Author Institution: Sandia National LaboratoriesAuthor Institution: Atomic Weapons Establishment (UK)Slides presented at the 4th Annual Photonic Doppler Velocimetry (PDV) Workshop held at the University of Texas, Austin, Texas, November 5-6, 2009

Chantler, Gary R.

Covert, Timothy T.

Hughes, Adrian

Jones, Scott C.

Sibley, Andrew

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Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energyʼs National Nuclear Security Administration  under contract DE-AC04-94AL85000.Directional Velocity Measurements Using Frequency-Shifted Reference Leg in a PDV System Scott C. Jones, Gary R. Chantler, and Timothy T. Covert, Sandia National Laboratories, Albuquerque, NM Adrian Hughes and Andrew Sibley, Atomic Weapons Establishment, Aldermaston, UK PDV Workshop, Austin, TX Approved for public release. Distribution unlimited. November 2009 Introduction Ed Daykin and Carlos Perez, PDV Workshop 2008, described advantages of using an up-shifted laser frequency in a PDV system in order to provide direction-of-travel information from a single channel PDV record. The promise of this technique is very attractive for developing a large probe number, direction-sensitive velocimetry system for Sandia’s LIHE (Light-Initiated High Explosive) impulse testing facility – potentially very robust and economical. Should require one oscilloscope channel/probe, and Er-fiber lasers are much less expensive than 532 nm CW lasers of sufficient power to anchor a 10+ probe system. Up-shifted PDV, PDI and conventional VISAR were tested side-by-side to measure LIHE-driven flyer velocities required to determine the momentum imparted to test objects in a three shot demonstration effort. Light Initiated High Explosive (LIHE) Impulse Response Testing Dv Objectives of diagnostic development are to provide a many probe (10+) system that can measure the flyer-delivered impulse over many points of a test structure accurately, easily and economically. Impulse (momentum transferred/unit area)      I = mDv where m = flyer mass/area. Need to accurately measure both the impact and rebound (negative) velocities in order to obtain the desired Dv Rebound Up-Shifter Concept and Test Schematic NP Photonics 1 W, 3 kHz LW 1X2 circ AO Modulator 500 MHz Up-shift 1X2 Scope Thorlabs 2 GHz IR det OZ 60 dB probe LIHE-driven 8 mil Al flyer 1-2 mm ½” PMMA Plate atten •   With 3 kHz line-width, no need to match leg length •   Up-shift Modulator:  Brimrose XXX-XX-YYZ •   Probe:  OZ 60 dB, 6.2 mm aperture, 28 mm WD •   Flyer – 8 mil, 1100 Aluminum foil, rough polished no n = no(1 + 2v/c) nref = no + nus  ndet = nref – ntarg ndet = nus – 2no(v/c)       v ≥,≤ 0 v no Air! Up-Shift PDV, PDI and VISAR Comparison The up-shift PDV was fielded along with 3-phase Photonic Displacement Interferometer (PDI) and conventional VISAR at 532 nm as a head-to-head test for deciding future diagnostic direction at SNL’s LIHE facility Flyer & Target Hardware Data & Analysis 500 MHz beat frequency pre-shot ndet = nref – ntarg ndet = nus – 2no(v/c) “Initial” velocity for nus = 500 MHz vi = lnus/2 = 387.5 m/s Full record Motion start PDV Vers. 2.1, NSTec LAO Results To obtain the final velocity profile, vf, from the PDV analysis result, vo,      vf = -(vo – 387.5 m/s)  Results PDI data not analyzable Results Comparison to Normal PDV Up-shift PDV One PDI Channel, same shot Direction of travel is automatic result of technique Conclusion The up-shifted reference PDV system was demonstrated to work very well in this first attempt at fielding – a fairly difficult first try. This method appears to be more forgiving of poor and varying return signal than PDI using the same probes – a result of extracting frequency rather than interference phase Optimizing probe configuration should pay off with even easier set-up and more robust signal quality Economics relative to conventional VISAR is self-evident for a large probe number system – single scope channel per probe vs 3 for PDI and 2-4 for VISAR A 10+ probe system is presently under development at Sandia’s LIHE facility     Backup Slides Laser 1 231 231233x3 coupler Det Det Det Scope Circulator Probe Target Reference 1x2 splitter Laser • Analysis of Lissajous (2 ch) enables automated displacement analysis for arbitrarily long records (up to 1 Mpoints to date) • Reduces uncertainty in displacement analysis-Unambiguous direction, numerically Probe Target Radiation pulse Radiation pulse • Target and reference signals mix in 3x3 coupler • 3x3 coupler output signals have stable φ = 120° phase difference. • Symmetric target and reference legs for simple proof-of-principle.  Not required for multiple probe system   Single Channel PDI PDI with Quadrature Recording Det Scope Signal Reversal Signals 2 Ch Lissajous Reversal 

Directional Velocity Measurements

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Directional Velocity Measurements

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