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 radiographyo 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 camerao 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 shieldingo 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