Advanced Virgo Giovanni Losurdo Advanced Virgo Coordinator for the Virgo Collaboration.
Paolo La Penna Virgo Commissioning StatusN5-WP1 8 TH MEETING, Frascati, 20/03/2006 1 VIRGO...
Transcript of Paolo La Penna Virgo Commissioning StatusN5-WP1 8 TH MEETING, Frascati, 20/03/2006 1 VIRGO...
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
Paolo La PennaVirgo Commissioning StatusN5-WP1 8TH MEETING, Frascati, 20/03/2006 2
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)
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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
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I – Injection system restart
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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
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Changes in Virgo after September shutdown
IB+RFC
EIB
PR mirror
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Injection systemLower stage
Upper stage
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Difference old-new IB
Old IB New IB
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IMC alignment: december 2005
HeNe autocollimation on the MC mirror
Acting on the IB alignment
(checked with a ccd)
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IMC alignment: december 2005
YAG beam direct beam centering
on the MC mirror acting on the
external steering mirrors
laser
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IMC alignment: december 2005
MC mirror alignment
until IMC resonances are visible
laser
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IMC locking: december 2005
IMC locking
Feedback on laser pzt
using the reflection as a trigger
laser
Pout 8 W
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ITF alignment: 13 january 2006
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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
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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
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Contrast improvement and alignment
YAG probe Reflected beam
Contrast = 0.7
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RFC alignment using PR alignment
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RFC alignment using PR alignment
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Near Field of M13 and Far Field
1m-f
FF
NFScreens
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M14 movement
1m-f
NFMove M14 and observe overlapping with NF ccd
FF
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M13 movement
1m-f
Move M14 and observe overlapping with NF ccd
Correct with M13 to overlap on the FF ccd
NF
FF
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After alignment: the 20 W beam resonates in the RFC
ccd
PhD
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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
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RFC locked, reflected 20 W YAG beam: 1 March 2006
Contrast = 54 %
(it was 80% before the shutdown)
Good alignment
+
longitudinal mismatching
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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
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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
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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
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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:
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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.
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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)
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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
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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
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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
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New PR mirror: monolithic and higher R (0.95 vs 0.925)
Comparison between the old (black) and new monolithic (red) PR mirror
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II- ITF restart
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IB LC after RFC locking
The IB LC filters were changed after restart: frequency noise was reintroduced
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Frequency noise after RFC locking (ITF misaligned)
IB transfer function
Frequency noise
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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)
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MC-RFC locking filter: after restart
Too small G SSFS couldn’t engage
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Frequency noise after RFC locking (ITF misaligned)
Purple: C7
Black: after new IB RFC locking
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New MC-RFC locking filter upgrade
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New frequency noise: SSFS can engage
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Frequency noise: C7 (beam attenuated) vs now
C7
Now
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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:
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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
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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
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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)
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ITF locking
Status on 16th March: ITF locked up to step 7 (0.05 of the dark fringe)
Here we are
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Parabolic telescope T2: M6 mirror misalignment
3 closed loop picomotors
Tilted: tx (650 rad) and ty (850
rad)
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Effect of M6 misalignment
M6 aligned (beam at 3 km)
M6 misaligned (beam at 3 km)
(x=650 rad
y=850 rad)
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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)
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Short telescope T1 centering
YL1
f=130L2
f=-80
D=60mm
ccd
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Beam shape after the Faraday isolator
y=4 mm w/w = 9%y=2 mm w/w = 2%
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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