grating phase-contrast imaging for diagnostic of high energy density plasmas d. stutman, m.p....
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Grating Phase-Contrast Imaging for Diagnostic of High Energy Density Plasmas
D. Stutman, M.P. Valdivia, M. Finkenthal
Department of Physics & AstronomyJohns 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 GratingsGarmisch-Partenkirchen, January 22 2014, Germany
High Energy Density Plasmas are extreme state of matter
ICF ignition108
106
104
1020 1022 1026
Temperature (K)
Electron density (cm-3)
Solar core
Planetarycores
ICF compression
Solids1024
Energy density> 105 J/cm-3 (p>1 Mbar )
102
HEDP in Inertial Confinement Fusion
D-Tfuel
300 TW laser power for 4 ns
6mmBe shell
200µm600 g/cm3
108 K
Ignition Nuclear burn(100x energy gain)
CompressionAblation
Density is fundamental plasma parameter in HEDP
Koch et al JAP 2009
2 1024
1 1024
2 1024
1 1024
Electron density N at mid-compression in ICF (cm-3)
0 0.6 1.2
R (mm)0.53 0.54 0.55 0.56
• 10-1000 µm scales
• 10 µm resolution
Density -> ConfinementGradient-> Stability
Capsule mixing (HYDRA computation)
Density(g/cm-3)
Burnpossible
Burnnot 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 µmpinhole
Target plasma
Gated X-raydetector
Backlighterlaser
100 cm
Main laser
2 cm
Pinhole backlighters for <10 keV radiography
Hot V-Geplasma
Micro-foil backlighters for 20-75 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)0.53 0.54 0.55 0.56
200
100
0
-100
Talbot-Lau radiography has great potential for HEDP
Attenuation radiograph T-L Moiré deflectometry
3 mm Be rodM=25x25kVp 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-raytube
G0
DetectorP≈2.5 cm
shield
G1G2
Good fringe contrast achieved at high Talbot magnification
G0=2.4 µm, G1=3.8 µm, G2=10 µm (MT=5.2) E~17 keV (Mo anode 25 kVp), A=80 µrad
M.P. Valdivia et al JAP 2013
m=3
100 µm fringe periodat object
SNR fringe periodlimit of ~30 µm
Accurate, high resolution density profiles
• Remarkable accuracy for angles << interferometer angular width
Density gradient in 3 mm Be rodMo anode 25 kVp, M=20x
Areal density profile
Simultaneous density gradient and attenuation maps
RefractionAttenuation
• Simultaneous density and Zeff diagnostic
1.5 mm Al rod, 17 keV, M=20x
1.5 mm
Plastic doped withmicro-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
4 µm
Free-standing phase gratingAu 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 2008
• 1 GW/cm2 soft X-rays on G0
• Few ns lifetime for G0 on Si substrate + photoresist
Backlighter
Alternate G0 solutions explored
Micro-periodic mirrorMicro-layered backlighter
1 µm
100 ps laser
Pt
Si
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 1020 cm-3 plasma jet using soft X-ray laser
Resolution improves with smaller source size
80 micron
40 micron
10 micronMO = 8-25 Weff = 80 µrad
58 µm
30 µm
8 µm
M=20