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Background on GIMM studies in HAPL
Challenges for a final optic optical requirements
environmental threats
system integration
Design choices
Logic pursued in Phase I
Status materials development
damage studies
HAPL Web Conference, 15 Feb 2006
Slide 1
Early requirements were established in 2001
2 yrs lifetime @5 Hz = 3x108 shots
4-5 J/cm2 normal to the beam
1% beam balance, 1% uniformity on target
20 µm aiming
80 nm (/3) wavefront
Later added:
5 nm rms, 25 nm PV
1% scattering
Prometheus reactor layout
Slide 2
These are subject to review and revision
Environmental threats are known
Laser (5 mJ/cm2 absorbed in 4 ns)
X-rays (20-80 mJ/cm2 @3-4 keV)
Ions: diverted using B-fields
Neutrons and gamma rays
5x1012 n/cm2-s @14 MeV
1013 n/cm2-s total
Still ill-defined:
Contaminants
Vibration, mount stability
Slide 3
Al @248 nm
• Al for UV reflectivity
• S-polarized
• 85˚ angle of incidence
• ~5000 GIMMlets
The reference mirror concept consists of a stiff, light-weight (neutronically thin), radiation-resistant substrate with a thin metallic coating optimized for high reflectivity
Slide 4
A GIMM was chosen for the perceived advantage of neutron damage resistance
248 nm
Slide 5
Phase I activities
Coating development
available Al mirrors do not meet requirements
vendors engaged in R&D
scalable, affordable technologies sought
Laser damage testing
emphasis on prototypicality
248 nm, beam smoothness, shot count, pulse length
X-ray and ion analysis and testing (at LLNL)
SiC and Al substrates
not yet prototypical
Slide 6
Status of mirror development and testing
Coating development 2 candidates: electroplating and evaporative coatings
50 µm thickness, 1–10 µm grains, 5 nm rms, 10 J/cm2 @25 ns
Readily available on Al alloy substrates
LIDT testing New 100-Hz laser has excellent beam quality at the target and
end-of-life testing capability. Pockels cell provides 5 ns pulses.
X-ray and ion damage Analysis performed, ion irradiations performed, x-ray data pending
Substrate development and component integration Need more effort on this – subject of this call