Evolution Of The Internal PDV Diagnostic in Z Targets

Evolution Of The Internal PDV

Diagnostic in Z Targets

K. Tomlinson,1 R. Lemke,2 D. Dolan,2 P. F. Knapp,2 D. Dalton,2 J.L. Taylor,1 B.E. Blue,3

S.J. Price,1 L. Twyeffort,2 G. Robertson, 2 R.R. Paguio,1 and M.P. Mauldin1

1General Atomics, P.O. Box 85608, San Diego, California 92186-56082Sandia National Laboratory, P.O. Box 5800, Albuquerque, NM 87185-11683Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550

22nd Target Fabrication Meeting

Las Vegas, Nevada

March 12-16, 2017

IFT/P2017-004

This work performed under the auspices of the U.S. Department of Energy by General Atomics under Contract DE-NA0001808, by

Sandia National Laboratories under Contract DE-AC04-94AL85000, and by Lawrence Livermore National Laboratory under Contract

DE-AC52-07NA27344.

Layout Of Cylindrical DMP Target and

PDV Diagnostic

PusherSample

Al AnodeInternal PDV

Cathode

Current Current

• Magnetic pressure implodes

and compresses pusher and

sample (i.e., the “liner”).

• Cylindrical target geometry

produces 3-4 times greater

stress vs. planar geometry

providing the motive to

develop this platform.

• Compressed state of sample

diagnosed with Photon Doppler

Velocimetry (PDV) and used to

determine equation of state

(EOS).

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Early cylindrical EOS experiments used multi-frame x-

ray images to diagnose density and motion of Be liner*

*Martin et al et al., Phys. Plasmas

19, 056310 (2012).

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Disadvantages

• 3 radiographs are required

to measure acceleration but

only 2 are possible on Z, so

multiple experiments are

required to get sufficient

data to measure EOS.

• Due to Z radiography

capability (6.151 keV), liner

material restricted to

beryllium.

Time lapse radiographs of 3 Be liner experiments.

Red lines denote initial inner wall position.

Breakthrough introduction of internal PDV diagnostic

enables measurement of velocity continuously*

2600 2700 2800 2900 30000

5

10

15

20

25

Time (ns)

Fre

qu

en

cy (

GH

z)

Rel. p

ow

er

(dB

) (d

B)

−60

−50

−40

−30

−20

−10

0

liner

baseline

~18 km/s

PDV measurement Cu liner

*D. H. Dolan et al., Rev. Sci. Instrum. 84, 055102 (2013).

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Advantages

• One experiment yields all the data necessary to determine EOS.

• Material’s x-ray opacity is not a factor enabling the study of Any material.

Experimental Summary

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• From March 2012 to present, 38 experiments on Z have used the

internal PDV diagnostic.

• Two papers have been published in technical journals presenting

experimental results obtained with the internal PDV:

• D. H. Dolan et al., Rev. Sci. Instrum. 84, 055102 (2013)

• R. W. Lemke, et al., J. Appl. Phys. 119, 015904 (2016)

A Physics of Plasmas paper about the D2 experiments is in review.

• Materials examined so far:

• Aluminum

• Beryllium

• Tantalum

• Deuterium

• Gold

• Rhenium

• Copper

• Uranium

Single PDV (2012)

PDV Design Features

• Single 0.7mm dia. Agiltron PDV probe

• 1.0/0.7 mm OD/ID Au housing

• 45 degree flat SPDT aluminum mirror

• Aluminum end caps.

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Innovation

• PDV system inside a cylindrical Z target

to measure motion of imploding walls.

Driver

• To permit EOS determination in

cylindrical DMP target platform.

Multipoint PDV (2013)

PDV Design Features

• Six 0.25mm dia PDV probes

• 1.2/1.0 mm OD/ID, Pt housing

• Fluted probe guide

• 0.33 mm dia steel pin through center

• 45 degree conical SPDT aluminum mirror


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Innovation

• 6 PDV probes instead of just 1.

Driver

• Provide redundancy and ability to

measure implosion symmetry.

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PDV Design Features



• 1.2/1.0 mm OD/ID, fused quartz housing

• Fluted aluminum probe guide


MPDV In Liquid D2 (2013)

Innovation

• PDV in liquid deuterium on Z (cryogenic

target).

Driver

• Measure motion of imploding Be liner and

motion of shock wave through deuterium to

determine EOS of liquid deuterium.

Smaller Probes & ID Surface Engineering (2014)

PDV Design Features



• 0.55/0.40 mm OD/ID Al housing spacer

• Probe guide eliminated.




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Innovations

1. PDV probe diameters reduced from 0.250mm

to 0.125mm.

2. ID bead blasting and ID surface

characterization.

Drivers

1. Reduce PDV diagnostic bundle diameter to

allow higher convergence/pressure.

2. Disperse reflection and improve PDV signal

and ensure proper bead blasting results.

IFT/P2017-004

PDV Design Features

• Six 0.125mm dia PDV probes.

• 0.97/0.87/0.70 mm OD/OD/ID, fused quartz

housing

• Drilled aluminum probe guide.

• Two-level 45 degree conical SPDT aluminum

mirror.

2-Level MPDV (6) In Liquid D2 (2014-2016)

Innovation

• 2-level PDV configuration using stepped,

conical mirror.

Driver

• PDV measurement through 2 different

thicknesses of quartz to permit obtaining an

impedance match measurement when the

deuterium shock impacts the quartz.

Conical Tantalum End Caps (2014-2015)

PDV Design Features



• Al housing spacer eliminated.



• Conical tantalum end caps to protect PDV

from pressure wave.

IFT/P2017-004

Innovation

• Conical tantalum end caps.

Driver

• Prolong life of PDV enabling motion

measurement to higher convergence.

*Revealed discrepancy between liner current and Al

anode current in late time in experiment with Al

liner (i.e., no sample) suggesting late time power

flow problem.

2-Level (3+3) PDV (2016)

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PDV Design Features




• Upper and lower 45 degree conical SPDT

aluminum mirrors.

• Conical tantalum end caps with extensions to

protect PDV from pressure wave.

Innovation

• 2-level MPDV with smaller diameter and

greater axial separation than possible with

previous (deuterium) design.

Driver

• Proof of principle for planned use of PDV for

direct measurement of current in liner to

circumvent power flow problem discovered

previously.

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Prism PDV With Dual Thickness Liner (2016)

PDV Design Features


• Six 0.65 mm OD, Cu housing segments.


• Six individual turning mirror prisms.

• Conical tantalum end caps with extensions to

protect PDV from pressure wave.

Innovation

• Prisms mounted on stackable segments.

• Dual thickness liner with PDV at both levels.

Driver

• Facilitate flexible PDV arrangements.

• Direct measurement of liner current

circumvents previously discovered problem

of current loss between Al anode and liner.

Micro Prisms Installed Between Cu Segments

Cu segment with one

micro prism installed

prism

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3x 180um

* Precision Optics Corp., www.poci.com, 45-45-90 Micro Prism #8531-607-1.

ID Bead Blasting

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• Tests show 200nm-600nm Ra bead

blasted surface is better than a

highly reflective surface for best

PDV light return.

• Crystal Mark micro bead blaster

with #39 glass beads is used.

• 1.75mm dia right angle tip is fed

down the axis while sample is

rotating in lathe.

Sample

Right angle

blasting tip After Bead

Blasting

Before Bead

Blasting

ID Surface Characterization

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3mm diameter, 45 degree turning mirror used with surface profiler to ensure

surface roughness of target ID’s is within spec.

Same surface after blasting at 20psi.

Ra=443nm

Diamond bored Al1100 aluminum alloy.

Ra=28nm.

Before After

Documents

Evolution Of The Internal PDV Diagnostic in Z Targets