-edge Launching slot discharge glass tube Magnetron 2.45 GHz W cw Coaxial cable 1kV Brass cavity Triggering spark Surfatron® applicator Dissymetric Creating a localized excess of E z at the muzzle NOT a leak of µ-wave through the aperture Exploiting long-life ions and excited species z axis

10 10 Surfatron® device coaxial cable Movable capacitive antenna Gas inlet Plunger Steel knife-edge Launching slit (typ 1mm) discharge glass tube Magnetron 2.45 GHz W cw Coaxial cable 1kV Brass cavity Triggering spark E 0.sin  t E z =k.sin  t U 0.sin  t E 0.sin  t E z =k.sin  t

11 11 Spark-triggered surfatron® device coaxial cable Movable capacitive antenna Gas inlet Plunger Steel knife-edge Launching slit Plasma discharge glass tube Magnetron 2.45 GHz W cw Coaxial cable 1kV Brass cavity Triggering spark 40mm Pre-plasma in optimal position at the gap level, ready to receive µ-waves. Glass tube is the one broken by excess heating.

12 End of the 8-mm pyrex tube Air ignition is triggered by a spark at the end of a miniature in air flow at 1bar with 2.45GHz magnetron 600W, after 3s. Plasma torch length is around 5cm. Colors come from copper (braid) and fluor (PTFE cable dielectric) Air flow plasma 5-cm long 6-mm diam. plasma torch Spark-triggered surfatron® device

13 13 Coaxial cable Capacitive coupling antenna Gas inlet Plunger Knife edge Lauching slit Filamentary Plasma with starting point chosen in the launching zone SiO 2 tube Magnetron 2.54 GHz W cw Clear hole for fs-Laser propagation NO visual evidence of a plasma modification Supplementary diagnostics are needed Brass cavity Adapted Surfatron® for fs-laser coupling

14 14 Supplementary diagnostics Usual tools for studying fs-filaments : side-on emission at 12 GHz side-on emission at 91 GHz radiofrequency detection side-on luminescence at 337 nm and at 391 nm electrical diagnostic Surfatron® F = 2 m THz detectors UV-Vis spectrometer Electrical diagnostic LEAT antenna fs laser z

15 15 Position : 3 cm black : 0 Watt green : 100 watt red : 200 watt Position : 8 cm black : 0 Watt green : 100 watt red : 200 watt Single shot laser Effect of HF application on 12 GHz detection Time (s)

16 16 Black : 0 Watt Green : 100 Watt unstable Red : 200 Watt 1 seul tir laser Effect of HF application on 91 GHz detection Peak 0.04 V Dt 1/2 8ns integral 0.32V.ns Time (s) 0.00E E E E VOLTS TEMPS Time (s) Single shot For 200 Watt, hint of a continuum

17 17 Black : 0 Watt Red : 200 watt Single shot laser Antenna from L.E.A.T. lab Laser Watt 200 shots Time (s)

18 18 Side-on luminescence spectroscopy F1 = 75mmHV PM= VF2 = 200mm 17cm10cm18cm monochromator photomultiplier Lambda nm

19 19 Sensors 2011, 11, 32-53; doi: /s Femtosecond Laser Filamentation for Atmospheric Sensing Huai Liang Xu and See Leang Chin (U. Laval) Long pulse 200ps Short pulse 42fs

20 20 Side-on line luminescence 337 nm 300 Tirs N 2 * 391 nm 100 Tirs N 2 + HV PM= Volt 100 shots 300 shots

21 21 One fs filament cannot provoke plasma spike development with a 0.6kW 2.45GHz applicator and relatively large difference of radii. For HF power up to 300W some observations were performed :  emission of waves : the detectors at 12 GHz and 91 GHz and a THz antenna detect an augmented signal when laser + HF  so far, it is not possible to discriminate the 2.45 GHz surface waves  Luminescence : two lines were tested, corresponding to different emission mechanisms, but with intensity sensitive to the electron density. No evidence of modification.  Electrical diagnostics are in progress Summary

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