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FS Suspension for Virgo+. Michele Punturo On behalf of the Thermal noise working group of Virgo+. Scientific Motivation. The reduction of the Suspension thermal noise will improve the sensitivity at low frequency:. Scenarios. Many effects to be considered: Mirror thermal noise (see curve b)

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Fs suspension for virgo

FS Suspension for Virgo+

Michele Punturo

On behalf of the Thermal noise working group of Virgo+

Scientific motivation
Scientific Motivation

  • The reduction of the Suspension thermal noise will improve the sensitivity at low frequency:


  • Many effects to be considered:

    • Mirror thermal noise (see curve b)

    • Newtonian Noise (compare curve c and a)

Virgo commissioning plan
Virgo Commissioning Plan

  • The Virgo collaboration defined the evolution of the commissioning for the next two years

Science Run 1

Science Run 2

Noise hunting

Noise hunting

ITF Shutdown

ITF restart










2008 virgo upgrade
2008: Virgo+ upgrade

  • FS suspension

    • Huge engineering effort

      • To upgrade the ITF at the beginning of 2008 a well detailed plan must be defined

        • VIR-PLA-DIR-4700-109

  • 4 tasks:



of a prototype

Control test

of the


Definition of

the mounting



of the

4 payloads

Task 1
Task #1

  • Realization of a Static payload

    • Fibre production

      • O2-H2 facility under completion in Cascina (H.Vocca)

      • CO2 laser facility in delay (June 2006)

    • Upper clamp design

      • New component to be designed to connect the FS fibre to the Steel marionette

    • Lower clamp design

      • “Ears”: large experience in GEO within the LSC

    • Suspend a dummy test mass

      • In progress in Perugia

    • Steel Marionette

      • Similar as much as possible to the current Virgo design

    • Dielectric reference mass

      • Eddy current issue

      • Able to accommodate current Virgo coils

    • Full payload realization

Task 2
Task #2

  • Mechanical response characterization and control test

    • Setting up the position sensing apparatus

      • Virgo “local control” design

      • New marker design exploration

    • Setting up the digital control chain

      • Virgo “local control” design

    • Error signal calibration and diagonalization + Mechanical TF measurements

      • Decoupling of the different D.O.F.

    • Payload control

      • Virgo “local control” design

      • Frequency dependent driving matrix to compensate for nasty couplings

    • Monolithic payload robustness tests

Task 3
Task #3

Ceramic glue



  • Definition and test of the mounting procedures

    • Mirror preparation procedures

      • Realization of a new design for magnet glueing.

      • Direct painting of the markers on the mirror (?).

      • Spacers bonding before coating (?)

    • Payload assembling and transportation procedures

      • Definition of the procedures for payload assembly.

      • Realization of a test prototype in clean room.

      • Test of the transport and hanging procedures

Task 4
Task #4

  • Production of the four payload components

    • Preparation of the four mirrors

      • Currently three Susprasil substrates are available. They are used as spare of the current Virgo mirrors, but can be coated and used for Virgo+ (one of them must be used as PR because it have a small defect that can reduce the Q). Obviously 3 other mirrors must be produced (2+1 spare). The four mirror for Virgo+ must be coated with the best coating available (in terms of optical and mechanical performances) in such a may to reduce the dissipation due to the mechanical losses in the Tantalum. The possibility to paint the markers (if needed) directly on the coating must be investigated.

    • Preparation of the four marionette

      • Defininition of the procedure for marionetta series production: construction, material tests, assembly, mechanical and electrical tests before coupling with the monolithic suspension and reaction mass, storage space and structure

    • Preparation of the four reference masses

      • Defininition of the procedure for RM series production:

        • construction, assembly, mechanical and electrical tests to be performed before coupling with marionetta and mirror, storage space and structure

    • Assembling of the four payloads

      • The four payload will be assembled as soon as we are ready to mount them (no storing seems possible).


  • To be compatible with the commissioning plan, new infrastructures are needed

    • Experimental area for the fiber production

    • Two (or one large) clean room in the 1.5km building

    • Experimental area for the payload assembling

  • Time schedule and the success of this operation are related to the quick availability of these infrastructures

  • EGO is investigating for this large effort

    • Meeting the 19th of January in Cascina