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MAGIC II Mirrors

MAGIC Collaboration Meeting Sofia May, 27-31 (2007). MAGIC II Mirrors. Features Production Calendar. M.Doro for the Padova group. Summary. MAGIC I mirrors replacement MAGIC II reflector Padova mirrors INAF-Medialario mirrors Production status and fundings Calendar of installation.

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MAGIC II Mirrors

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  1. MAGIC Collaboration MeetingSofia May, 27-31 (2007) MAGIC II Mirrors FeaturesProductionCalendar M.Doro for the Padova group

  2. Summary • MAGIC I mirrors replacement • MAGIC II reflector • Padova mirrors • INAF-Medialario mirrors • Production status and fundings • Calendar of installation

  3. 1) MAGIC I mirrors replacement • Status checked • October 06 (Dazzi) • April 07 (Garcz) • Merged analysis to decide substitutions: table of substitution produced • Possibility to put 2 glass mirrors to check performances • In LP already 47 mirrors since Sept06 • Damaged mirrors • 22 very bad • 3 empty places • 16 pretty bad (>1 bubble) • 8 still to be decided • (47 in total) • With this installation all the BAD mirrors are replaced

  4. 1) MAGIC I for 2008 • Additional ~50 mirrors show already small bubbles probable replacement 2008 • Also possibility to make future replacements with 1m^2 mirrors instead of small mirrors • Installation: July, 2-3week • 2 technicians + Francesco (PD) • Markus Garczarczyk • 2 more people needed for 2nd crews

  5. 2) MAGIC II reflector scenarios • The reflector of MAGIC II will be entirely of 1m^2 mirrors of two types: • PADOVA design (aluminum mirrors) • INAF-Medialario design (glass mirrors) • Two possible installation scenarios (PADOVA - INAF): 88 120 160 128

  6. Radii of curvatures Inner rings (Padova) • Radius of each mirrors depends on the position • It is a compromise, chosen solution: average radius • Histograms produced for production of Padova and Medialario mirrors Outer rings (Medialario)

  7. 3) Design of Padova mirrors • Aluminum “skin” 985x985mm • Aluminum box • Honeycomb 60mm with microholes • Structural glue inside to keep all together (curing in autoclav) • Epoxy glue on the outside perimeter for insulation • Sink at the center for housing the AMC laser • Back holes for mounting the actuators

  8. Improvements • MAGIC I mirrors were 0.5x0.5m^2 • Good quality but problem with inter-alignment of 4 mirrors in a panel • MAGIC II • All reflector bu 1m^2 mirrors • Design similar but enhanced performances • The increase width of the honeycomb inside the mirrors increased the rigidity of the structure: • increased results of milling: very good PSF • increased reproducibility of radius of curvature • reduced astigmatism

  9. Spot PSF • Performed on 4 mirrors at LT • Technique: the mirrors is illuminated by a pixel twice the focal length far. A CCD camera analyze the image on the focal plane. • WE NEVER PRODUCE SO NICE MIRRORS! • They image the LED at 34 m LED SPOT isd90=5mm 1/6 of the pixels diameter

  10. Insulation • Performed on 2 mirrors in MPI • Technique: immersion inhot water that heat the mirrors so that air is pressured outward • Results: a lot of bubbles came out, due to bad sealing • Action: changed sealing technique

  11. Reflectivity • Measures: • 4 mirrors measured at LT by Padova • 2 mirrors measured at MPI (preprod) • Padova (Enrico Giro): • Spectrophotometer Ocean Optics HR2000 + integrating sphere • Range 450-750 nm • Average reflectivity is for (87,87,89,87)% for mirror 1,2,3,4 • Total refl. is 95% • MPI (Ralf Kosyra) • Range 350-750 nm • Reflectivity between 80-90% • Diffuse light <1-10% depending on lambda

  12. Radii of curvature • 4 mirrors measured • Radii in good agreement within prescription • We could mount the mirrors in a ordered way from the center outward • Low astigmatism • Other 20 mirrors will be measured in June and better statistics

  13. Conclusions on new Padova mirrors • Quality of the reflected spot is very good • Astigmatism reduced • Increased rigidity enhanced performances • The design is ultimated and tests almost confirm the quality • More statistics on 20+ mirrors begin of June • The best mirror we ever built

  14. 4) INAF mirror (Medialario company) • INAF = Italian National Astro-Physics Institute • Medialario = Optics company (Intel), Milan (I) • INAF received fundings for covering 1/3 of MAGIC II reflective surface (>200k) • New design for their mirrors: • Glass mirrors • Cold slumping technique

  15. COLD SLUMPING Technique • A thin glass sheet (1-2 mm) is elastically deformed so to retain the shape imparted by a mould having convex profile. If the radius of curvature is large, the sheet can be pressed against the mould using the vacuum suction. • On the deformed glass sheet (under vacuum force) is glued an honeycomb structure that provide the structural rigidity. • Then a second glass sheet is glued on the top to create a sandwich. • After releasing the vacuum, on the concave side is deposited a reflecting design for their mirrors coating (Aluminum) and a thin protective coating (Quartz)

  16. Features • Mirrors with spherical or parabolic profile are possible (once a master with adapt profile is available) • Weight of the panels extremely contained, 9.5 kg/m2 • Low production costs (about 1.5 K€/m2) • Massive production with short manufacturing times. For ex. 5 mirrors per day if 5 masters are available. But… • the quality is worse than the Padova ones • Many characterization/commisionings are still missing (ageing, mechanical resistance, laser positioning, mounting on the telescope…)

  17. First prototypes • A diamond turned mould has been realized by the LT-ULTRA (German company) • A number (4) of cold slumped mirrors has been realized and characterized in collaboration with MedialarioTech. • 1 panel at ETH (Zurich) for test on mechanical implementation • 1 panel at MPI for water immersion and optical testing • 2 panels now in La Palma to be installed in Magic II (or MAGIC I?) • All these activities has been carried out in tight collaboration with INFN-Padua

  18. Optical characteristics • 80% of the light within d=10mm • 90% of the light within d=15mm Inner pixel Spot is saturated to see the image tails (few bits camera)

  19. INAF Calendar • Until july 2007: finish tests and ideation • Mechanical tests • Thermic stresses • Measures of radii of curvature • Insulation • Decision on laser housing • Decision on installation • September 2007 - star massive production • February 2008 - delivering of the entire batch • Spring 2008 - installation

  20. 2) Status of the production • Raw blanks • 80 raw blanks ready, all 128 by end June. • 69 ready to be milled (+laser sink and +screw holes) • LT rate is low (0.5-1 mirror/ working day) • (learning curve?) • >15 already milled • 4+2 measured (4=Padova, 2=MPI) • Begin June second measurement (Padova) + expedition to Bremen for coating • 60-80 ready for end September • Quartz coating • 2 already done • 60-80 ready by October • Shipping with container(?) from Munich in October

  21. 3) Funding • Mirror cost: • Raw blank = 950  • Milling+quartz = 1850  total = 2800 /mirror • Already paid (270k) • 128 raw blanks (thanks to BCN(24k), Udine (8k)) • 80 millings • Additional funds for future • 40 k (Tuorla) • 20 k (UAB) • Ask for 120 k (INFN) • 80+ mirrors funded by INAF • We have already all the money for 128 Padova mirrors plus money for 88-100 INAF mirrors

  22. Installation scenarios • BASIC: end October/begin November we install all the mirrors we have for that moment: • 50-80 from Padova (internal rings) • 20+ from INAF (external rings) • 128/160 ready in spring 2008 • remaining INAF mirrors delivered in February 2008 • All surface installed for spring 2008. • Still missing agreement on installation procedure: • Horizontal telescope • Cherry picker • … END

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