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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


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)


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


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


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


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


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


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


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


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


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)


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


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


Signal dominated from dense inward moving material

Model fitting of XRTS signal shows strong sensitivity to Carbon charge state


Density weighted averages (HYDRA):

<ρ> = 6.7g/cc <T> = 109eV <ZC> = 4.40


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


0.5ns after stagnation


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


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


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


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


contours: 95% 99%

550 ps before stagnation 400 ps before stagnation

Approaching stagnation


contours: 95% 99%

550 ps before stagnation 400 ps before stagnation

Approaching stagnation


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


2014 call for NIF-DS shots


“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


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


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