Equation-of-State Measurements with Z-Pinch Sources Page: 4 of 8
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illustrated in Fig. 1, and used to ablatively produce shock waves
in samples attached to the hohlraum.
a ry Hohlraum
Fig. 1. Z-pinch technique for producing ablatively driven shock
waves.
A standard hohlraum configuration for shock physics
experiments is illustrated in Fig. 2. In this case, three separate
secondary hohlraums are attached to a single primary hohlraum
containing a z-pinch source. Various interferometer and optical
breakout diagnostics are used to detect and measure shock wave
properties on samples located on the end of the secondary
hohlraums. The FOSBO technique is a fiber optic shock
breakout technique, which is a primary diagnostic for
measuring shock velocities. Typically, the arrival of the shock
wave can be determined to a time resolution of less than 1 ns
with optical streak recording. OBSBO refers to an open beam
shock breakout technique [3], which is an alternate technique
for measuring shock arrival at the rear surface of the sample.'
LiF Window .. VISAR Probes
Entrance Covering St Aluminum Sample
OBSBO Diagnostic i
' Secondary Hohlraum
S2 Pinch S3
FOSBO Probes
Primary Hohlraum Hohlraum
Temperature
Diagnostic
Fig. 2. Top view schematic of hohlraum geometry for
producing planar shock waves.
The accelerator can also be used to produce high currents
in a direct current mode, in which the anode and cathode of the
machine are directly connected, as illustrated in Fig. 3. In this
case, the high currents produced in the anode and cathodesduring operation create an intense magnetic field in the
evacuated region between the two that can produce pressure on
the boundary of a specimen located in either conductor. The
pressure is applied during development of current, with a
- -6mm Fe
VISAR VISAR
0.5-mm-thick Current
sample 0.8-mm-thick C(t)
sample
Fig. 3. Configuration for magnetically loading specimens using
the direct current mode on Z.
resulting time scale of about 100 ns, so that a shock wave is not
immediately formed in the specimen. Instead, a continuous
compression wave referred to as an Ice wave (for Isentropic
Compression Experiment) with a risetime correspond to the
input risetime of the current is initially produced. The resulting
thermodynamic process produced in the specimen is adiabatic
and essentially isentropic [4].
Current Pressure
VISAR P(t4
Specimen 2
is! 300
Anode t0 200 P
X X X X XX Gap j
Cathode .s l1oo
0 0.1 0.02 0.3 .4
Time, As(a)
(b)
Fig. 4. (a) Technique for specimens exposed to magnetic
pressures. (b) Calculated current and pressure profiles.
Source Development for EOS Studies
A major objective is to demonstrate the capability for
performing accurate EOS measurements with the Z
accelerator. To perform this evaluation, experiments are
planned to cover the pressure range from about 1.5 Mbar
to over 5 Mbar in order to overlap with existing gas gun
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Asay, J. R.; Hall, C.; Bailey, J. E.; Knudson, M. D.; Holland, K. G.; Hanson, D. L. et al. Equation-of-State Measurements with Z-Pinch Sources, article, July 22, 1999; Albuquerque, New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc791621/m1/4/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.