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

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Evolution

Evolution of the of the mirror mirror suspension

suspension in in Virgo Virgo and and beyond beyond

Helios Vocca Helios Vocca

INFN Perugia INFN Perugia

GWADW - Isola d

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

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The Present Solution The Present Solution

The Virgo present solution for The Virgo present solution for the the suspension last suspension last stage stage uses four uses four 200 200 µµmm diameter

diameter C85 steel C85 steel wireswires..

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

The Present Solution The Present Solution

The Virgo present solution for The Virgo present solution for the the suspension last suspension last stage stage uses four uses four 200 200 µµmm diameter

diameter C85 steel C85 steel wireswires..

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Status of the

Status of the Monolithic Monolithic Suspensions for Virgo Suspensions for Virgo + +

••

Two fibre pulling machines available (in Perugia and Cascina Two fibre pulling machines available (in Perugia and Cascina); );

••

One laser CO One laser CO

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machine available in Cascina machine available in 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 days A new approach for the suspension is under test in these days

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

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

Profiles of the necks are equal within a 10 µm accuracy level

Florence Group

Fiber Profiles

Fiber Profiles

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Laser Power

(%)

Violin mode

Bouncing Mode (Hz)

Distance between bend. 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 Group Florence Group

Bending Points

Bending Points and and Frequencies

Frequencies

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

Steel

Steel Wire Suspensions Wire Suspensions LC LC

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New New Suspension Approach Suspension Approach

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

 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 clamp

aluminum 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 Tests

Preliminary Tests

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Dummy Payload suspended

Dummy Payload suspended

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

Dummy Payload suspended

Dummy Payload suspended

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Advanced Virgo Advanced Virgo

Suspensions Suspensions

••

A final design for the Advanced Virgo suspensions is under study; A final design for the Advanced Virgo suspensions is under study;

••

Fused Fused Silica monolithic suspensions Silica monolithic suspensions will be used; will be used;

••

Mirrors in Suprasil of about 40 kg mass (35 cm diameter, 20 cm Mirrors in Suprasil of about 40 kg mass (35 cm diameter, 20 cm thickness) are

thickness) are assumed assumed ; ;

••

Fibre length and separation are maintained the same as in Virgo: 70 Fi bre length and separation are maintained the same as in Virgo: 70 cm cm and 5 cm respectively; and 5 cm respectively;

••

The The possibility possibility of of machining machining the the lateral ears lateral ears out of the test mass out of the test mass lateral surface was proposed

lateral surface was proposed ; ;

••

Various solutions for the Various solutions for the whole suspension whole suspension are under are under study study (e.g. (e.g.

MRM).

MRM).

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

Monolithic

Monolithic Design Design

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oo EGO R&D EGO R&D for for a new payloada new payload configuration that includes

configuration that includes a a referencereference mass

mass for for the marionettthe marionette e hosting hosting thethe coils for

coils for the the actuation actuation systemsystem

(proposed by (proposed by Roma 1, Pisa and LMA);Roma 1, Pisa and LMA);

MRM R&D MRM R&D

MRMMRM

Marionette Marionette

Mirror Mirror RMRM Coils

Coils

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

Third

Third Generation Generation Suspensions

Suspensions … …

••

The idea is to develope The idea is to develope a cryogenic suspension; a cryogenic suspension;

••

The suspension has to be monolithic; The suspension has to be monolithic;

••

Mirrors in Silicon Mirrors in Silicon or or Saffire seems to be Saffire seems to be the most realistic choises the most realistic choises ; ;

••

The The suspension elements have to extract suspension elements have to extract the heat from the heat from the the mirrors ; mirrors ;

••

Silicon ribbons Silicon ribbons are under are under study study ; ;

••

Silicate bonding between silicon and Silicate bonding between silicon and saffire is saffire is under test under test for for the the mechanical

mechanical and and thermal point thermal point of view of view ; ;

••

A cryogenic facility has been developed A cryogenic facility has been developed in Cascina. in Cascina.

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Facility cryostat: design Facility cryostat: design

 The cryostatThe cryostat consists of anconsists of an external vacuum-proof steel external vacuum-proof steel cylindrical vessel (2.6m cylindrical vessel (2.6m height, 1.4 m diameter).

height, 1.4 m diameter).

 Inside the room temperatureInside the room temperature vessel there are two nested vessel there are two nested super-insulated Al chambers super-insulated Al chambers which are foreseen to reach which are foreseen to reach their thermal equilibrium their thermal equilibrium respectively at about 70K and respectively at about 70K and 5K.5K.

 The 5K chamber is able toThe 5K chamber is able to host the payload and one host the payload and one anti-seismic filter. It has a anti-seismic filter. It has a height of 2m and a diameter height of 2m and a diameter of 1.2m (about 2.2 m

of 1.2m (about 2.2 m33).).

70K70K 5K 5K

See Puppo & Rapagnani’s talk

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

Payload Payload

design design

 The designed test payload consistsThe designed test payload consists of a mono-crystalline silicon mirror of a mono-crystalline silicon mirror (350mm

(350mm diam., 100 mm thick)diam., 100 mm thick) suspended to a silicon marionette by suspended to a silicon marionette by two couples of low dissipative, two couples of low dissipative, monolithic silicon ribbons (30mm x monolithic silicon ribbons (30mm x 0.8 mm x 300 mm).

0.8 mm x 300 mm).

 The ribbons should be silicateThe ribbons should be silicate bonded on the two mirror and bonded on the two mirror and marionette sides

marionette sides

 This payload will be cooled down toThis payload will be cooled down to about 5K to make measurements of about 5K to make measurements of the temperature dependence of the the temperature dependence of the mirror Q, without and with coating.

mirror Q, without and with coating.

5K

5K 70K70K

Proposed by R.Passaquieti (Pi)

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Si Si and Al and Al 2 2 O O 3 3 silicate bonding silicate bonding

 The INFN Perugia group hasThe INFN Perugia group has performed room temperature performed room temperature

measurements of the silicate bonding measurements of the silicate bonding shear stress strength on

shear stress strength on Si Si and Aland Al22OO33 cylinders (diameter of 5 mm, height cylinders (diameter of 5 mm, height of 10 mm ) of different crystal

of 10 mm ) of different crystal orientations.

orientations.

 The breaking strength has beenThe breaking strength has been evaluated on the

evaluated on the λλ/10 , /10 , λλ/7 and /7 and λλ/4/4 for bonding times of 1, 2 and 3

for bonding times of 1, 2 and 3 weeks.

weeks.

 A maximum strength of ~15 A maximum strength of ~15 MPaMPa waswas measured.

measured.

The breaking of the Si-Si bonded sample The breaking of the Si-Si bonded sample starts in the surface of the bonding starts in the surface of the bonding continuing inside the silicon, probably continuing inside the silicon, probably following some crystal plane.

following some crystal plane.

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

Silicon mono-crystalline fibers have been produced

Silicon 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 characteristics Fiber 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 fibers

Mono-crystalline Silicon fibers

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

Mono-crystalline Silicon fibers

Mono-crystalline Silicon fibers

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

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

Excess losses are evident on the Excess losses are evident on the thermoelastic

thermoelastic peak: peak:

→ → Etching in HNA: Etching in HNA:

→ → diameter is decreased of about 170 diameter is decreased of about 170 µ µ m m

Mono-crystalline Silicon fibers

Mono-crystalline Silicon fibers

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Fiber length L=308 mm, mean diameter 574 mm Fiber length L=308 mm, mean diameter 574 mm

Mono-crystalline Silicon fibers Mono-crystalline Silicon fibers

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

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

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

Mono-crystalline Silicon fibers Mono-crystalline Silicon fibers

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

Fiber length L=308 mm, mean diameter 574 mmFiber length L=308 mm, mean diameter 574 mm

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Silicon thermal conductivity with Silicon thermal conductivity with

and without silicate bonding and without silicate bonding

Samples have Samples have been bonded by been bonded by the Glasgow

the Glasgow groupgroup and and measured inmeasured in Florence

Florence..

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

•Loss •

Loss angle angle for for the 6680 the 6680 Hz Hz mode mode

••

Excess losses Excess losses are are evident evident , , probably probably due due to to the clamping the clamping

Cryogenic loss

Cryogenic loss angle angle

• The •

The measure has been performed measure has been performed down to down to 80 K 80 K

• The •

The clamping is made clamping is made in copper with in copper with the the pression pression of a spring of a spring. .

Perugia group

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Conclusions Conclusions : :

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

• Monolithic Suspensions for AdV are still under study but the approach 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 under study in various laboratories (Cascina, Florence, Perugia, Pisa and Rome)

• We are converging…

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