Author Institution: National Security Technologies, LLC Special Technologies Laboratory; Lawrence Livermore National Laboratory; Los Alamos National LaboratorySlides presented at the 2016 Photonic Doppler Velocimetry (PDV) unclassified program, Bankhead Theater, Livermore, California, June 7 - 9, 2016. Plenary Talk 3, June 9, 2016

Bennett, C. V.

Daykin, E.

La Lone, Brandon

Marshall, B.

Miller, K.

Younk, P.

KnowledgeBank at OSU

Managed and Operated by National Security Technologies, LLCNevada National Security SiteBroadband laser ranging for explosive experimentsB. La Lone, B. Marshall, C. V. Bennett,a P. Younk,b K. Miller, E. DaykinNational Security Technologies, LLC Special Technologies Laboratorya Lawrence Livermore National Laboratoryb Los Alamos National LaboratoryJune 9, 2016UNCLASSIFIEDThis work was done by National Security Technologies, LLC, under Contract No. DE-AC52-06NA25946with the U.S. Department of Energy and supported by the Site-Directed Research and Development Program.1DOE/NV/25946--2828Managed and Operated by National Security Technologies, LLCNevada National Security SiteThe time integral of the PDV velocity does not always give material position, independent position measurements are neededExtreme Case: motion perpendicular to probe axis * (Briggs et al. )PDV ProbeTarget-Probe Distance0TimeDistance DecreasingMeasured Velocity0TimeVelocity = 02* Briggs et al, J. Phys.: Conf. Ser. 500, 142005 (2014)Off-normal motion may be important, VISAR and PDV can not detect it.Managed and Operated by National Security Technologies, LLCNevada National Security Site3Examples of PDV experiments in the literature with potential off-normal motionExpanding cylinder testsImploding cylindrical liners on ZExplosively driven frangible jointsShaped charge linersTime history of positions useful for comparing to PDV as well as to x-ray images and impact pins.Managed and Operated by National Security Technologies, LLCNevada National Security SiteRequirementPosition measurement needs for dynamic experiments are unique and are not met by traditional time-of-flight range finders Goals of ranging systemAccuracy and resolution < 100 µm and sampling rates > 1 MHzFull range from mm to many cm depending on experimentIndependent of target velocity (immune to Doppler shift)High dynamic range for returning signal from time varying surfaceCompatible with existing PDV probesCapable of simultaneous detection of multiple targets (fragments or particle clouds)4Managed and Operated by National Security Technologies, LLCNevada National Security SiteWe discovered a potential solution to the ranging problem while searching the literatureIn April of 2014 we found a journal article describing a technique for optical ranging that is immune to the Doppler shift*They tracked small position fluctuations of a vibrating speaker cone and had       a total range of about 10 mmWe had all equipment and local expertise to try a quick bench testThe technique looked promising for use on explosive experiments with some minor modifications* Dynamic ranging idea from: H. Xia and C. Zhang, Optics Express, 18, 4118 (2010) 5Managed and Operated by National Security Technologies, LLCNevada National Security SiteEssentially a fiber broad spectrum interferometer where the interfered spectrum is converted to the time domain using a short pulsed laser and fiber dispersionOur innovation was to modify the diagnostic for use on explosive experiments by adding PDV and extending the full rangeOur first system for Broadband Laser Ranging (BLR) and PDV6Femtosecond Fiber laser1533-1567 nm40 MHzPDV 1550 nmTargetPhotoreceiver and Digitizer35 km fiber spoolEDFAadd/drop probe1533-1567 nmTarget PositionTime (or spectrum)Free Spectral RangeManaged and Operated by National Security Technologies, LLCNevada National Security SiteIn June of 2014 we built a prototype system and began fielded it on small-scale experimentsPrototype System Single Pulse SignalPulse rep rate at 40 MHzFFT analysis is used to extract the beat frequency/position informationSingle position per peak in the FFT7Managed and Operated by National Security Technologies, LLCNevada National Security SiteDopplerTime DelayDispersionBeat frequencyOptical Frequency Spectrum (ν)TimeTargetReferenceDispersion preserves the delay between pulses at each optical frequency. Doppler doesn’t change the delay (or beat frequency) if there is zero dispersion when the pulse is on targetTime Delay = Beat frequency/(dF/dt), independent of the Doppler shiftPosition = c*Time Delay/28Frequency domain description demonstrates the insensitivity to the Doppler shiftIntensityManaged and Operated by National Security Technologies, LLCNevada National Security SiteExperiments9Explosive ExperimentsSpinning SquareManaged and Operated by National Security Technologies, LLCNevada National Security SiteWhy do we need to measure both velocity and position?Example: Spinning object Calculating the time integral of PDV velocity to be obtain distance can be misleadingA spinning square emphasizes this difference (similar to Dan Dolan’s “spinning cam” demonstration)We performed simultaneous velocity and ranging data on a spinning square target10Managed and Operated by National Security Technologies, LLCNevada National Security SitePDV spectrogram from spinning square shows constant speedRange spectrogram from spinning square shows changing distanceVelocityPositionDistance to the surface of a spinning square by range measurement is correct; time integral of PDV is notgeometric calculationtime integral of PDVtime (milliseconds)time (milliseconds)mmm/s11Managed and Operated by National Security Technologies, LLCNevada National Security SiteRecent explosive tests at Santa Barbara Boombox12Tin targetHigh ExplosiveBLR hereor herePreshot X-ray image Dynamic X-ray imageEjectaManaged and Operated by National Security Technologies, LLCNevada National Security Site13PDV1544.5 nmPhotoreceiver1560 x 30 nmDCF90/101462 nmPump1465 nmPump-1.8 ns/nmCh 41Ch 41PBCAu retroDigital Delay StagePolarization controllerUpdated system used on recent HE driven experimentsK-photonics12.5 MHz80 m prechirp0.8 nJ/pulseTargetManaged and Operated by National Security Technologies, LLCNevada National Security Site14Recent explosive tests at Santa Barbara BoomboxBLR Spectrogram PDV SpectrogramManaged and Operated by National Security Technologies, LLCNevada National Security Site15Comparison of BLR range and PDV integral for recent BoomboxexperimentsProbe on center axis of HE drive Probe 5.6 mm off-center axis of HE driveAverage deviation between BLR distance and PDV integral = 15 µm, max = 60 µm, Good Match! Average deviation between BLR distance and PDV integral = 150 µm, max = 560 µm, Measureable Difference! Managed and Operated by National Security Technologies, LLCNevada National Security SiteDoppler free ranging in the frequency domain demonstrated on dynamic experiments (believed to be a first) *Multiplexing with PDV is simplePosition is determined every 10 to 40 ns with <30 µm accuracy?, 2-surface resolution  < 100 µmMaximum range tested was about 150 mm – no real upper limits to this valueHeterodyne gain enables measurements with low signal return (–50 to –60 dB return loss), similar to PDVMultiple positions can be resolved simultaneously, including fragments and clouds of ejectaConclusions (the good parts)16* La Lone et al, Rev. Sci. Instrum. 86 023112 (2015)Managed and Operated by National Security Technologies, LLCNevada National Security Site17Complications that make this system more difficult to field than PDVHigher order dispersion in the DCF causes nonlinear mapping of the optical frequency to the time domain. Result is a chirped signal. We correct for this in the analysis but it leads to systematic errors (See Natalie Kostinski’s and Ted Strand’s talks)Fiber interferometer dispersion must be balanced to < 6 fs/nm (about as much dispersion as 0.3 meters of fiber). (See LaLone’s talk)Nonlinear optical effects, such as self-phase modulation, limit laser energy (in present experiments to ~ 0.8 nJ/pulse). (See Patrick Younk’s talk)If pulses are not transform limited on target, there may be some sensitivity to the Doppler shift. (See Patrick Younk’s talk)Calibration is not as simple as PDV.Managed and Operated by National Security Technologies, LLCNevada National Security Site18Extra SlidesManaged and Operated by National Security Technologies, LLCNevada National Security Site19Pulses from target arrive every 121.8 nsNonlinear time stretch corrects for the 2nd order dispersion in fiber, red is original, blue is correctedCorrecting for 2nd order dispersion narrows FFT peak and increases amplitude. Also shifts to lowest frequency. FWHM ~ 0.02 GHzHigher order dispersion results in chirped signals

Broadband Laser Ranging for Explosive Experiments

https://kb.osu.edu/bitstream/1811/78162/1/PDV_2016_LaLone_Plenary3.pdf

Broadband Laser Ranging for Explosive Experiments

Abstract

Similar works

Full text

Available Versions

KnowledgeBank at OSU