ICFT/P2006-054 PERSISTENT SURVEILLANCE FOR PIPELINE PROTECTION AND THREAT INTERDICTION 9 th International Fast Ignition Workshop Cambridge, MA 3 November.

ICFT/P2006-054

PERSISTENT SURVEILLANCE FORPIPELINE PROTECTION AND THREAT INTERDICTION

9th International Fast Ignition WorkshopCambridge, MA

3 November 2006

Designing and Fabricating a Proton Beam Source Suitable for Fast

Ignition Targets

Richard B. Stephens General Atomics

ICFT/P2006-054

P.PatelM. Roth et al

ICFT/P2006-054

Contributors from a large collaboration

M Mauldin, E Giraldez,C Shearer

M Foord, A J MacKinnon, P Patel, R A Snavely, S C Wilks,

K Akli, F Beg, S Chen, H-K Chung, D J Clark, K Fournier, R R Freeman, J S Green, C D Gregory, P-M Gu, G Gregori, H Habara, S P Hatchett, D Hey, K Highbarger, J M Hill, J A King, R Kodama, J A Koch, K L Lancaster, C D Murphy,, H Nakamura, M Nakatsutsumi, P A Norreys, N Patel, J Pasley , H-S Park, C Stoeckl, M Storm, M Tabak, M Tampo, W Theobold, K Tanaka, R Town, M S Wei, L van Woerkom, R Weber, T Yabuuchi, B Zhang

•This work is from a US Fusion Energy Program Concept Exploration collaboration between LLNL, General Atomics, UC Davis, Ohio State and UCSD

•International collaborations at RAL have enabled the experiments

•Synergy with an LLNL ‘Short Pulse’ S&T Initiative has helped the work

ICFT/P2006-054

Proton ignition concept has evolved

• Initial concept avoided complexity– External focusing surface– Simple proton transport

• Velocity spread cause problems– Energy must be delivered in short time

• Simple solutions …– Reduce energy spread (M. Hegelich, LANL)

Reduce separation

• Introduce new problems Protection from the imploding shell

25

10

20

30

40

50

60

70

00 5 10 15 20

Tp (MeV)

Eig (

kJ)

d = 4 mm

d = 2 mm

d = 1 mm

Roth et al., Phys. Rev. Lett. 86, 436 (2001)

Atzeni et al., Nucl Fusion 42, L1 (2002)

ICFT/P2006-054

Use a reentrant cone for protection

Laser

Protects proton source from coronal plasma

Limits accelerating surface

Causes focusing edge effects

Scatters proton beam

ICFT/P2006-054

Tested concept by making prototype

• Cone dimensions same as for electrons– 30° full cone opening

• Focusing surface same as for hemi tests(existing focal length data)

– rc= 170 m

– dfocus ~290 m

Limits accelerating area (125 m dia)

• Target Cu foil - 32 m thick (29 mg/cm2)– Stops < 4 MeV protons

ICFT/P2006-054

Proton source area depends on energy

• Accelerating electrons cool off as they travel to the edge

Hybrid PIC LSP simulation

M. Foord - LLNL

100 fs, 50 m FWHM Gaussian beam 45 J beam

Patel et al., Phys. Rev. Lett. 91, 125004 (2003)

200 m dia includes most useful protons (flat foil data)

Our source will have limited energy output

ICFT/P2006-054

Low energy protons are most important to ignition

t [ps]

Temporal et al., Phys of Plasma 9 3098 (2002)

45 65 85 105 125

100

200

300

10

20

30

40

Pro

ton

En

ergy

[M

eV]

Pow

er [

TW

]

Fusion Emission

Proton Deposition

Useful for

ignition

Protons must deliver energy in short time for ignition

limits useful proton energy range

Sim parameters: Proton spectrum: Tp = 3 MeV, dn/desqrt()e-

/Tp

Total proton energy = 26 kJ Proton beam radius = 10 m

Source distance = 4 mmTarget density = 400 g/cc

ICFT/P2006-054

Protons are not easily scattered

• Scattering angle E-

2

3 Mev Protons ~ 5° 15 Mev Protons ~ 1°

• Broadens spot 5-10 m

15°

5 m Au

1-5°

200 m

The cone tip can be far from the compressed core

End wall scattering is insignificant

ICFT/P2006-054

Prototype proton focusing cone was constructed

Construction is feasible

ICFT/P2006-054

Kimager

600 650 700 750 800 850 900 950 1000

-1000

-500

0

500

( . .)Intensity a u

160 m

0

500

1000

1500

2000

2500

7.8 8 8.2 8.4 8.6 8.8 9 9.2

Energy (KeV)

back surface

front surface

K

Kβ

HOPG

Initial tests show moderate proton focusing and heating

ICFT/P2006-054

Proton heating is reasonable for conditions

• Ratio of HOPG intensities gives slope temp 1-4 MeV for protons

• K spots have 106 counts - to be compared to equivalent shots using full hemi

• Focal spot is rather large - 160 m– Could be consequence of side walls

changing the proton focus.

ICFT/P2006-054

Measure focus changes by radiographing grids

• Send proton beam through grid and detect with RCF stack

• Magnification determines focus position, fuzziness of grid shows focus size, number of grids show source area

• These experiments are in preparation

Put grids in flat washers for simpler construction

ICFT/P2006-054

ICFT/P2006-054

Hi-Z mix?

more compact?

improve eff’y?

Conversion to protons, focusing/ heating?

Blob R ~ 0.44 g cm-2

<> ~ 120 g cm-3

<T> ~ 0.4 keVTotal Energy in blob ~ 0.6 kJ

Backlit radiograph (8 keV) at imploded max R

457

µm

40 µm

CD2vacuum

PW laser55* beams,pulse-shape“26”

Omega EP hydro simulations (S. Hatchett)

• What is signature of heating, increased emission? Ka fluorescence? X-ray scattering? neutron production? Abs spectroscopy?

Will use data to design integrated experiments for Omega EP

ICFT/P2006-054

• The proton focal spot radius reduces as laser focal spot increases

50 um spot

z=50 m 55 m 60 m

10 um spotz=50 m (long axis) 55 m 60 m

• Trade-off between fully illuminating surface, and building edge effect

Laser spot size influences proton focus

ICFT/P2006-054

Tight laser spot gives ‘aberrated’ proton focus

X-

20m heated spot

PW laser

Laser

Proton heating

Cu K image

Gekko PW data

320 m Al shell

Protons

X-ray phc image Cu Kimage

X-ray phc image

Cu Kimage

RAL PW

data