Presented at the 15th International Symposium on Heavy Ion Driven Inertial Confinement Fusion

in Princeton, June 7, 2004

by

Matthias Geissel1,2, Markus Roth2,

M. Allen3, P. Audebert4, M. Basko5, A. Blažević2, E. Brambrink2, J. Cobble6, T.E. Cowan7, M. Cuneo1, J.C. Fernández6,J. Fuchs4,7, J.-C. Gauthier4, M. Hegelich6, S. Karsch8

1Sandia National Laboratories, Albuquerque2Darmstadt University of Technology & GSI, Darmstadt

4LULI – École Polytechnique, Palaiseau

7University of Nevada, Reno & GA, San Diego 8Rutherford Appleton Laboratory

3University of California, Berkeley

TU Darmstadt

6Los Alamos National Laboratory

UN Reno

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000

5Inst. for Theor. and Exp. Physics, Moscow

1. Intro: Combining Lasers and Ion Drivers2. Concept: How Does It Work?3. Experiments: Probing the Models4. Fast Ignition: Some Considerations5. New Projects: Perspectives at SNL

Laser Drivers

+ High Power Densities+ Good Pulse Shaping

– Low Driver Efficiency– Low Repetition Rate

Heavy Ion Drivers

+ High Efficiency+ Beam-Target Coupling+ High rep-Rate

– Lower Power– Lower Focusability

e-

FAST IGNITOR

+ Relieved compression requirements

- Problematic energy transport from critical density layer to core via hot electrons

PROTON

fuel pellet

hohlraum

Mechanism

gold foil

Pre Pulse / ASE

MAIN PULSE@ >1019 W/cm2

e-+

++

+

protons

return current

1012 V/m

TNSATarget Normal Sheath Acceleration

TNSATarget Normal Sheath Acceleration

+ -

Acceleration of surface contaminants1. Influence of sheath formation

(bulk material/conductivity)2. Influence of rear surface

(roughness/features/curvature)

electron cloud

pre-plasma

1. Target:• Investigation of different materials• Investigation of foil curvatures• Investigation of surface structures

2. Beam:• Spatial distribution• Emittance• Energy distribution

Experimental Issues

ion spectrometer*and / or

Thomson parabola*

Setup of the Experiment

RCF*

* radiochromic film* @ 0° or 13°

20-30J @ 300-400fs

50-100TW

protons

Conductivity

laserlaser

gold plastic

• high conductivity• well established e--sheath• intense, collimated protons• smooth proton beam

• no conductivity• filamented e– and proton beams• low proton intensity

1D Defocusing

60µm gold wire

apertures for ionspectrometers

protons protons

RCFRCF

laserlaser

Rear Surface Features

laser

Example: Line Pattern

false color pictureof the RCF response(beam imprint)

interpretation

• proton source size ~60µm*

• emittance < 0.01 mm mrad

* for protons > 10 MeV:source size < 15µm < 0.002 mm mrad

Proton Energy Spectra

Tayloring the energy spectrumof laser generated protons is animportant issue to be solved(mono-energetic ions for FI).

Fast Ignitor Scenario

• Conversion efficiency: 1-10% so far (increasing with laser performance).• Need for a Multi-Beam-Ignitor.• Conversion window as concave multi-lenslets.

Production Target Issues:• Cold rear surface• Acceleration vacuum gap• Proximity to the hohlraum/capsule

Thin shield must protect from driver-induced soft X-rays

Multiple (Multi-) PW Beams

Radiation Shields

Production Target StabilityPlanar Gold Wall Response on Driver Radiation (M. Basko)

50µm15µm

30µm

IGNITION

0 10 20 30 40 500,01

0,1

1

Rrear(t)R

(m

m),

T e (

eV)

time (ns)

Te,rear(t)

• a 50µm shield is displaced by 230µm at the time of ignition (maximum compression)• the shield is heated up to 2-3 eV at the time of ignition

15µm

30µm

50µm

Petawatt-beams

DT capsule

protonbeams

p+ target

main shield

main cavity

600 µ

m

2nd shield

1. Ultra intense lasers can generate ion beams of superior beam quality

2. TNSA is the primary process3. Spatial distribution and divergence ca be taylored4. Fast Ignition:

• Multiple PW laser necessary• Sophistically shaped p+-production target• Careful heat shielding essential• Complex but feasible scenario

Conclusion

Sandia Multi-TW Facilities

OPCPA at High Energies

• General Atomics custom design OPCPA front end: ~30mJ @ 10Hz.• Nd:glass (phosphate) rod amplifiers push to ~4J @ 1 shot / 15 min.• Nd:glass (phosphate) slab amplifier (Beamlet design) push to 40-400 J (depending on available gratings and compressor design).

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000

The ZBL Laser Complex

Z-BeamletControl Room100 TW LaserOptics Support Facility100TW Target Area

10TW Experiments Small Scale – 15 min. Rep-Rate

CCD+LDM,HeNe

compressor

targetchamber

100TW Project Status

Petawatt Experiments Fast Ignition Experiments on Z

Petawatt Target Area

100 TWTarget Area