m. mariotti padova university/infn, cta meeting berlin 3-4 may 2006 >1 m 2 metallic mirror...
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M. Mariotti Padova University/INFN , CTA meeting Berlin 3-4 May 2006
>1 m2 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
R
R
r
r
θ
r
milling tool
Milling toolrotating axis
Axis of rotatingtable
θ=arcsin(r/R)
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 assemblingin 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 panel A panel in the alignment tripod
M. Mariotti Padova University/INFN , CTA meeting Berlin 3-4 May 2006
Alignment tools
Alignment tools
Artificial parallel beam source
Rotating tripod for panel alignment
M. Mariotti Padova University/INFN , CTA meeting Berlin 3-4 May 2006
4 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
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
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
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 ofDiamond 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 reliable
@34m
M. Mariotti Padova University/INFN , CTA meeting Berlin 3-4 May 2006
Impact of 1m2 in the reflector optical quality
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
M. Mariotti Padova University/INFN , CTA meeting Berlin 3-4 May 2006
3 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=850+1600=>~2500 €/m**2
Production time & costs