Bulletin of the American Physical Society
17th Biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 56, Number 6
Sunday–Friday, June 26–July 1 2011; Chicago, Illinois
Session C5: Spectroscopy and Optical Studies II |
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Chair: Jack Yoh, Seoul National University Room: Renaissance Ballroom D |
Monday, June 27, 2011 11:00AM - 11:15AM |
C5.00001: Fourier Transform and Reflective Imaging Pyrometry Gerald Stevens A stationary Fourier transform pyrometer was used to record mid-wavelength IR spectra in dynamic shock experiments. The gated-IR camera used with this system was also used to record images of light produced and light reflected from shocked metals in order to constrain the dynamic emissivity and provide temperature estimates. [Preview Abstract] |
Monday, June 27, 2011 11:15AM - 11:30AM |
C5.00002: Temperature measurement in condensed phases using femtosecond stimulated Raman scattering Nhan Dang The primary motivation for this work is the desire to observe the initial evolution of temperature following shock loading that occurs on the picosecond time scale, which may be crucial in determining the shock-induced reaction mechanism in explosives. In this presentation, we show that the Stokes to anti-Stokes intensity ratio of femtosecond stimulated Raman scattering (FSRS) data can be used to measure vibrational temperatures in condensed phases. We have validated a decades old, yet untested, theoretical prediction by studying the temperature dependence of FSRS in a calcite single crystal from cryogenic to room temperature. Experimental results of Raman loss to Raman gain ratios for low frequency modes as a function of temperature are presented and shown to be in agreement with theoretical predictions. We also report temperature jump measurements following a femtosecond ultraviolet pump pulse, demonstrating that FSRS can measure the nonequilibrium time evolution of mode specific vibrational temperatures. These measurements require no material dependent parameters or prior calibration, and should be universally applicable. [Preview Abstract] |
Monday, June 27, 2011 11:30AM - 12:00PM |
C5.00003: Neutron resonance spectrometry for temperature measurement during dynamic loading Invited Speaker: NRS has been used to measure the temperature inside a metal during shock loading. The initial experiments on Mo at the LANSCE accelerator gave higher than expected temperatures. We have reconciled the temperatures with the known properties of Mo by considering strength and curvature of the shock, demonstrating that the NRS measurement worked as intended. We have developed improved designs for the explosively-driven projectiles and NRS configurations used at LANSCE: these should give much flatter shocks with less explosive, allowing NRS to be used for a wider range of studies. Pulsed neutrons can also be produced by nuclear reaction of laser-accelerated ions. We are investigating the use of high energy short pulse lasers such as TITAN to produce neutron pulses orders of magnitude higher intensity than at LANSCE. Such pulses could be used to make NRS temperature measurements on samples shock or ramp-loaded by nanosecond laser ablation to kb-Mb pressures, enabling a huge range of interesting physics to be explored. Collaborators: James McNaney, Drew Higginson (LLNL); Vincent Yuan (LANL). Work performed under the auspices of the U.S. DOE under Contract DE-AC52-07NA27344. [Preview Abstract] |
Monday, June 27, 2011 12:00PM - 12:15PM |
C5.00004: Shock Timing and Radiation Temperature in National Ignition Campaign Holhraum Tuning Experiments using the Dante X-Ray Spectrometer H.B. Radousky, H.F. Robey, K. Widmann, J.D. Moody, O.L. Landen Indirect drive ignition on the National Ignition Facility (NIF) utilizes a sequence of four shocks to compress a spherically-shaped fuel capsule within a laser heated gold hohlraum target. The soft x-ray power diagnostic DANTE, provides the important capability of measuring the spectrally and temporally resolved absolute x-ray emission flux from the hohlraum. Up to 18 x-ray diodes are fielded on DANTE which allows continuous spectral coverage from 50eV to 20,000 eV. This spectral range fully covers the black body radiation and the characteristic M-band and L-band emission from the high-Z target. Energetics experiments on NIF produce over 10 TW/sr of peak x-ray flux which corresponds to peak radiation temperatures near 300 eV (3.5 Million Deg. K). The Dante measured flux and radiation temperature are correlated with measurements of important shock parameters such as the break out times and shock velocity for the complex shock timing sequence. We will discuss the rationale for this shock configuration and show how recent Dante data can improve confidence in tuning adjustments to the laser and target parameters for achieving ignition. [Preview Abstract] |
Monday, June 27, 2011 12:15PM - 12:30PM |
C5.00005: Irreversible phase transitions in doped metal oxides as temperature sensors in explosions Hergen Eilers, Ray Gunawidjaja, Thandar Myint, James Lightstone The temperature of post-detonation fireballs produced by advanced energetic formulations is commonly determined using optical methods such as pyrometry and spectral line fitting. These methods provide an average temperature mostly from the surface of the fireball. However, for many applications the ability to probe the internal temperature and temperature gradients within the fireball is highly desirable. One method that has shown promise is seeding micron to nano-sized temperature sensors into the fireball which can be collected and analyzed post-detonation. In this work, disordered Eu3+-doped nanoparticles were subjected to various heat treatments, incl. furnace, T-Jump, pulsed laser, and explosive heating. This treatment leads to irreversible phase transitions which are monitored by the Eu dopants. Optical signatures such as the ratio of electric and magnetic dipole transition intensities, energy level splitting, FWHM, etc. are evaluated to monitor the phase transitions. Also, the kinetics of particle growth is evaluated as an indicator for the time-dependence of the heating process. The information is used to establish a correlation with the temperature profile. Temperature profiles collected from a series of lab-based tests and small-scale detonations of an aluminized explosive will be presented. [Preview Abstract] |
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