MAGIC II Mirrors and reflector

M. DoroUdine. MAGIC Collaboration Meeting. 2006/05/10-13

Summary

• Prototypes and measurements• Layout of the mirrors• Layout of MAGIC II reflector• REFLECTOR implementation• Outlook

1m2 first prototypes

• Different prototypes– Different internal

glue– Different box shape– Different insulation

• 7 mirrors realized– 2 with new 3M glue

discarded– 3 already installed

on MAGIC I– 2 in Munich for tests

1. Prototypes and measurements

1m2 mirror layout

• Very similar to last MAGIC I small mirrors

Central hole for the laser housing

1. Prototypes and measurements

Mirror box + honeycomb

Front plate

Layout comparison

50 cm mirrors

1 m mirror

AMC motors

Layout comparison1. Prototypes and measurements

Mirror HeatingNew heating system for

small mirrors tested:

• Small box with resistors set behind the mirror panel

• Lab test: 0.1 deg/minute @ 25W

1. Prototypes and measurements

Realization steps

1.Raw blank assemblingFront plate glued with al box

and honeycombAlready spherical shape

2. Diamond milling (LTech)a) Old system Rotating

machineb) New systemLateral

machine (?...)3.Quartzum layer surfacing4. Ready!

1. Prototypes and measurements

Old milling machines

R

R

r

r

r

milling tool

Milling toolrotating axis

Axis of rotatingtable

arcsin(r/R)

New machine maybe founding problems if money, 3 months for delivering

1. Prototypes and measurements

Test on the mirror spot

• Already performed on 3 mirrors

• Results:

The rigidity of the new mirrors and the tune-up of the milling machine are now delivering very good results

Spot is comparable to the one had for

0.5m mirrors!0.5 cm

1. Prototypes and measurements

3 large mirrors already installed in Oct 05

but..winter has passed…

Adrian analysis

Out of 3 new large mirrors installed• 1 mirror shows very large reflected spot• 2 mirror show scarse reflectivity

They are test mirrors!!

more aging investigation needed absolute reflectivity tests required

1. Prototypes and measurements

Road to massive production

• Almost finalized decision on shape– 98.5 cm x 98.5 cm– 60mm thick hexcel structure – 3mm Al plate– 2mm back plate

• Realization steps already tested one by one

• After final tests massive production can start!

1. Prototypes and measurements

Tests

• Understand degradation of mirror mounted in MAGIC I

• Measure of reflectivity vs wavelength– Method to be investigated– Spectrometer? (with UAB)

• Aggressive test (in Munich)– load– temperature– humidity– Insulation

• To be performed in Munich next 2-3 weeks

1. Prototypes and measurements

[2] MAGIC II Mirror layout

• Situation up to now:– Already taken decision: innermost

6 rings of large mirrors (about 120 mirrors)

• 2 outer rings have larger contribution to aberration- Possible solution

- Small mirror outside- Aspherical mirrors- Normal 1m mirrors

Simulations

simulation performed with REFLECTOR(thanks to Abelardo and Jordi Z.)

• All mirror 1m^2• All mirror 0.5 x 0.5m

consistency test with raytracing macro

Vertical incidence2. Reflector layout

Case perfect reflector: RMS worsen from

0.28cm to 0.56cm (100%)

Real (actual) reflector: RMSworsen from

0.76cm to 0.91cm (19%)

Inner pixel

Tilted incidence

• Worsening decrease with angle

• Reason is that coma aberration is determinant at high angles

angle Worse

0 19%

0.5 10%

1 5%

1.5 3%

2. Reflector layout0deg

0.5deg1deg

1.5deg

Simulation with raytracing• Basically same testsconfirms results

Conclusions2. Reflector layout

• Conclusions– The effect of worsening is most remarkable for

vertical incidence, but in any case the spot is almost within a small pixel.

– The effect is more relevant at low energies– At large angles the coma aberration makes the two

layouts almost equal.

• Only if delivering companies can ensure a better reflecting surface, a mixed layout with small mirror on the outside rings can be taken into account…

Advantages

• Smaller number of items (248 vs 960)• Faster production• Lighter structure• Faster and easier installation on the telescope• Self supporting (no panel needed)• No manual interalignment necessary• No need for taggering

• …nicer reflector

2. Reflector layout

REFLECTOR code

• Simulation with REFLECTOR:– Implementation of new reflector layout in

REFLECTOR is ongoing– Occasion to clean software– Start estimation of MAGIC II sensitivity

2. Reflector layout

[3] Calendar (tentative)

• May ‘06 Tests and new test mirrors• June ‘06 Tooling realization• July ’06 Starting production first mirrors• Spring ‘07 First batch installation• End ’07 Reflector completed

Important to tests subsystems

Summary

• Tests are required, then production can start

• Question about aging of mirror installed to be understood

• Measurements of absolute reflectivity required

• Homogeneous 1m^2 reflector could be the best compromise

END