Bond, E.

Celliers, P.

Datte, P.

Hibbard, R.

Kalantar, D.

Krauter, K.

Moody, J.

Nelson, J.

Warrick, A.

UNT (University of North Texas) Digital Library

LLNL-CONF-643035Operational Experience with OpticalStreak Cameras used on the NationalIgnition FacilityP. Datte, E. Bond, P. Celliers, R. Hibbard, D. Kalantar,K. Krauter, J. Moody, J. Nelson, A. WarrickAugust 28, 2013SPIE ConferenceSan Diego, CA, United StatesAugust 25, 2013 through August 29, 2013Disclaimer  This document was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor Lawrence Livermore National Security, LLC, nor any of their employees makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or Lawrence Livermore National Security, LLC. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or Lawrence Livermore National Security, LLC, and shall not be used for advertising or product endorsement purposes.  Operational Experience with Optical Streak Cameras used on the National Ignition Facility SPIE 2013, Target Diagnostic Physics and Engineering for Inertial Confinement Fusion  P. Datte, E. Bond, P. Celliers, R. Hibbard, D. Kalantar, K. Krauter, J. Moody, J. Nelson, A. Warrick National Ignition Facility (NIF) • The National Ignition Facility (NIF) is a 192 beam laser facility designed to support the Inertial Confinement Fusion (ICF) program. • The facility was designed to have the capability of producing a deuterium-tritium (D-T) target shot in excess of 20 MJ of energy or 7.1E18 neutrons at 14 MeV.  • Optical streak camera systems reside on all levels of the facility and are typically located  5.5 meters from target chamber center.  2 National Ignition Facility Intro National Ignition Facility NIF Target Chamber Optical streak camera system used on NIF 3 Optical Streak Camera System NIF uses a single optical streak camera style for all of NIF, the sweep speeds are what is managed differently from diagnostic to diagnostic. Optical streak camera specifications 4 Optical Streak Camera Specifications Optical Streak Camera Specifications (Typical) Wavelength Band 350nm – 1053nm Covered with two tubes Time Windows 2 ns – 90 ns Choice of 4 windows per streak camera Spatial Aperture 20 mm Streak Tube P510-P43 Photonis with P43 Phosphor CCD 4096 x 4096 Spectral Instruments Pixel Size 9 mm Before binning Number of Bits 16 Bits Binning 3x3 27 mm after binning Slit Spacing 500 mm Streak camera specifications are typical values and the results may vary once the calibration files have been applied. Optical streak cameras require calibrations  5 Streak Camera Calibrations • Optical streak cameras are not inherently linear and require calibration. • Calibrations increase the measurement accuracy to the 2% level. • Calibrations are used to generate a warp (2D) correction file that is applied to each sweep speed.  • This warp correction file removes the nonlinear effects in both space and time. • For calibration techniques see: • “Reliable and Repeatable  Characterization of Optical Streak Cameras”, M. Charest Jr., P. Torres, C. Silbernagel, D. Kalantar, APS Topical Conference on High Temperature Plasma Diagnostics, Albuquerque, NM. May 11, 2008  Measured streak camera calibration performance values 6 Measured Performance Values Specifications Sweep Speeds Sweep Speeds  3 6 16 40 Dynamic Range (Temporal) 230:1 41:1  35:1  28:1  Dynamic Range (Spatial) 193:1 139:1 N/S N/S Dynamic Spatial Resolution Line Spread Function (50% CTF) 3.8 4.0 4.1 4.3 lp/mm (50% CTF) 3.5 3.5 3.4 3.3 Dynamic Temporal Resolution (ps) 19.1 28.46 54.73 159.29 All streak cameras go through an extensive calibration to generate a Dynamic Warp Correction for each sweep speed. The listed values are typical for these sweep speeds. The warp correction removes the nonlinear effects in two dimensions, time and space. Example Calibration Report Summary: GSCP104, NOV 2012  Backscatter implementation of optical streak cameras 7  FABS Q31 FABS Q36  Q31 Q36 NBI Q31 NBI Q36 & Calibration Laser Backscatter Diagnostic Summary FABS and NBI requires optical streak cameras for the time resolved spectral measurements associated with Stimulated Raman and Stimulated Brilloun scatting. NBI requires the cameras for time resolved Stimulated Raman Scattering measurements off the scatter plate located on the wall of the target chamber. Full Aperture Backscatter (FABS) Near Backscatter Imager (NBI) •  Backscatter measurements on the National Ignition Facility (NIF) are an important part of understanding laser-target coupling All backscatter measurements require band-pass filters to select wavelength band a the fiber input 8 Filter Requirements for all Measurements Fiber Interface All filters have a tilt to prevent backscatter from effects from front surfaces All fiber based measurements contain a band-pass filter and an unique instrument response flattening filter.  Filter Callout •Instrument Flatting Filter •Band-pass Filter, selects (SBS or SRS) •ND Filter FABS backscatter time resolved configuration  9 Time Resolved Spectral Measurement  • Time resolved 1 meter spectrometer fiber delayed multiplexed configuration.  • System includes spectrometer, optical streak camera, fiber injection with delay offsets and filter pack.  • Sweep window is set to 40 ns, which is optimized for the fiber delay. Time resolved spectral measurements are accomplished by a multiplexed fiber arrangement and a sweep window optimized for full coverage of sequential two input measurements on the same window. A 40ns window has ~160ps/pixel resolution. Time resolved spectral measurement results 10 Spectral Measurement Results  1 3 2 4 The Stimulated Raman Scattering output from FABS. Four beams on a quad are measured via a fiber on one sweep record. Spectral calibration and fiber dispersion correcting are required for final analysis. Time resolved NBI implementation 11 Near Backscatter Imager Time Resolved Imager The NBI time resolved system  •Light collection lens •Filter pack •Fiber plate •Optical streak camera •CCD camera • Scatter plate Time resolved backscatter imager spatially samples the NBI scatter plate and measures the time evolution of the backscatter light for the SRS band.  Projects complete image of scatter plate onto fiber plate NBI- Scatter Plate Time resolved backscatter imager fiber map 12 Time Resolved of Near Backscatter Imager Data review   NBI – Scatter Plate Imager fiber collects backscatter light in a unique 2D spatial pattern and is interface to the streak camera in a linear array across the spatial orientation of the slit.    NBI – Fiber Plate NBI – TR Assembly NBI – Fiber Sampling Map 2D fiber measurement translated to 1D spatial measurement 13 Time Resolved 2D Measurement Map NBI – Fiber Plate Image NBI – Time Resolved Measurement Fiber 1                                                             37 Imager fiber collects backscatter light in a unique 2D spatial pattern and is interface to the streak camera in a 1D linear array across the spatial orientation of the slit.    2D spatial image of the NBI scatter plate on the diagnostic fiber plate 1D spatial fiber recording of the fiber output on the streak camera Time Time resolved SRS backscatter measurement  14 Time Resolved Reduced Data Set The time resolved measurement requires the spatial interpolation of the 2D sampled data and is displayed as a function of time.  2D reconstruction of the fiber measurement on the streak camera Temporal reconstruction of  the  backscatter measurement Play Movie: Velocity Interferometer for Any Reflector (VISAR)  15 VISAR Facility Implementation VISAR is an imaging type “line” VISAR mounted at the equator in the target bay. Collection optics and relay telescope are mounted on a positioner that extends in the target chamber. VISAR description  16 VISAR Overview •The Velocity Interferometer for Any Reflector (VISAR) functions as a shock timing measurement system that operates with thee optical streak cameras.  •The VISAR measures the Doppler shift of a reflected optical probe beam. The light is reflected from a surface of the target and the surface velocity is inferred from the Doppler shift and knowledge of the target.  •This type of diagnostic is typically used for the measurements of shock breakout events, velocities of ionizing shocks in transparent media, wave profiles at interfaces and free surfaces to name a few.  •The system includes a (660 nm) probe laser, light collection beam path that extends to target chamber center, an interferometer table, support electronics and camera alignment systems Example VISAR data, double mirror shot (N130109)  17 Example of VISAR Data Output The VISAR example data was collected on a double mirror shot (N130109). The data has been warp corrected and includes the outer combs and fiducial pulse. Example streak from a double mirror shot (N130109).  • logarithmic gray scale over the range 50 and 10000 counts.  • 3 groups of data  • Equatorial view, x = -200,  • Polar view, x = –50  • Theta, phi=45,135 view, x = +175 (mirrors are part of the target assembly) VISAR interferometer table assembly 18 Interferometer Table Assembly The VISAR interferometer table contains three optical streak cameras, two are associated with an interferometer and the third serves as the streak optical pyrometer (SOP) measurement and provides spatial temperature information of the target. Mach-Zehnder interferometer arrangement Interferometer table configuration with two interferometers and one streaked optical pyrometer (SOP) . Each interferometer uses one streak camera with different time windows. VISAR requires higher accuracy than the standard calibration files can provide 19 Calibration Correction Files The multi optical comb injection system provides a way to dynamically calibrate the streak camera moments before a shot. Post shot signal processing uses new dynamic calibration data. • Additional calibration is required for key VISAR measurements • Additional calibrations account for long term drift • Sweep window jitter • Temperature variations associated with the electronics that vary from shot to shot  Dynamic multi comb calibration increases measurement accuracy • In situ calibration is accomplished with a multi optical comb injection system mounted on the outside of the streak camera.  Multi optical comb mechanical assembly externally attached to streak camera  20 Mechanical Fiber Assembly The multi optical comb mechanical assembly is externally attached to the streak camera and allows fiber light to be injected through the slit minutes before a shot. Multi optical comb implementation 21 Multi Comb Mechanical Implementation  The multi comb hardware implementation where the two outer optical combs are fixed and the 8 multi comb group can be cycled in and out of the beam path. Multi comb data after initial corrections applied 22 Multi Comb Data The multi comb data based on a known frequency is used to generate a second warp correction that increases the measurement accuracy down to (0.5% - 1%).  Summary 23 Closing Summary • Optical streak cameras are complex instruments and play an important role on several NIF diagnostics systems requiring sophisticated measurement techniques.  • Camera warp correction calibrations are required in order to get reproducible accuracies of 2%. • Fiber based recording systems allow for multi channel acquisition of complex data sets that can reduce the channel cost of the program.  • External comb injection capability can extend the camera accuracy for critical measurements . (0.5%-1%)  

Operational Experience with Optical Streak Cameras used on the National Ignition Facility

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Operational Experience with Optical Streak Cameras used on the National Ignition Facility

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