Channel 1

Crystalchamber

X-ray streakcamera

X-ray CCD

Channel 2

Re-entrant tubewith collimators

Chamber wall

1.65 m

P. M. NilsonUniversity of RochesterLaboratory for Laser Energetics

CEA–NNSA Joint Diagnostic MeetingRochester, NY

29–30 June 2016

High-Resolving-Power, Ultrafast Streaked X-Ray Spectroscopy on OMEGA EP

1

Summary

2

A high-resolving-power, streaked x-ray spectrometer is being developed and tested on OMEGA EP

• The instrument will ultimately be used to measure temperature-equilibration dynamics and material response to ultrafast heating at depth

• The goal is to achieve a resolving power of several thousand and 2-ps temporal resolution

• To understand system performance, a time-integrating survey spectrometer has been deployed on OMEGA EP

• Survey spectrometer measurements and offline testing show

– focusing fidelity: ~50-nm line focus

– several thousand resolving power

– throughput: ~10–7 ph/ph

– shielding: 5 to 15 cm of lead

• These measurements provide a firm foundation for designing and implementing the time-resolved instrument

E25274b

Development is underway to deploy the time-resolved instrument on OMEGA EP by Q2FY17.

Collaborators

3

F. Ehrne, C. Mileham, D. Mastrosimone, R. K. Jungquist, C. Taylor, R. Boni, J. Hassett, C. R. Stillman, S. T. Ivancic, D. J. Lonobile, R. W. Kidder, M. J. Shoup III, A. A. Solodov, C. Stoeckl, and D. H. Froula*

University of RochesterLaboratory for Laser Energetics

*also Department of Physics

K. M. Hill, L. Gao, M. Bitter, and P. Efthimion

Princeton Plasma Physics Laboratory

D. D. Meyerhofer

Los Alamos National Laboratory

Outline

E25089

• Motivation

– temperature-equilibration dynamics

– material response to ultrafast heating at depth

• Conceptual design

– high-resolution spectrometer (HiResSpec)

• Phase I

– time-integrating x-ray spectrometer

• Phase II

– time-resolved x-ray spectrometer

4

E21173h

Motivation

A high-energy ultrafast laser can heat solid-density material on a time scale much faster than the material expands

These studies require dense, high-temperature plasmas that are well characterized.

• Heating at high density produces exotic states of matter in extreme thermodynamic conditions1

• The possible extremes in temperature enables novel material and radiative properties experiments2

– e.g., mean opacity of solar interior matter3

• New diagnostic techniques are sought for testing

– plasma-dependent atomic processes4

– plasma opacity5

– equation-of-state models6

Classic plasma

Coresof largeplanets

Degen

erat

e

Quantumdegeneratehot matter

Denseplasma

10–41

10

100

1,000

10,000

10–2

Density (g/cm3)

Tem

per

atu

re (

eV)

100 102 104

C = 1

Iso

cho

ric

hea

tin

g

P ~ Gbar

Conditions deep

in a star

1 A Report on the SAUUL Workshop, Washington, DC (17–19 June 2002).2 K. Nazir et al., Appl. Phys. Lett. 69, 3686 (1996).3 J. E. Bailey et al., Nature 517, 56 (2015).4 D. J. Hoarty et al., Phys. Rev. Lett. 110, 265003 (2013). 5 R. A. London and J. I. Castor, High Energy Density Phys. 9, 725 (2013).6 M. E. Foord, D. B. Reisman, and P. T. Springer, Rev. Sci. Instrum. 75, 2586 (2004).

5

An experimental platform is being developed to study heating of dense matter by laser-generated hot electrons

E25090c

6

Motivation

• Source and coupling: K-line emission PI’s—P. Nilson (LLE)/K. Hill (PPPL)

– laser-to-electron coupling1 L eh -– mean hot-electron energy2 GEH– relaxation rate3 xe

– ionization distribution GZH

• Bulk response: thermal emission PI—C. Stillman (Ph.D. student, DOE SSGF)

– Al, Fe, and Mg spectroscopy

– density and temperature: ne, Te

• Surface response: XUV emission PI—S. Ivancic (Postdoc, DOE/FES Grant)

– heat flow and pressure relaxation

– density and temperature: ne, Te

Multi-Terawatt (MTW) Laser: 10 J, 1 psFrequency: 1~ or 2~Intensity: >1018 W/cm2

OMEGA EP Laser System: 2.6 kJ, 10 psFrequency: 1~Intensity: >1018 W/cm2

PI: Principal InvestigatorDOE SSGF: Department of Energy Stewardship Science Graduate FellowshipDOE/FES: Department of Energy/Fusion Energy SciencePPPL: Princeton Plasma Physics LaboratoryXUV: extreme ultraviolet

1P. M. Nilson et al., Phys. Rev. Lett. 105, 235001 (2010).2P. M. Nilson et al., Phys. Rev. Lett. 108, 085002 (2012). 3P. M. Nilson et al., J. Phys. B 48, 224001 (2015).

Thin foil

Laser

Buried layerwith dopants

E18508c

7

Motivation

Outer shell ionization affects the energy and shape of the characteristic Ka line in a partially ionized plasma

• Hot electrons create K-shell vacancies when colliding with ions

• Ionization by thermal electrons removes electrons from the ions outer shells

• As the ionization progresses, the Ka1,2 lines increase their energy1–5

1K. Słabkowska et al., High Energy Density Phys. 15, 8 (2015).2K. Słabkowska et al., High Energy Density Phys. 14, 30 (2015).3G. Gregori et al., Contrib. Plasma Physics 45, 284 (2005).4P. M. Nilson et al., Phys. Plasmas 18, 042702 (2011).5J. F. Seely et al., High Energy Density Phys. 9, 354 (2013).

The transition energies are sensitive to the configuration of bound electrons.

K (1s)

L1 (2s)L2 (2p1/2)L3 (2p3/2)

Fine structure of the characteristic Ka line

Ka1Ka1 Ka2

Ka2

1.0

0.8

0.6

Sig

nal

X-ray energy (eV)

0.4

0.2

0.08000 8040 8080 8120

500 × 500 × 20 nm3

50 × 50 × 2 nm3

MTW laser: 5 × 1018 W/cm2

Target: Cu foil

Survey experiments on the MTW laser have demonstrated temporal spectral shifts on the Cu Ka line

Survey Experiments

E25092c

8

Higher ionization and excited states are populated as the plasma heats.

Ka1

Heating

Ka2

350

300

250

200

150

100

50

07950

70

50

30

10

8000 8050

Energy (eV)

Shot 5708: 1 J, 0.8 ps500 × 500 × 20 nm Cu

Tim

e (p

s)

8100 8150 795070

50

30

10

8000 8050

Energy (eV)

Shot 5698: 10 J, 7 ps60 × 60 × 2 nm Cu

Tim

e (p

s)8100 8150

The instrument is based on two diagnostic channels, each with a spherical Bragg crystal

E23446

Conceptual Design

Channel 1

Source 2.2 m

Si220 sphericalcrystal #1

X-ray streakcamera

Channel 2

Source 2.2 m

Si220 sphericalcrystal #2

X-ray charged-coupled

device (CCD)

9

The instrument parameters are set by the expected Cu Ka line shifts

E23449c

Spectrometer Design

10

Parameter Requirements

X-ray source size ~100 nm2

Spectral range 7.97 to 8.11 keV

Crystal and Bragg angle

Si220 crystal— Bragg angle = 22.8°

Crystal radius of curvature

330 mm

Crystal size 25 mm × 100 mm

Source-to-crystal distance

2.2 m

Resolving power ~5000—streak-camera limited

Spectral shifts Few eV to 20-eV Ka line shifts

Streak-camera slit 6-mm-long, 400-nm-wide50-nm-high-throughput region

Temporal resolution 2 ps

–3 –2 –1 0

8040

8020

8060

8080Cu Ka

Si220 dispersion curve

Position on PJX slit (mm)

En

ergy

(eV

)

1 2 3

1

Exteriorchamber

Gate valve and bellows

OMEGA EPchamber wall

Entrant-tubeassembly

Deck 2 modifications

Crystalassemblies

Pbshielding

CCD’s

The Phase I spectrometer was deployed in January 2016 on OMEGA EP for experiments and diagnostic development

Survey Spectrometer

E25094b

11

The Phase I spectrometer was deployed in January 2016 on OMEGA EP for experiments and diagnostic development

Survey Spectrometer

E25095b

12

Exteriorchamber

Gate valve and bellows

OMEGA EPchamber wall

Entrant-tube assemblyand collimators

Si440CCD

Crystalassemblies

Pbshielding

Si220CCD

OMEGA EP data show average background signals per pixel of up to 1000 ADU at 1.65 m from the source

E23454

Shielding Tests

A 5-cm direct line-of-sight lead shielding reduced the background to ~50 ADU.

100 101

101

Laser energy (J)

Ave

rag

e b

ackg

rou

nd

(A

DU

)

102

102

103

103

MTW: 1 psOMEGA EP: 1 psOMEGA EP: 10 ps

13

Inrad Optics manufactured the crystal assemblies

E23450a

• The silicon crystal is 100 nm thick and

25 mm × 100 mm in size

• The crystal is optically bound to a glass substrate that is shaped to a radius of R = 330 mm

Crystal Manufacturing

14

100 mm

The focusing properties and resolving power of the OMEGA EP crystal were measured

E23452b

• W La1 line width at 8.3976 keV agrees with the estimated line width of ~7 eV

plus the additive width caused by the finite rocking curve width of ~0.48 eV*

• The measured line width did not change as the crystal was masked—

the curvature is good

Crystal Tests

8250 8350

X-ray energy (eV)

Pilatus detector: 172-nm pixel size

Co

un

ts (

×10

6 )

0.0

0.4

0.8

1.2

8450

*A.-M. Vlaicu et al., Phys. Rev. A 58, 3544 (1998).

15

W La1

W La2

High-power experiments show excellent focusing fidelity, resolving power, and throughput

Spectrometer Measurements

E25096

16

Shot 22854100 J, 1 ps—Si220

1000

Raw data Filtered data

1400

1200

1000

800

Ka1

Ka2

Ka1

Ka2

1200

Pixels

Imaging

Pix

els

En

ergy

Pixels

1400 1000 12000.0

0.5

1.0

1.5

2.0

Signal(×104 ADU’s)

1400

Imaging

The Si220 throughput will provide a measurable signal on the PJX-3 streak camera

E25287a

17

Spectrometer Measurements

• The measured throughput is 1.4 × 10–7 ph/ph

• The predicted peak signal at the streak camera is ~1000 ADU per pixel

• Photometric estimates are based on

– laser energy: 100 J

– x-ray flash duration: 10 ps

• Shifted spectra are well-matched to the length of the streak-camera slit

Phase I has provided the foundation for designing and implementing the time-resolved instrument.

X-ray energy (eV)

8000 8050 8100 8150

1.0

0.8

0.6

0.4

0.2

0.0No

rmal

ized

sig

nal

500 # 500 # 20-nm Cu+ 3-nm CH tamper; 100 J, 1 ps 250 # 250 # 10-nm Cu+ 3-nm CH tamper; 650 J, 10 ps

Ka1

Ka2Heating

The Phase II instrument adds a second crystal assembly and the PJX-3 x-ray streak camera for time-resolved measurements

E23455b

18

Mechanical Design

Channel 1

Crystalchamber

X-ray streakcamera

X-ray CCD

Channel 2

Re-entrant tubewith collimators

Chamber wall

1.65 m

Significant shielding assemblies are required for the x-ray streak camera

E25098

19

Mechanical Design

CCD

CCD

Lead bunker4r shielding4-cm thick3300 lbs

Line-of-sight shield15-cm-thick lead550 lbs

Alignment plate

PJX-3 x-raystreak camera

Crystalchamber

Fine adjust along four degrees of freedom is provided near the PJX-3 cathode*

E25101b

20

Streak-Camera Alignment

*For detailed tolerance analysis, see D-HS-R-121 Rev A (March 2015).

Temporaladjustment

Spectral adjustment

Spectral preload

Rotationpreload

Rotationadjustment

Cathode

Guide pad(clocking + centering)

Guide pad(centering)

Spectral direction

Temporaldirection

Rotation

Temporalpreload

HiResSpec will be deployed in Q2FY17 for commissioning and first high-power shots.

Summary/Conclusions

21

A high-resolving-power, streaked x-ray spectrometer is being developed and tested on OMEGA EP

• The instrument will ultimately be used to measure temperature-equilibration dynamics and material response to ultrafast heating at depth

• The goal is to achieve a resolving power of several thousand and 2-ps temporal resolution

• To understand system performance, a time-integrating survey spectrometer has been deployed on OMEGA EP

• Survey spectrometer measurements and offline testing show

– focusing fidelity: ~50-nm line focus

– several thousand resolving power

– throughput: ~10–7 ph/ph

– shielding: 5 to 15 cm of lead

• These measurements provide a firm foundation for designing and implementing the time-resolved instrument

E25274b

Development is underway to deploy the time-resolved instrument on OMEGA EP by Q2FY17.

Temporal spectral shifts on the Cu Ka line in rapidly heated solid matter will validate the spectrometer performance

E25130c

• Synthetic spectra from hot, dense matter are required

• LSP1 calculates– energy-transport physics– electromagnetic-field

generation– target heating

• LSP is post-processed based on tabulated PrismSPECT2 calculations using

– the local density and temperature at the time of emission

– line-of-sight and high-Te opacity effects

• The calculations use an occupation probability model3 and the ionization potential depression formalism of More4

22

8000

5

10

15

20

25

8050X-ray energy (eV)

Tim

e (p

s)

5

10

15

20

25

Tim

e (p

s)

0.0

0.0

0.5

1.0

No

rmal

ized

sig

nal

8100 8150 8000 8050X-ray energy (eV)

8100 8150

OMEGA EP20-nm Cu foil

100 J, 1 ps

OMEGA EP20-nm Cu foil

100 J, 1 ps

OMEGA EP10-nm Cu foil

400 J, 1 ps

OMEGA EP10-nm Cu foil

400 J, 1 ps0.5

1.0

Model Update

1D. R. Welch et al., Phys. Plasmas 13, 063105 (2006).2Prism Computational Sciences Inc., Madison, WI 53711.3D. G. Hummer and D. Mihalas, Astrophys. J. 331, 794 (1988). 4R. M. More, J. Quant. Spectrosc. Radiat. Transf. 27, 345 (1982).

Time-integrated measurements on OMEGA EP show spectral shifts increasing with target energy density

E25203b

23

Spectrometer Measurements

The dispersed x-ray signals are well-matched to the length of the x-ray streak-camera slit.

X-ray energy (eV)

8000 8050 8100 8150

Pulse duration: 10 ps

X-ray energy (eV)

8000 8050 8100 8150

1.0

0.8

0.6

0.4

0.2

0.0

No

rmal

ized

sig

nal 500 # 500 # 20-nm Cu; 100 J

250 # 250 # 10-nm Cu; 400 J250 # 250 # 2-nm Cu; 500 J

500 # 500 # 20-nm Cu; 400 J250 # 250 # 10-nm Cu; 650 J250 # 250 # 2-nm Cu; 650 J

Pulse duration: 1 ps

Ka2

Ka1

Ka2

Ka1