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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