TCS-Aberra*on Control: status and perspec*ves

V.Fafone

24/07/2018 1

Outline

•  AdVTCSoverview;•  TCSperformancesinAdV:

•  In-situabsorpEonmeasurementwithHWS(@13Winputpower);

•  ITFinputpowerincreasefrom14Wto26.5W;

•  DoubleAxiconSystemtests;

•  Lessonslearnedforfutureupgrades:

•  AdV+

224/07/2018

AdV TCS overview

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•  HWS-RC(onINJandDETbenches)tomeasurethermaldistorEonsinrecyclingcavity;

•  HWS-HR(4)tomeasurechangeinTMRoCs;

•  RHs,tocontrolthearmcavitymirrorsRoCs(andPRaswell…);

•  CO2projectors:correctopEcalaberraEons(coldandthermal)intherecyclingcavity.

AdV TCS overview

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•  HWS-RC(onINJandDETbenches)tomeasurethermaldistorEonsinrecyclingcavity;

•  HWS-HR(4)tomeasurechangeinTMRoCs;

•  RHs,tocontrolthearmcavitymirrorsRoCs(andPRaswell…);

•  CO2projectors:correctopEcalaberraEons(coldandthermal)intherecyclingcavity.

AdV TCS overview

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•  HWS-RC(onINJandDETbenches)tomeasurethermaldistorEonsinrecyclingcavity;

•  HWS-HR(4)tomeasurechangeinTMRoCs;

•  RHs,tocontrolthearmcavitymirrorsRoCs(andPRaswell…);

•  CO2projectors:correctopEcalaberraEons(coldandthermal)intherecyclingcavity.

AdV TCS overview

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•  HWS-RC(onINJandDETbenches)tomeasurethermaldistorEonsinrecyclingcavity;

•  HWS-HR(4)tomeasurechangeinTMRoCs;

•  RHs,tocontrolthearmcavitymirrorsRoCs(andPRaswell…);

•  CO2projectors:correctopEcalaberraEons(coldandthermal)intherecyclingcavity.

AdV TCS overview

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•  HWS-RC(onINJandDETbenches)tomeasurethermaldistorEonsinrecyclingcavity;

•  HWS-HR(4)tomeasurechangeinTMRoCs;

•  RHs,tocontrolthearmcavitymirrorsRoCs(andPRaswell…);

•  CO2projectors:correctopEcalaberraEons(coldandthermal)intherecyclingcavity.

HWS-INJ

HWS-DET

HWS-RC

24/07/2018 8

}  On-axisdoublepassmeasurementinreflecEonwithauxiliarydedicatedbeamsoneachITM+CPpairs;

}  HWSopEcsinstalledonEIBandEDB:◦  ExploitmagnificaEonofinjecEonanddetecEonMMTs;

}  POPandBSalsosensed(allPRcavityopEcsopEmizedincollaboraEonwithLMAforHWSsensingbeamssincetheTCSdesignphase);

}  INJandDETHWSbeamsatthesamewavelength:cross-samplingavoidedbycustomBSHRcoaEng(>98%R@790nm)thankstointeracEonwithLMA;

Fromsource

BacktoHartmannsensor

OpEcundertest

WITM absorp*on measurement

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•  HWS-INJdatacollectedduringtheshortTCScommissioningphasebeforeO2(on28/03/2017at18:14UTCfor5hours);

•  WemeasurethethermallensinducedbytheYAGwhosemaincontributoristheabsorpEonintheHRcoaEng

•  EsEmatedcoaEngabsorpEon:(0.28±0.06)ppm

•  LMAmeasurement(VIR-0543A-14)is:(0.22±0.06)ppm

}  WavefrontreconstrucEonsolwaredevelopedincollaboraEonwithAdelaideUniv;}  Pre-installaEontestsatRomeTorVergataUniversity.FirstcharacterizaEononAdVdoneduringMSinstallaEon(March2018);

HWS-HR

24/07/2018 10In-vacuumretro-reflector

Fromsource

BacktoHartmannsensor

}  Off-axisdoublepassmeasurementinreflecEonwithauxiliarydedicatedbeamsoneachTM–uniquefeatureofVirgo;

}  HWSopEcsinstalledondedicatedbenches;}  In-vacuumopEcsrequiredforbeamsteeringandback-reflecEon;}  SameHWSsensorsasforrecyclingcaviEes;}  SensesthechangeofRoCduetoabsorpEonswithasensingbeamabout15cmindiameterontheTMs;

RHs

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}  ControlRoCsofalltestmassesandPRmirror;}  FortheITMs,providelimitedcompensaEonofthermallensing;}  CanbeusedtomiEgateparametricinstabiliEes:tuningtheRoCmovestheresonantfrequencyofhigherordermodes;

}  ProvidealmostsphericallensandidenEfyITMscentersinHWSimages;

RHs

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}  Comparisonwithexpectedbehaviorshowsverygoodagreementàthesystemiswellunderstoodandwellbehaving;

CO2 projectors

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}  ThreeactuaEonlines:◦  DoubleAxiconSystem(DAS):correctforthermallensingoraxisymmetricaberraEons;◦  CentralHeaEng(CH):addforthermallensing,opEmizecontrastdefect;◦  ScanningSystem(SS):correctfornon-uniformaberraEons;

ITF input power increase

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•  SidebandsrecyclinggainmeasuredatdifferentITFinputpowerswithnothermalcompensaEon;

•  TwosetsofopEcalsimulaEonscarriedonusingabsorpEonsmeasurementsdone:•  atLMAbeforeinstallaEon.SeeVIR-0543A-14:0.22ppm

forWIandVIR-0544A-14:0.19ppmforNI;•  onsitewiththeHWSontheWestITM(VIR-0244A-17):

0.28ppm;NorthITMabsorpEonslelattheLMAvalue.•  On-sitemeasurementofNIabsorpEonneedstobeperformed;•  ComparisonwithsimulaEonswillberepeatedaler

measurementofNIabsorpEon.

PITF[W] SimulatedGsid MeasuredGsid ΔG/G

14 12 11.35+/-0.07 6%

17 11.4 10.83+/-0.04 5%

20 10.8 9.73+/-0.03 10%

26.5 8.8 8.90+/-0.04 2%

ComparisonofmeasurementsandsimulaEons

Double Axicon System tests: November 2017 •  14WITF:accordingtosimulaEons,correcEonofthermallens

withDASmakestherecyclinggaintodecreaseàconfirmedbymeasurements;

•  25WITF:DASrequiredtocorrectlensinordertoimproverecyclinggainàconfirmedbymeasurements;

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P=14W

P=17W

P=20W

P=26.5W

P=26.5WDASON

Summary of the first commissioning rounds •  AllTCScomponentstestedandworkingasperspecificaEons;•  FirstcommissioningtestsdonelastNovember:

•  resultsseemtogointherightdirecEon:•  recyclingcavitygainimprovedwithDASON•  RCgainwasbeqerwithadifferenEalpowerapplied(asexpectedfromsimulaEons)•  alsoITFstabilityappearedposiEvelyinfluencedbytheDASacEon

•  comparisonofthemeasuredandsimulated56MHzrecgainreasonablygood

•  PathtomaketheITFwork@25Wseemstobeunderstood,noshowstopperduetoaberraEonsfound

•  ….Then….•  ITFsensiEvity•  Etalon•  Parametricinstabili?es•  …..

•  TCScanhelpimprovingthings24/07/2018 16

Lessons and requirements for AdV+

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}  CorrecEonofwavefrontaberraEons:◦  CO2lasersextensivelyusedsofar:

�  SiO2absorbsallradiaEonatλ>5µm;◦  AdV+withincreasedbeamsizeinrecyclingcavitymoresensiEvetoaberraEonsthanAdV;◦  QualityofcompensaEonreliesoncapabilityofproducingtheopEmalheaEngpaqern:�  Inthefuturetherewillbeanincreasedneedfornon-symmetricheaEngpaqerns;�  Preciselaserbeamshapingrequiresgoodqualitylaseroutputbeam:

�  SpaEalbeamfilterinstalledonAdVCO2benches;�  OngoingacEvitytobuildamodecleaneratUToV.

Op*mal hea*ng paSern

Lessons and requirements for AdV+

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•  Laserbasedtechniques:•  Scanningsystem–installedinAdV;•  InjectsdisplacementnoiseintotheITF:

•  Peakduetothermo-refracEvecouplingatthescanningrepeEEonfrequency(andharmonics);

•  ComboflinesduetotorqueappliedonCP(radiaEonpressure);

•  DevelopmentofDCactuatormandatory;•  MEMSdeformablemirrors–underinvesEgaEonatUToV;

•  LargeareahighsensiEvityCCDrequired(pyroelectricsensorarray).

R.Lawrence

The simula*on is obtained for flat incident intensity on an array of 40x40 micromirrors with 1 mm side M. Lorenzini

Lessons and requirements for AdV+

24/07/2018 19

•  NotmuchtocomplainabouttheHWS:•  Noisefloorandaccuracyareverygood.

•  However…thereisroomforimprovement:•  Thesensorisaffectedbyroomtemperaturechanges;•  More,achangeintemperaturewillalsomodifythedistancebetweentheopEcsoftheimagingtelescope,inducingafakecurvature(thermalde-focus);

A.Brooks

MeasuredinVirgo

x10-10mMeasuredintheTorVergatatestfacility(TETIS)

Lessons and requirements for AdV+

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•  KnownsoluEons:•  TemperaturestabilizaEonoftheHWS–doneatUToV;•  Twocolorsystem:anaddiEonalbeam(atadifferentλwrttothesensingbeam)thatmeasuresthethermalde-focusàmayworkfineinthelab,maybelesspracEcalonAdV+(requiresspecialcoaEngsoncoreopEcs…);

L.Aiello

•  SpaEalresoluEon:•  Atpresent,areaonTMprobedisabout200mmindiameter;•  ConsideringthetelescopemagnificaEonanddistance

betweentheholesàresoluEonabout7mm;•  AdV+implieslargerbeamsize,resoluEonwilldegrade;

•  ThepresentlyusedCCDisnolongerbeingproducedàimpliesare-designandopEmizaEonoftheHP;

•  RequestconcernsasetupforCCDcandidatecharacterizaEon.

Lessons and requirements for AdV+

24/07/2018 21Credits: J. Degallaix

•  AdV+:•  ThermalnoisereducEon;•  IncreasesizeoftestmassesandbeamdimensionsonTMs;•  ArmcaviEesclosertoinstability;

Lessons and requirements for AdV+

24/07/2018 22Credits: J. Degallaix

•  AdV+:•  ThermalnoisereducEon;•  IncreasesizeoftestmassesandbeamdimensionsonTMs;•  ArmcaviEesclosertoinstability;

Lessons and requirements for AdV+

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•  AdV+:•  ThermalnoisereducEon;•  IncreasesizeoftestmassesandbeamdimensionsonTMs;•  ArmcaviEesclosertoinstability;

MoresensiEvetoopEcalaberraEons

Lessons and requirements for AdV+

24/07/2018 24

•  AdV+:•  ThermalnoisereducEon;•  IncreasesizeoftestmassesandbeamdimensionsonTMs;•  ArmcaviEesclosertoinstability;

Richieste

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•  LerichiestefinanziarievannosoqoAdV+(tag:AdV+LM-TCS)

•  Richieste:61.5kEuro•  CO2:46kEuro•  RH:8kEuro•  HWS:8kEuro