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