Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session O2: Experimental Developments V: Velocity Measurement Techniques 1 |
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Chair: Philip Rae, Los Alamos National Laboratory Room: Grand Ballroom AB |
Wednesday, July 12, 2017 9:15AM - 9:30AM |
O2.00001: An overview of Broadband Laser Ranging Architecture and Measurement Considerations Edward Daykin, Brandon La Lone, Edward Miller, Patrick Younk, Corey Bennett, Jared Catenacci Broadband Laser Ranging (BLR) is a developmental diagnostic intended to measure the position of rapidly moving surfaces in combination with optical velocimetry. Design and employment of a BLR diagnostic on dynamic experiments requires consideration for both the inherent measurement system tradeoffs as well as architectural choices appropriate to the nature of investigation.~ The diagnostic uses spectral interferometry to measure distance by mapping femtosecond laser pulses to the time domain via chromatic dispersion within the fiber-optic architecture. The system parameters and governing equations that describe measurement range, resolution, and Doppler sensitivity will be discussed.~ We will also briefly review the impact of diagnostic architectural choices including: nature of interferometer, Interferometric dispersion matching, optical amplification, integration of optical velocimetry, BLR calibration, and field operability.~ To summarize we will present the architectural and operational approach currently being pursued by NSTec within an on-going collaboration between NSTec, Lawrence Livermore and Los Alamos National Labs. [Preview Abstract] |
Wednesday, July 12, 2017 9:30AM - 9:45AM |
O2.00002: Broadband Laser Ranging for Position Measurements in Shock Physics Experiments Michelle Rhodes, Corey Bennett, Edward Daykin, Patrick Younk, Brandon LaLone, Natalie Kostinski Broadband laser ranging (BLR) is a recently developed measurement system that provides an attractive option for determining the position of shock-driven surfaces. This system uses broadband, picosecond (or femtosecond) laser pulses and a fiber interferometer to measure relative travel time to a target and to a reference mirror. The difference in travel time produces a delay difference between pulse replicas that creates a spectral beat frequency. The spectral beating is recorded in real time using a dispersive Fourier transform and an oscilloscope. BLR systems have been designed that measure position at 12.5-40 MHz with better than 100 micron accuracy over ranges greater than 10 cm. We will give an overview of the basic operating principles of these systems. [Preview Abstract] |
Wednesday, July 12, 2017 9:45AM - 10:00AM |
O2.00003: 8-Channel Broadband Laser Ranging Hardware Development Corey Bennett, Brandon La Lone, Patrick Younk, Ed Daykin, Michelle Rhodes, Daniel Perry, Vu Tran, Edward Miller Broadband Laser Ranging (BLR) is a new diagnostic being developed to precisely measure the position vs. time of surfaces, shock break out, particle clouds, jets, and debris moving at kilometers per second speeds. The instrument uses interferometry to encode distance into a modulation in the spectrum of pulses from a mode-locked fiber laser and uses a dispersive Fourier transformation to map the spectral modulation into time. Range information is thereby recorded on a fast oscilloscope at the repetition rate of the laser, approximately every 50 ns. Current R{\&}D is focused on developing a compact 8-channel system utilizing one laser and one high-speed oscilloscope. This talk will emphasize the hardware being developed for applications at the Contained Firing Facility at LLNL, but has a common architecture being developed in collaboration with NSTec and LANL for applications at multiple other facilities. [Preview Abstract] |
Wednesday, July 12, 2017 10:00AM - 10:15AM |
O2.00004: 1550nm Fiber Optic TOAD Time Of Arrival Diagnostic for measuring sub-nanosecond resolution of detonation break out Michael Shinas, Dean Doty We report on the design and testing of an eight-channel 1550 nm TOAD system that we have shown to resolve the arrival of a detonation wave front on explosive dynamic experiments with a timing resolution of \textless 250ps. The TOAD probe consists of a 1550 nm single mode optical fiber, which is mounted, in a flat polished ferrule. The exposed optical fiber is coated with 1000 angstroms of aluminium. We have demonstrated that the TOAD system can measure detonation arrival times on metal or bare high explosives. By omitting the 1000 angstroms of aluminium on the end of the single mode optical fiber the 1550 nm TOAD system can be converted into a very simple PDV (Photon Doppler Velocimetry) diagnostic. [Preview Abstract] |
Wednesday, July 12, 2017 10:15AM - 10:30AM |
O2.00005: High-Speed Velocimetry Using Dispersive Frequency Modulation Interferometry Jason Mance A new velocimetry technique was developed for measuring velocities that are typically outside of the range available using standard PDV techniques. Current oscilloscopes can record as fast as \textasciitilde 70 GHz limiting measurement velocities to \textasciitilde 50 km/s using standard PDV methods. The new technique encodes the PDV signal onto a chirped pulse then optically stretches the PDV signal in dispersive fiber. The stretch reduces the beat frequency, effectively bypassing the bandwidth limitations imposed by the detectors and oscilloscopes. Measurements presented using laser driven foils demonstrate PDV signals recorded onto a 180 ns pulse, stretched by factor of 3.6, with an effective record time of 110 ns. PDV signals with stretch factors up to 10 times have been recorded, which would theoretically increase the maximum measurable velocity to \textasciitilde 500 km/s. Further optimization of the system may result in a larger record times and stretch factors. This work was done by National Security Technologies, LLC, under Contract No. DE-AC52-06NA25946 with the U.S. Department of Energy and supported by the Site-Directed Research and Development Program. DOE/NV/25946---3136. [Preview Abstract] |
Wednesday, July 12, 2017 10:30AM - 10:45AM |
O2.00006: Heterodyne interferometer arrangement for combined normal and transverse velocity measurements in pressure-shear plate impact experiments Michael Mello, Christian Kettenbeil, Guruswami Ravichandran, Moriah Bischann Traditional pressure-shear plate impact experiments rely on the transverse displacement interferometer (TDI) [Kim \& Clifton, J. Appl. Phys., 1977] for the measurement of in-plane displacement histories. Alternative schemes have leveraged dual VISAR arrangements [Chhabildas, J. Appl. Phys., 1980]. In recent years, there has been a paradigm shift towards the application of heterodyne photonic Doppler velocimetry (PDV) for normal velocity measurements. A similar approach can be taken to measure transverse particle velocity. We present a heterodyne fiber optic interferometer configuration designed to simultaneously monitor normal and transverse particle velocity histories. The technique relies upon a 400 line/mm diffraction grating deposited onto the polished rear surface of the target plate. A PDV measurement system interferes the $0^{th}$ order beam to probe the normal particle velocity, while a transverse PDV (TPDV) arrangement utilizes a pair of symmetrically diffracted beams to extract the transverse velocity. The novel interferometer configuration was validated through a series of normal plate impact experiments conducted on Y-cut quartz. [Preview Abstract] |
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