center for radiative shock hydrodynamics fall 2011 review experimental data from crash experiments...
TRANSCRIPT
Center for Radiative Shock Hydrodynamics
Fall 2011 Review
Experimental data from CRASH experiments
Carolyn Kuranz
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CRASH experiments have produced data from shock breakout to 30 ns
Shock Breakout data (~450 ps)o Diagnostics
Active Shock Breakout (ASBO)
Streaked Optical Pyrometer (SOP)
Early-time data (~2 – 7 ns)o Diagnostic Techniques
Gated imaging x-ray radiography
Streaked x-ray radiography
Late-time data (~13 – 30 ns)o Diagnostic Technique
Ungated x-ray radiography
o Preliminary Variations in Geometry Elliptical Nozzle Tubes
Cylindrical Nozzle Tubes
Wide Cylindrical Tubes
Nominal CRASH experiment
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ASBO and SOP can detect the shock breakout from a Be disk
Active Shock Breakout (ASBO) uses a probe beam to detect the rate of change in the derivative of the optical path to a surface
A Streaked Optical Pyrometer (SOP) passively detects the thermal emission from a surface
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Shock breakout time is observed on both diagnostics
SOP ASBO
Pos
ition
Pos
ition
Time Time
shockbreakout
shockbreakout
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We have obtained breakout data nominally 20 µm Be disks
Systematic erroris ± 50 ps
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Early-time data is obtained using gated x-ray radiography
The detector can use a gated camera or streak camera
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Early-time data are obtained using gated x-ray radiography
A V foil and gated 4-strip camera are usedo 16 (4x4) pinhole array is
in front of the camera
o We have obtained data at magnifications of 6 and 8
Possible to obtain a time sequence and multiple data points
Can be done in 2 views or with streaked radiography
Target design yields highly accurate targets
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The strips on the camera can be pulsed at different delays corresponding to a long pulse backlighter
(2,2)
The shock is at 606 ± 30 µm at 4.5 ns
t = 3.5 ns
t = 4.0 ns
t = 4.5 ns
t = 5.0 ns
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We have obtained data with this technique from ~ 3 - 7 ns
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Streaked radiographs provide shock position over several nanoseconds
Streak cameras are time-resolved detectors that convert x-ray signal to an electron pulse
Electrons are accelerated by an electric field and deflected by a voltage ramp
Resulting image is resolved in space and time
Can be done in conjunction with area radiography
fiducial wire
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We used streaked radiographs to obtain early-time shock position
shock front
fiducial wire
Tim
e
Space
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Late-time data can be obtained using ungated radiography
A pinhole backlighter is used to create one image onto ungated filmo Technique requires large amount
of shielding
o Can observe target from 2 views
We have used varying tube geometries
Tube is inserted in acrylic shield
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Ungated x-ray radiographic images of cylindrical tube experiments
13 ns 26 ns
We have obtained data with this technique at ~13 ns and ~26 ns
Doss, HEDP 2010
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We have performed preliminary experiments to vary tube geometry to prepare for the 5th year experiment
To fabricate the unique nozzle targets we utilized 2 methods
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All-polyimide tubes were almost good enough
Manufactured at General Atomics and Luxel with parts provided by Michigan
Copper mandrels were dipped in polyimide and rotated while heated
Desired thickness difficult to obtain (measured by interferometry)o However, both vendors
learned a lot about the process and can improve it
See SR Klein poster
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Acrylic nozzles with polyimide tubes is the approach that worked well
Acrylic nozzle is machined and elliptical or cylindrical tube is inserted into acrylic
Elliptical tube is formed by sandwiching between 2 plates and heatingo A repeatable method has
been achieved and results in within 3% of specification
o Fairly easy to make so we make a large batch and choose the best
See SR Klein poster
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Target tubes were secured with an acrylic cap
Narrow view Wide view
Acrylic nozzle
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Radiographic images from an elliptical nozzle target at 28 ns and 30 ns
t = 28 ns
t = 30 ns
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Radiographic images from a cylindrical nozzle target at 26 ns
t = 26 nst = 26 ns
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Radiographic images from a wide cylindrical target at 26 ns
t = 26 nst = 26 ns
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Shock positions of different tube geometries
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We have obtained a wide range of data with several diagnostic techniques
Differences among shots:• Geometry• Laser energy• Disk Thickness• Xe pressure• Tube material
(acrylic/polyimide)
Error bars are the size of the markers or smaller
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Conclusions and future directions
We have obtained over 100 data points from ~ 35 data shots
Data ranges from shock breakout (~450 ps) to 30 ns and is obtained with several diagnostics techniques
We use a new technique to measure the Be disks that reduces uncertainty in thickness
We have worked with the Omega Laser Facility to reduce timing uncertainty in backlighter pulse timing relative to the drive pulse
We plan to work with General Atomics and Luxel to improve polyimide tubes for Year 5 experimentso This will allow us to observe shock evolution in the nozzle