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M. S. Tillack, Y. Tao, J. Pulsifer, F. Najmabadi,L. C. Carlson, K. L. Sequoia, R. A. Burdt, M.

Aralis

Laser-matter interactions and IFE research at UCSD

TITAN Kick-off Meeting7-8 May 2007San Diego, CA

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Center for Energy Research

Thermal, mechanical and phase

change behavior

Relativistic laser plasma

(fast ignition)

optics damage

Laser plasmas:EUV lithography, WDM and HED studies (XUV, electron transport)

Laser ablation plume dynamics,

LIBS, micromachining

Laser-matter interactions at UCSD spana wide range of intensities and applications

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1.IFE surface heating experiments

• Metal mirrors for laser-IFE final optics, chamber armor thermo-mechanics

2.Ablation plume dynamics

• Particle acceleration, structure of plumes, mitigation, phase change physics

3.EUV lithography

• 13.5-nm light emission, particle transport

Our group has 10 years of experience studying laser heating

and ablation

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We lead the HAPL final optics program (~108 W/cm2 absorbed)

1. Damage-resistant metal mirror development

• Coating techniques

• Surface finishing techniques

2. Prototypical high-cycle testing (248 nm)

3. System integration

Grain motion in thick Alumiplate coating

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We recently found a surprising dependence on pulse length

(2x energy in Compex)

Long pulse

Short pulse

Predicted short-pulse

• Damage does not scale like pulselength1/2 (i.e., like Tmax)

• Is this a result of cumulative damage? ∫f( dt

mirror M109

6 of 16We are testing chamber armor for

HAPL (~109 W/cm2 absorbed)

Time (10-7s)

Tmelt

1. 10 Hz exposure with Nd:YAG laser

2. High base temperature (up to 1000 ˚C)

3. Nanosecond time resolved optical thermometer

4. In-situ microscopy

7 of 16We discovered that damage is far

more sensitive to temperature than T

103 shots 105 shots104 shots

Initially 20˚C, maximum 2,500K (~2,200K T)

Initially 500˚C, maximum 3,000K (~2,200K T)

8 of 16Laser ablation plume dynamics were originally studied for liquid wall IFE

(1010 – 1011 W/cm2)

0.01Torr

1Torr

0.1Torr

10Torr

100Torr

Al (396 nm) at 18 mmin 150 mTorr air

Imaging plus time-of-flight spectroscopy led to the discovery of a triple plume structure in a laser ablation plume

1. Explosive evaporation

2. Plume transport

3. Condensation

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Magnetic diversion was studied as a means to protect IFE walls

• 0.6 T transverse field in gap

• Free expansion until th drops below ~10

• Axial and cusp fields were also studied

10 of 16Our EUVL studies emphasize particle

control (1010 – 1012 W/cm2)

lasers

pre-plasma mainplasma

Pre-pulsing was found to have a dramatic effect on ion energy

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Collaborations have begun between our lab and PISCES

1. Support studies of heating and ablation for

2. Develop a laser blow-off impurity injection diagnostic

3. Perform time-resolved SXR imaging

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400 mm

40 mm

10 mm

Film material: NiFilm thickness: 700 nmSubstrate: 1 mm glassWavelength: 1.064 mPulse duration: 7 nsLaser Energy: 500 mJIntensity: 1 GW/cm2

200 mm

1 mm

We began to explore laser blow-off as a diagnostic technique for MFE plasmas

13 of 16Studies were performed on the ejecta velocity and structure vs.

composition, thickness, and intensity

100 ns 500 ns 800 ns

Visible emission

Shadowgraphy

14 of 16Confinement of ejecta and avoidance

of ionization are important to penetrate the plasma and retain

spatial resolution

Vis

ible

em

issi

on@500

ns

• FWHM=1 mm

• V=3 km/s

• Emission and witness plate shows plume is mostly neutral

10 m

15 of 16Soft x-ray imaging is proposed together with blowoff to study

transport physics

Stutman et al.,RSI 77, 330 2006.

We use similar diagnostics for EUVL research

JenOptik E-mon

13.5 nm EUV mirror,NTT Advanced Technology Corp.

Example lines:Li-II 13.5 nm

C-V 24.8 nm

He-II 30.4 nm

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Summary

• We have experience and existing experimental capabilities in several topics of potential interest to TITAN:

Sub-ablation threshold rapid surface heating

Ablation plume dynamics

EUV diagnostics

• These capabilities are relevant to both IFE and MFE