Evolution of a radiative shock system in a high- energy-density - - PowerPoint PPT Presentation

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Evolution of a radiative shock system in a high- energy-density regime

Carolyn C. Kuranz

University of Michigan Center for Radiative Shock Hydrodynamics Center for Laser Experimental Astrophysical Research TST 2013

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Shock waves become radiative when…

• Radiative energy flux would exceed incoming material energy flux

Where post-shock temperature is proportional to us

2

The ratio of these energy fluxes is proportional to us

5/ρo

Implying threshold velocities ….

Material

• Xe
• Foam (NIF)

Density

• 0.01 g/cc
• 0.02 g/cc

Threshold velocity 60 µm/ns (km/s) 150 µm/ns (km/s) Drive Pressure 40 Mbar (106 atm) 200 Mbar (106 atm)

downstream Upstream preheated

σTs

4 ρous 3/2

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Radiative shocks are abundant in our universe

— Supernova shocks

— During propagation

through the star and as it emerges

— Supernova ejecta can

develop into a radiative shock

— Supernova remnants

can enter a radiative phase

— Some accretion

phenomena

3

SN1993J, (Bartel, Science, 2000)

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Many radiative shock experiments have been performed at HEDP facilities (an abbreviated list)

— Driven radiative shock waves

— Bouquet, PRL 2004, Koenig, PoP 2006, Reighard, PoP

2006, Doss PoP 2009, Kuranz 2013 and others

— Radiative blast waves

— Grun, PRL 1991, Edwards PRL 2001, Peterson, 2006,

Hansen, PoP 2006, Moore PRL 2008 and others

— Reverse radiative shock waves (relevant to

accretion phenomena)

— Facilities include LULI, Omega, Pharos, Janus,

Vulcan, Z machine, Z-beamlet, MAGPIE, NIF (soon) and others

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Experiments are performed at Omega laser facility

— Ten Omega Laser

beams to drive shock

— ~400 J each, ~4 kJ

total energy

— λ = .35 µm, UV light — 1 ns square pulse

— Produce intensity of

about 1015 W/cm2

— Pressure of ~40

Mbars or 40 million atmospheres

Inside the Omega target chamber

Nominal tube Be ! disk 625 µm dia. Xe-filled tube 1200 µm !

• dia. section

Laser

Radiative Shock Target

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We have performed several experiments exploring the base experiment

We have also used velocity interferometry, streaked optical pyrometry and streaked x-ray radiography to diagnose these experiments

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We have obtained radiative shock data from 0.5 ns to 30 ns

Differences among shots:

• Laser energy
• Disk Thickness
• Xe pressure
• Tube material (acrylic/

polyimide)

Error bars are the size of the markers

• r smaller

Kuranz, PoP 2013 Kuranz, HEDP 2012 Doss, HEDP 2010

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We also seek to understand the effect

• f geometry on radiative shocks

Nominal tube Side Views! (diameters are outer diameters) Be ! disk 625 µm dia. Xe-filled tube 1200 µm !

• dia. section

Laser Rear Views 625 x 1200 µm ! elliptical tube Be ! disk Laser Elliptical nozzle tube polyimide! tube acrylic shield Be disk

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Targets are fabricated at U of Michigan

target stalk polyimide tube gas fill hose diagnostic shield acrylic superstucture

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Elliptical nozzle is created with machined acrylic

Narrow view Wide view

10 ¡

Acrylic nozzle

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Radiographic images from an elliptical nozzle target at 26 ns from orthogonal views

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Radiographic images from an elliptical nozzle target at 26 ns from orthogonal views

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Radiographic images from an elliptical nozzle target at 26 ns from orthogonal views

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One quantity of interest is shock location

Shock position varied from 3165 µm to 3818 µm with a mean shock location of 3589 µm and a standard deviation of 164 µm.

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Variation of experimental parameters

Disk Thickness (µm) Xe pressure (atm) Laser energy (J) Maximum 20.8 1.19 3925 Minimum 20.5 1.06 3850 Mean 20.7 1.12 3886 Standard Deviation 0.1 0.05 20

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Shock location vs. time for nominal and elliptical tube CRASH experiments

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We have also compared experimental data with CRASH output

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Conclusions and future directions

— We have completed our Year 5 experiment

exploring a variation in tube geometry

— We create driven radiative shocks in the laboratory

with velocities of over 130 km/s!

— We have applied a variety of diagnostic techniques

including x-ray radiography, optical pyrometery, and x-ray Thomson scattering

— We are using the CRASH code to model the

experiment

This research was supported by the DOE NNSA under the Predictive Science Academic Alliance Program, Stewardship Sciences Academic Alliance and National Laser User Facility program

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Backup Slides

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We have observed radiative shocks from 0.5 ns to 30 ns

— Shock Breakout data (~0.5 ns)

— Diagnostics

— Active Shock Breakout (ASBO) — Streaked Optical Pyrometer (SOP)

— Early-time data (~2 – 7 ns)

— Diagnostic Techniques

— Gated imaging x-ray radiography — Streaked x-ray radiography

— Late-time data (~13 – 30 ns)

— Diagnostic Technique

— Ungated x-ray radiography

— Preliminary Variations in Geometry

— Elliptical Nozzle Tubes

Be ! disk 625 µm dia. Xe-filled tube Laser

Nominal radiative shock 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

• ptical path to a

surface

— A Streaked Optical

Pyrometer (SOP) passively detects the thermal emission from a surface

21 ¡

Omega ! laser beams

20 µm Be

ASBO ! probe beam ASBO ! and! SOP

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Shock breakout time is observed on both diagnostics

SOP ASBO Position Position Time Time shock breakout shock breakout

22 ¡

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We have obtained breakout data from nominally 20 µm Be disks

Systematic error is ± 50 ps

23 ¡

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We seek to understand the early-time evolution of a driven radiative shock waves

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We obtained early-time data using gated x-ray radiography

The detector can use a gated camera or streak camera

25 ¡

Drive beams! t = 0 ns 4 - 10 ! backlighter ! beams delayed ! from drive x-ray photons ~5 keV! x-ray source Detector shock

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We observe these shocks with x-ray radiography from 2 views

The shock is at ~600 µm at 4.5 ns

Kuranz, HEDP (in press)

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Results from data analysis of streaked and area radiography

Average shock velocity over 130 km/s!

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The CRASH code simulated the experiment

— The CRASH code includes

— 3D Radiation

Hydrodynamics

— Flux-limited multigroup

diffusion

— Models laser energy

deposition

t = 4.5 ns Grosskopf Tuesday

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We obtained late-time radiative shock data using x-ray radiography

— Ungated

radiography uses x-ray film as a detector

— This technique

requires a large amount of shielding to protect film from unwanted signal t = 13 ns t = 26 ns Doss, HEDP 2010