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Progress Towards X-Ray Scattering Diagnostics of Matter at Extreme Densities
Paul Neumayer, GSI NIF & JLF User Group Meeting 2016
Livermore/CA, USA January 31 – February 3, 2016
P. Neumayer, NIF & JLF User Group Meeting 2016 1
Our object is the study of Warm Dense Matter
Warm-dense matter is complex: • Strong coupling: Epot ≥ kBT (Γ
≥ 1, „non-ideal“) • Quantum effects: EF ~ kBT
(θ<1, partly degenerate) • Collisions (conductivity, heat
transport): ΛC<0 • Partial ionization • Continuum lowering
(pressure ionization) • ...
Warm-dense matter occurs in: • Planetary interiors • ICF implosions • Transition solid-to-plasma • Matter in extreme conditions
P. Neumayer, NIF & JLF User Group Meeting 2016 2
from HEDLP Research Needs (2009)
The 2009 call for NIF fundamental science proposals
“Characterization of matter at extreme densities using x-ray Thomson scattering and radiography”, PI: P. Neumayer, EMMI/GSI “Gigabar to Petabar shocks on NIF”, PI: R. W. Falcone (UCB)
P. Neumayer, NIF & JLF User Group Meeting 2016 3
The Gbar collaboration
• Carnegie Institute of Washington R. Hemley, et al.
• Imperial College, London, UK S. Rose, et al.
• GSI, Germany P. Neumayer
• UC Berkeley /LBNL, USA R.W. Falcone, D. Kraus, A. Saunders
• LLNL, USA
T. Doeppner, A. Kritcher, D. Swift, J. Hawreliak, B. Bachmann, S. Le Pape, J. Gaffney, S. Hamel, L. Benedict, T. Ma, P. Sterne, J. Nilson, E. Dewald, P. Celliers, J. Eggert, O. Landen, G. Collins
• LCLS, USA S. Glenzer, H.J. Lee, D. Milathianaki, L. Fletcher
• Univ. of Rostock, Germany R. Redmer et al.
• AWE, UK S. Rothman, D. Chapman
• University of Warwick, UK D. Gericke, R. Baggott
P. Neumayer, NIF & JLF User Group Meeting 2016 4
Expt. Hugoniot data for Polystyrene
Omega laser
Gecko
Nova
NIF
Goal: 1 Gbar
Hugoniot curve structure is related to ionization of atomic shells.
Purgatorio*
Thomas- Fermi
*P. Sterne et al., HEDP 2007 L. Benedict et al., PRB 2014
Producing shocks at Gbar pressures
P. Neumayer, NIF & JLF User Group Meeting 2016 5
Shock measurements test material EOS along the Hugoniot curve
At high pressures, ionization of inner shells affects Hugoniot structure
Goal: reach Gbar regime
Streaked Radiography
Spectroscopy, Penumbral imaging
Au shield
- Au Hohlraum (5.75 x 9.42 mm) -Fill: 0.03 mg/cc 4He
Kritcher et al., HEDP 10, 27 (2014). Hicks & Dewald, PoP 19, 122702 (2012).
Spherical shocks are launched into solid CH using a symmetry-tuned hohlraum radiation drive
Convergence of shock waves leads to pressure increase
P. Neumayer, NIF & JLF User Group Meeting 2016 6
Zn-Heα backlighter (@9keV)
Solid CH-sphere
Streaked radiography data (CH)
radius (mm)
Tim
e (n
s)
6
4
8
10
2 0 0.5 0.5 1.0 1.0
self emission
fiducial wire
N130701
Rankine-Hugoniot Relations:
Measure: • shock velocity us
(100 … 200 km/s) • compression ρ/ρo
Tracer layer for mass conservation
Simultaneous opacity unfold
Shock Front
Radiography allows for absolute EOS measurement
P. Neumayer, NIF & JLF User Group Meeting 2016 7
For pressures up to 60 Mbar data closely follow Purgatorio-type EOS*
Softening in Purgatorio at ~100 Mbar related to beginning carbon K-shell ionization
High-pressure NIF data are close to Sesame 7592 Hugoniot (Thomas-Fermi)
*P. Sterne et al., HEDP 2007 L. Benedict et al., PRB 2014
NIF data suggests that carbon K-shell ionization starts at ~60 Mbar (Te ~ 35 eV)
Absolute shock Hugoniot measurements of plastic equation of state
*
Omega laser
Gecko
Nova
NIF
Doeppner, Kritcher, Swift et al., in preparation
Purgatorio*
Thomas- Fermi
We obtained plastic (C9H10) Hugoniot data for pressures up to 720 Mbar
P. Neumayer, NIF & JLF User Group Meeting 2016 8
N130103 N130701 N140529.1 N140529.2 N140928
time
radius
5 NIF Gbar EOS experiments studied 3 different materials in pressure range of 25 – 800Mbar
N130103 N130701 N140529.1 N140529.2 N140929
Sample CH: PAMS, CH: PAMS CH: PAMS diamond CD2
Density (g/cm3) 1.136 (cryo) 1.085 1.085 3.4 1.094
Laser energy (MJ) 1.2 1.1 0.3 0.8 1.1
Pressure range (Mbar) 100 - 420 120 - 720 25 – 125 180 - 630 120 - 800
P. Neumayer, NIF & JLF User Group Meeting 2016 9
X-ray Thomson scattering is a powerful tool to study the microphysics in dense plasmas
k0
k1 k
E0
fe(v)
EC
energy
scat
tere
d in
tens
ity
( )ωσω
σ ,dd
d
0
1Th
2
kSkk
=Ω
Chihara, PRE (2000), Gregori et al, PRE (2003)
Ion feature Electron feature Bound-free
Z f See0 (k,ω) + Zb
˜ S ce (k,ω −ω ')Ss(k,ω')dω'∫
S(k,ω) =
f I (k) + q(k) 2 Sii(k,ω) +
Schematic scattering spectrum
P. Neumayer, NIF & JLF User Group Meeting 2016 10
θS
k-resolved scattering measurements assess microscopic structure of dense plasmas...
TCC
MCP (in GXD)
20 40 60 80 100 120 1400
2
4
6
8
10
12
ion
feat
ure
scat
terin
g st
reng
th
scattering angle [deg]
ρ [g/cm3] 5 10 15 20
20 40 60 80100
150
200
250
plasm
on sh
ift [e
V]
k [1/nm]
BMA+LFC RPA
Ideas for a scattering spectrometer at NIF
• 4 curved HOPG crystals • 4 angles (±12°, ±24°) @8.6 keV
P. Neumayer, NIF & JLF User Group Meeting 2016 11
Ionic structure: strong coupling, partial binding
Electron dynamics: degeneracy, coupling, collisions
We have built MACS, a gated, high-efficiency x-ray spectrometer for x-ray Thomson scattering on the NIF
• Highly efficient HOPG crystals (flat+curved) • Energy range 7.4-10keV, E/∆E≈220 • DIM-based (0-0, 90-78) • Gated (GXD) double-cylinder
photon energy
Zn He-α (9 keV)
Cu He-α Cu He-β
Mo He-α (18 keV)
curved crystal
flat crystal flat xtal, 2nd order
Doeppner et al., RSI (2014)
P. Neumayer, NIF & JLF User Group Meeting 2016 12
N130701: time-resolved x-ray spectrum
First x-ray scattering signal obtained from Gbar-target
Doeppner et al. JPCS (2014)
X-ray Thomson Scattering
Zn-Heα backlighter (@9keV)
Au shield
Scattering Signal
X-ray Continuum emission
Photon energy
Zn source plasma and/or gold L‐shell
emission
ungated hard x-ray
background
P. Neumayer, NIF & JLF User Group Meeting 2016 13
D. Chapman et al., PoP 21, 082709 (2014)
Modeling of x-ray scattering in full 3D-geometry
Model fitting of XRTS signal shows strong sensitivity to Carbon charge state
Fitting synthetic spectra to the measurement
Density-weighted averages (HYDRA):
<ρ> = 6.7g/cc <T> = 109eV <ZC> = 4.40
Scattering from inhomogeneous, mm-scale, multi-component dense plasma samples
P. Neumayer, NIF & JLF User Group Meeting 2016 14
Signal dominated from dense inward moving material
Model fitting of XRTS signal shows strong sensitivity to Carbon charge state
Fitting synthetic spectra to the measurement
Density weighted averages (HYDRA):
<ρ> = 6.7g/cc <T> = 109eV <ZC> = 4.40
P. Neumayer, NIF & JLF User Group Meeting 2016 15
0.5ns after stagnation
Signal dominated from dense inward moving material
Inferred charge state indicates deviation from traditional S-P-model
• Thomas-Fermi (HYDRA) seems to underestimate K-shell ionization • Debye-like model (SP-limit for small coupling) yields good agreement
P. Neumayer, NIF & JLF User Group Meeting 2016 16
0.5ns after stagnation
Fitting synthetic spectra to the measurement
rel. weight
Top view Side view from Spectrometer
• Scale-0.8 hohlraum (<1MJ) • Shielding, small backlighter stand off • Cone-in-shell design • Diamond-window to spectrometer (DIM90-78) • Large scattering angle
30 m
m
9 keV
CH capsule radiograph
Over the past year we have developed a new NIF platform that is optimized for XRTS
P. Neumayer, NIF & JLF User Group Meeting 2016 17
XRTS signal
XRTS signal
Time-resolved spectrum Time-resolved spectrum
Elastic scattering
Compton scattering
Photon energy
New XRTS target
Gbar EOS target
First new target experiments, N150330 & N150621, demonstrated excellent background reduction
P. Neumayer, NIF & JLF User Group Meeting 2016 18
New XRTS target
Gbar EOS target XRTS signal
Time-resolved spectrum Time-resolved spectrum
Successful background rejection allows to measure multiple time-resolved spectra on future experiments
N150621
16.6 ns
17.6 ns
First new target experiments, N150330 & N150621, demonstrated excellent background reduction
P. Neumayer, NIF & JLF User Group Meeting 2016 19
N150621-002, 17.6 ns
NIF XRTS spectrum
Te = 37 eV
ZC = 4.45 ρ = 9.10 g/cm3
ne = 2.3e+24 cm-3
EFermi = 65 eV
ZC
Te
ne
High-quality scattering spectra allow detailed fits to extract plasma parameters
contours: 95% 99%
550 ps before stagnation
P. Neumayer, NIF & JLF User Group Meeting 2016 20
contours: 95% 99%
550 ps before stagnation 400 ps before stagnation
Approaching stagnation
P. Neumayer, NIF & JLF User Group Meeting 2016 21
contours: 95% 99%
550 ps before stagnation 400 ps before stagnation
Approaching stagnation
P. Neumayer, NIF & JLF User Group Meeting 2016 22
1st shock
2nd shock
3rd shock
4th rise
Electron temperature (eV)
Max
ele
ctro
n de
nsity
(1/c
c)
1023
1025
1024
101 10-1 100 102
2
5
2
5
Omega expts Fletcher PRL 2014 Kritcher PRL 2011
NIF post-shot simulation of N150330-001
N150330
N150621
physics goal for FY 16
N150915
EF
Spectrally resolved x-ray Thomson scattering (XRTS) is sensitive to ne and Z*
E0 = 9keV θS = 120°
At densities reaching 1e25/cc in Be IPD, IP1s and EF become comparable
Science goal: Test of pressure ionization modeling in Be at unprecedented densities
• Ionization Potential Depression: fundamental phenomenon in plasma physics • Recent measurements (LCLS, Orion) at high densities disagree with each other,
and with widely used IPD models
P. Neumayer, NIF & JLF User Group Meeting 2016 23
2014 call for NIF-DS shots
P. Neumayer, NIF & JLF User Group Meeting 2016 24
“Pressure ionization at extreme densities”
“Characterization of matter at extreme densities using x-ray Thomson scattering and radiography”, PI: P. Neumayer, EMMI/GSI “Gigabar to Petabar shocks on NIF”, PI: R. W. Falcone (UCB)
We are developing a slow Be capsule implosion
t = 21 ns t = 22 ns t = 23 ns t = 24 ns t = 25 ns
Be mass density ρ (g/cm3)
Austin Yi, LANL
• Sc575 Au hohlraum • Be-capsule (un-doped), OR1000µm, 200µm thick • 1.6 mg/cc hohlraum gas fill
Goal: create ρ>50 g/cm3 and ne>1e+25cm-3 at near homogeneous plasma conditions
Laser pulse shape
P. Neumayer, NIF & JLF User Group Meeting 2016 25
Conclusion & Outlook
• The Gbar-EOS campaign has yielded Hugoniot measurements at pressures approaching 1 Gbar
• A highly efficient crystal spectrometer (MACS) has been built and qualified • First X-ray scattering measurements from Gbar-EOS targets suggest
increased ionization compared to standard IP-models • A new platform for XRTS on imploding shells has been developed, yielding
high-quality scattering spectra
• Upcoming shot day Febr. 18: - 2D Con-A on CH-shell - XRTS on slow-implosion Be-shell
- DS on NIF: huge opportunities for academic users, but - Substantial NIF support is crucial
P. Neumayer, NIF & JLF User Group Meeting 2016 26