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 DoE/NNSA Grant DENA0001B35 Presented at the 2014 International Workshop on X-ray and Neutron Phase Imaging with Gratings Garmisch-Partenkirchen, January , Germany

High Energy Density Plasmas are extreme state of matter ICF ignition Temperature (K) Electron density (cm -3 ) Solar core Planetary cores ICF compression Solids Energy density> 10 5 J/cm -3 (p>1 Mbar ) 10 2

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

Density is fundamental plasma parameter in HEDP Koch et al JAP Electron density N at mid-compression in ICF (cm-3) R (mm) µm scales 10 µm resolution Density -> Confinement Gradient-> Stability

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

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

Micro-foil backlighters for keV radiography High-Z foil 10µm K-a 100ps/1 kJ (1 petawatt) laser Poor attenuation contrast in low-Z plasmas Density gradient hard to diagnose

Refraction angles in the 100 µrad range expected in HEDP Koch et al JAP 2009 Refraction angles for 8 keV photons in ICF (µrad) R (mm)

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

How to implement Talbot-Lau interferometry in HEDP Small G0 ≤ 2.5 µm (A=G0/P≈100 µrad) High Talbot magnification, Talbot order Moiré deflectometry with ≥10% contrast for 10s of µm fringe period at object In-situ phase background Removable X-ray tube G0 Detector P≈2.5 cm shield G1 G2

Good fringe contrast achieved at high Talbot magnification G0=2.4 µm, G1=3.8 µm, G2=10 µm (M T =5.2) E~17 keV (Mo anode 25 kVp), A=80 µrad M.P. Valdivia et al JAP 2013 m=3 100 µm fringe period at object SNR fringe period limit of ~30 µm

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

Simultaneous density gradient and attenuation maps Refraction Attenuation Simultaneous density and Z eff diagnostic 1.5 mm Al rod, 17 keV, M=20x

1.5 mm Plastic doped with micro-particles Scatter imaging also works Scatter image µ-turbulence diagnostic without µm spatial resolution T-L Moiré deflectometry at 8 keV also very encouraging

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

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

Pinhole aperture (µm) Will G0 survive long enough to produce useful images? Pinhole closure experiments Reighard et al RSI GW/cm 2 soft X-rays on G0 Few ns lifetime for G0 on Si substrate + photoresist

Alternate G0 solutions explored Micro-periodic mirror Micro-layered backlighter 1 µm 100 ps laser

SUMMARY Talbot-Lau method has great potential for HEDP diagnostic G0 survival, 2-D gratings, phase-retrieval without Moiré fringes High M interferometry for biomedical, material applications

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

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