A Simple Dual-Beam Time-Multiplexed Photon Doppler Velocimeter for Pressure-Shear Plate Impact Experiments
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Pressure-shear plate impact experiments generate normal and transverse particle velocities during high strain rate deformations. Traditionally, freespace lenscoupled tabletop laser interferometry techniques are used together with diffraction gratings to interrogate the evolving velocity vector at the back face of the target plate. Recently, fiberoptic velocimetry (photon Doppler velocimetry or PDV) has become commonplace for measuring normal particle velocities above 200m/sec. In this work, we demonstrate transverse velocity detection using a modified PDV system where we subtract the measured normal velocity history from a concurrent velocity history measured at a canted angle to the target surface to obtain the transverse velocity component. This modified system is time-multiplexed to reduce the number of components, and uses an erbium doped fiber amplifier (EDFA) to boost the angled signal intensity while maintaining low noise. The system operates as a heterodyne interferometer, but features a frequency upshifted reference leg to improve data analysis at the particle velocities expected in the experiment. We demonstrate by direct comparison that this inexpensive and simple approach is as effective as traditional grating methods.
KeywordsPDV Photon doppler velocimetry Interferometry Velocimetry Pressure-shear plate impact
We thank the Borg group at Marquette University for their input into this work. We also thank Christian Kettenbeil at California Institute of Technology for his input. Finally, we thank the Hopkins Extreme Materials Institute for their support, specifically Steve Lavenstein, David Eastman and Dr. Ravi Shivaraman. This research was sponsored by the Army Research Laboratory and was accomplished under Cooperative Agreement Number W911NF-12-2-0022. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the Army Research Laboratory or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein.
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