R&D for metal mirrors

Masaki MoriICRR, Univ. Tokyo

CTA meeting, Berlin, May 4-5, 2006

In collaboration with:

Akiko Kawachi (Tokai), Midori Yuasa, Michiko Ohishi (ICRR)

Mirror materialsFRP Glass Aluminium

Surface Not bad Good Good /not bad

Weight 1.4g/cm3 2.4-2.6g/cm3 2.66g/cm3

Stiffness Very good Not good Good

Heat conductivity

0.3W/m/K 1.4W/m/K 100W/m/K

Heat expansion

210-5/K 8-1010-6/K 210-5/K

Cost Depends on yield

Not so expensive

?

CANGAROO-II/III plastic mirror

Light (~6kg), durable, but…

A. Kawachi et al., Astropart. Phys. 14, 261 (2001)

T2

T1

Sample aluminium mirror

Without coating

With SiO coating

With Al+SiO coating

Just machine-ground (no polishing) !

ReflectivityCf. Literature

Surface measurement

3D measurement

Focus

Image size in X-axis Image size in Y-axis

ImageIntegrated CCD counts

89% within 0.1 degree

Weathering

Reflectivity of a sample mirror before and after exposure in Woomera

Summary We are developing aluminium mirrors by simple

manufacturing process. Samples show modest quality (89% light within

0.1 degree). Weathering tests are going on. Anti-dew mechanisms should be developed. In real use we may form a segment from multipl

e mirrors to save the number of tuning mechanism.