paolo la penna ilias n5-wp1 meeting commissioning progress hannover, 23-34 july 2004 virgo...

Paolo La PennaILIAS N5-WP1 meetingCommissioning Progress

Hannover, 23-34 July 2004

VIRGO commissioning progress report



Status in C4

Recombined locked (full Virgo with PR misaligned)

Arms automatic alignment

Top stage tidal hierarchical control

Second stage of frequency stabilization (laser frequency controlled with the ITF common mode)



C4 sensitivity



After C4: hardware operation

Installation of new terminal benches support: terminal photodiode movements solved, possibility to perform DC drifts control

Rearrange optics on terminal benches: spherical aberrations solved, Gouy phase and telescope tuning for AA possible

MC mirror cleaning & check: attempt to reduce the scattering inside the Mode Cleaner, with no result (scattering still there)

….



After C4: action performed

IB drift from the NE quadrants DC: not finished BS drift control from the WE quadrants DC: complete BS automatic alignment (as on the WI mirror): not yet finished Low noise coil drivers (switch from high power for lock acquisition

to low noise for lock keeping): complete Compact DSP cards to overcome DSP memory limits: complete IB local control acting from the marionette: complete ‘New’ cavities automatic alignment: complete Cavity full hierarchical control via marionette: not yet finished M6 replacement (beam attenuation to 10%) to reduce the

feedback from the PR in the IMC: complete



After C4: main control upgrades summary

NE filter 7 control: chain resonance (16 mHz) and filter 7 movement damping

IB control from the marionette: reduction of resonances in the IB control (introduced through the bench coils)

New coil drivers: reduction of DAC noise on the RM coils

Beam splitter automatic alignment: BS drift control and AC AA on the BS as on the WI mirror

Marionette control started (demonstrated successfully on a single arm) but need AA and SSFS to go on

Recycling locking started (stable lock of state 3) but need AA and new M6 to go on (PR feedback inside the IMC makes the system unstable)



Filter 7 control

LVDT used as sensor and actuator (in different frequency ranges) to damp the Filter 7 motion;

Damp the 16 mHz motion (chain mode), active up

to 100 mHz;

Used only for damping



Chain resonance damping from Filter 7

ONOFF

OFF

32 mHz

16 mHz32 mHz



IB marionette control

In C4 the Injection Bench was controlled locally through the IB bench coils;

Many resonances (bench, wires, Reference Cavity, …) where detected in the ITF signal;

A new control of the IB through the marionette has reduced or made disappear many of these peaks.



IB marionette control

IB coils control

Marionette control



New low noise coil drivers

10-1

100

101

102

103

10-20

10-15

10-10

10-5

Actuators noise: current status

Frequency (Hz)

m/H

z1/2

Reference Mass - Mirror Actuators NoiseFilter #7 - Marionetta Actuators NoiseVIRGO Sentivity

DAC noise: 300 nV/sqrt(Hz) (17.5 effective bits) Coil Driver noise: 80 nV/sqrt(Hz)



New low noise coil drivers

The required additional force for lock acquisition is provided by a transconductive amplifier.

During lock acquisition phase only DAC 1 is used.

During linear phase DAC 1 output set to zero and DAC 2 is used to keep the lock.

LCoil3mH

1

2

RCoil10

Ref. Mass Coil

+

-

OUT

R2

R

R1R

Coil DriverDAC 2

RN

500

DAC 1Transconductance Amplifier

1

2

Relay

+

-

OUT

R1

R

R2

R

C11 2

De-emphasys Filter



BS control

AC control of the AA added to the BS: local controls switched off;

DC BS drift using the West End quadrants on;

Never tested AC and drift correction together;



Cavity marionette control

Full hierarchical control of a cavity closed: RM+Marionette+IP tidal control

Yet without AA and Second Stage of Frequency Stabilization

Tested soon the full hierarchical control with AA and SSFS



North cavity full hierarchical control

No change in the cavity power when control starts



North cavity full hierarchical control

RMS reduction by a factor 3 at low frequency



Recycling locking: state 3

• Lock of the central cavity (CITF) on the sidebands + lock of the north arm (on the carrier) achieved

B2_ P B1_ Q

B2_ Q



Virgo in state 3: effect of the PR alignment in the IMC

When the PR is aligned fringes in the power inside the IMC appears: frequency noise, prenvents locking



Beam attenuation: M6 replacement

The light reflected in the IMC is partially scattered by the MC in the Virgo beam direction, creating spurious fringes;

The fringes in the IMC make frequency noise,which prevents the PR locking;

To temporary solve the problem of the PR feedback in the IMC it has been decided to attenuate the beam entering in the ITF by a factor 10 (factor 100 attenuation of fringes in the IMC;

To do this the last mirror injecting the beam in the ITF has been replaced with a 10% reflective mirror.



M6 replaced with a 10% reflecting

From the laser

To the interferometer

M6 IMC

Reference Cavity



After M6 replacement

Virgo is now working with 10% of the C4 power (about 0.7 W on the PR instead of the former 7 W);

Electronics and controls scaled to 10% power;

Recombined realigned and locked;

Arms automatic alignment restarted;

Fringes in the IMC when the ITF and the PR are aligned are strongly reduced;

Tests for full Virgo locking have started.



Future upgrade: new Injection Bench?

The PR reflection inside the IMC are a problem: the MC scattering in the IMC axis direction creates instabilities;

An isolation is necessary: on the present Injection Bench there is no space for a Faraday Isolator;

A new Injection Bench will be probably made: its main difference will be the presence of a Faraday Isolator;

The expected installation should take place in the begin of next year. In the meanwhile Virgo will work with 10% of its power.



New Injection Bench

900 mm

Faraday Isolator



Progress in sensitivity

10 100 1000 1000010-2010-1910-1810-1710-1610-1510-1410-1310-1210-1110-1010-910-8

C1 (North Arm) C2 (North Arm) C3 (North Arm) C3 (recombined) C4 (recombined) Design

m/s

qrt(H

z)

Hz



Changes with respect to C4

Sensitivity measured before replacing M6 with the 10 % reflecting mirror (7 September 2004):

Low noise RM coils drivers;No BS control at the level of the RM (no drift;

correction, no marionetta notches compensation);BS drift control (WE quadrants DC through BS

marionette);IB marionette control;Input mirrors coils disconnected



7 September data taking

BS control upgrade

Frequency stab.problems (?)



Next steps

In the next month the activity will be directed to the locking of the full Virgo;

The PR locking test have already started;

In the 10-100 Hz the noise is dominated by frequency or angular jitter noise coming from the Injection system: coupling with acoustic noise? IB internal resonances? This problem is being investigated.



Next run planned conditions

PR locking Arms marionette control Better BS control New coils drivers Full Automatic Alignment … When? (in one month from now?)

paolo la penna ilias n5-wp1 meeting commissioning progress hannover, 23-34 july 2004 virgo...

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