Gated IR images of shocked surfaces. Page: 2 of 5
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GATED IR IMAGES OF SHOCKED SURFACES
Stephen S. Lutzl, W. Dale Turley', Paul M. Rightleyz, and Lori E. Primas2
'Bechtel Nevada (B), Special Technologies Laboratory, 5520 Ekwill St., Suite B, Goleta, CA 93117
2Los Alamos National Laboratory (LANL), Los Alamos, NM 87545
Abstract. Gated infrared (IR) images have been taken of a series of shocked surface geometries in tin.
Metal coupons machined with steps and flats were mounted directly to the high explosive. The
explosive was point-initiated and 500-ns to 1-microsecond-wide gated images of the target were taken
immediately following shock breakout using a Santa Barbara Focalplane InSb camera (SBF-134).
Spatial distributions of surface radiance were extracted from the images of the shocked samples and
found to be non-single-valued. Several geometries were modeled using CTH, a two-dimensional
Experimental methods used to determine the
state of a shocked material are extensive and in
many cases return data with a reported accuracy of
a few percent(l). Although significant progress has
occurred in the advancement of diagnostic methods
in shock experiments, one opportunity for
improvement is extension of a single-spatial-point
measurement to a high-resolution multipoint image.
A number of single-spatial-point studies have been
reported describing the measurement of time-
resolved temperature change on the surface of a
metal subjected to shocks on the order of 100 GPa
(2-7). Using the most advanced detectors and
radiometric methods, these researchers report the
ability to resolve a 100*K temperature rise above
ambient to a few percent accuracy, with time
resolution on the order of 100 ns.
With recent advances in single-pixel detectors
have come significant improvements in gated
thermal cameras. One such example is the SBF-
134. This camera is based on an indium antimonide
(InSb) detector, bump bonded to a silicon CID array
readout structure. With a gate time of 500 ns, we
found that ~500 photons/pixel were required to
produce an image with 2:1 signal-to-noise ratio. In
practical terms, this camera is able to resolve
distinct facial features of a human using a 500 ns
gate width. We used this camera to capture free-
surface thermal images of metal samples shocked to
pressures on the order of 20 GPa. By modifying
surface inish and surface structure we were able to
affect the apparent residual temperature of the
shocked materials. We modeled shock-induced
temperature rise and compared the results with the
Experiments were carried out in a RISI
explosive test chamber. Signal from the shocked
coupon was reflected off a gold-coated mirror,
through a sapphire viewing port and imaged onto
the camera focal plane. A sketch of a typical high
explosive experiment package is shown in Figure 1.
A RP80 detonator single point initiated a two gram
charge of Detasheet (Dupont C2-EL-506). The
Detasheet charge directly contacted the metal
coupon under study. The whole assembly was
housed in a black Delin package.
- RP8o HE c
a I rn
FIGURE 1. Shat package dedigL
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Lutz, S. S. (Stephen S.); Turley, W. D. (William Dale); Rightley, P. M. (Paul M.) & Primas, L. E. (Lori E.). Gated IR images of shocked surfaces., article, January 1, 2001; United States. (digital.library.unt.edu/ark:/67531/metadc929127/m1/2/: accessed November 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.