Grating PhaseContrast Imaging for Diagnostic of High Energy

Grating Phase-Contrast Imaging for Diagnostic of High Energy Density Plasmas D. Stutman, M. P. Valdivia, M. Finkenthal Department of Physics & Astronomy Johns Hopkins University, USA Work supported by US Do. E/NNSA Grant DENA 0001 B 35 Presented at the 2014 International Workshop on X-ray and Neutron Phase Imaging with Gratings Garmisch-Partenkirchen, January 22 2014, Germany

High Energy Density Plasmas are extreme state of matter Energy density> 105 J/cm-3 (p>1 Mbar ) Temperature (K) 108 ICF compression ICF ignition Solar core 106 104 1020 Planetary cores Solids 1022 1024 1026 Electron density (cm-3)

HEDP in Inertial Confinement Fusion 300 TW laser power for 4 ns Ablation Compression Ignition Nuclear burn (100 x energy gain) D-T fuel 6 mm Be shell 200µm 600 g/cm 3 108 K

Density is fundamental plasma parameter in HEDP Electron density N at mid-compression in ICF (cm-3) 2 1024 Density -> Confinement Gradient-> Stability 1 1024 0 0. 6 1. 2 2 1024 • 10 -1000 µm scales • 10 µm resolution 1 1024 0. 53 0. 54 0. 55 0. 56 R (mm) Koch et al JAP 2009

Plasma turbulence makes gradients also on the µm scale Capsule mixing (HYDRA computation) Burn possible Burn not possible 50 µm Clark et al LLNL report 2011 Density (g/cm-3)

X-ray radiography for density diagnostic in HEDP Pinhole backlighters for <10 ke. V radiography 10 µm Main laser Backlighter pinhole laser Hot V-Ge plasma Target plasma 2 cm 100 cm Gated X-ray detector

Micro-foil backlighters for 20 -75 ke. V radiography 10µm High-Z foil 100 ps/1 k. J (1 petawatt) laser K-a • Poor attenuation contrast in low-Z plasmas • Density gradient hard to diagnose

Refraction angles in the 100 µrad range expected in HEDP Refraction angles for 8 ke. V photons in ICF (µrad) 200 100 0 -100 0. 53 0. 54 R (mm) 0. 55 Koch et al JAP 2009 0. 56

Talbot-Lau radiography has great potential for HEDP Attenuation radiograph T-L Moiré deflectometry 3 mm Be rod M=25 x 25 k. Vp Mo tube 1 mm • Much more sensitive than attenuation • Direct density gradient diagnostic

How to implement Talbot-Lau interferometry in HEDP Removable X-ray tube G 0 P≈2. 5 cm G 1 G 2 shield Detector • Small G 0 ≤ 2. 5 µm (A=G 0/P≈100 µrad) • High Talbot magnification, Talbot order • Moiré deflectometry with ≥ 10% contrast for 10 s of µm fringe period at object • In-situ phase background

Good fringe contrast achieved at high Talbot magnification G 0=2. 4 µm, G 1=3. 8 µm, G 2=10 µm (MT=5. 2) E~17 ke. V (Mo anode 25 k. Vp), A=80 µrad 100 µm fringe period at object M. P. Valdivia et al JAP 2013 m=3 SNR fringe period limit of ~30 µm

Accurate, high resolution density profiles Density gradient in 3 mm Be rod Mo anode 25 k. Vp, M=20 x Areal density profile • Remarkable accuracy for angles << interferometer angular width

Simultaneous density gradient and attenuation maps 1. 5 mm Al rod, 17 ke. V, M=20 x Refraction Attenuation • Simultaneous density and Zeff diagnostic

Scatter imaging also works Plastic doped with micro-particles Scatter image 1. 5 mm • µ-turbulence diagnostic without µm spatial resolution • T-L Moiré deflectometry at 8 ke. V also very encouraging

High magnification interferometry below 10 ke. V Au grating on membrane Free-standing phase grating 40 mm MICROWORKS INC • Early ICF stages, smaller HEDP experiments

Moiré deflectometry at 8 ke. V (Cu anode) Be rod Fruit-fly Wax drop • >30% fringe contrast with free-standing grating

Will G 0 survive long enough to produce useful images? Pinhole closure experiments Pinhole aperture (µm) Reighard et al RSI 2008 • 1 GW/cm 2 soft X-rays on G 0 • Few ns lifetime for G 0 on Si substrate + photoresist

Alternate G 0 solutions explored Micro-layered backlighter 100 ps laser 1 µm Micro-periodic mirror

SUMMARY • Talbot-Lau method has great potential for HEDP diagnostic • G 0 survival, 2 -D gratings, phase-retrieval without Moiré fringes • High M interferometry for biomedical, material applications

Moiré deflectometry demonstrated in low density plasmas Moiré deflectometry of 1020 cm-3 plasma jet using soft X-ray laser Grava et al 2008

Resolution improves with smaller source size M=20 80 micron 58 µm 40 micron 30 µm 10 micron 8 µm MO = 8 -25 Weff = 80 µrad