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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
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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
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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)
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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
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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
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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
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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
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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