Paolo La Penna Virgo Commissioning StatusN5-WP1 8 TH MEETING, Frascati, 20/03/2006 1 VIRGO commissioning progress Paolo La Penna for the VIRGO collaboration.

Paolo La PennaVirgo Commissioning StatusN5-WP1 8TH MEETING, Frascati, 20/03/2006 1

VIRGO commissioning progress

Paolo La Pennafor the VIRGO collaboration

European Gravitational Observatory


Status in December 2005

Virgo shutdown had started after C7 (19 September 2005) The new IB had been installed in the IB tower (end November 2005 The fake dihedron was still mounted on the bench The Nd:YAG beam (up to 5 W for the moment) had been sent into

the bench: some light (with even some interference) was visible at the end of the MC

The optics on the bench were being realigned using the IB actuators: this operation was performed staying inside the tower, with the laminar flux on and the LC closed

The alignment of the IMC was going on

(http://www.ego-gw.it/ILIAS-GW/WP1docs/lapenna_121205.ppt)


Since then:

The IMC was fully aligned in vacuum at about mid December.

IMC locked at end of 2005. Beam at the end of the ITF at begin of January 2006. ITF alignment at mid of January. First ITF cavities lockings at end of January. Full RFC alignment at end of February. Full locking of the ITF going on now (mid of March).

The full restart of the ITF, after IB installation, took about three months


I – Injection system restart


Operation performed on the Injection System

Alignment and locking of the IMC in vacuum Alignment of the IB optics in vacuum Alignment of the beam on the ITF and telescopes tuning Alignment and locking of the RFC Setup and alignment of the EIB BMS IMC matching improvement IMC automatic alignment Power stabilization RFC automatic alignment


Changes in Virgo after September shutdown

IB+RFC

EIB

PR mirror


Injection systemLower stage

Upper stage


Difference old-new IB

Old IB New IB


IMC alignment: december 2005

HeNe autocollimation on the MC mirror

Acting on the IB alignment

(checked with a ccd)



YAG beam direct beam centering

on the MC mirror acting on the

external steering mirrors

laser



MC mirror alignment

until IMC resonances are visible

laser


IMC locking: december 2005

IMC locking

Feedback on laser pzt

using the reflection as a trigger

laser

Pout 8 W


ITF alignment: 13 january 2006


RFC alignment and locking: february 2006

The Reference Cavity alignment has taken more time than expected

A first attempt to align it using the 20 W beam failed A second attempt after having aligned a probe beam

coming from the opposite direction, and looking at the RFC transmission, led to a poor RFC alignment (but it allowed to lock and start working on the ITF)

A third attempt overlapping the probe beam and the 20 W beam was successful

From the beginning to the end almost one month was necessary


YAG from inverse path: fringes

Secondary YAG beam

1 V @ 25 Hz pzt scanning

Probe beam from the inverse pathProbe beam superposed to a HeNe passing through the RFC in the lower partCamera looking at the coils frame (hit by the RFC transmission): mode flashing visible

ccd photodiode

ccd CCD and PhD looking at

RFC reflection


Contrast improvement and alignment

YAG probe Reflected beam

Contrast = 0.7


RFC alignment using PR alignment


RFC alignment using PR alignment


Near Field of M13 and Far Field

1m-f

FF

NFScreens


M14 movement

1m-f

NFMove M14 and observe overlapping with NF ccd

FF


M13 movement

1m-f

Move M14 and observe overlapping with NF ccd

Correct with M13 to overlap on the FF ccd

NF

FF


After alignment: the 20 W beam resonates in the RFC

ccd

PhD


The RFC transmission is not visible with the RFC aligned

Inverse path beam and direct beam are being superposed below acting on M13 and M4 mirrorsWhen superimposed both beams should resonate

ccd

PhD


RFC locked, reflected 20 W YAG beam: 1 March 2006

Contrast = 54 %

(it was 80% before the shutdown)

Good alignment

+

longitudinal mismatching


RFC alignment: conclusion

The RFC alignment was more difficult than expected: the cavity axis was not where it was expected, maybe the RFC was not aligned inside its tank, or it had moved slightly during new IB assembling

The RFC is locked in a stable way, with the beam transmitted by the IMC: more stable with the alignment with respect to the previous setup

We cannot see the RFC transmission


Further activities on RFC

RFC locking filter change: a new filter has been implemented, which allows a reduction of the frequency noise of the prestabilized beam

RFC automatic alignment: this activity is going on; it will allow to keep the beam aligned on the RFC using the two closed loop pzt placed before the RFC. This allows shifts of the beam on the upper part, in order to better align the upper part optics, without losing the RFC alignment


Problems encountered

DPS misaligned

PM stuck

TS damaged

Wrong PSD

electronics

Beam clipped

RFC_trans clipped

Several problems/failure have occurred:

it has been necessary to open the IB tower twice


Further activities involving the injection system

Beam Steering System IMC matching improvement IMC automatic alignment restarted Input power stabilization (the photodiode measuring the

IMC transmission has been changed) RFC automatic alignment PSD on the IB working (new homemade electronics)

After the restart of the IB, some new features and other activities have been performed:


BMS: DC quadrants, ABP actuation

ABPs

(on laser

bench)

NF QFFF QF

BMS allows to keep beam aligned with respect to DC_quadrants placed on the External Injection Bench.

The signal from the DC quadrants is sent to the ABP (Automatic Beam Positioning) mirrors (pzt steered mirrors).

It allows a stable and repetitive positioning of the beam entering into the IMC; It allows performing pure translations and angle of the beam.


IMC matching

With the help of BMS, IMC matching has been improved:

96% matching (it was 82%), 91% contrast (should correspond to about 1500 ppm

losses in the IMC).

IMC transmission is now about 8 W (at about the same level as before the shutdown)

This power is entering into the ITF (we had 0.7 W entering into the ITF before the shutdown)


IMC automatic alignment

The AA of the MC is working again as before the shutdown (for the moment acting only on the MC mirror, correcting the FF_vert and the NF_horiz degrees of freedom.

The (new) AA of the IB is ready to be implemented: it should replace the LC of the IB


Power Stabilization

Data from spectrum analyser is 50 times lower in the 100Hz region than dataDisplay measurent (above) (to be investigated)

Master laser

Diode current

IMC_trans HF


RFC automatic alignment

Closed on the vertical DOF (1 Hz bandwidth) Horizontal DOF not working (M16_PZT horiz. not working properly)

M16

M15

Wavefront sensing

quadrants on the EIB

RFC AA now

separated from IMC AA


New PR mirror: monolithic and higher R (0.95 vs 0.925)

Comparison between the old (black) and new monolithic (red) PR mirror


II- ITF restart


IB LC after RFC locking

The IB LC filters were changed after restart: frequency noise was reintroduced


Frequency noise after RFC locking (ITF misaligned)

IB transfer function

Frequency noise


IB LC filter upgrade

IB in high noise control IB in low noise control

Blue curves: MC in high/low noise (factor 100 G difference)

Red curves: MC in high/low noise (factor 100 G difference)


MC-RFC locking filter: after restart

Too small G SSFS couldn’t engage


Frequency noise after RFC locking (ITF misaligned)

Purple: C7

Black: after new IB RFC locking


New MC-RFC locking filter upgrade


New frequency noise: SSFS can engage


Frequency noise: C7 (beam attenuated) vs now

C7

Now


ITF restart: locking

Photodiodes gains readjusted for the higher power (10 times more than before shutdown) Automatic alignment restarted:

Tested the drift control of the two cavities Quadrant photodiodes gains adjusted Not gone further because it needs the full locking of the ITF

PR-NI PR-NE CITF NE-WE-BS NA WA Recombined SSFS Variable Finesse with PR misaligned ….

Now the full recycled ITF is being locked

Since end of January:


SSFS

L1

L2l2l1

l0

B1p_DC

B5_ACpSSFS using CARM for the

Beam Frequency stabilization

B2_3f_ACp PR (PRCL)B1p_DC BS (MICH)B5_ACp SSFS (CARM)B8_ACp NE-WE (DARM)

B8p

B2_3f_ACp


SSFS restart

The restart of SSFS required some gain tuning because:

RFC locking filter was different Frequency noise was different RFC gains are different

After tuning readjustment, IB LC filters and RFC locking filter SSFS is now working properly


Towards the dark fringe

L1

L2l2l1

l0

STEP 7

B5_ACpSSFS using CARM

DF 0.05

B8p

B2_3f_ACp

B1p_DC

B2_3f_ACp PR (PRCL)B1p_DC BS (MICH)B5_ACp SSFS (CARM)B8_ACp NE-WE (DARM)


ITF locking

Status on 16th March: ITF locked up to step 7 (0.05 of the dark fringe)

Here we are


Parabolic telescope T2: M6 mirror misalignment

3 closed loop picomotors

Tilted: tx (650 rad) and ty (850

rad)


Effect of M6 misalignment

M6 aligned (beam at 3 km)

M6 misaligned (beam at 3 km)

(x=650 rad

y=850 rad)


Resulting beam shape

Beam size at NE:

wx= 60mm wy= 60mm

Beam size on Cam5:

wx= 0.7mm wy= 0.42mm

To fit these measurements, the beam parameters inside ITF with respect to BS position are (perfect matching for w=21.3, z=0):

wx= 15mm, zx= -400m wy= 23mm, zy= 800m

The matching on the FP cavities should be around 89% in these conditions: confirmed by measurement (88%).

Beam parameters before shutdown: wx= 18mm, zx= -500m wy= 18mm, zy= 500m)


Short telescope T1 centering

YL1

f=130L2

f=-80

D=60mm

ccd


Beam shape after the Faraday isolator

y=4 mm w/w = 9%y=2 mm w/w = 2%


Conclusion

The restart of the Injection System has required more than two months

The new Injection System is now working The ITF is close to final locking with full power (8 W)

Some problems involving the new IB remain open:

The RFC matching is poor and the RFC transmission is not sent out of the IB tower

The astigmatism of the beam has to be corrected

For the moment the effort is in achieve the full locking again and, since we can go on in these conditions, to pospone the solving of this problems to a later moment

Paolo La Penna Virgo Commissioning StatusN5-WP1 8 TH MEETING, Frascati, 20/03/2006 1 VIRGO commissioning progress Paolo La Penna for the VIRGO collaboration.

Documents

th meeting

imc alignment

ib alignment

itf alignment

virgo shutdown

pr alignment

rfc automatic alignment

imc automatic alignment