1 Advanced Virgo Monolithic Payloads P.Rapagnani Thermal Noise Workshop 2012_02_24-25

2 Virgo Payload, until now:

Main new requirements coming from Advanced Virgo Optical Layout The necessity to suspend large (~ 1 m) and heavy baffles close to the mirrors. The necessity to suspend the Compensation Plate (CP) close to the input mirrors, with a significant tilt. The necessity to control the alignment of the CP within 10  rad Installation and pre-alignment of a Pick-off on the Recycling mirror. Moreover, experience with Virgo+MS indicate excess losses in present setup that must be revised.

Filter 7 Marionetta Mirror Reaction Mass Actuatio n Filter 7 Marionetta Mirror Actuation Standard Payload Scheme New Payload Scheme Supporting Cage The new requirements made us think of a new Payload Scheme (with the constraint of keeping Virgo axial symmetric suspension configuration) The new requirements made us think of a new Payload Scheme (with the constraint of keeping Virgo axial symmetric suspension configuration) Actuation Further optical elements

Schematic Thermal Noise: pendulum

the three schemes are equivalent and there is no relevant difference in adopting a double or a double-branched scheme.

Removing the reaction mass: is “a way” to avoid resonances the region between 10 and 20 Hz. makes full lock reallocation to the marionette easier Schematic Thermal Noise: vertical

Red line: residual motion at the level of the actuators when the suspension is in standalone operation. Green line: shows how the disturbance on the actuators support is reduced by controlling F7 pitch with respect to the ground. Blue line: If no F7 pitch control is active, as the interferometer is locked, the recoil on the actuator frame will depend on the applied correction. Cyan line: such a correction recoil is cancelled by means of F7 pitch control. Filter 7 Marionetta Mirror Preliminary Modelling Pitch Control Needed 3 point hierarchy

Test bench design: the AdV BS Filter 7 Marionetta with 8 coils, 2 motors, suitable for monolithic clamps improvement, for FP payloads Marionetta with 8 coils, 2 motors, suitable for monolithic clamps improvement, for FP payloads Side Shafts (Mirror actuators and Baffle Holders) Mirror Cradle Possibility to hold very large baffles Larger room to assemble large optics: vacuum enclosures of the 4 marionette actuators holders (thepots) would disappear and only two shafts will be used Possibility to hold very large baffles Larger room to assemble large optics: vacuum enclosures of the 4 marionette actuators holders (thepots) would disappear and only two shafts will be used Intermediate Vacuum chamber, removing it is very expensive !

10 Essential to the new scheme: Concept Design of a New IVC New IVC Flanges VAC-SAT prj. Design T. Zelenova  1m New Conduct. pipe - The actual pumping system configuration is preserved - Vacuum separation is to be better checked SAT

Main Issues for SAT-BS F7 adapt F7 parts to higher vacuum Requirements (motors, magnets) adapt cablings to tighter space constraints reshuffle enhancement of F7 control system is necessary SAT WE HAVE TO :

Input Mirrors Payloads The F7-Cage will be used also to suspend the CP, according to the design developed in last months. CP frame will be equipped with piezoelectric or electromagnetic actuators. The F7-Cage will allow an effective clamping of the needed cabling. The F7-Cage will be used also to suspend the CP, according to the design developed in last months. CP frame will be equipped with piezoelectric or electromagnetic actuators. The F7-Cage will allow an effective clamping of the needed cabling. Scheme of Compensation Plate holder The new scheme will be used also for the Input Payloads. Filter 7 Marionetta Mirror Pitch Control Compensation Plate Actuators for plate alignment Monolithic Suspension lock

13 Preliminary Design of Input Payloads Cage Compensation Plate The marionette will be similar to that developed for the BS

14 CO 2 Upper cone 1.5 mm rod Lower “anchor” CO 2 Current Monolithic Mirror Suspensions geometry P.Rapagnani - PAY

15 AdV monolithic suspension Mirror suspension ears, machined or silica bonded Upper clamps, on marionette Machining the ears on the mirrors improves reliability: Interaction with MIR to find a possible solution compatible with substrates and coating production.

16 We have found that the Q values, both for pendulum and bulk modes, of the mirrors suspended with fused silica fibers are not high as expected We must improve the technology, finding the simple and affordable solution to the problem (still under investigation). So we shall proceed gradually, trying to implement first the simplest solutions, and increase the complexity as simpler approaches fail. But we have a limited time schedule, so we are working on two parallel lines: Extensive measurement campaign on old payloads and sample items. Study of the most complex solution, to be ready to implement it, if necessary: The Monolithic Marionette Study of the most complex solution, to be ready to implement it, if necessary: The Monolithic Marionette

Paths to Q improvement: Bulk Modes Series of tests to be performed in Rome, on old payloads and test mirrors 17 Bulk Modes: current value 20 times lower than expected, with an erratic behavior (e.g. Q of WI drum mode: ) Bulk Modes: current value 20 times lower than expected, with an erratic behavior (e.g. Q of WI drum mode: ) Possible causes Dissipation in silica bonding of Ears Dissipation between anchor and ear Solution Improve silica bonding, reduce bonded surface Improve silica bonding, change shape of anchors and contact surface Or use spot welding technology as in aLIGO Related Issues Recovery strategy to be redefined Large impact on schedule and costs

18 The Bulk Modes will be measured in Rome in our Vacuum Test Chamber. We shall measure both the old monolithic payloads and the test mirror, with standard bonded ears, used during Virgo+MS development. The Bulk Modes will be measured in Rome in our Vacuum Test Chamber. We shall measure both the old monolithic payloads and the test mirror, with standard bonded ears, used during Virgo+MS development. Virgo+MS Test Mirror Rome Test Vacuum Chamber Excitation will be provided by the standard coils on the Reaction Mass. As a readout we shall use a small interferometer developed by the Naples Group Excitation will be provided by the standard coils on the Reaction Mass. As a readout we shall use a small interferometer developed by the Naples Group

19 We shall be able to test the bulk modes of a mirror both suspended to the marionette, and simply supported on two knife edge bars. In this way we should be able to measure the coupling of the bulk modes with the violin modes of the fibers, and we hope to identify the sources of excess losses at high frequency.

Paths to Q improvement: Pendulum Modes Series of tests to be performed in Perugia and Rome, on old payloads and test mirrors 20 Pendulum modes: diagnostic measurements: Q of violin modes current value 30 – 100 times lower than expected Pendulum modes: diagnostic measurements: Q of violin modes current value 30 – 100 times lower than expected Possible causes Upper Clamp: Motion of clamp box on the marionetta Friction of silica part inside the clamp box Motion of silica part inside the clamp box Lower Clamp: Friction of anchors on ears Solution Improve clamp box blocking Improve the contact between surfaces Increase the size of the silica part...or use a monolithic marionette... Improve silica bonding, change shape of anchors and contact surface...or use spot welding technology as in aLIGO Related Issues More complex payload, additional DOF to control Recovery strategy to be redefined Large impact on schedule and costs

21 We shell test the upper and lower clamp dissipations on a sigle fiber in the Perugia facility, and we shall also measure the violin modes of the old monolithic payloads in Rome. Set up to measure violin modes on a single fiber We hope to be able to optimize the clamp box, avoiding the complication of a monolithic marionette: However, just in case, we are studying possible solutions also in that direction... Indeed, in a test performed in 2010 on a free fiber clamped with the standard clamp box, we have found:  ≈ , close to the nominal value. A 1.5 mm fused silica bar has been welded to the upper block and clamped in the “monolithic suspension” way. The free loaded bar dissipation has been measured from about 20 Hz to 1200 Hz.  = No excess losses appear in the upper clamp system

Input Mirrors Payloads: Monolithic Marionette The simplest approach to a monolithic marionette is to interpose a third mass of fused silica between the standard marionette and the mirror. The standard marionette will keep its functions and hardware: balancing motors and magnets, while the monolithic marionette would have only the ears for the anchors of the fibers and, eventually, some magnets for control and mode damping. The monolithic marionette will be suspended with standard steel wires. The simplest approach to a monolithic marionette is to interpose a third mass of fused silica between the standard marionette and the mirror. The standard marionette will keep its functions and hardware: balancing motors and magnets, while the monolithic marionette would have only the ears for the anchors of the fibers and, eventually, some magnets for control and mode damping. The monolithic marionette will be suspended with standard steel wires. Filter 7 Standard Marionette Mirror Pitch Control Compensation Plate Actuators for Alignment Monolithic Suspension Steel Suspension Monolithic Marionette Currently we are starting the study of this configuration: Optimization of wire lenghts and masses for a cylindric fused silica marionette, in two possible configurations: with the axis parallel to the axis of the mirror, or orthogonal to it. Currently we are starting the study of this configuration: Optimization of wire lenghts and masses for a cylindric fused silica marionette, in two possible configurations: with the axis parallel to the axis of the mirror, or orthogonal to it.

23 In any case, we shall make a diagnostic of dissipations (violin modes and bulk modes) of all payloads, before their integration into Advanced Virgo. For this, we are building a test vacuum chamber to be integrated in the 1500 W Clean Room. In any case, we shall make a diagnostic of dissipations (violin modes and bulk modes) of all payloads, before their integration into Advanced Virgo. For this, we are building a test vacuum chamber to be integrated in the 1500 W Clean Room.

24 END

25 Spare Slides

26 Upper clamp measurements A 1.5 mm fused silica bar has been welded to the upper block and clamped in the “monolithic suspension” way. The free loaded bar dissipation has been measured from about 20 Hz to 1200 Hz. No excess losses appear in the upper clamp system  =