E. M. CampbellDeputy Director,University of RochesterLaboratory for Laser Energetics

Presentation at George Washington University

Washington, DC14 December 2015

Ultrahigh Brightness Laser Development at the Laboratory for Laser Energetics

1

Seed

Pump

Time

Plasma wave

Depleted pump

Amplified

seed

EP OPAL beamline

EP OPAL compressorUltra-broadband front end

OMEGA EP OPAL

Short-pulsetransport

and focusing

Collaborators

D. Haberberger, A. Davies, S.-W. Bahk, J. Bromage, J. D. Zuegel, and D. H. Froula

University of RochesterLaboratory for Laser Energetics

J. Sadler and P. A. Norreys

University of Oxford

...and many others

2

LLE and collaborators are pursuing two paths for the development of multipetawatt, high-brightness lasers

Outline

I2270

• Raman plasma-wave amplifier

– parametric amplification of a short seed pulse by stimulated Raman scattering in a matched plasma medium

• Optical parametric amplifier (OPA) pumped by multikilojoule Nd:glass laser

– ~12-kJ (0.532-nm), 2.5-ns pulse pump (OMEGA EP) for OPA

– large-aperture (80-cm), high-damage (300-mJ/cm2) grating for pulse compression [chirped-pulse amplification (CPA)]

3

Raman amplifiers: Exploit the nonlinear physics of laser–plasma interactions (LPI)’s

I2271

4

• Intense laser radiation can excite electrostatic waves in plasmas

Laser light propagates through the plasma

Oscillations in the plasma begin to radiate scattered light (linear Thomson scatter)

The beating of the two light waves creates a ponderomotive force, pushing the particles into the troughs of the envelope

If the bunching of the particles matches an electrostatic mode, the three waves become resonant and grow

E E E E

Electrostatic plasma wave

Step 1

Step 2

Step 3

Step 4

If there is a resonance with electrostatic modes of the plasma, instabilities can result (example SRS, SBS)

I2272

5

Raman amplifiers are “seeded” SRS.

• Simulated Raman scattering (SRS)

• Simulated Brillouin scattering (SBS)

• SRS occurs when:

• SBS occurs when:

Laser light Electron plasma wave (EPW)

Scattered-light wave

Laser light Ion sound wave (IAW)

Scattered-light wave

k k kEPW

EPW0 2

0 2

~ ~ ~= +

= +

k k kIAW

IAW0 1

0 1

~ ~ ~= +

= +

National Plasma Science reports have identified plasma-wave (Raman) amplifiers as a potential for the next generation of pettawatt-class lasers

I2273

6

Seed

Pump

Time

Plasma wave

Depleted pump

Amplified

seed

High-energy compression gratings are NOT required.

Manley–Rowe (energy and momentum conservation)

• ~pump = ~seed + ~EPW

• kpump = kseed + kEPW

• Plasma [EPW (dne/ne ~1%)] is the medium that transfers energy from a long-pulse (ns) pump, high-energy laser to a short-pulse (~15 fs), low-energy seed laser

Raman amplifiers require understanding and control of nonlinear plasma physics

I2274

• Goal: efficient energy transfer from long pulse pump to seed

– pump depletion

• Challenges that limit efficiency and resonance condition and brightness (focusability)

– filamentation– frequency detuning– amplitude of EPW

- wave breaking- mode coupling

– competition with plasma-wave interactions- Raman forward scattering of the seed pulse- Raman backscatter of the pump pulse

7

Pump intensity and plasma density are key controlling parameters.

– /v k n n

c1ph

e c0

0~= =

– /index of refractionn n n1 /plasma e c

1 2=^ ^h h

Low-light pressure

Low-light pressure

Laser“Hotspot”

High-lightpressure Laser light

self-focuses

Electrondensity

Multidimensional particle-in-cell (PIC) codes have identified operating parameters for efficient pump-seed conversion

I2275

• Strategy

– maximize Raman amplification of the pump

- limit forward Raman scattering (gain < 10)

– limit filamentation of the seed (gain < 10)

• Strategy defines experimental parameters

– Ipump < 5 × 1014 W/cm2

– 2.5 × 1018 < ne < 5 × 1018 cm–3

– Iseed < 4 × 1017 cm3

8

n/n

c

10–3

10–2

1012 1013

Pump intensity (W/cm2)

1014 1015

30

25

20

15

10

5

0

psto fsps

to fs

nsto ps

nsto ps

3535 2020

6060

40404545

Max

imu

m p

rop

agat

ion

dis

tan

ce (

cm)

1150

1140

1130

1120

1110

1100

109031 5 7

Plasma density (×1018 cm–3)

See

d w

avel

eng

th (n

m)

1.00.8

0.6

0.4

0.2

0.01000 1050 1100950 1150

Wavelength (nm)

Sp

ectr

a (n

orm

aliz

ed)

SignalIdler

A tunable seed laser is being built to access the optimal Raman amplification regime for a 1053-nm pump laser

E23502b

9

The plasma density and seed wavelength will be varied to optimize amplification.

20pe0

~~

=

peseed 0 -~ ~ ~=

14pe0

~~

=

PumpMulti-Terawatt (MTW) Laser SystemNd:glass: 1053 nmEmax = 75 JDt = 25 ps

SeedOptical parametric amplifier line (OPAL)Emax = 50 mJ (1100 nm to 1300 nm)Dt ~ 0.1 ps

Research at LLE is exploring the laser–plasma physics with the goal of demonstrating an efficient petawatt plasma-wave amplifier

E23501a

• Optical plasma densities– tunable pump and seed wavelengths

• Laser pump energy– ~75 J

• High-intensity seed pulse– Eseed ~ 75 mJ– Iseed ~ 2 × 1014 W/cm3

• Homogeneous plasma– 4-cm-long gas cell– cold plasma (<70 eV)

- limit EPW wave breaking

• Sophisticated diagnostics– optical Thomson scattering

- EPW characterization– interferometry

- plasma density– spectral phase interferometry (SPIDER)

- phase and electric field of amplified laser pulse

10

*Epump/Eseed ~104 to 106 (limits pump depletion and efficiency).

1.1

***

1.0

0.9

0.8

0.7

0.6

0.55 10 15 20

Plasma density (1018 cm–3)

~0/~pe = 14~0/~pe = 20Previous experimentsLLE experiments

Pu

mp

wav

elen

gth

(n

m)

The goal of the present effort is to demonstrate the feasibility of a plasma-wave amplifier in the pump-depletion regime

I2276

11

The next-generation ultrahigh-power, short-pulse system at LLE could use plasma-wave amplification as the final amplifier to achieve 100 PW.

10 J, 15 fs

MTW OPAL

EP OPAL100 J, 20 fs, 5 PW

20 kJ, 20 fs

1 exawatt1025 W/cm2

30 kJ, 500 ps

Plasma-wavepump

Plasma-waveamplifier

OMEGA EP

LLE and collaborators are pursuing two paths for the development of multipetawatt, high-brightness lasers

Outline

I2270a

• Raman plasma-wave amplifier

– parametric amplification of a short seed pulse by stimulated Raman scattering in a matched plasma medium

• Optical parametric amplifier (OPA) pumped by multikilojoule Nd:glass laser

– ~12-kJ (0.532-nm), 2.5-ns pulse pump (OMEGA EP) for OPA

– large-aperture (80-cm), high-damage (300-mJ/cm2) grating for pulse compression [chirped-pulse amplification (CPA)]

12

LLE is developing a concept for a >50-PW single-aperture laser based on pumping an OPA with two OMEGA EP beamlines

I2286

• The EP OPAL design at full scale would produce 75 PW (1.5 kJ at 20 fs) with high contrast

13

OMEGA EPbeamlines

EP OPAL beamline

EP OPAL compressor

Ultra-broadbandfront end (UFE)

Short-pulse transport and

focusing1234

Only KDP** and DKDP*** can be grown in boule sizes large enough for kilojoule amplifiers.

Nd:glass lasers can pump large optical parametric amplifiers, producing bandwidth for sub-20-fs pulses*

E24282b

14

*I. N. Ross et al., Opt. Commun. 144, 125 (1997); V. V. Lozhkarev et al., Laser Phys. 15, 1319 (2005).**KDP: potassium dihydrogen phosphate

***DKDP: deuterated potassium dihydrogen phosphate

Nonlinear crystal |(2)Signal

Amplifiedsignal

Signal gain when wave vectors

conserve energy AND momentum

(Angles exaggerated for clarity)

Idler

OMEGA EPpump

Signal bandwidth

kPkS kI 800 850 900 950 1000 1050

0

500

1000

Wavelength (nm)

DKDP small-signal gain2-GW/cm2 pump,

45-mm crystal thickness

Sm

all-

sig

nal

gai

n

170 nm

The multikilojoule Nd:glass OMEGA EP laser can serve as a pump for an OPA

I2287

• OMEGA EP

– four beams

- ~50 kJ at 1.05 nm

- >25 kJ at 0.53 nm

- >16 kJ at 0.35 nm

15

EP OPAL is an OPCPA* system, consisting of an ultra-broadband front end, large-aperture NOPA’s,** a compressor, and focuses on the OMEGA EP target chamber

E24287b

16

Beamline 36.3 kJ2.5 ns

NOPA7

Beamline 4

NOPA6

6.3 kJ2.5 ns

NOPA5 pump

NOPA5

100 J2.5 ns

OMEGA EP

Ultra-broadband front end(NOPA1 to NOPA4)

Beamline 1pulses to

EPTC

Beamline 2ps (IR)

+ns (UV)

EP OPAL beamline

0.25 J, 2.5 ns, 160 nm

Compressor

1.6 kJ, 20 fs

OMEGA EPtarget

chamber(EPTC)

~75 PW~1024 W/cm2

1053 nm527 nm810 to 1010 nm

*OPCPA: optical parametric chirped-pulse identification**NOPA: noncollinear optical parametric amplifier

Schematic of OPCPA pumped by OMEGA EP

E24288a

17

*VSF: vacuum spatial filter**FWHM: full width at half maximum

Pump parameters for all noncollinear optical parametric amplifiers (NOPA’s): 527 nm, 2.5 ns, 2 GW/cm2

80-cm beam (FW 1%)300 mJ/cm2 at gratings" 75 PW

UFE

Pu

mp

/sig

nal

Pu

mp

/sig

nal

Pu

mp

/sig

nal

Pu

mp

/sig

nal

Co

mp

ress

or

NO

PA6

NO

PA7

VSF*8×

VSF1.0×

VSF2.2×

NOPA5Pump/signal

Pump/signal

Pump in: 4.5 cm (FWHM**) 100 J Signal out: 25 J

Pump in: 35.5 cm (FWHM) 6.3 kJ Signal out: 1.5 kJ

Pump in: 35.5 cm (FWHM) #6.3 kJ Signal out: #3 kJ

Signal in: 73 cm (FWHM) 2.3 kJ Signal out: 20 fs 1.6 kJ 300 mJ/cm2

A single-aperture >50-PW laser will require advances in several areas

I2288

• Advanced broadband, efficient, damage-resistant gratings

• Ultra-broadband wavefront control and focusing

• Large-aperture, high deuterated DKDP

• Damage-resistant short-pulse (broadband) coatings

• Diagnostics

• Ultra-broadband dispersion control

• NOPA gain control and adjustment

• Ultra-broadband front end

18

LLE is developing a scaled facilty (MTW OPAL) to develop/demonstate ultra-peak-power OPCPA lasers.

MTW OPAL has several technical and scientific goals

E24300b

19

Goal 1: Develop and demonstrate laser technologies required for EP OPAL

Goal 2: Build operational experience with a mid-scale user facility

Goal 3: Grow a science program with ultrashort pulses

Although MTW OPAL is significantly smaller than EP OPAL, it uses the same technologies

E24301a

20

Parameter MTW OPAL EP OPAL

Pulse width (FWHM) 15 fs 20 fs

Compressor beam size (FW 1%) 9 cm 60 to 80 cm

Compressor output energy 7.5 J 300 to 1600 J

Power 0.5 PW 14 to 75 PW

Technologies MTW OPAL EP OPAL

Advanced grating types { {

Achromatic image relays { {

DKDP amplifiers { {

Short-pulse coatings { {

Short-pulse diagnostics { {

The MTW OPAL system uses the existing MTW laser at LLE to pump the final amplifier (NOPA5)

E24302a

21

*SHG: second-harmonic generation

MTW front end+6 nm FWHM

OPCPA pumplaser

UFE+200 nm FWHM

Radial-group-delay compensator

(RGDC)

OPCPA Rod amplifierDisk amplifier

SHGtable

NOPA5NOPA4

32

1

Picosecondcompressor

New targetchamber

Femtosecondcompressor

MTW targetchamber

SHG*

Laser Development Laboratory (LDL)

LDL-Annex

Activated

527 nm 830 to 1010 nm 1053 nm

Operational

Underconstruction

Ordered(except crystal)

Optical designin progress

Underconstruction

TestingUnder

construction

The UFE consists of a white-light–seeded chain of NOPA’s and a 1.5-ns stretcher

E24303a

22

Oscillator

1053 nm160 fs

Delayand sync

CompressorNOPA12~

2~

NOPA2

NOPA3

Dazzler™

Beam relay

Stretcher

WLC*

Yb fiber

Fiber CPA pump laser

250 fs, 14 nJ, 500 kHz 5 nJ, 0.3 ps

0.3 mJ, 1.5 ns

11 ps, 70 mJ, 5 Hz

Stretch

Nd:YLF pump laser

Regen with self-phase

modulation (SPM)compensation

527 nm 810 to 1010 nm 1053 nm

Poweramplifier

*WLC: white-light continuum

The prototype UFE is operational and available to support MTW OPAL development

E24304a

23

0

0

–5

–5

5

5

x axis (mm)

y ax

is (

mm

)

Stretcher near field

00

40

60

120

160

200

0

500–500

400

–400

x (nrad)

y (n

rad

)

Stretcher far field

Diffractionlimit FWHM

Symmetric withnegligible wings

Delay (ps)

Prestretch temporal contrast

0

10–16

10–12

10–8

10–4

1

–200 200

Diagnosticnoise floor NOPA1

+ NOPA2+ NOPA3

†††

Diagnosticreflection

†

Cro

ss-c

orr

elat

ion

(d

B)

NOPA1 pulse afterprism compressor

0

Time (fs)

Inte

nsi

ty

(arb

itra

ry u

nit

s)0.0

0.5

1.0

50–50

Fouriertransform

limit(11.9 fs)

Measured(12.8 fs)

Wavelength (nm)

Sp

ectr

um

(a

rbit

rary

un

its)

Stretcher output spectrum

900

210 nm

10008000

40

80

120mean!rms*

• UFE has been thoroughly characterized

• Additional measurements will be required after the full system is built (e.g., recompression)

*rms: root mean square

Activation of the NOPA4 stages and transport to NOPA5 (DKDP final amplifier) will be completed this year

E24305a

24

SHGtable

NOPA5 pump and signal transporthave been designed and ordered

NOPA4 stages areunder construction

NOPA5

A compressor chamber is being designed for multiple functions

E24306a

25

Short-pulse diagnostics

Double plasmamirror

To target chamber

Periscope

Achromatic image relay

Compressor

Periscope

From NOPA5

• Demonstrate an achromatic relay (2× magnification)

• Recompress pulse from 1.5 ns to 15 fs

• Test gold (p-pol) and hybrid gratings (s-pol)

• Demonstrate femtosecond coatings (s- and p-pol)

• Develop a double-plasma mirror option for improved temporal contrast (~100×)

• Sample beams for short- pulse diagnostics

Optical design is underway and a full optomechanical design must be completed in 2016.

After MTW OPAL is completed, the technology readiness levels (TRL’s) for the main technical challenges will have improved to TRL 5–TRL 6

E24309a

26

Technical challenge Current TRL

MTW OPAL Progress

Advanced gratings 2 5 Technology concept " Lab-scale prototype

Ultra-broadband wavefront control and focusing 2 5 Technology concept " Lab-scale prototype

Large-aperture, highly deuterated DKDP 2 5 Technology concept " Lab-scale prototype

Short-pulse coatings 3 5 Active R & D " Lab-scale prototype

Short-pulse diagnostics 3 6 Active R & D " Pilot-scale prototype

Ultra-broadband dispersion control 3 6 Active R & D " Pilot-scale prototype

NOPA gain adjustment 2 6 Technology concept " Pilot-scale prototype

Ultra-broadband front end 5 6 Lab-scale prototype " Pilot-scale prototype

LLE vision: three world-class user laser facilities

I2289

• OMEGA (60 beams)

– 30 kJ

– 30 TW

– 0.35 nm

27

• OMEGA EP (four beams)

– four beams (option 1)

- ~16 kJ

- ~8 TW

- 0.35 nm

– two beams (option 2)

- ~2 kJ

- ~10 ps

- 1.05 nm

• EP OPAL (one beam)

– one beam

- ~1.5 kJ

- 20 fs

- ~0.83 to 1 nm

Backup

28

A number of petawatt facilities are operational, but multipetawatt facilities are only in development

E24284a

29

Name Facility Technology Peak power Status

Apollon-10P

Laboratoire pour l’Utilisation des Lasers Intenses + Laboratoire d’Optique Appliquée +

Institute Optique

OPCPA + Ti:sapphire 5 PW Under

construction

L4

Extreme Light Infrastructure-CZ +

National Energetics

OPCPA + Nd:glass 10 PW Under

contract

–Extreme Light

Infrastructure-NP + Thales

OPCPA + Ti:sapphire 2 × 10 PW Under

contract

Vulcan 20 PWRutherford Appleton

Laboratory (RAL)OPCPA 20 PW On hold

Exawatt Center for

Extreme Light Studies

Institute of Applied Physics (IAP) OPCPA 12 × 15 PW Concept

The UFE consists of a white-light–seeded chain of NOPA’s and a 1.5-ns stretcher

E24303b

30

Oscillator

1053 nm160 fs

Delayand sync

CompressorNOPA12~

2~

NOPA2

NOPA3

Dazzler™

Beam relay

Stretcher

WLC

Yb fiber

Fiber CPA pump laser

250 fs, 14 nJ, 500 kHz 5 nJ, 0.3 ps

0.3 mJ, 1.5 ns

11 ps, 70 mJ, 5 Hz

Stretch

Nd:YLF pump laser

Regenwith SPM

compensation

527 nm 810 to 1010 nm 1053 nm

Poweramplifier

A UFE prototype has been built and testing is underway

E24316a

31

• All parameters measured so far meet requirements

• Testing will be ongoing

– operational maturity

– spectral phase control for recompression

– temporal contrast and prepulses

• A new stretcher is required for an EP OPAL-scale compressor

– prototype: 1.5 ns/200 nm (7.5 ps/nm)

– EP OPAL: 2.5 ns/150 nm (16.6 ps/nm)

Ultra-broadband front end for MTW OPAL

High power and intensity require large-aperture beams that are tightly focused

E24283a

32

• Damage thresholds for femtosecond mirrors and gratings are in the 100’s of mJ/cm2 range (cf., few J/cm2 for ps)

• Tight focal spots place challenging requirements on the beam wavefront and the final-focusing optics

20

10

30

50

70

90

40 60

Beam full width at 1% (cm)

Power versuscompressor-beam size

Pea

k p

ow

er (

PW

)

80

Grating fluence = 300 mJ/cm2

100 mJ/cm2

200 mJ/cm2

20-fs pulse (FWHM)

43

2

4

6

8

10

5 6 6 8

Focal spot FWHM (nm)

Intensity versusfocal-spot width

Inte

nsi

ty (

× 1

023

W/c

m2 )

9 10

P = 75 PW

I = P/rR2

50 PW

25 PW

EP OPAL performance depends on the grating fluence and compressor beam size

E24286d

33

Grating fluence (20 fs)

100 mJ/cm2

Compressor beam size (FW 1%)

60 × 60 cm

Diagonal for 45° angle of incidence 110 cm

Compressor output energy 300 J

f-number and focal spot (nm)

f/6 13

f/1.3 4.2

Energy on target 290 J 230 J

Power 14 PW 12 PW

Intensity (W/cm2) 1 × 1022 9 × 1022

300 mJ/cm2

60 × 60 cm

110 cm

900 J

f/6 13

f/1.3 4.2

860 J 700 J

43 PW 35 PW

3 × 1022 3 × 1023

300 mJ/cm2

80 × 80 cm

149 cm

1600 J

f/4.6 10

f/1 3.2

1500 J 1200 J

75 PW 62 PW

1 × 1023 8 × 1023

Advancedgratings

Increasedbeam size

Limited by size of current optics fabrication Full scale

Challenges remain to scale femtosecond coating capability for meter-scale laser applications

G10251c

34

• Current uniformity for 1 m " masks with phase discontinuities

• Scaling femtosecond system geometry " 3.5-m chamber

• High film stresses for fully dense coatings

• m/4 on a 1-m optic would require ~16-cm thickness (4-nm-thick coating)

• Match the dispersion over a curved optic aperture

• Enhanced/protected metals are preferred with sufficient laser-damage thresholds

Laser-damage thresholds at the correct pulse length, spectral bandwidth, and large aperture are critical to successful system scale-up.

Enhanced-metal coatings have been developed for the compressed-pulse section

E24318a

35

• Several practical benefits for short-pulse transport – femtosecond damage thresholds comparable to dielectric mirrors – s- or p-polarized beam – low group-delay dispersion, stress-induced wavefront and sensitivity

to coating thickness

R (p-pol, 810 to 1010 nm) >97.4% >98.6% >99.3%GDD** (810 to 1010 nm) 2 fs2 13 fs2 35 fs2

LDT (N:1, 800 nm, 59 fs) 0.60 J/cm2 0.68 J/cm2 0.49 J/cm2

HfO2/SiO2: larger band gap

versus Nb2O5 for improved LDT*Cu: environmental

durability/adhesion

Al2O3: adhesion,environmental

protection

Ag: high %R

Nb2O5/SiO2:maximum bandwidth

and reflectivity

SiO2

Nb2O5

AgCuAl2O3

HfO2Nb2O5

*LDT = laser-damage threshold**GDD = group-delay dispersion

Intermediate power levels are possible with smaller optics and two amplifiers

E24289a

36

Pump parameters for all NOPA’s: 527 nm, 2.5 ns, 2 GW/cm2

60-cm beam (FW 1%)100 mJ/cm2 at gratings" 14 PW300 mJ/cm2 (with NOPA7)" 43 PW

UFE

Pu

mp

/sig

nal

Pu

mp

/sig

nal

Pu

mp

/sig

nal

Co

mp

ress

or

NO

PA6

NO

PA7

VSF6×

VSF1.0×

VSF2.2×

Pu

mp

/sig

nal

Pump in: 4.5 cm (FWHM) 100 J Signal out: 25 J

Pump in: 26.6 cm (FWHM) #3.5 kJ Signal out: #0.88 kJ

Signal in: 55 cm (FWHM) 0.43 kJ Signal out: 20 fs 0.30 kJ 100 mJ/cm2

NOPA5Pump/signal

Pump/signal

• The full-scale infrastructure would be built for the NOPA crystals, compressor gratings, and mirrors

• Sub-aperture optics could be used for a >10-PW system during the early stages of operation

To support the science program, a concept for a joint target area is being developed

E24310a

37

• A target area will be added west of LDL

• Both MTW and OPAL beams will be available for experiments

• The existing “Raman chamber” is shown

• Additional shielding, similar to what is used on MTW (5 cm of lead), would enable a large number of shots Joint target

chamber

f/20

f/2

OPAL Single shot, 7.5 J, 15 fs

(5 Hz, 50 mJ, 15 fs)

MTWSingle shot,50 J, ~1 ps

Room 136

LDL

LDL Annex

Height =37.5 in.

NOPA5 pump andsignal diagnostics

CompressorCab

A concept for the compressor chamber has been developed

E24293a

38

• A detailed optomechanical design is required to advance this concept

• Requires novel beam-sampling schemes to effectively operate the system (no leaky mirror)

Las

er d

iag

no

stic

s

Laser diagnostics

G1

G2

G4

G3

To EPTC

50 ft

North

M2

M1

M4 15 ft

M3

EP OPAL will use a two-element focusing system to provide experimental flexibility

E23395f

39

*A. Kon et al., J. Phys., Conf. Ser. 244, 032008 (2010).

Target chamberTarget chamberRefocusingplasma

mirror/target

Refocusingplasma

mirror/target

FoldmirrorFold

mirror

OAPOAP

Target chamberTarget chamberRefocusingplasma

mirror/target

Refocusingplasma

mirror/target

FoldmirrorFold

mirror

OAPOAP

a b

t: defocal length tl: focal length

i: incident angle

Laser

Ellipsoid mirror

Min

or

axis

(2b

)

(Minor axis length) (major axis length)

Inte

nsi

ty- e

nh

ance

men

tfa

cto

r0.0 0.4 0.8

10

100

1000

1

0°4°7°13°18°25°

Major axis (2a)Major axis (2a)

i

• f/4.6 off-axis parabola (OAP) outside the target chamber

• Ellipsoidal plasma mirror* (EPM) inside the target chamber

– part of the experimental design/target

– disposable

– could be concave or convex to tune the f/#

The scalability must be investigated to the kilojoule level.