Advanced Virgo Status - LISA symposium 2012 - APC

Menu~Overview of the Advanced Virgo designThe foreseen challengesStatus and plan

Advanced Virgo optical designDual recycled Michelsoninterferometer with Fabry-Perotarm cavities200W125W 5 kW 650 kW6

The recycling cavities in detailsSimilar to Virgo9

The recycling cavities in detailsSimilar to Virgo but with additional opticsCompensation Plate (CP):used for thermal actuationPick Off Plate (POP) usedto extract control signalSignal Recycling Mirror(SRM)10

The 200 W laser●●Fiber laser allows a simpler design and less optics200W is the coherent sum of two 100W beamsYtterbium dopedrob fiber with singlemode operation1W Nd:YAG laser11

The injection system●●Between the laser and the interferometerModulate, stabilize and shape the beam12

The detection setup●●●Give signals to control the interferometerRead the GW signalDedicated benches at the dark port (right)and also behind the arms (below)×214From ITF

Suspension: the superattenuator and co.●●●Isolate optics from the ground motionMain attenuator already compliant butsome upgrades are foreseenNew isolated benches for injection ordetectionIsolation for mini towerSuspended benchSAT for SRM15

Upgrade of vacuum system and infrastructureAdd 4 cryotrapsBuild liquid nitrogen tankEnlarged central vacuum linkAdd new clean rooms16

To know furtherThe reference document for the Advanced Virgo design isavailable here:https://tds.ego-gw.it/itf/tds/file.php?callFile=VIR-0128A-12.pdf17

Part II:Challenges ahead!Mode cleaner tube and the west arm

Reaching the surface quality of the mirror●●Requirement: 0.5 nm RMS on the central 150 mmA two steps strategy to reach such a flatness:Mechanical polishing down to 2 nm RMSIon beam polishing OR corrective coatingHeight color scale:4 nm P-VRMS: 0.20 nmRMS: 0.36 nmStarting with a 2.1 nm RMS mirror19

The strategy●●Requirement: 0.5 nm RMS on the central 150 mmA two steps strategy to reach such a flatness:Mechanical polishing down to 2 nm RMSCorrective coatingInstallation of the robotin the coater chamberRMS: 0.36 nmStarting with a 2.1 nm RMS mirror20

The thermal compensation system●●●Goal: aberration free interferometerCorrect the effects of optical absorption but also all the othercold distortion (RoC error, surface flatness,...)Required from the start even at low powerExample of cold defect: the input mirror substrate inhomogeneity21

The thermal compensation system3 main sensors....Hartman wavefront sensing Phase camera HR surface sensing… for 3 main actuatorsHeating ring CO 2 laser with 2 axicons Scanning CO 2 laser22

Payload●Goal: attach the mirror to the suspension●More complex than in Virgo+ (now heating ring, CPs, bafflesmust also be attached)●New quality factor measurement facilityMirrorBaffleCP andheating ringLast stage of the suspensionfor the input mirrorVacuum facility for Qmeasurement23

Managing the scattered light●Goal: trap the 100W of scattered light●Solution: add new baffles●Extensive research to know size, positionand material for the bafflesLight fallingoutside a mirrorExamples of baffles already installed24

Part III:Advancement and planThe north arm

The decommissioning of Virgo+Started since the end of the last year, making room for Advanced Virgo26

Parts are coming...●●All the mirror substrates deliveredCall for tender for polishing sent●100W fiber laser build and tested● At high power, > 90% in TEM 00●●Suspended bench testedSuspension for mini towerassembled27

Conclusion and brief timeline●●●Advanced Virgo design (almost) finalizedProcurement and prototyping of parts at full speedInstallation on site has startedSome key dates:●Mid 2014●End 2014●Beginning 2015●Mid 2015●Mid 2017● Latermirrors coated and polishedinstallation completedone arm lock25W input power, interferometer locked (no SRM)installation SRMrise the input power to 200W28

Advanced space time simulation