Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session J4: Heterodyne Velocimetry |
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Chair: Dan Dolan, Sandia National Laboratories Room: Fairmont Orchid Hotel Plaza II |
Tuesday, June 26, 2007 3:45PM - 4:15PM |
J4.00001: Using the Heterodyne Method to Measure Velocities on Shock Physics Experiments Invited Speaker: Velocimetry is an important diagnostic for shock physics experiments. Velocities for these types of experiments can be in the kilometer-per-second range. We have developed a new velocimetry diagnostic for use on shock physics experiments that is based upon the heterodyne method. This diagnostic is easily assembled from commercially available parts developed for the telecommunication industry. The entire system uses single mode fibers to transport the signals from the laser to the probes and back to the detectors. We mix the Doppler-shifted light from the moving surface with non-shifted light from the laser itself to generate a beat signal at the detector. For this system using 1550 nm lasers, a velocity of 1 km/s generates a beat signal of 1.29 GHz. The detectors and the digitizers must have high-bandwidth capabilities to faithfully follow the beat waveform to allow a determination of the frequency as a function of time. Our current system has a maximum velocity capability of over 5 km/s. This paper will describe the heterodyne velocimeter and will present some of the data that has been taken with it. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory, under contract No. W-7405-Eng-48. [Preview Abstract] |
Tuesday, June 26, 2007 4:15PM - 4:30PM |
J4.00002: Low-Power Heterodyne Velocimetry of shocked metal surfaces Andrew Critchley, Ed Price, Martin Philpott, Nathan Routley A low-power variant of a Heterodyne Velocimeter (HetV) based on a LLNL design\footnote{O.T. Strand \textit{et al}., \textit{Velocimetry using heterodyne techniques}, 26$^{th}$ Intl. Congress on High Speed Photography and Photonics, Sept. 19$^{th-}$24$^{th}$ 2004.} has been constructed to study motion of shocked metal systems. The system benefits from utilising a class 1 laser system enabling its safe usage and easy transfer between facilities. A number of experimental systems have been studied to establish the limits of the low power system including shocked metal targets on a large bore gas gun and H.E. driven systems. It is shown here how high quality absolute velocity measurements may be obtained from a variety of surface conditions without recourse to higher power lasers. Advanced analytical techniques have also been developed which complement the simple set-up and use of the HetV system which are presented here. [Preview Abstract] |
Tuesday, June 26, 2007 4:30PM - 4:45PM |
J4.00003: Hugoniot and velocity history data using heterodyne techniques P. Asoka-Kumar, R. Chau, N.C. Holmes, W.P. Ambrose, K. Krauter, O.T. Strand, J. Nguyen, M. Kumar, J. Stolken Heterodyne interferometry using Doppler-shifted coherent laser light offers a novel way to access the instantaneous velocity of a moving surface. Light scattered from a moving surface is shifted in frequency and when allowed to superpose with the original light will result in intensity modulation at the beat frequency of the two light fields. Such a system is capable of recording shock arrival time and particle velocities in a gas gun experiment. We describe a 13-channel heterodyne interferometry system that measures shock arrival times in materials to a wide range of pressure values. The response time for shock arrival detection is similar to or better than the conventional pin recording system. EOS measurements from single crystal copper show no orientation dependence in the pressure range of 9-45 GPa. The U$_{s}$-U$_{p}$ relationship for all crystal orientations is consistent with previously reported data on polycrystalline copper. We compare velocity history data derived using several software analysis tools, short-time Fourier transform, Gabor transform, Wigner-Ville transform, and wavelet transform. \\\\ The work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7450-ENG-48. [Preview Abstract] |
Tuesday, June 26, 2007 4:45PM - 5:00PM |
J4.00004: Recent Advances in All Fiber Doppler Velocimeter at LSD. Xiang Wang, Jidong Weng, Hua Tan, Yun Ma, Xianmin Zhou At LSD, we have developed series novel Interferometers and using these techniques to measure velocities up to several kilometers-per-second on different types of shock experiments for the past three years. These Interferometers possess of a very simple structure, which we called the All Fiber Velocimeter (AFV) and consist of some commercially available products developed for the communications industry. We use a fiber laser and single mode fibers to deliver light to and from the target. The return Doppler-shifted light is mixed with the original laser light to generate a beat frequency proportional to the moving velocity. The beat signals were recorded directly onto fast digitized scope. Compared with traditional Optical Velocity Interferometer, such as VISAR or F-P, the AFV have more compact, reliable and less cost. This paper describes our applications to measuring velocities in shock or detonation experiments and presents recent data obtained with the AFV. [Preview Abstract] |
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