M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 >1 m 2 metallic mirror technology AIM find a suitable technology for large reflecting surfaces reduce the overall cost with respect the current tecnology Improve or maintain the actual optical quality Avoid the use of panels for Active Mirror Control Develop technologies for very large reflectors

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Technology used for MAGIC I: raw blank prduction

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Magic I technology: pre-milling Front plate Honeycomb sandwich

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Current technology: Diamond milling

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Panel assembling in Eching Cabling of the mirror for internal heater Adjustment legs screwed on the mirror 2 mirrors mounted on a panel

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Pre-alignment of a mirror in a panelA panel in the alignment tripod

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Alignment tools Artificial parallel beam source Rotating tripod for panel alignment

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May mirrors spots after the pre-alignment close to the virtual center of the MAGIC camera Final spot of a panel after The precise alignment of the mirrors Final alignment

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Large single mirror vs 4 small mirrors in a panel 50 cm mirrors 1 m mirror AMC motors 4 mirrors: better optics more labor + expensive panel needed hand made first aligment (+?) many high tech elementsto build a panel Diamond turning prooven technology Single large mirror: Astigmatism important at large radii Self supporting ->no panel needed No manual alignment necessary Big labor for the premilling Diamond turning OK

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Ongoing R&D in Padova Built 1m mirror with native spheric shape ⇒ aluminum sandwich glued on a spheric mould mould Mirror box + honeycomb Front plate

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Ongoing R&D in Padova Built 6 “1mx1m” mirror with native spheric shape ⇒ aluminum sandwich glued on a spheric mould

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Ongoing R&D in Padova 6 Prototype produced in 2005: Light weight : <18 Kg, to be installed in the telescope without any support panel.

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Diamond milling of 1M mirror

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Diamond milling first round - Good reflectivity - Bad sphere ~ donuts: - Error in the alignment of Diamond tool

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Diamond milling second round Almost a perfect sphere. The rigidity of the new mirrors and the tune-up of the milling machine are now delivering very good results: The technique is

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Impact of 1m 2 in the reflector optical quality

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May mirrors mounted in the MAGIC frame for test

M. Mariotti Padova University/INFN, CTA meeting Berlin 3-4 May 2006 Production time: raw blanks = 4/day Diamond Polishing= (1 + /day in pipeline)*#machine => 10m**2/week Cost for 250 pieces (magicII): Raw+polishing= =>~2500 €/m**2 Production time & costs