Transcript ppt - Fusion Energy Research Program

Final Optic Research – Progress and Plans
M. S. Tillack
with contributions from:
Z. Dragojlovic, F. Hegeler,
E. Hsieh, J. Mar, F. Najmabadi,
J. Pulsifer, K. Sequoia,
M. Wolford
HAPL Project Meeting, PPPL
27-28 October 2004
Overview
1. Final optic program summary
2. New mirror fabrication and testing
3. Larger scale testing
4. Contaminant transport modeling
5. Gas puff modeling
The steps to develop a final optic
for a Laser IFE power plant (1 of 2)
1. “Front runner” final optic – Al coated SiC GIMM:
UV reflectivity, industrial base, radiation resistance
•
Key Issues:
• Shallow angle stability •
• Laser damage resistance •
goal = 5 J/cm2, 108 shots •
85Þ
Contamination
Optical quality
Fabrication
Radiation resistance
~50 cm
2. Characterize threats to mirror:
LIDT, radiation transport, contaminants
3. Perform research to explore damage mechanisms, lifetime and mitigation
Bonding/coating
Al: 20-500 nm
q”=10 mJ/cm2
SiC: 10 m
Microstructure
Fatigue
Ion mitigation
The steps to develop a final optic for a
Laser IFE power plant (2 of 2)
4. Verify durability through exposure experiments
10 Hz KrF laser
UCSD (LIDT)
XAPPER
LLNL (x-rays)
5. Develop fabrication techniques
and advanced concepts
ion accelerator
neutron modeling
and exposures
6. Perform mid-scale testing
Diamond-turned, electroplated mirrors survived
105 shots at 18 J/cm2 on a small scale (mm2)
1. Relatively small grains (10-20 m)
2. Relatively dense, thick coating
Still, these mirrors ultimately
fail due to grain motions, ...
... and we would like to improve
the high-cycle fatigue behavior
Post-processing after thick (35-50 m) thin-film
deposition should provide good optical quality
with a damage-resistant microstructure
rough substrate
polish/turn
35 m “thick thin-film” mirror,
turned at Schafer Corp. and
exposed to 104 shots at 5 J/cm2
coat
final polish/turn
no damage to elecroplated
mirror (turned at GA) under
the same exposure conditions
Ringdown reflectometry (now @266 nm)
indicates somewhat high absorption at 85˚
reflectivity of 35 m Schafer mirror
photodiode
polarizer
lens
output
coupler
test specimen
output
coupler
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
<1 ns
nanolaser
Diamond turning lines are too deep
– 50 nm rms –
(A new Pacific
Nanotechnolgy AFM has
been added to our surface
analysis capabilities)
Peaks grow during exposure (unlike earlier
results which exhibited etching)
etching observed
previously in diamondturned polycrystalline foils
It’s time to start making smoother mirrors
MRF systems are popping up all over the place
(this one is at Edmund Optics)
Larger mirrors are being fabricated with
increasing emphasis on surface quality
1. Mid-scale 4” optics
• Thick e-beam coatings
• Electroplated Al
2. Other improvements under consideration
• MRF surface finishing
• Hardening techniques
• nanoprecipitate, solid solution hardening
• friction stir burnishing (smaller grains)
Scaled testing was initiated at Electra
during late August
we spent 1 week assembling the optical
path, developing test procedures, and
exploring issues for large scale testing
Experimental Layout
Beam Dump
Wave Plate
UV Window
Beam Profiler
Cube
Lens
Beam Sampler
Mirror
Window
Camera
43”
12”
Laser energy measurements showed
dramatic energy loss along the beam path
2” graphite aperture
3” lead aperture
0.14 J to 5.2 J
(measured with a
2” calorimeter)
80 cm
periscope
10 cm
5.2 J
polarizer cubes
1/2
waveplate
p-polarized
Electra oscillator
3.9 J
Nike
mirror
telescope
10 cm
0.14 J
0.57 J
1” aperture
1.04 J
vacuum
chamber
12.8 J
(measured with a
30cm x 30 cm
calorimeter)
14.2 – 15.3 J
(measured with a
30 cm x 30 cm
calorimeter)
13.2 J
with a 2” dia.
aperture
We don’t see this with our Compex laser
1 = 86 mJ
2 = 84 mJ
1
1
3 = 86 mJ
4 = 85 mJ
2
3
3
4
4
5
1 = 228 mJ
2 = 119 mJ
3 = 95 mJ
4 = 92 mJ
5 = 13
6 = 75
7 = 58
8 = 56
mJ
mJ
mJ
mJ
6
2
7
8
An alternative idea for scaled testing:
large-aperture uncoated FS window @56˚
700 J blunderbuss
12” FS window
($5250)
beam
dump
34˚
30 cm square
aperture
10” round
aperture
10” diameter,
6-m fl Nike lens
assume 700 J in 900 cm2 ~ 0.75 J/cm2
~25% of s-light reflected = 0.09 J/cm2
10” round on 6x12 rectangle ~ 362 cm2
35 Joules (polarized) available
8” port
6.7”
10”
chamber
30 cm
Another alternative idea for scaled testing:
Contrast is >100:1 over a 7˚ range
700 J blunderbuss
10” diameter,
6-m fl Nike lens
30 cm square
beam with 9”
round aperture
beam
dump
32˚
12” FS
window
8” port
•
•
•
•
assume 700 J in 900 cm2 ~ 0.75 J/cm2
~25% of s-light reflected = 0.09 J/cm2
9” round ~ 410 cm2
37 Joules (polarized) available
6”
12”
chamber
Contamination transport from the chamber
to the final optic was explored using Spartan
Displacement field after 1st shot
• 160 MJ NRL target
• 50 mTorr Xe @RT
• Bucky hand-off at 500 s
• Net flow toward chamber
•
center is predicted
– we need to include
rad-hydro displacements
Net flow toward optic?
Particles transport rapidly toward the
final optic
Test particle trajectories
4
Pressure at 100 ms
Pa
3
2
1
• We need to run multiple shots to establish the long-term behavior
Gas puffing was examined as a
posssible optic protection technique
• ~1 Torr-m may help reduce ion and x-ray damage
• Fast gas puff could be used immediately preceding implosions
• Might also help cool chamber gas
A gas puff sufficient to protect optics would
increase the base pressure beyond 100 mTorr
Pump speed per duct
1.5x105 l/s
Duct diameter
75 cm
Duct length
3m
Number of ducts
64
Orifice conductance
44 l/s/cm2
Target mass
4 mg
Rep rate
5 Hz
Chamber radius
7m
It doesn’t look
promising!
5-yr plan and progress to date
2001
start
2002
KrF
initial promising
results at 532 nm
2003
2004
electroplate
success
lower limits at 248
nm, chemistry control
larger
optics
new lab,
cryopump
attempts at thin
film optics
2005
2006
Phase I
evaluation
extended database,
mid-scale testing,
radiation damage,
mirror quality,
design integration