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 CLEAR
Shock waves become radiative when… � Radiative energy flux would exceed incoming material energy flux � 2 � Where post-shock temperature is proportional to u s 5 / ρ o � The ratio of these energy fluxes is proportional to u s Implying threshold velocities …. � 4 ρ o u s 3 /2 � Upstream � σ T s preheated � downstream � 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) � � 40 Mbar (10 6 atm) � 200 Mbar (10 6 atm) � Drive Pressure � CLEAR
Radiative shocks are abundant in our universe � Supernova shocks During propagation through the star and as it emerges Supernova ejecta can develop into a SN1993J, radiative shock (Bartel, Science, Supernova remnants 2000) � can enter a radiative phase Some accretion phenomena 3 CLEAR
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 CLEAR
Experiments are performed at Omega laser facility Ten Omega Laser Inside the Omega target chamber beams to drive shock ~400 J each, ~4 kJ total energy λ = .35 µ m, UV light 1 ns square pulse Produce intensity of about 10 15 W/cm 2 Be ! disk Nominal tube Pressure of ~40 Laser 625 µm dia. Xe-filled tube Mbars or 40 million atmospheres 1200 µm ! Radiative Shock Target dia. section CLEAR
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 CLEAR
We have obtained radiative shock data from 0.5 ns to 30 ns Doss, HEDP 2010 Differences among shots: • Laser energy • Disk Thickness Error bars are the • Xe pressure size of the markers or smaller • Tube material (acrylic/ polyimide) Kuranz, HEDP 2012 Kuranz, PoP 2013 CLEAR
We also seek to understand the effect of geometry on radiative shocks Be ! disk Nominal tube Laser 625 µm dia. Xe-filled tube 1200 µm ! dia. section polyimide ! Be disk Be ! tube disk Elliptical nozzle tube 625 x 1200 µm ! acrylic shield Laser elliptical tube Side Views ! Rear Views (diameters are outer diameters) CLEAR
Targets are fabricated at U of Michigan diagnostic shield polyimide tube gas fill hose acrylic superstucture target stalk CLEAR
Elliptical nozzle is created with machined acrylic 10 ¡ Wide view � Narrow view � Acrylic nozzle CLEAR
Radiographic images from an elliptical nozzle target at 26 ns from orthogonal views CLEAR
Radiographic images from an elliptical nozzle target at 26 ns from orthogonal views CLEAR
Radiographic images from an elliptical nozzle target at 26 ns from orthogonal views CLEAR
One quantity of interest is shock location Shock position varied from 3165 µ m to 3818 µ m with a mean shock location of 3589 µ m and a standard deviation of 164 µ m. CLEAR
Variation of experimental parameters Disk Thickness Xe pressure (atm) Laser energy (J) ( µ m) 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 CLEAR
Shock location vs. time for nominal and elliptical tube CRASH experiments CLEAR
We have also compared experimental data with CRASH output CLEAR
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 CLEAR
Backup Slides CLEAR
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) Be ! Early-time data (~2 – 7 ns) disk Diagnostic Techniques Laser 625 µm dia. Xe-filled tube Gated imaging x-ray radiography Streaked x-ray radiography Late-time data (~13 – 30 ns) Nominal radiative shock Diagnostic Technique experiment Ungated x-ray radiography Preliminary Variations in Geometry Elliptical Nozzle Tubes CLEAR
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 ASBO ! Omega ! derivative of the and ! laser beams optical path to a SOP ASBO ! surface probe beam A Streaked Optical Pyrometer (SOP) 20 µm Be passively detects the thermal emission from a surface 21 ¡ CLEAR
Shock breakout time is observed on both diagnostics ASBO SOP Position Position shock shock breakout breakout Time Time 22 ¡ CLEAR
We have obtained breakout data from nominally 20 µ m Be disks Systematic error is ± 50 ps 23 ¡ CLEAR
We seek to understand the early-time evolution of a driven radiative shock waves CLEAR
We obtained early-time data using gated x-ray radiography Detector shock Drive beams ! t = 0 ns x-ray photons The detector can use a gated ~5 keV ! camera or streak camera � x-ray source 4 - 10 ! backlighter ! 25 ¡ beams delayed ! from drive CLEAR
We observe these shocks with x-ray radiography from 2 views Kuranz, HEDP (in press) The shock is at ~600 µ m at 4.5 ns CLEAR
Results from data analysis of streaked and area radiography Average shock velocity over 130 km/s! CLEAR
The CRASH code simulated the experiment The CRASH code includes 3D Radiation Hydrodynamics t = 4.5 ns Flux-limited multigroup diffusion Models laser energy deposition Grosskopf Tuesday CLEAR
We obtained late-time radiative shock data using x-ray radiography Ungated Doss, HEDP 2010 radiography uses x-ray film as a detector t = 13 ns This technique requires a large amount of shielding to protect film t = 26 ns from unwanted signal CLEAR
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