Transcript MAGIC II Mirrors - Padua Astroparticle group.

MAGIC Collaboration Meeting
Sofia May, 27-31 (2007)
MAGIC II Mirrors
Features
Production
Calendar
M.Doro for the Padova group
Summary
1)
2)
3)
4)
5)
6)
MAGIC I mirrors replacement
MAGIC II reflector
Padova mirrors
INAF-Medialario mirrors
Production status and fundings
Calendar of installation
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
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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
1) MAGIC I for 2008
• Installation: July, 2-3week
• 2 technicians + Francesco (PD)
• Markus Garczarczyk
• 2 more people needed for 2nd crews
• Additional ~50
mirrors show already
small bubbles 
probable
replacement 2008
• Also possibility to
make future
replacements with
1m^2 mirrors
instead of small
mirrors
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
128
160
Radii of curvatures
Inner rings (Padova)
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Outer rings (Medialario)
 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
3) Design of Padova mirrors
1.
2.
3.
4.
Aluminum “skin” 985x985mm
Aluminum box
Honeycomb 60mm with microholes
Structural glue inside to keep all
together (curing in autoclav)
5. Epoxy glue on the outside perimeter
for insulation
6. Sink at the center for housing the
AMC laser
7. Back holes for mounting the
actuators
Improvements
 MAGIC I mirrors were 0.5x0.5m^2
 Good quality but problem with interalignment 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
Spot PSF
LED  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
mirror # r_90 (mm)
11
12
13
14
2,86
3,90
2,34
3,12
PSF
5,72
7,80
4,68
6,24
SPOT is
d90=5mm
1/6 of the pixels
diameter
Insulation
 Performed on 2 mirrors in MPI
 Technique: immersion in hot
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
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
Radii of curvature
mirror #
p (m)
q (m)
11
12
13
14
33,99
34,07
34,00
34,04
34,26
34,33
34,26
34,30
average
34,13
34,20
34,13
34,17
 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
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
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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
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)
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…)
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
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)
INAF Calendar
 Until july 2007: finish tests and ideation
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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
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
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 Quartz coating
 2 already done
 60-80 ready by October
 Shipping with container(?) from Munich in October
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
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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
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