Report on mirror support tests

M.Lenti

Latest news from Marcon

• Mirrors optical surfaces finished• Since last week start cutting (from circular to

hexagonal shape) with water jet tool• After cutting: re-checking of optical surfaces• Shipping of all the mirrors at CERN foreseen by

the end of the year• At CERN: aluminization and coating

Outlook

• Tests with “single dowel” prototype• Tests with “leaf springs” prototype (double

dowels)• Use an aluminum mock-up in place of a true

mirror (same dimensions and weight)• Small mirror fixed on the aluminum hexagon

for laser beam reflection• Position sensitive photodiode used (x,y)

Single dowel• Full prototype realized• “single dowel”: mirror hung at the center• Mirror movement around u and v axis

(instead of x and y)• pulled at ±45 degrees (axis decoupling)• Mirror weight: counterbalance for both

movements• Piezo-motor (final) used• 0.25 mm thick aluminium ribbon (direct

traction, no 90 deg deviation), 13 mm widedowel

piezo piezo

piezo

dowel

dowel

Single Dowel Controller

Piezo Motor

Laser PhotoDiode0.25 mm thick ribbon

mirrorPiezo Motor

12

Piezo Motorscontroller

BA

kinematics

P QO

G

A, B ribbon joint on the mirrorO dowel touching pointG mirror barycenterP, Q piezo-motor

x

yz

mm :units 500BQAP);0,0,0(O );3,0,0(G

);480,205,500(Q );13,205,205(B);480,205,500(P );13,205,205(A

A

P

O

G

y

xz

ll

;mm 400

;mm 400

:B Piezo

;mm 400

;mm 400

:A Piezo

Bxz

Byz

Axz

Ayz

ll

ll

Single dowel: try a closed loop

100 μm

Startingpoint

End point

P1F

P2FP1R

P2RP1: piezo n.1P2: piezo n.2F: forwardR: backward

100

μm

Spot position on the PhotoDiode

Laser-mirror distance: 60 cmMirror-photodiode dist:90 cm

100 μm on the phtdiode→ 70 μrad on the mirror

From one point to the next: 100 microstepmovements of the Piezo(31.25 μm)

y

x

Single Dowel: forward and backward

y

x

time10

0 μm

Spot position on the PhotoDiodePiezo n.1

Single Dowel: forward and backwardSpot position on the PhotoDiode

Piezo n.2

y

x

time10

0 μm Different scale

w.r.t. previous slide

Single dowel: stability• Day one, time: 15:20 PM. x=+0.0335, y=+0.0329 (photodiode)• Day two, time: 9:00 AM. x=+0.0374, y=+0.0327 (photodiode)

Leaf Springs• Full prototype realized• “leaf springs”: mirror hung through two holes• Mirror movement around x and y axis • pulled at 0 and 90 degrees • Mirror weight: counterbalance for vertical

movement• Leaf springs: counterbalance for horizontal

movement• Piezo-motor (final) used• 0.25 mm thick aluminium ribbon (direct

traction, no 90 deg deviation); l=250mm

dowel

piezo

piezo

piezo

dow

el

dowels

dowel

Leaf springs

Leaf Springs prototypedowels

0.5 mm aluminium foils

Leaf Spring prototype

Laser PhotoDiode0.25 mm thick ribbon

mirrorribbon

Piezo Motor

Leaf Springs

Leaf Spring: try a closed loopSpot position on the PhotoDiode

Startingpoint

End point

PV: piezo “vertical”PH: piezo “horizontal”F: forwardR: backward

PVF

PHF

PVR

PHR

100 μm

100

μm

From one point to the next: 100 microstepmovements of the Piezo (31.25 μm)

y

x

Laser-mirror dist. 40 cmMirror-phtdiode dist:70 cm

100 μm on phtdiode→ 90 μrad on mirror

Leaf Spring: forward and backwardSpot position on the PhotoDiode

Piezo Horizontal y

x

time10

0 μm

Leaf Spring: forward and backwardSpot position on the PhotoDiode

Piezo Vertical y

x

time10

0 μm

Leaf Spring: stability• Day one, time: 16:20 PM. x=+0.0000, y=+0.0004 (photodiode)• Day two, time: 12:40 AM. x=-0.0031, y=+0.0040 (photodiode)

Conclusions

• Both approaches (single dowel and leaf spring) prototyped

• New piezo motors used (never stucked, “small” differences in fw and bw movements)

• Need for encoders?• In preparation: ribbon with 90 degree

deviation (care on cutting…)• In preparation: test with glass resistance