Lab tests on Mirror Support

M.Lenti

M.Lenti 2

Glass robustness

• Test if mirror glass is robust enough to be supported in a single point (single dowel approach)

• Used first an available pre-series mirror (w/o central hole), supporting it through one of the lateral hole (turned 90 deg)

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M.Lenti 3

Mirror supported in one point

Turned 90 deg Single dowel

Left in place for a couple of days:• no mechanical crack• no optical deformation

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M.Lenti 4

Next text: add a weight20 Kg W disk on top of the glass

Left in place for a couple of days:• no mechanical crack• no optical deformation

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M.Lenti 5

Check again….Unplug the mirror…. No crack close or inside the hole

Turn the mirror by 180 deg,use the other side hole,play again

No damage

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Anticorodal aluminum dowel

M.Lenti 6

Dummy mirrors

• Marcon prepared 4 “dummy” mirrors• Same dimensions, same glass, same holes as

true final mirrors (central hole present)• These dummy are also transparent (true

mirrors opaque on the back)• Use dummy mirrors for glass robustness test

and for alignment tests

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M.Lenti 7

Dummy mirror

No crack well visible

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M.Lenti 8

My proposal

• Endorse now the “single dowel approach” for supporting the 18 hexagonal mirrors

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M.Lenti 9

Semi-hex ??

Only two holes (barycenter in between the two holes)A third (central) hole was not drilled (too many holes too close…)

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M.Lenti 10

Semi-hexProposal to be discussed:• two dowels• top-down alignment similar to hexagonal mirror but without piezo• left-right with a screw in the dowels lodging frame• Semi-hex to be aligned once and then left fixed (reference for hex mirrors)

Pulling ribbon for top-bottom alignment

screw

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M.Lenti 11

Other tests• Improving piezo alignement with encoders (see talk by Roberto C.)

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Use solid state switch software-drivento commute from one piezo to another

piezoencoder

ribbon

M.Lenti 12

-0.03 -0.02 -0.01 0 0.01 0.02 0.03

-0.07

-0.06

-0.05

-0.04

-0.03

-0.02

-0.01

0

0.01

Y

Y

15.3.2011

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10 μm step of the piezo

Spot position on the photodiode

Test with aluminum segment:dist. Mirror-phtdiode 700mm

Spot position:0.0015u → 10 μm→(10μm/700mm)= 15 μrad

Piezo 1

Piezo 1

Piezo 2

Piezo 2

Piezo with encoder in target mode

13

Conclusions

• Glass robustness tests passed• Proposal to endorse “single dowel” approach

for 18 hexagonal mirrors• Solution for two semi-hex to be worked-out• Piezo+encoders: see Roberto’s talk• Mirror support wall: Philippe and Piet

presentation on Feb 9, 2011

6/04/2011 M.Lenti