CP620, Shock Compression of Condensed Matter - 2001
edited by M. D. Furnish, N. N. Thadhani, and Y. Horie
© 2002 American Institute of Physics 0-7354-0068-7/02/$ 19.00
TEMPERATURE MEASUREMENT OF TIN
UNDER SHOCK COMPRESSION
Pierre-Louis Hereil, Catherine Mabire
Centre d'Etudes de Gramat - 46500 GRAMAT - FRANCE
Abstract. The results of pyrometric measurements performed at the interface of a tin target with a
LiF window material are presented for stresses ranging from 38 to 55 GPa. The purpose of the
study is to analyze the part of the interface in the temperature measurement by a multi-channel
pyrometric device. The results show that the glue used at target/window interface remains
transparent under shock. The values of temperature measured at the tin/LiF interface are consistent
with the behavior of tin under shock.
INTRODUCTION
used remains transparent under shock, the measured
interface temperature is close to the temperature of
the metallic target. The final difficulty is to evaluate
the emissivity of the measurement surface.
This
paper
presents
the
temperature
measurements obtained at the interface between a
tin target and a LiF window for stresses ranging
from 38 to 55 GPa. The purpose of this study is to
analyze the part of this interface composed of glue.
The experimental determination of temperature
of materials under shock has been the subject of
numerous studies since the works of Kormer [1] in
1968. The measurement of temperature under shock
has been obtained for transparent materials, rocks,
metallic materials and explosives [2-13]. Temperature measurement, which is difficult to perform, is
essential to understand the behavior of materials
under shock and, notably, to identify phase changes
of the matter.
The most common technique used to measure
the temperature under shock is to record the
radiation evolution (or luminance) of the target with
an optical pyrometer, and to determine its
temperature through Planck's law. While the
luminance measurement technique is well
characterized, the calculation of the actual
temperature of the material is not : the main
difficulty concerns the emissivity evaluation of the
measured surface. The experimental configura- tion
used by numerous authors consists in depositing a
metallic material on a transparent window to obtain
the most ideal interface. Blanco [14] proposed an
alternative which consists in gluing the window
material on the metallic target to insulate the
metallic target from the window material. If the glue
EXPERIMENTS
The configuration of the plate impact
experiment is depicted in Figure 1 and the
parameters of the three experiments performed on
tin are presented in Table I.
The experiments were performed in CEG with
the single-stage powder gun ARES. The relative
error of impact velocity measurement is 1%. For the
three experiments performed, the impact tilt varies
from 1 to 2 mrad. The impactor disks, buffer plate,
target and window all present a 1/100 mm flatness
on their two faces and the parallelism defect
between two faces is lower than 2/100 mm. The
face of the tin disk aimed by the pyrometer presents
a polished surface with a rugosity of 0.01. The faces
of window material are optically flat.
1235
projectile
Ta
Cu
(j> 50 mm
(j> 60 mm
e=5.0 mm e=5.0 mm
Sn
(J> 43 mm
e=1.5+1.5mm
self shorting pins
(impact velocity and tilt)
PYROMETER
FIGURE 1. Experimental configuration of plate impact tests for temperature measurement at tin/LiF interface
The targets consisted of two tin disks because of
a supplying problem. The window and the tin target
were glued together with L358 glue (UV-hardened
LOCTITE 358). The three experiments have
different interface conditions.
In the first experiment (#A25), the glue
thickness of each interface was less than 10 jam and
in the second one (#A31) this thickness was 50 jiim.
In these two cases, the window is composed of two
LiF disks glued together with L358. In the third
experiment (#A30), the window is composed of a
single LiF disk which is 15-mm thick and the target
surface is coated with a 1-jim thick graphite film by
cathodic sputtering. The glue thickness between the
window and the target is less than 10 jim as in the
first experiment. The goal of this experiment was to
increase the emissivity of the measurement surface
by using a highly emissive material (graphite).
The optical pyrometer used in this study has
been exhaustively described by Leal [15]. The
pyrometer uses six measurement channels with
different wavelengths : 500 nm, 650 nm, 850 nm,
1100 nm, 1270 nm and 1510 nm. Its response time
is 5 ns and its operating conditions are limited to a
low temperature of 1500 K. The relative error
associated with the luminance measurement is 3 %.
Figure 2 presents the luminance profiles
obtained in the experiment A25 for the six
wavelengths of the pyrometer. These signals exhibit
an initial ramp when the shock reaches the Sn/LiF
interface and, after 0.4 jis, a singularity which
corresponds to the reflection of compression and
release waves from the different interfaces (Sn/Sn
and LiF/LiF). The large increase in signals after 2.2
^s corresponds to the emergence of the shock wave
at the free surface of LiF.
This shows that the propagation of the shock
wave through the 10 ^im thick glue interface, at 2
mm in depth in the LiF window, does not modify
the pyrometric signal. The L358 glue remains
Table 1. Plate impact parameters for temperature measurement at Sn/LiF interface
Shot
number
A25
LiF (2.0 mm)
A31
LiF (2.0 mm)
A30
Windowl
Window2
LiF (15.0 mm)
Target / window
interface
L358 (< 10 jim)
Projectile
velocity (m/s)
2258 ± 25
LiF (15.0 mm)
L358 (50 jim)
2240 ± 20
LiF (15.0 mm)
graphite (1 jim) +L358 (<10 jim)
2253 ± 25
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0.08
E
0.10
,i
#A30 (1 |jm Graphite +10 pm glue)
tti
0.08
: 0.06 -
#A25(10Mmglue)
20.04(0
| 0.04
_3
0.02-
| 0.02
!
0.00
S 0.00
0.5
1.0
1.5
2.0
2.5
3.0
0.0
Time (microsec.)
0.2
0.4
0.6
0.8
1.0
Time (microsec.)
FIGURE 2 : Experimental profiles measured at tin/LiF interface
for shot #A25.
transparent under shock at this stress and
temperature. Otherwise, a substantial drop in the
luminance would have been observed when the
shock reached the LiF/LiF interface.
In Figure 3, the luminances measured during the
three experiments for the 1100-nm wavelength are
compared. It appears that a glue thickness of 50 um
does not modify significantly the shape of the
luminance profile whereas a 1-uin thick graphite
layer highly influences the profile. The essential
information provided by these results is that the glue
remains transparent under shock for these stresses
and temperatures. If the glue became opaque under
shock, the influence of graphite on the luminance
profile would not be observed since the graphite
deposit is in direct contact with the tin sample.
Moreover, it is noticeable that the rise times of the
first shock are similar for 10-jim and 50-um
thickness of glue. This implies that the measured
radiation comes from the rear side of the tin sample
FIGURE 3. Comparison beween the experimental profiles measured during the three experiments for the 1100 nm wavelength.
and that the glue remains transparent under shock.
Concerning the signal shape measured in the
experiment with a graphite layer, this phenomenon
can be linked either to a progressive loss of
emissivity of graphite, or to a modification of the
conduction phenomena resulting from the presence
of graphite at the interface.
The values reached in stress and temperature for
the three experiments are listed in Table 2 [16]. The
stresses in tin and, after release, in the LiF window
are estimated from the known properties under
shock of the material used and from the impact
conditions.
The as-calculated values of temperature are
compared in Figure 4 with the phase diagram of tin.
The points obtained under shock and symbolized by
circles have been calculated from the phase change
model of tin [17]. The first shock results in a mixed
solid-liquid state and the release occurs along the
melting curve. Thus the points calculated from
Table 2. Values of stress, temperature and emissivity calculated at Sn/LiF interface
Shot
Impact
Interface
Grey body
Grey body
number
stress (GPa)
stress (GPa) temperature (K)
emissivity
55.3
A25
38.8
2180
0.26
55.2
A30
38.7
2180
0.23
A31
54.7
38.3
2220
0.18
!
temperature calculated with emissivity bounded between 0.1 and 1.0
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Calculated *
temperature (K)
2125 ±235
2120 ±230
2078 ±219
Calculated
emissivity
0.33 ±0.15
0.28 ±0.18
0.29 ±0.14
4000
ACKNOWLEDGMENT
gsooo
0)
measured points
at Tin/Glue/LiF interface
This work was supported by the French Ministry
of Defense (Delegation Generate pour rArmement).
The autors are grateful to Pascal Bouinot and
Yannick Sarrant for shock experiments.
liquid
1
052000
REFERENCES
1000
20
40
60
Kormer S. B., Sov. Phys. Usp. 11, 2 (1968) 229-254
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7. Costeraste J. and Perez M, rapport CEG n° S87-0003
(1987)
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Pike C., Phys. Rev. Letters 70,25 (1993) 3931-3934
13. Mondot M., These du Conservatoire National des
Arts et Metiers, Paris (1993)
14. Blanco E., These de Doctoral, Universite Paris X Nanterre (1997)
15. Leal B., These de Doctoral, Universite de Poitiers
(1998)
16. Hereil P.L. and Mabire C., Conference DYMAT,
Cracow (2000)
17. Mabire C. and Hereil P.L., Shock Compression of
Condensed Matter, Snowbird (1999)
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CEA/DAM(1998)
80
Stress (GPa)
FIGURE 4 : Comparison between experimental point and phase
diagram of tin
temperature measurements at the tin/LiF interface
are coherent with the previous modelling.
CONCLUSION
The purpose of this paper was to analyze the
influence of an interface in an optical pyrometry
temperature measurement. The stresses obtained in
three plate impact experiments ranges from 38 to
55 GPa in tin.
The main lessons drawn from these experiments
are the following :
- the LOCTITE 358 glue used for interface
joining remains transparent under shock,
- the tested glue thickness (from 10 jj.m to 50
jim) does not result in significant difference of the
measured signal,
- the existence of a 1-j^m thick graphite deposit
on the tin target modifies considerably the shape of
the signals.
These results confirm those obtained on bismuth
[18], particularly the part of the glue interface under
shock. The temperature measurements are
consistent with the results obtained in a previous
study on the phase change of tin under shock. If
these initial results are confirmed in subsequent
experiments, the experimental technique consisting
of gluing a window on a metallic target would be an
original and attractive alternative to the deposition
technique due to its ease of use.
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