Alignment : Hardware & Software Status

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25/01/2006 European Gravitational Observatory 1

Alignment :

Hardware & Software Status

Henrich Heitmann, Julien Marque with the contribution of:

INFN Frascati, Mario Favati, Dominique Le Galliot, Alain Masserot, Flavio Nocera, Tatania Zelenova

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1a. The quadrant (Frascati)

• Silicon photodiode,

type EG&G YAG 444

• sensitivity = 0.45 A/W

• DC power = 2.77 mW_max

• transimpedance = 2 k 

• Bias voltage = 180 V

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1b. Quadrant electronics (Frascati)

Demodulation board Phase shifter board

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1c. The translation stages (Frascati)

2 translation stages / quadrant (PI/M-125.90)

1 translation stage control module : 4 translation stages control boards + quadrant power supply

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1d. Flippers, Shutters (Frascati)

Shutter used to measure DC offsets.

- shutter control card by Frascati.

Mirrors (or neutral densities) mounted on flip-mount to attenuate the light when diode used in 2 different configurations

recombined/recycled (ratio of 1000 in DC power).

- will install next week proper power supply.

- need for their own electronics?

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2a. The photodiode readout,

translation stage control (LAPP/Napoli)

Phase tuning, Gain control…

Quadrant motion control…

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2b. The Global Control (LAL)

Compute correction signals to be sent to the DSP of each mirror to be applied to the reference mass

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2c. The automation (LAPP/Napoli)

Alignment automation consits of: prealignment of the direct beam, prealignment of the north and west arm cavities, closing linear alignment loops on all mirror.

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2d. The alignment UI (EGO)

Used for the commissioning of the linear alignment

(need to migrate to Labview?)

+ automatic measurement and reconstruction of the optical matrix (Maddalena, Gabriele)

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3a. Rearrangement of the electronics

Operation needed to:

-separate analogic fron digital electronics

-accommodate the electronics for the 9^th quadrant

+Hardware monitoring completed

+New electronics for DC remote control gain

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3b. The 9

^th

Quadrant

Everything installed but the cables

(+ problem of communication between a 3^rd translation stage driver and the rio to be fixed)

No more spare!!!!! Need for a 10^th quadrant next year?

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3c. Global Control news

New features for the alignment part of GC:

-All matrices on the fly,

-Integrated filters in GC (output and input),

-Possibility to inject coherent lines on all mirrors for matrix measurement comodity,

Need to write some code still…

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3d. The offset issue

Where the offsets of AC error signals are coming from?

a)DC offsets between different elements of the quadrant => beam not centered on diode =>

coupling with longitudinal signals => offset on alignment AC signals

This should have been fixed by a better DC tuning

b)Multireflection in the splitters of the optical setup =>

secondary beam combined with main beam => offset on alignment AC signal

Optics with 3 degrees wedge have been acquired: will be installed soon