alignment status & plans

1 Commissioning meeting, Cascina 02.04.2007H. Heit mann

Alignment status & plansAlignment status & plans


22ndnd modulation frequency modulation frequency

Virgo mod. (6.26 MHz)

2nd mod. (8.35 MHz)

2nd modulation frequency:absolute (demodulated) reference for common end alignment

(not available with one fmod)

Previously aligned with ITF reflection Q21_DC

IMC mod. (22.4 MHz)

2nd mod. on the same EOM => line forest => difficult

Solution: 2nd EOM=> Much less problemsbut modulation must be weak (m=0.01 instead of 0.17)for avoiding perturbations => to be investigated


22ndnd f fmodmod layout layout

6.26 MHz8.35 MHz

WSR10 alignment layout


22ndnd f fmodmod: results: results

8 MHz modulation is working Low modulation index => Q22 signal noisy => use at LF

Common end loop adaptedError signal remains Q21_DCAbsolute 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_DCQ22_8 MHz


B7_q1

B7_q2

B7

B8_q2

B8

B8_q1

WE

WI

NI NE

BS

PR

End mirror beam centering - beforeEnd mirror beam centering - before

BeforeDSP Drift controlQD error signalB8_q1_DC B8_q2_DCB7_q1_DCB7_q2_DC


B7_q1

B7_q2

B7

B8_q2

B8

B8_q1

WE

WI

NI NE

BS

PR

End mirror beam centering - nowEnd mirror beam centering - now

NowAlp Drift controlAlp error signal7...8 Hz line on NE/WE tx/tyLocking correction in z=> control input mirrorsNoise reductionbut: upconversion 10-15 Hz ?!

10 Hz

beforeafter

(high ISYS noise!)


Alignment noise in dark fringeAlignment 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 upgradesRecent Gc-Ali upgrades

Sensing – Filtering – Driving availableDriving switch needed during thermal transient(switch NE-WE => Common-Differential)

Noise injection For measurement of open loop transfer functions

Filtering gain change on-flyFor migrating all gain changes from DSP to Gc

Sensing Filtering DSP

Global control

Driving

Noise


Alignment OL transfer function measurementsAlignment OL transfer function measurementsDifferential end tx

Excellent fit with Matlab model

Gain adjustment => matrix calibration

Differential end ty

? Less excellent fit

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


Other improvementsOther improvements

Thermal transient robustnessImproved by switching on 1. differential 2. common end alignmentDriving matrix NE/WE => NE+WE/NE-WE after thermal transientPR 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

HistogramDiff end tx error signal


Plans up to scientific run IPlans up to scientific run I

Improve alignment stability (filter work)Sometimes oscillations during thermal transientCheck stability in bad weather conditions

Reduce alignment noise10-50 Hz: alignment noise starts becoming important

Error signal improvement (B1p: more light + preshaping)

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

Continue transfer function measurementsLine injections for better coherence

Understand model deviationsMeasure resonance frequencies: rad. pressure effects?

Update sensing matrix

Continue alignment globalizationMore logical system: all gain adjustments in Gc, …


Plans up to scientific run IIPlans up to scientific run II

Common mode error signal improvementCreate composite error signal (mix Q22_ACLF + Q21_DCHF)

Observe beam centering loopsImprove if needed (up-conversion, better centering, …)

Centering of input mirrors?TBC


To be done if neededTo be done if needed

Switch BS/ISYS <-> NI/WI controlLA on NI/WI mirrorsBS/ISYS steer beams in arms

Globalize other LA degrees of freedomPR, BS

PR alignmentKeep LC on marionette on?

Optimize IMC alignment filtersReduce LF beam jitter (higher gain)

Increase 8 MHz modulation indexFirst understand where locking signal perturbation comes from


Alignment configurationsAlignment configurations

C7 14/09 – 19/09/2005

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

10 d.o.f. fast alignment

WSR1 08/09 – 11/09/2006

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 09/03 – 12/03/2007

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 alignmentXX LA (ref. mass)XX Drift controlXX Local controlXX DC error signalXX DC + AC err.sig.


WSR10 sensing matrixWSR10 sensing matrix

BMS PR BS NI NE WI WE ThetaX 0.5 B1p_q1_ACq4 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_ACq4 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

* Filtered in Gc sensing


WSR10 alignment control overviewWSR10 alignment control overview

Beam

Diode

Demod.

Loop

Arm diff.

B1p Q Fast

Arm common

B2 12 for

centering

- Fast

PR B5 1 Q Fast

BS B8 1 P (tx)Q

(ty)

Fast (tx)Drift (ty)

NI B7 1+2 - Drift

WI B8 1+2 - Drift

BMS B2 1 P (tx)Q

(ty)

Drift


WSR10 alignment filteringWSR10 alignment filtering


Sensing Filtering 1DC

Filtering 2Initial

Filtering 3Boost

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 drivingWSR10 alignment driving


Driving 1Initial_Driving

Driving 2Driving

CommonEnd => NE => NE+WE

Differ.End => WE => NE-WE

Global control

Driving

alignment status & plans

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