evolution of the mirror suspension in virgo and beyond · evolution of the mirror suspension in...

Evolution Evolution of the of the mirrormirrorsuspension suspension in in Virgo Virgo and and beyondbeyond

Helios VoccaHelios VoccaINFN PerugiaINFN Perugia

GWADW - Isola dGWADW - Isola d’’Elba - Elba - May May 1414thth 2008 2008

H.Vocca – GWADW Isola d’Elba, Italy, May 14 2008

The Present SolutionThe Present SolutionThe The Virgo present solution for Virgo present solution for the the suspension last suspension last stage stage uses four uses four 200 200 µµmmdiameter diameter C85 steel C85 steel wireswires..


Status of the Status of the MonolithicMonolithicSuspensions for VirgoSuspensions for Virgo++

•• Two fibre pulling machines available (in Perugia and Two fibre pulling machines available (in Perugia and CascinaCascina););•• One laser COOne laser CO22 machine available in machine available in Cascina Cascina (developed by the(developed by the

Glasgow group);Glasgow group);•• A validation procedure for fibre production has been defined;A validation procedure for fibre production has been defined;•• A new approach for the suspension is under test in these daysA new approach for the suspension is under test in these days

The monolithic team is composed by the groups of Firenze, Perugia and Roma


Profiles of the necks are equalwithin a 10 µm accuracy level

Florence Group

Fiber ProfilesFiber Profiles


LaserPower

(%)

Violinmode

BouncingMode (Hz)

Distance betweenbend. Points (mm)

55 453±1 6.0±0.1 669.5±0.2

50 453±1 6.0±0.1 669.8±0.2

50 452±1 6.0±0.1 670.2±0.2

50 451±1 6.0±0.1 669.6±0.2

50 450±1 6.0±0.1 669.6±0.2

Florence GroupFlorence Group

Bending Points Bending Points andandFrequenciesFrequencies


Steel Steel Wire Suspensions Wire Suspensions LCLC


New New Suspension ApproachSuspension Approach


Alluminum Alluminum Alloy samples of the lower clamp have been producedAlloy samples of the lower clamp have been produced A fused silica head (5mm diameter with conical tip) is inserted in theA fused silica head (5mm diameter with conical tip) is inserted in the

aluminum to mimic the lower clampaluminum to mimic the lower clamp Using the laser machine, a 1.5 mm FS bar is welded to the tipUsing the laser machine, a 1.5 mm FS bar is welded to the tip The fiber is then pulled directly from the barThe fiber is then pulled directly from the bar The upper clamp is welded to the fiber head using the flameThe upper clamp is welded to the fiber head using the flame

Preliminary TestsPreliminary Tests


Dummy Payload suspendedDummy Payload suspended


Advanced VirgoAdvanced VirgoSuspensionsSuspensions

•• A final design for the Advanced Virgo suspensions is under study;A final design for the Advanced Virgo suspensions is under study;•• FusedFused Silica monolithic suspensionsSilica monolithic suspensions will be used;will be used;•• Mirrors in Suprasil of about 40 kg mass (35 cm diameter, 20 cmMirrors in Suprasil of about 40 kg mass (35 cm diameter, 20 cm

thickness) are thickness) are assumedassumed;;•• FiFibre length and separation are maintained the same as in Virgo: 70bre length and separation are maintained the same as in Virgo: 70

cmcm and 5 cm respectively;and 5 cm respectively;•• The The possibilitypossibility of of machining machining the the lateral ears lateral ears out of the test massout of the test mass

lateral surface was proposedlateral surface was proposed;;•• Various solutions for Various solutions for the the whole suspension whole suspension are under are under study study (e.g.(e.g.

MRM).MRM).


Monolithic Monolithic DesignDesign


oo EGO R&D EGO R&D for for a new a new payloadpayloadconfiguration that includes configuration that includes a a referencereferencemass mass for for the marionettthe marionette e hosting hosting thethecoils for coils for the the actuation actuation systemsystem((proposed by proposed by Roma 1, Pisa and LMA);Roma 1, Pisa and LMA);

MRM R&DMRM R&DMRMMRM

MarionetteMarionette

Mirror Mirror RMRM

CoilsCoils


Third Third GenerationGenerationSuspensionsSuspensions……

•• The idea is to The idea is to develope develope a cryogenic suspension;a cryogenic suspension;•• The suspension has to be monolithic;The suspension has to be monolithic;•• Mirrors in Mirrors in Silicon Silicon or or Saffire seems to be Saffire seems to be the the most realistic choisesmost realistic choises;;•• The The suspension elements have to extract suspension elements have to extract the the heat from heat from the the mirrors mirrors ;;•• Silicon ribbons Silicon ribbons are under are under studystudy;;•• Silicate bonding between silicon Silicate bonding between silicon and and saffire is saffire is under test under test for for thethe

mechanical mechanical and and thermal point thermal point of of viewview;;•• A A cryogenic facility has been developed cryogenic facility has been developed in Cascina.in Cascina.


Facility cryostat: designFacility cryostat: design

The cryostatThe cryostat consists of anconsists of anexternal vacuum-proof steelexternal vacuum-proof steelcylindrical vessel (2.6mcylindrical vessel (2.6mheight, 1.4 m diameter).height, 1.4 m diameter).

Inside the room temperatureInside the room temperaturevessel there are two nestedvessel there are two nestedsuper-insulated Al chamberssuper-insulated Al chamberswhich are foreseen to reachwhich are foreseen to reachtheir thermal equilibriumtheir thermal equilibriumrespectively at about 70K andrespectively at about 70K and5K.5K.

The 5K chamber is able toThe 5K chamber is able tohost the payload and onehost the payload and oneanti-seismic filter. It has aanti-seismic filter. It has aheight of 2m and a diameterheight of 2m and a diameterof 1.2m (about 2.2 mof 1.2m (about 2.2 m33).).

70K70K

5K5K

See Puppo & Rapagnani’s talk


PayloadPayloaddesigndesign

The designed test payload consistsThe designed test payload consistsof a mono-crystalline silicon mirrorof a mono-crystalline silicon mirror(350mm (350mm diamdiam., 100 mm thick)., 100 mm thick)suspended to a silicon marionette bysuspended to a silicon marionette bytwo couples of low dissipative,two couples of low dissipative,monolithic silicon ribbons (30mm xmonolithic silicon ribbons (30mm x0.8 mm x 300 mm).0.8 mm x 300 mm).

The ribbons should be silicateThe ribbons should be silicatebonded on the two mirror andbonded on the two mirror andmarionette sidesmarionette sides

This payload will be cooled down toThis payload will be cooled down toabout 5K to make measurements ofabout 5K to make measurements ofthe temperature dependence of thethe temperature dependence of themirror Q, without and with coating.mirror Q, without and with coating.

5K5K 70K70K

Proposed by R.Passaquieti (Pi)


Si Si and Aland Al22OO33 silicate bonding silicate bonding The INFN Perugia group hasThe INFN Perugia group has

performed room temperatureperformed room temperaturemeasurements of the silicate bondingmeasurements of the silicate bondingshear stress strength on shear stress strength on Si Si and Aland Al22OO33cylinders (diameter of 5 mm, heightcylinders (diameter of 5 mm, heightof 10 mm ) of different crystalof 10 mm ) of different crystalorientations.orientations.

The breaking strength has beenThe breaking strength has beenevaluated on the evaluated on the λλ/10 , /10 , λλ/7 and /7 and λλ/4/4for bonding times of 1, 2 and 3for bonding times of 1, 2 and 3weeks.weeks.

A maximum strength of ~A maximum strength of ~15 15 MPaMPa waswasmeasured.measured.

The breaking of the Si-Si bonded sampleThe breaking of the Si-Si bonded samplestarts in the surface of the bondingstarts in the surface of the bondingcontinuing inside the silicon, probablycontinuing inside the silicon, probablyfollowing some crystal plane.following some crystal plane.


Silicon mono-crystalline fibers have been producedSilicon mono-crystalline fibers have been produced at the Pisa at the Pisa INFNINFN (M. (M.TonelliTonelli))with with the the micro-pulling micro-pulling down down techniquetechnique::

Fiber characteristicsFiber characteristics::

•• mono-crystallinemono-crystalline•• diameter between diameter between 0.4 and 3 mm0.4 and 3 mm•• pure pure silicon silicon at 10 at 10 ppmppm•• surface opaque surface opaque

Mono-crystalline Silicon fibersMono-crystalline Silicon fibers


Fiber length L=308 mm, mean diameter 746 mmFiber length L=308 mm, mean diameter 746 mm




Excess losses are evident on theExcess losses are evident on thethermoelastic thermoelastic peak:peak:

→→Etching in HNA:Etching in HNA:

→→diameter is decreased of about 170 diameter is decreased of about 170 µµmm



Fiber length L=111.5 mm, mean diameter 242 mm Fiber length L=111.5 mm, mean diameter 242 mm





Silicon thermal conductivity withSilicon thermal conductivity withand without silicate bondingand without silicate bonding

Samples haveSamples havebeen bonded bybeen bonded bythe Glasgow the Glasgow groupgroupand and measured measured ininFlorenceFlorence..


••Loss Loss angle angle for for the 6680 the 6680 Hz Hz modemode

••Excess losses Excess losses are are evidentevident, , probably probably due due to to the clampingthe clamping

Cryogenic loss Cryogenic loss angleangle•• The The measure has been performed measure has been performed down down to to 80 K80 K•• The The clamping is made clamping is made in in copper with copper with the the pression pression of a of a springspring..

Perugia group


ConclusionsConclusions::

• Monolithic Suspensions for Virgo+ are now at a good point interms of reproducibility and stability

• Monolithic Suspensions for AdV are still under study but theapproach of the suspension seems to be at a good point

• Other evolutions have been proposed and will be studied

• A cryogenic suspension for third generation detectors is understudy in various laboratories (Cascina, Florence, Perugia, Pisa andRome)

• We are converging…

evolution of the mirror suspension in virgo and beyond · evolution of the mirror suspension in...

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