T.E. Cowan, Y. Sentoku,M. Bakeman, B. Chrisman*, E. d’Humieres, S. Gaillard, J. Rassuchine*

Department of PhysicsUniversity of Nevada, Reno

Fusion Science Center of Excellence for Fast Ignition and Extreme States of Matter

NTF Status, Cone Target Physics

Chicago O’Hare Hilton 28 February 2007

Fusion Science Center of Excellence for Fast Ignition and Extreme States of Matter

NTF Status, Cone Target Physics

Chicago O’Hare Hilton 28 February 2007

*partial graduate support from FSC

• Schedule shift due to budget continuing resolution (CR)

• Commissioning and laser characterization planned through FY07

• Insufficient support for outside “users” while under CR

• Minimal “start up” test experiments might be possible within limited UNR program (i.e., collaboration, not as user)

• Point of Contact: T.C., or Jeff Thompson, Acting Director

Leopard laser commissioning in progress

On the brighter side…. Good progress with nanofabricated cone-shaped laser targets….

Free Standing Au (10 m wall)

Free Standing Cu (10m wall)

x-ray

proton

x-ray

HED

Smoother (!) than prior cones

Inside sub-micron tip apex: conical, with vestige of Si etch planes. Closer to sharp-tip, Sentoku simulation

37.3 um

16.7 um 3.33 um

1.0 um 500 nm

March 2006 LANL-Trident, enhanced proton beam, Au “pizza” tops~2.5% conversion efficiency to protons, 1.5x max energy(M. Hegelich, K. Flippo)

June 2006 LLNL-Titan, proton acceleration(P. Patel, J. Rassuchine, S. Gaillard)

July 2006 LULI-100 TW, Au “pizza” tops, reduced mass, pre-pulse!(S. Gaillard, J. Rassuchine, M. Bakeman, J. Fuchs, M. Borghesi, O. Willi)

August 2006 LANL-Trident, systematics of Au “pizza” tops, alignment!(K. Flippo, S. Gaillard, J. Rassuchine, M. Bakeman, M. Hegelich)

December 2006 LULI-100 TW, 1, 2 comparison with Cu cones & funnelsx-ray emission from hot Cu – similar to 50 m reduced mass(S. Baton, M. Koenig, J. Rassuchine, R. Kodama)

summer/fall 2007 LBNL-L’OASIS (3 J, 30 fs); LULI; LANL; Leopard

Experiment summary of x-ray production and proton beam generation

50 / 30 / 90 m

25 / 5 / 80 m

Typical Reduced-Mass “Pizza” Target Parameters: Neck OD / Neck ID / Top Diameter

Enhanced laser-coupling efficiency, and some increase in proton energy observed at Trident (LANL, UNR, GSI)

Range of neck and top parameters explored

Alignment is crucial… a postieri determination of laser coupling to cone (central or offset) from proton pattern

PIC simulation of longitudinal E-field

(E. d’Humieres)

Offset: acceleration from cone sides,lower peak proton energy

Central: acceleration from pizza top;1.5x higher peak proton energy,better collimation, conversion eff.compared to flat foil

dN/dE = 1.5e11 [p/MeV] * exp(-E / 4.5 MeV)

N ~ 6.1011 protons, 0.49 J, Elaser = 19 J, ~ 2.5%

1 10 100

0.01

0.1

1

10

C4+ heated

(~10% H+)

F7+ heated

(no H+)

F7+ unheated

H+ unheated

La

ser-

Ion

Co

nv.

Eff

ic.

(%)

Laser Pulse Energy (J)

several-fold increase in laser-proton acceleration

efficiency !

HH++ unheated unheatedpizza-toppizza-top

Enhanced acceleration efficiency, despite no surface treatment….more to come?

Titan: 200 J/500 fs(10 m Au, flat)

Nov-Dec 2006 S. Baton, M. Koenig, D. Batani, R. Kodama, J. FuchsJ. Rassuchine, Y. Sentoku, T.E. Cowan, E. d’Humieres (UNR)

Cu cones – sharp, blunt, “funnel”, with Cu Ka imaging & spectroscopy

Concerns about plasma pre-fill on reproducibility 2 vs. 1 comparison at LULI-100 TW

Pro

be b

eam

interferometry

2D-K imaging(rear side)

2D-K imaging(transverse)

Visible imageGOI

HISAC

K spectroscopy

Transverse Cu Ka imaging: 1#119)

2

High contrast improves laser penetration to cone neck…

Defocused 50umDefocused 50um with New PHA

- Smaller transverse size of emission zone at 2 (further into neck)

- Laser absorption occurs approx. further 50 m upstream, for 1 (ASE/prepulse contrast ~ 10-7:1)

2w,PH: Shot #96: Cone #47 2w,PH: Shot #98: Cone #432w,PH: Shot #97: Cone #48

Dcrystal= 8mm ∆lambda =

[1.5408:1.5402] = 0.0006 A

Defocused 50um

1w: Shot #120: Cone #501w: Shot #119: Cone #49Defocused 50um

with New PHADefocused 50um

with New PHA

Dcrystal= 8mm ∆lambda =

[1.5407:1.54] = 0.0007 A

1w: Shot #121: Cone #31

New PHA

Dcrystal= 8mm ∆lambda =

[1.5407:1.54] = 0.0007 A

Rear-side (end-on) Cu Ka imaging:

Rear surface imaging consistent with transverse…

- Smaller transverse size of emission zone at 2 (further into neck)

2w,Shot #96: Cone #47Defocused 50um

1w,Shot #119: Cone #49

Defocused 50um with New PHA

Rearside Cu Kalpha Imager

0

50

100

150

200

250

0 20 40 60 80 100 120

Shot Number

FW

HM

(u

m)

Sharp Tip Cone Blunt Tip Cone Funnel Cone Multilayer (0.2)V(10)Cu(10)Al Reduced Mass Multilayer

1w 2w 1w

Target Type FWHM(1w) (um) FWHM(2w) (um) ΔFWHM

Sharp Cone 143.9/126 56.7 42-52%Blunt Cone 105.2/102/7 59.7 62-66%

Funnel Cone 95.5 50.1 69%Multilayer Disk 178.42 94.9 8.90%

0 100 200 300 400

0

1000000

2000000

3000000

4000000

Inte

grat

ed In

tens

ity (

a.u.

)

Distance (um)

1w Blunt Cone is 22-37% smaller than Sharp Cone

1w Funnel Cone is 32% and 8% smaller than Sharp and Blunt cone respectively

2w Funnel Cone is 11% and 19% smaller than Sharp and Blunt cone respectively

Funnel Cone is 87% smaller than 300um Disk at 1w and 90% at 2w

Defocused 50um

Defocused 30um up

7.4 7.6 7.8 8.0 8.2 8.40

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

Inte

nsity

(a.

u.)

Wavelength

Spectrometer Data Definition

Lower energy continuum

Kα1 and Kα2

Total hot spectrum

Hot Spectrum

Continuum background

X-ray spectroscopy: increased emission from “hot” ionized-Cu for high contrast (5th order)

7.6 7.8 8.0 8.2 8.4

0

500

1000

1500

2000

2500

3000

3500

Inte

nsi

ty (

a.u

.)

Wavelength

1w Au Cone+(20)Al(50)Cu(20)Al #123 1w Funnel Cone #120 1w Blunt Cone #49 1w Multilayer (.2)V(10)Cu(10)Al

Hot Cu (K pk-to-valley) observed for cones vs. flat at 1

7.6 7.8 8.0 8.2 8.40

500

1000

1500

2w Blunt Cone #98 2w Funnel cone #87 2w Funnel Cone #96 2w D=50um Reduced Mass (.2)V(20)Cu(5)Al #103 2w Au Cone+D=300um (.2)V(10)Cu(10)Al #74

Inte

nsi

ty (

a.u

.)

Wavelength

2: ionization above F-like. Comparable yield/heating to 50 m dia. reduced mass, despite huge mass

1w: Total Cold Cu Ka for cones ~ 1.5x higher yield than Multilayer

2w: Total Cold Cu Ka for cone~ 2-4x higher yield than Multilayer and Reduced Mass

Conical Crystal Spectrometer

0

20000

40000

60000

80000

100000

120000

140000

0 10 20 30 40 50 60 70 80 90 100 110 120

Shot Number

To

tal

Inte

gra

ted

Ka

lph

a1

an

d

Ka

lph

a2

(a

.u.)

Sharp Tip Cones Blunt Tip Cones Funnel Cones Multilayer Targets Reduced Mass Targets

1w 2w 1w

“Cold” K yield (Ne-like to neutral)

Conical Crystal Spectrometer

0

5000

10000

15000

20000

25000

0 10 20 30 40 50 60 70 80 90 100 110 120

Shot Number

Ho

t S

pe

ctu

m (

a.u

.)

Sharp Tip Cones Blunt Tip Cones Funnel Cones MultiLayer Flat Reduced Mass Targets

1w 2w 1w

“Hot” Cu x-ray yield (Li-like to F-like)

- Nanofabrication techniques are promising.….

- Preplasma filling (laser contrast) appears to be very important….

- Enhanced proton acceleration observed (confined hot electron sheath)

- X-ray emisison from hot matter observed (similar to reduced mass foils)

- Interesting alternative/complement to reduced mass targets:- hot electron concentration- maintains sheath quality for acceleration- more mass for x-ray production- mass produced on wafer- relaxed handling (at cost of more stringent contrast & pointing)- complex geometries possible

2006 progress in sharp-tip cone target physics: