the monolithic suspension status for the virgo interferometer - Fisica

24 luglio 2009 

THE MONOLITHIC SUSPENSION 

STATUS FOR THE VIRGO 

INTERFEROMETER 

Helios Vocca 

University of Perugia 

on behalf of the Virgo collaboration 

helios.vocca@pg.infn.it


NEW VIRGO+ SENSITIVITY 

Sensitivity curve of Virgo+ including monolithic suspensions: 

New thermal noise evaluation by Piergiovanni, Punturo and Puppo includes 

the viscous contribution of the marionette 

10 Hz 

Qmario=300 

Qmario=1000 

No viscous 

Simple pendulum 

F. Piergiovanni, M.Punturo, P.Puppo, The 

thermal noise of the Virgo+ and Virgo Advanced 

Last Stage Suspension (The PPP effect), Virgo 

Note: VIR-015C-09. 

MG12 Paris - July 12 - 18, 2009 2


MONOLITHIC SUSPENSIONS 

Activity tasks 

MG12 Paris - July 12 - 18, 2009 

Involved Virgo groups: 

!Firenze/Urbino 

!Perugia 

!Roma 

!EGO 

General Strategy for 

Monolithic Suspensions 

Planning: 

!Payload parts assembled in 

the new 1500West Clean Room 

!Mirrors prepared at LMA 

(Lyon) 

! IF Possible (by cleanliness 

tests): payloads assembled in 

1500W Clean Room 

3


THE MONOLITHIC ASSEMBLY 

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MG12 Paris - July 12 - 18, 2009 

4


FIBRES PRODUCTION 

100 W CO2 laser 

Laser pulling of 1.5 mm thick 

silica bars: 

!Welding 

!Annealing 

!Controlled pulling 

MG12 Paris - July 12 - 18, 2009 

5

100 W CO2 laser pulling facility developed in collaboration with Glasgow group 

Produced fibres are: 


FIBRES PRODUCTION 

!Very reproducible in diameter and length 

!Ready to be characterized and assembled 

MG12 Paris - July 12 - 18, 2009 

6


FIBRES CHARACTERIZATION 

Inspection of the diameter regularity and check of neck 

reproducibility 

Profiles of the necks are equal 

within a 10 µm accuracy level 

MG12 Paris - July 12 - 18, 2009 

7

!Measurement of bending lenghts and violin/bouncing frequencies 

!Statistics on breaking strength 

Violin 

mode 


FIBRES CHARACTERIZATION 

Bouncing 

Mode (Hz) 

4 GPa 

5 kg 

Distance between 

bend. Points (mm) 

453±1 6.0±0.1 669.5±0.2 

453±1 6.0±0.1 669.8±0.2 

452±1 6.0±0.1 670.2±0.2 

451±1 6.0±0.1 669.6±0.2 

450±1 6.0±0.1 669.6±0.2 

Bending lengths fix the low frequency dynamics of 

the suspension. 

MG12 Paris - July 12 - 18, 2009 

8

PAYLOAD SUSPENSION AND 

LOCAL CONTROL 


• Steel AlSl304 Marionetta prototype with PVC arms 

• Dummy reaction mass, coils with peek supports 

• A mirror is inserted in the holder and the system is balanced 

• All the pieces are secured by safety structures 

• Fibre bending points placed on the marionetta and mirror CoM 

marionette and coils 

reaction mass 

mirror and magnets 

MG12 Paris - July 12 - 18, 2009 9

July ‘08 - Shocks, Dust and Humidity tests 


m/s 2 

Transportation test (Fi, Pg, Rm with EGO support) on the dummy payload 

Mechanical vibration monitored with accelerometers 

The test was successful (no broken fibers! untill January 2009: see next slide); 

MG12 Paris - July 12 - 18, 2009 10

Jan. ‘09 - Shocks, Dust and Humidity tests 

Equivalent weight of the mirror is 70 kg at the moment of breaking 

Crash test movie on youtube (search monolithic crash)

DUMMY SUSPENSION IN PERUGIA 


shadowmeter 

Dummy payload installation in the 

vacuum chamber actuators 

MG12 Paris - July 12 - 18, 2009 

12


LOSS MEASUREMENTS 

Pendulum oscillation 

decay measurement 

loss angle = 2.7 10 -7 

K p /K s.b. =2.8 10 -14 

K p /K epoxy =5.6 10 -12 

Evidence of excess losses, maybe recoil or support losses 

! Further investigation needed, measurements in progress 

MG12 Paris - July 12 - 18, 2009 

epoxy glue 

waterglass 

No excess losses are 

expected from epoxy or 

silicate bonding 

silicate bonding 

13


LOSS MESUREMENTS 

Tests are going on to identify the source of excess loss: 

Friction in the support: 

direct upper clamp 

measurement 

Measure a 1.5 mm fused 

silica bar welded to the upper 

block and clamped in the 

“monolithic suspension” way. 

Recoil losses: measurement 

with new suspension 

MG12 Paris - July 12 - 18, 2009 

Different loads (1 kg, 

3 kg, 5 kg…) suspended 

using two marionette-like 

clamps 

If the losses are due to 

recoil of the supporting 

structure, a linear 

relation between Q 

and mass should be 

measured 

14

New (full) suspension is in preparation 


MG12 Paris - July 12 - 18, 2009 

Silicate bonding 

has been made 2 

weeks ago in Lyon 

clean room. 

In august the FS 

suspension will be 

mounted. 

Measurements on 

it will go on in 

Cascina and 

Perugia 

15


Toward Advanced Virgo 

MG12 Paris - July 12 - 18, 2009 

Even if a final 

geometry for AdV 

mirrors has not 

been decided yet, 

an important 

evolution will be to 

remove the silicate 

bonded supports 

for the monolithic 

suspension. 

16


CONCLUSIONS 

!Fiber production validated and well defined; 

!Monolithic design for fused silica components is ok; 

!Payloads are under construction; 

!Virgo mirror (old north end) with supports, markers and magnets 

ready to be suspended; 

NEXT STEPS 

!Complete FS suspension to be performed in summer in the new 

1500W clean room (almost ready); 

!Measurements of the mechanical losses and identification of the 

excess losses will follow; 

!Final design of the assembly structure to be fixed. 

Ready to install at the end of 2009 

MG12 Paris - July 12 - 18, 2009 

17

the monolithic suspension status for the virgo interferometer - Fisica

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