Alignment status & plans Alignment status & plans

Alignment status & plans

Alignment status & plans

2 2

modulation frequency modulation frequency

Virgo mod. (6.26 MHz) 2^nd mod. (8.35 MHz)

2^nd modulation frequency:

absolute (demodulated) reference for common end alignment

(not available with one f_mod) Previously aligned with ITF reflection Q21_DC

IMC mod. (22.4 MHz)

2^nd mod. on the same EOM

=> line forest => difficult Solution: 2^nd EOM

=> Much less problems

but modulation must be weak (m=0.01 instead of 0.17) for avoiding perturbations => to be investigated

2 2

f f

layout layout

6.26 MHz 8.35 MHz

WSR10 alignment layout

2 2

f f

: results : results

8 MHz modulation is working

Low modulation index => Q22 signal noisy => use at LF

Common end loop adapted

Error signal remains Q21_DC

Absolute Q21 position set by shifting until Q22_AC = 0 (Alp loop; stopped in science mode)

Alternative possibility

“Mix” Q22_AC (LF) <=> Q21_DC (HF)

One error signal; filters in sensing matrix Advantage: absolute DC reference is kept

during science mode

Q21_DC Q22_8 MHz

B7_q1 B7_q2

B7

B8_q2

B8

B8_q1

WE

WI

NI NE

BS PR

End mirror beam centering - before End mirror beam centering - before

Before

DSP Drift control

QD error signal

B8_q1_DC B8_q2_DC B7_q1_DC B7_q2_DC

B7_q1 B7_q2

B7

B8_q2

B8

B8_q1

WE

WI

NI NE

BS PR

End mirror beam centering - now End mirror beam centering - now

Now

Alp Drift control

Alp error signal

7...8 Hz line on NE/WE tx/ty Locking correction in z

=> control input mirrors Noise reduction

but: upconversion 10-15 Hz ?!

10 Hz

before after

(high ISYS noise!)

Alignment noise in dark fringe Alignment noise in dark fringe

Differential end mirror tx mode almost limiting

=> more power on Q1p diode + whitening filter

=> alternative: improve corrector cut-off (but: need all margin for high LF gain)

G. Vajente Automated alignment noise projections (10 min.)

Coherence

Recent Gc-Ali upgrades Recent Gc-Ali upgrades

Sensing – Filtering – Driving available

Driving switch needed during thermal transient (switch NE-WE => Common-Differential)

Noise injection

For measurement of open loop transfer functions

Filtering gain change on-fly

For migrating all gain changes from DSP to Gc

Sensing Filtering DSP

Global control

Driving

Noise

Alignment OL transfer function measurements Alignment OL transfer function measurements

Differential end tx

Excellent fit

with Matlab model

Gain adjustment

=> matrix calibration

Differential end ty

?

But still good in the important region (a few Hz)

Other improvements Other improvements

Thermal transient robustness

Improved by switching on 1. differential 2. common end alignment Driving matrix NE/WE => NE+WE/NE-WE after thermal transient PR alignment acts on reference mass

Local control on marionette remains on

High gain filters (end mirror control)

Further tuning needed

Sometimes more gain than needed

=> Rather invest in HF cut-off

Histogram

Diff end tx error signal

Plans up to scientific run I Plans up to scientific run I

Improve alignment stability (filter work)

Sometimes oscillations during thermal transient Check stability in bad weather conditions

Reduce alignment noise

10-50 Hz: alignment noise starts becoming important

Error signal improvement (B1p: more light + preshaping)

Filter tuning (LF gain / HF cutoff trade-off)

Continue transfer function measurements

Line injections for better coherence

Understand model deviations

Measure resonance frequencies: rad. pressure effects?

Update sensing matrix

Continue alignment globalization

More logical system: all gain adjustments in Gc, …

Plans up to scientific run II Plans up to scientific run II

Common mode error signal improvement

Create composite error signal (mix Q22_ACLF + Q21_DCHF)

Observe beam centering loops

Improve if needed (up-conversion, better centering, …)

Centering of input mirrors?

TBC

To be done if needed To be done if needed

Switch BS/ISYS <-> NI/WI control

LA on NI/WI mirrors

BS/ISYS steer beams in arms

Globalize other LA degrees of freedom

PR, BS

PR alignment

Keep LC on marionette on?

Optimize IMC alignment filters

Reduce LF beam jitter (higher gain)

Increase 8 MHz modulation index

First understand where locking signal perturbation comes from

End

Alignment configurations Alignment configurations

C7

tx IB PR BS NI NE WI WE ty IB PR BS NI NE WI WE

10 d.o.f. fast alignment

WSR1

tx BM PR BS NI NE WI WE ty BM PR BS NI NE WI WE

6 d.o.f. fast alignment; input beam and BS control

WSR10

tx BM PR BS NI NE WI WE ty BM PR BS NI NE WI WE

7 d.o.f. fast alignment; input beam and BS control

XX Linear alignment XX LA (ref. mass) XX Drift control XX Local control XX DC error signal XX DC + AC err.sig.

WSR10 sensing matrix WSR10 sensing matrix

BMS PR BS NI NE WI WE ThetaX

0.5 B1p_q1_ACq 4 B2_q1_ACp 2 B5_q1_ACq -0.5 B8_q1_ACp -1.5 B2_q1_DC 1 B7_q1_DC -1.5 B7_q2_DC 1 B8_q1_DC -0.8 B8_q2_DC BMS PR BS NI NE WI WE ThetaY

-0.6 B1p_q1_ACq 4 B2_q1_ACq 2 B5_q1_ACq 0.4 B8_q1_ACq 4 B2_q1_DC 1 B7_q1_DC -1 B7_q2_DC 1 B8_q1_DC -0.7 B8_q2_DC

17 Commissioning meeting, Cascina 02.04.2007 H. Heitmann

WSR10 alignment control overview WSR10 alignment control overview

Bea m Dio

de De mo d.

Loop

Arm diff. B1p Q Fast

Arm commo n

B2 1

2 for centering

- Fast

PR B5 1 Q Fast

BS B8 1 P

(tx) (ty) Q

Fast (tx) Drift (ty)

NI B7 1+2 - Drift

WI B8 1+2 - Drift

BMS B2 1 P

(tx) Q

Drift

WSR10 alignment filtering WSR10 alignment filtering

Sensing Filtering DSP

Sensing Filtering 1

DC Filtering 2

Initial Filtering 3

Boost DSP

PR tx

--- --- --- --- Ref.mass

+ mario LC

PR ty

--- --- --- --- Ref.mass

+ mario LC

End tx

--- --- INITIAL BOOST ---

End ty

--- --- INITIAL BOOST ---

Global control

Driving

WSR10 alignment driving WSR10 alignment driving

Sensing Filtering DSP

Driving 1

Initial_Driving Driving 2 Driving

Common

End ^{=> NE} => NE+WE

Differ.

End ^{=> WE} => NE-WE

Global control

Driving