Heterodyne velocimetry and detonics experiments

P. Mercier; J. Bénier; P. A. Frugier; G. Contencin; J. Veaux; S. Lauriot-Basseuil; M. Debruyne

doi:10.1117/12.820433

10 February 2009 Heterodyne velocimetry and detonics experiments

P. Mercier, J. Bénier, P. A. Frugier, G. Contencin, J. Veaux, S. Lauriot-Basseuil, M. Debruyne

Proceedings Volume 7126, 28th International Congress on High-Speed Imaging and Photonics; 71261O (2009) https://doi.org/10.1117/12.820433
Event: 28th International Congress on High-Speed Imaging and Photonics, 2008, Canberra, Australia

Abstract

Heterodyne Velocimetry (or Photonic Doppler Velocimetry) has been used in detonics experiments for a few years now, mainly thanks to the recent evolution of telecom components. In its principle it is nothing else but a displacement interferometer, delivering beats versus time. A sliding Fourier transform processing on the raw signal thus allows to derive velocity versus time. The device is made up of a 1.55 μm Erbium laser delivering 2 W (split into 4 channels), single-mode optical fibers, fast photodetectors and digitizers (8 GHz bandwidth, 20 GS/s sampling). To begin with, we present a new heterodyne velocimeter setup embedding a second low-power frequency-tunable laser (50 mW) acting as a local oscillator. Its frequency can be shifted, to make it higher than the main laser, up to the bandwidth of the digitizer (13 GHz soon). The Doppler wave coming from the first laser and reflected by the moving target interferes with this shifted reference, therefore doubling the overall bandwidth of the system. On top of enhancing the measurable velocity range, the existence of beats at static gives a convenient means to tune the power levels of the laser and match the electric signal to the dynamics of the detector. Finally, three applications are presented: the first one deals with the classical measurement of free surface velocity on metallic shock loaded plates, in the second part we present the velocity distribution of tin particles ejected under shock. The third application relates to direct measurement of the velocity of detonation wave into nitromethane, by using immersed optical fibers.

Citation Download Citation

P. Mercier, J. Bénier, P. A. Frugier, G. Contencin, J. Veaux, S. Lauriot-Basseuil, and M. Debruyne "Heterodyne velocimetry and detonics experiments", Proc. SPIE 7126, 28th International Congress on High-Speed Imaging and Photonics, 71261O (10 February 2009); https://doi.org/10.1117/12.820433

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