The installation of the new VIRGO Injection Bench
Paolo La Penna
for the VIRGO collaboration
European Gravitational Observatory
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Recombined configuration: first half of 2004
3 km
INPUT
MODE
CLEANER
WE
Rc urv= 3500 m
R= 0.99995
(144 m)
5.6 m
Nd:YAG
= 1064 nm
20 W
WI
plane
R= 0.88
IB
Modulator
single frequency
6.26 Mhz
3 km
6m
6.4 m
BS
NI
plane
R= 0.88
PR
plane
R= 0.925
NE
Rc urv= 3500
R= 0.99995
OMC
DETECTION
SYSTEM
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Recycled interferometer: July 2004
3 km
INPUT
MODE
CLEANER
WE
Rc urv= 3500 m
R= 0.99995
(144 m)
5.6 m
Nd:YAG
= 1064 nm
20 W
WI
plane
R= 0.88
IB
Modulator
single frequency
6.26 Mhz
3 km
6m
6.4 m
BS
NI
plane
R= 0.88
PR
plane
R= 0.925
NE
Rc urv= 3500
R= 0.99995
OMC
DETECTION
SYSTEM
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
PR reflection inside IMC: frequency noise
Black:
PR
misaligned
Red:
PR aligned
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
PR reflection scattering inside IMC
MC scattering (10 ppm)
IMC
Cavity effect
(10% fringes)
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
PR
Paolo La Penna
Plane Power Recycling mirror
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The old PR was made by two parts: a curved one inside an external cylindrical
glass mass (it was a lens, part of the telescope for collimating inside the ITF)
The curved part was fixed to the cylindrical by means of a steel ring and pression
screws;
There was evidence of mechanical resonances (drifting in time): problems in
locking acquisition and in the future Frequency Stabilization: need of a monolitic
mirror
Decided to make it plane (get rid of transverse movements of the beam induced
by the suspension displacements)
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
IMC and RFC alignment
10%
ABP OFF
ABP
dismounted
The beam was atomatically aligned on the RFC (fixed below the IB) with ABP
The IMC was partly automatically aligned (feedback only on the MC mirror
The RFC was more stable than IMC:
the AA of the RFC worked quite well
the poor AA of the IMC couldn’t correct the drifts
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
PR reflection: Input Beam Attenuation (temporary solution)
IMC
10% M6
From the laser
Reference Cavity
N5-WP1 7TH MEETING, Hannover, 12/12/2005
To the interferometer
700 mW (10% of the
full power)
The New Virgo Injection Bench installation
Paolo La Penna
The PR feedback inside the IMC (mid of 2004)

Simulations on a lock acquisition technique developed
following the LIGO experience

Locking trials with this baseline technique failed
(first half of July)

Beam attenuation installed (summer)
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
HR M6 vs attenuated M6
HR M6
Hz
N5-WP1 7TH MEETING, Hannover, 12/12/2005
(Same y-scale)
R=10% M6
Hz
The New Virgo Injection Bench installation
Paolo La Penna
The PR feedback inside the IMC (end of 2004)

Restart of the locking trials with the baseline technique
(21st September)

Establishement of theVariable Finesse lock acquisition
technique (October)

PR locking acquisition after one month (end of October
2004)
CONFIRMATION OF THE BACKSCATTERING PROBLEM
NEED OF AN OPTICAL ISOLATOR (FARADAY)
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Resume: why to build a new Injection Bench
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The reflection of the light inside the Input Mode Cleaner increased
the frequency noise, thus making it impossible to lock the recycling
cavity
The use of a Faraday isolator was necessary
There was no way to accomodate a Faraday isolator and
respective telescope on the old IB: the bench had to be replaced
In addition to this:
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It was decided to replace the curved PR with a plane PR (less
coupling with the transverse PR displacement): a short (parabolic)
telescope on the IB was necessary
It was decided to change the automatic alignment system of the
injection system: separate alignment of the Input Mode Cleaner
and Reference Cavity
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
How did we proceed
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The aforementioned problems were individuated in
many data takings (C1-C4)
The mechanical design of the bench was performed
using essentially Autocad and Ansys
The optical simulation of the bench was performed
using mainly Zemax (simulation of optical aberrations
and stray light), and by Optocad
The Faraday isolator was tested in Nice with the 20W
laser
The new IB was mounted and prealigned in Class 10
room (after old IB dismounting)
Once prealigned it has been inserted into the tower
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Upper part layout
Autocad drawing
N5-WP1 7TH MEETING, Hannover, 12/12/2005
Optocad drawing
The New Virgo Injection Bench installation
Paolo La Penna
Lower (RFC) part layout
Autocad drawing
N5-WP1 7TH MEETING, Hannover, 12/12/2005
Optocad drawing
The New Virgo Injection Bench installation
Paolo La Penna
Autocad 3-D simulation (example)
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
ANSYS model
Marionette
Reference
Cavity
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
ANSYS simulation
30
40
Uy Tx Tz
50
60
70
80
90
Probably
Susp.
Dihedron
Wire
Legs
couplers (measured in
september 2005)
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Plane PR: Beam simulation with spherical mirrors
Input mirrors
N5-WP1 7TH MEETING, Hannover, 12/12/2005
End mirrors
The New Virgo Injection Bench installation
Paolo La Penna
Plane PR: Beam simulation with parabolic mirrors
Input mirrors
N5-WP1 7TH MEETING, Hannover, 12/12/2005
End mirrors
The New Virgo Injection Bench installation
Paolo La Penna
Plane PR: (new) 6 parabolic off-axis telescope
With plane PR:
a big magnification is needed,
the telescope has to be short (about 700 mm)
Parabolic mirrors are needed
The computed curvature radius are not off-shelf: custom mirrors (Optical Surface)
IMC: waist 4.9 mm
Condensing telescope
FI: waist 2.65 mm
M5: f= 75 mm
M6: f = 600 mm
Ø  10 cm
N5-WP1 7TH MEETING, Hannover, 12/12/2005
to PR: waist=20 mm
d= 675 mm
The New Virgo Injection Bench installation
Paolo La Penna
Parabolic telescope mechanical mount
Two open loop picomotors
Three closed loop picomotors
X and Z closed loop translators
Mounts designed by ourselves and
Machined by a workshop close to Virgo
Mounting commercial actuators
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Alignment of the parabolic telescope (Class 10 room)
Laser
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Starting conditions: misaligned, mismatched
AUTOCOLLIMATOR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
1st autocollimator alignment
AUTOCOLLIMATOR
REF. MIRROR
AUTOCOLLIMATOR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
2nd autocollimator alignment
AUTOCOLLIMATOR
AUTOCOLLIMATOR
REF. MIRROR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Autocollimators aligned
AUTOCOLLIMATOR
AUTOCOLLIMATOR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
1st mirror alignment
AUTOCOLLIMATOR
AUTOCOLLIMATOR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
1st mount alignment
AUTOCOLLIMATOR
AUTOCOLLIMATOR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
2nd mount alignment
AUTOCOLLIMATOR
AUTOCOLLIMATOR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
2nd mount alignment
AUTOCOLLIMATOR
AUTOCOLLIMATOR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Mirror matching
AUTOCOLLIMATOR
AUTOCOLLIMATOR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Focussing
AUTOCOLLIMATOR
AUTOCOLLIMATOR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Off-axis
AUTOCOLLIMATOR
AUTOCOLLIMATOR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Off-axis
AUTOCOLLIMATOR
AUTOCOLLIMATOR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Off-axis
AUTOCOLLIMATOR
AUTOCOLLIMATOR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Autocollimation
AUTOCOLLIMATOR
AUTOCOLLIMATOR
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Beam dumpers: aluminum boxes and buffle-glass plates
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Beam dumpers and PSDs
PSD
Beam dumpers
PSD
PSD
PSD
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Resume of the main differences between new and old IB
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Different shape and strutcture of the bench (octagonal, larger,
M6 grid of holes, …)
Thinner suspension wires
Presence of the Faraday isolator
Presence of a collimating (reducing) telescope between the
Input Mode Cleaner (two lenses)
Presence of a short (less than 1-m-long) off-axis parabolic
telescope (×8)
Separate alignment of the IMC and the RFC
RFC placed after the IMC (no beam on the RFC when the IMC
is not locked): it should make the beam on the RFC more stable
Use of several PSDs to monitor the beam on the bench
Use of larger mirrors
Use of specifically designed beam dumpers
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Beam diameter  10 mm
N5-WP1 7TH MEETING, Hannover, 12/12/2005
Beam diameter  40 mm
The New Virgo Injection Bench installation
Paolo La Penna
Actions after the recycling cavity locking
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Decision to revise the Injection Bench design (June 2004)
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Creation of a group charged to redesign the IB (July 2004)
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Choice of the Faraday isolator and simulation of several possible
telescopes (autumn 2004)
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Decision to install a plane PR (and therefore an off-axis parabolic
telescope) (November 2004)
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Develope of the IB optical and mechanical design and starting of
orders and (first months of 2005)
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Arrival of the main part of the components (May 2005)
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Arrival of the bench (July 2005)
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Arrival (delayed) of the last parabolic mirror (M5, 75 mm focal
length) (August 2005)
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Actions after the recycling cavity locking
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Dismounting of the old IB and starting of the mounting of the new
IB (September 2005)
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Insertion of the new IB into the IB tower (begin of november 2005)
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IB suspension tuning (november 2005)
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Bench prealignment and local controls tuning (end of November
2005)
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Mounting of the plane PR (end of November 2005)
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Local control of the bench (December 2005)
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Nd:YAG injection and beam alignment (December 2005)
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Alignment of the IB optics (now)
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Brewster dielectric polarizers
Rotator
February 2005
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Mid September 2005
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Begin of October 2005
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Main activities before inserting the bench into the tower
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Change of the input flange (larger windows)
Change of the Brewster link (to accomodate a larger
beam)
Suspension tuning (filter 0 and 7 blades): the bench
is heavier (about 150 kg)
Adjustment of the wires length
Full tuning and balancing of the suspension
Mounting of the coils: close to the center of mass
plane (more stable equilibrium of the bench)
Cabling (of coils and bench actuators)
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Insertion into the tower (begin November)
Detector table
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Insertion into the tower (begin November)
Detector table
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Begin of November 2005
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Now
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Now
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Main activities after inserting the bench into the tower
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Bench heigth setting: some difficulties with the
suspension point motors
Balancing of the bench
Orientation of the bench with an HeNe coming from
the MC tower: some difficulties in the filter 7 rotation
range
Test of the coils: some problems in the frames
interrupting RFC beams
Orientation of the local controls target: quite difficult
because the small angular range in its orientation
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Local controls
The IB local controls use a target, placed in front of the dihedron,
with reference markers (bench translations) and reflecting HeNe beams (angles)
The setup had not been changed with respect to the old IB
Beam diameter  10 mm
N5-WP1 7TH MEETING, Hannover, 12/12/2005
Beam diameter  40 mm
The New Virgo Injection Bench installation
Paolo La Penna
Old IB local controls
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
New IB local controls
After the realignment of the reference beams and target:
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Closing of the coarse and fine with the old IB correction
filters and essentially the same gains (end of November)
Adjustment of the reference spots
Fine alignment of the bench with the MC HeNe (begin of
December)
Measurement of the mechanical TF (last week)
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Preliminary: New TF measurement
(Henrich Heitmann and Paolo Ruggi)
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Full alignment procedure

After this first alignment in Class 100 room, the bench has been
mounted inside the tower.

The dummy dihedron is mounted, the LC target is realigned, the
local controls of the bench are restarted.
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The IB is aligned using the HeNe coming from the MC tower
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The Nd:YAG beam is injected into the bench and aligned until a
light spot is visible on the MC mirror
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The optics on the bench is realigned using the IB actuators
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The true dihedron is reinstalled, the IB is put in vacuum, the IMC
aligned and locked

After IMC locking, it should be possible to make the final tuning
and alignment using the bench actuators.
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna
Next steps
Present status:
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The fake dihedron is still mounted on the bench
The Nd:YAG beam (up to 5 W for the moment) has been sent
into the bench: some light (with even some interference) is
visible at the end of the MC
The optics on the bench are being realigned using the IB
actuators: we perform this operation staying inside the tower,
with the laminar flux on and the LC closed (they are very robust)
The true dihedron will be reinstalled this week, then the IMC will
be aligned (we hope it will be possible in air, in order to be able
check the RFC alignment)
the IB will put in vacuum, the IMC aligned and locked
After IMC locking, it should be possible to make the final tuning
and alignment using the bench actuators.
The beam will be aligned in the ITF
N5-WP1 7TH MEETING, Hannover, 12/12/2005
The New Virgo Injection Bench installation
Paolo La Penna