Alignment: Virgo+ changes Alignment: Virgo+ changes

(1)

H. Heitmann

Alignment: Virgo+ changes

(2)

• Fast quadrant centering system Fast quadrant centering system

• New Alignment electronics New Alignment electronics

• Anderson technique? Anderson technique?

Topics

(3)

H. Heitmann

Fast Quadrant Centering System

(4)

Present centering system Present centering system

Translation stage centering < 0.3 Hz Q1p

Q51 Q22

Q21

Q72

Q71 Q81

WSR10

(5)

H. Heitmann

Requirements for centering Requirements for centering

With the present centering configuration (activates every few minutes)

RMS change of a factor of 4 Extrapolating from these measurements…

Taking a reasonable range around the “minimum”, the maximum DC asymmetry must be less than 0.1

Even with the best centering rate now possible (every 4-5 seconds) we can’t reach this precision.

G. Vajente

(6)

Test of GEO system on NE bench Test of GEO system on NE bench

QD

B7_q2

(7)

H. Heitmann

Galvo feedback on NE bench (07/2006) Galvo feedback on NE bench (07/2006)

Quadrant

Electronics ADC

DC Signals

Asymmetry

computing DAC

Galvo Driver

Filter

Qr Server

Tilting Mirrors

DOL (DAQ)

• Digital feedback

• Used existing Qr server

(slightly modified)

• 30 Hz bandwidth

• Commercial galvo driver tested at EGO: OK

(8)

Galvo system performance I Galvo system performance I

Centering is given in normalized asymmetry

T-stage centering

Galvo centering

(9)

H. Heitmann

Galvo system performance II Galvo system performance II

Error signals

Correction signals

Galvo on

Beam position fluctuations become visible in the correction signal

Galvo of Galvo on

(10)

Fast galvo centering: cost Fast galvo centering: cost

Estimate; to be updated with recent information

(11)

H. Heitmann

Possible work plan Possible work plan

Suggestion: we should start preparing the system now

Last tests finished successfully (galvo drivers)

Procurement of material (2 months)

Delivery time of galvos, drivers, mirrors, mirror holders Realization of mechanics

Check space constraints on benches

Make new optics layout

Prepare new version of Gc

Reading galvo voltages instead of QD DC signals

Implementation (2 shifts per bench)

Rearrangement of mirrors Cabling

Reconfiguration of Qr server, connection to Gc Adaptations in Alp

=> Could be implemented after science run, or for Virgo+

(12)

Possible planninng Possible planninng

Implementation Plan

M1 M2 M3

Tasks and Deliverables W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4

Tasks

1: Order galvos, …

2: New bench designs

3: Modify mechanical drawings

4: Production of mechanics

5: Adapt global control

6: Install new centering system

Deliverables

1: Mechanics

2: Galvo assemblies

3: New centering system

(13)

H. Heitmann

New Alignment Electronics

(14)

New alignment electronics New alignment electronics

Demodulation board

Spares with slight improvements – Higher LF cut-of

– 4 gain settings (instead of 2) – …

QD front-ends

Improved version, but fully compatible (mechanical, connectors,…) – Higher light power

– Lower electronics noise – Lower ofsets

– Better geometrical configuration – Changeable gain

– …

See Virgo CHRQ 008/2006

(15)

H. Heitmann

LA electronics status LA electronics status

Demodulator

2 prototype boards received and tested - OK

One of these boards is now used for Q22 (8 MHz) 3 more (final) boards under production as spares

Front-end electronics

Large delay due to manpower problems

Tentative planning (CHRQ) was: delivery ~ Feb. 2007 Present plans:

1. Produce some spares (for run?) 2. Produce enhanced version

Design review needed before production of final FE’s CHRQ contains some big changes

Planning/status: See talk by Jo

=> Wait for discussions with Nikhef before making planning

But possible scenario:

– Spares for science run

– Enhanced version for IInd commissioning period or Virgo+

(16)

Anderson technique

(17)

H. Heitmann

Anderson:

Anderson: fundamental mode fundamental mode resonance resonance

Carrier

Upper Sideband Lower Sideband

TEM

₀₀

(18)

TEM

₀₁

Anderson:

Anderson: 1 1

^st^st

order order resonance resonance

Carrier

Upper Sideband

Lower Sideband

L

_MC

= 143.5722 m

f

_mod

= 6264287 Hz

(19)

H. Heitmann

Anderson: optical scheme Anderson: optical scheme

Get two more output

ports for alignment

(4 quadrant diodes)

(20)

What we should think about What we should think about

Necessity of end quadrants not clear

Present Virgo might function without them Virgo+ ?

Efects of Anderson frequency

Anderson ofset (during CITF): made locking more difficult Still an issue?

Stronger mixing of alignment error signals

Without Anderson frequency, maybe no need of 2^nd modulation Simulations to be done

Efort needed for abandoning Anderson frequency

Shift MC length (5 cm for 2 kHz freq. shift) Other?

No investigations started yet

If you have an opinion, please give your arguments

(21)

End

(22)

Fast galvo centering: cost Fast galvo centering: cost

ITF quadrant diodes + MC quadrant diodes

(caution: IMC QD’s have integrated demodulator!)