Insitu Aluminization of the MMT 6'5m Primary Mirror

1
In-situ Aluminization of the MMT 6.5m Primary
Mirror
D. Clark and J.T. Williams MMT Observatory Univers
ity of Arizona Tucson, Arizona 85721
Introduction
The Multiple Mirror Telescope (MMT), in service
as an array of six 1.8m primary mirrors since
1979, was re-commissioned in 1998 as a single
6.5m Cassegrain telescope. Space and budget
constraints led to the decision to attempt
in-situ aluminization of the primary mirror.
The MMT has twice been successfully coated in
situ, and many technical challenges have been
overcome along the way.
The MMT atop Mount Hopkins near Tucson. Photo
courtesy S. Criswell (FLWO)

• Among these are
• Safely installing a 22 metric ton, 7m vacuum head
  to the front of the mirror cell.
• Isolation of the process volume from integral
  mirror-support hardware in a dirty environment.
• Extensive modeling and design effort to achieve
  uniformity goals at a very short source-substrate
  distance.
• Limited facility power capacity led to
  development of a compact high-power delivery
  system using commercial arc-welder supplies.
• The MMT experience has shown that in-situ
  aluminzation is technically feasible,
  cost-effective, and compact for observatory sites
  with limited space.