Op#cs for AXISaxis.astro.umd.edu/images/zhang.pdfWilliam W. Zhang AXIS Workshop 27 Proof of Concept...
Transcript of Op#cs for AXISaxis.astro.umd.edu/images/zhang.pdfWilliam W. Zhang AXIS Workshop 27 Proof of Concept...
Op#csforAXISWilliamW.Zhang
NASAGoddardSpaceFlightCenter
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NextGenera#onX-rayOp#csTeam
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K.D.Allgood1,M.P.Biskach1,J.Bonafede1,K.W.Chan2,M.Hlinka1,J.D.Kearney1,L.D.Kolos,J.R.Mazzarella1,R.S.
McClelland1,H.Mori2,A.Numata1,T.Okajima,L.G.Olsen,R.E.Riveros2,T.T.Saha,M.V.Sharpe1,P.M.Solly1,W.W.Zhang
NASAGoddardSpaceFlightCenter1S6ngerGhaffarianTechnologies,Inc.
2UniversityofMaryland,Bal6moreCounty
J.M.Carter,J.A.Gaskin,W.D.Jones,J.J.Kolodziejczak,S.L.O’DellNASAMarshallSpaceFlightCenter
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KeyFeaturesofAXISOp#cs
•  Highangularresolu#on– 0.5”HPDonaxis,similartoChandra’s– CanbebeVer,butatexpenseofFOV
•  Largefieldofview(FOV)– 15arc-mindiameterwith0.5”PSF– Cf.4arc-minsofChandra-ACIS-I
•  Largeeffec#vearea– 10XChandra’sat1keV– 15XChandra’sat10keV
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Eff.Areavs.Energy(op#csonly)
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AXIS
Chandra
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Effec#veAreaRa#ovs.Energy
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PSFvs.Off-axisAngle
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Chandra
AXIS
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Op#csTopLevelErrorBudget
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ContributiontoHPD(") Notes
Axialfigure(sag) 0.1 ShownasofJune2017Axialfigure(otherthansag) 0.2 ShownasofJune2017Focus(roundness,coneangleanditsvariation)
0.2 Probablycanbeshownby2018
Coating(distortiontoaxialfigureandfocus)
0.1 Difficulttoassessduetoinssuficientdata.
Alignment 0.1 By2019
Bonding 0.2 Difficulttoassess.Emphasisofworkincomingyears.Tallestpole!!!
0.1 Canbedonerelativelyeasily.0.1 Needtobelookedat.0.1 ShownbyanalysisasofJune2017.0.1 ShownbyanalysisasofJune2017.0.4 RSSofallabovenumbers.0.3 TimoSaha'sdesignmemo.
0.5 RSSofabovetwonumbers.
MirrorAssemblyFabricationTotal
MirrorAssemblyOn-OrbitPerformanceMirrorAssemblyOpticalDesignTotal
ParameterorProcess
MirrorSegment
Integrationofsegmentstometa-shells
Integrationofmeta-shellstoassemblyLaunchshift
ThermalgradientsGravityrelease
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OutlineofPresenta#on•  Op#caldesign
–  Fundamentalgeometryandphysics– AXISmirrordesign
•  Technology–  Substratefabrica`on–  Coa`ng– Alignmentandbonding
•  Engineering–  Structural,thermal,andop`calperformance
•  MakingthecasetotheDecadal–  Casefortechnicalreadiness–  Caseforcostandschedule
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Op#calDesign
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GeometryandPhysics(1/2)
•  X-raysreflectonlyatgrazingangles– Grazinganglesdecreasewithenergy– à Fieldofviewdecreaseswithenergy
•  AnX-raytelescopeisreallya“lightbucket”– Manyconcentricshells– X-raysfromdifferentshellsaddincoherently
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GeometryandPhysics(2/2)•  Diffrac#onlimitsareaweightedaverageofmanyshells– Eachshell’sdiffrac`onlimitispropor`onaltof/(H*r*E),wherefisfocallength,Hshelllength,rshellradius,andEx-rayenergy
– Eachshell’seffec`veareaispropor`onaltoH*r*R2(E,r/f),Risreflec`vityanddependsonEandr/f.
•  Off-axisPSFisweightedmeanofmanyshells– Eachshell’sbeingpropor`onaltotheta2*H/r,wherethetaisoff-axisangle
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Prac#calImplica#ons•  On-axisPSFconflictswithFOV
– Goodon-axisPSFdemandslongshells– Goodoff-axisPSFdemandsshortshells
•  DichotomyofSo]andHardX-raysforanearlydiffrac#on-limitedTelescope– SoiX-rays:pooron-axisPSFbecauseofdiffrac`on,butlargeFOVbecauseofgeometry
– HardX-rays:goodon-axisPSFbecauseofdiffrac`on,butsmallFOVbecauseofgeometryandbasicphysics
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AnExampleDesignforAXIS
Parameters ValuesFocallength(mm) 9,000
OuterDiameter(mm) 1,500
InnerDiameter(mm) 400
MirrorSegmentAxialLength(mm) 200
MirrorSegmentThickness(mm) 0.5(1.0)
UnobstructedFOV(arcmin) 15
Coa#ng iridium
No.ofshells 163
Diffrac#onlimits(arcsec90%dia.) 0.2@1keV
MassofMirrorAssembly(kg) ~500(~1,000)
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TakeawayMessages
•  AXIScanhaveeffec#veareas(op#cs+detector)–  >5,000cm2at1keV–  >1,000cm2at5keV
•  AXIS’sPSFandFOV– Moreorlessuniform0.5”HPDina15-armindia.FOV–  BeVerPSFon-axisatexpenseofoff-axisPSF.Forexample,0.1”on-axis,1.5”at6-arcminoff-axis
Underreasonableassump#ons:Focallength:9meters
Outerdiameter:1.5meterMirrorthickness:0.5mm
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Technology
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TheMeta-ShellParadigm
•  Eachmirrorsegmentisfabricated,qualified,andthenalignedbyandbondedtofourspacerswhichkinema`callyconstrainit.
•  Severalhundredmirrorsegmentsarealignedandbondedtoformameta-shell.
•  Adozenorsometa-shellsofdifferentdiametersformthefinalmirrorassembly
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MirrorSegment
Meta-shell
MirrorAssemblyWilliamW.ZhangAXISWorkshop
ThreeBasicElements•  SegmentorSubstrates
– Figurequality,includingmicro-roughness– Thicknessandmass
•  Coa#ng– Highreflectance– Nofiguredegrada`on
•  AlignmentandBonding– Loca`ngandorien`ngeachmirrorsegment– Keepingitthereforgood– Doingsowithoutcausingfiguredistor`on
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SubstrateFabrica#on•  Material:mono-crystallinesilicon
–  Freeofstress–  Lowdensity:2.35g/cm3
–  Highthermalconduc`vity:150Wm-1K-1–  Highelas`cmodulus:130–188Gpa–  Lowthermalexpansion:2.6ppm/K–  Commercialavailability–  Beststudiedandunderstoodmaterial
•  Fabrica#onprocess:polishing–  Grinding,lapping,slicing,acidetching,full-aperturepolishing,&sub-aperturepolishing,etc.
–  Bestpossiblefigureandfinishquality– Massproduc`onandrobo`cstominimizecost
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Fabrica#onSteps
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ConicalformgeneratedMonocrystallinesiliconblock Light-weightedsubstrate
Etchedsubstrate Polishedmirrorsubstrate TrimmedmirrorsubstrateWilliamW.ZhangAXISWorkshop
StatusofSubstrateFabrica#on
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ImagePerformancePredic#onofaPair
SiliconMirrors:0.44”HPD
SlopePowerSpectralDensity
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SubstrateFabrica#onSummary•  Canrealizeanyop#caldesign
– Wolter-I– Wolter-Schwarzschild–  Oranyother:equal-curvature,polynomial,etc.
•  CanmakesubstratesbegerthanChandra’s–  BeVermicro-roughnessà beVer-behavingPSF–  Thicknessfrom0.5to1.5mm(cf.Chandra’s10-25mm)
•  Usenospecialorcustomequipment–  Allequipmentarecommercialofftheshelf.–  Alltoolingcanbemadeinordinarymachineshops.
•  Highthroughputandlowcost–  Fabrica`onprocessishighlyamenabletoautoma`on&massproduc`on
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Coa#ng•  Coa#ngisanessen#alpartofastrategytomeeteffec#vearearequirements– Agoodcoa`ngisanecessity,notanop`on
•  Noblemetalcoa#ng– Au:Lowstressßà Lowreflec`vity– Pt:Mediumstressßà Mediumreflec`vity–  Ir:Highstressßà Highreflec`vity
•  Otherpossibili#es– AniridiumlayerplusanovercoatofB4CorAl2O3
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Effectof15nmPtCoa#ng
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P-VSagchange54nmà 0.32”inHPDchange
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Solu#onsbeingPursued
•  Balancefrontandback–  Inves`ga`ngPtcoa`ngnow–  IfsuccessfulwithPt,willinves`gateIr
•  Balancethin-filmstressonthefrontwithSiO2stressontheback–  Coa`ngstypicallyhavecompressivestress–  SiO2alsohascompressivestress.Itsgrowthcanbecontrolledtoanaccuracyof1nm.
•  Polishafigureerrorinthesubstratethatwillcanceldistor#oncausedbycoa#ngstress,iftheeffectofcoa#ngstressishighlyrepeatable&stable.
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ApproachtoAlignment&Bonding
•  Usekinema#cmounttominimize/eliminatedistor`ontomirrorsegments
•  Usefiniteelementanalysistoop`mizeloca`onsofsupports
•  Useepoxyasadhesiveonly,notasafillerofanyspacethatisnotpreciselycontrolled
•  Usegravity,themostrepeatableforce,asthenes`ngforce
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MinimalConstraints•  Threespacersorpostsfullydeterminetheorienta#onofaflatmirror:–  pitch,yaw,&xbygravity–  roll,y,andzbyfric`on
•  Fourspacersorpostsfullydeterminetheorienta#onofanX-raymirror:–  pitch,yaw,x,andybygravity–  zandrollbyfric`on
•  Usevibra#onofop#malfrequencyandamplitudetoovercomefric#on
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ProofofConcept
•  Placementrepeatability–  Thesamemirrorfromplacementtoplacement–  Fromonemirrortoanotherofthesameprescrip`on–  Stabilityoverlongperiodsof`me:~10hours
•  Precisionmachiningofposts–  Currentprecisionat25nm,limitedbymetrology–  Enablessub-arcsecondmirrroralignment
•  Bondingmirrorwithepoxy–  Preservesalignment:noindica`onofalignmentshii–  Preservesfigure:onlylocalizeddistor`onsduetoepoxycurestress
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ProofofConceptModule
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AccomplishedasofMay2017Singlepairofmirrorsaligned,bonded,andX-raytested.
ExpectedtobeaccomplishedbyDecember2017Mul`plepairsofmirrorsaligned,bonded,andX-raytested.
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X-rayTestResult
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Engineering:Structural,Thermal,&Systems
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Meta-ShellApproach•  Meta-shellintegratesmanyfourspacer
mountedsegments–  Interlockinglayersofmirrorsegments
bondedontoacentralstructuralshell(silicon)
–  Mirrorsarecan`leveredoffstructuralshellsimilartoNuSTAR
–  Brick-likebuildupspreadstheload•  Oncecomplete,meta-shellissimilartoa
fullshellwithanorderofmagnitudemorecollec#ngarea–  Structurallys`ff(allsilicon)–  Rota`onallysymmetric–  Insensi`veto`lt–  LeverageChandraandXMM-Newton
heritage•  Integratedonaprecisionairbearing
–  Createsanop`calaxisreference–  PostheightsdeterminedbyHartmanntest–  Bondedindistor`on0.05”HPD(gravity
releaseerror) 31WilliamW.ZhangAXISWorkshop
MirrorAssembly•  Mul#pleconcentricmeta-shellsco-
alignedandmountedintoacarrierstructure–  SimilartoChandra(CAP)andXMM-
Newton(Spider)–  Aluminumstructure(orCFRP)–  Co-alignandbondmeta-shellsusing
Chandratechniques(CDAwithretro-reflec`ngflat)
–  Chandra-likeflexuremountallowsformechanicalisola`on
•  Heatedstray-light/thermalbafflesintegraltocarrierstructure(Aluminum)
•  MountwithinInterfaceRingthatprovidesinterfacetotelescope/spacecra](Aluminum)
•  Un-heatedthermalbaffles(G10)
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Meta-shell #1 Meta-shell #15
Carrier structure
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StructuralAnalysis
•  Analysisandtestshowweakpointisinnermostbond
•  Bondstressisdeterminedby:–  Bond/spacerdiameter–  Numberofsegmentsaroundthecircumference,i.e.,numberofbondsperlayer
–  Numberoflayers•  Mathema#cmodelofbondstress
developed–  Determinesfeasiblemeta-shelldesigns
–  VerifiedbydetailFEAandcoupontests
•  Determinis#cmethodtoderiveallmeta-shelldesignparameters
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PrototypeEnvironmentalTes#ng
•  Developedconserva#vepreliminaryrequirements–  Quasi-sta`cdesignloadsforIXOCLAwith2.0
MUF–  RandomloadsfromGEVS–  ShockloadsfromFalcon9
•  Can#leveredmassprototype–  Dummymasssimulateslayersofmirrors–  Singlesiliconsegmentwithfourspacerbonds–  Survivedrequiredrandomvibra`on–  Survivedrequiredshock(200g)–  Siliconisstrong(iftreatedproperly),has
gooddamping,andbondswell•  Meta-shellmechanicalmock-up
–  Aluminumandglassmeta-shell–  Bondedflexures–  3layers(54mirrors,432bonds)–  Survivedrequiredrandomvibra`on–  Survivedrequiredquasi-sta`cload(12.3g)
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500mm
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ThermalControl
•  FollowChandraapproach–  Op`csoperateat20°C(baseline,colderpossible)–  Heatlosttocoldspaceisreplacedbyheaters
surroundingtheop`calcavity–  Viewtocoldspaceislimitedbythermalbaffle
vanes(heatedandun-heated)•  DesignverifiedbypreliminaryStructural
ThermalOp#calPerformance(STOP)analysis–  Thermalmodelpredictstemperatures–  TemperaturesmappedtostructuralFEM–  Distor`onpredic`onsray-traced
•  LowCTEandhighthermalconduc#vityofsiliconresultinlowthermalsensi#vity–  Minimalgradientsoveramirrorsegment–  Currentresult0.16”HPD,roomforop`miza`on–  BestSTOPresultfromIXO6.6”HPDwithglass
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SummaryofEngineering•  Meta-shellapproach
–  Advantagesoffullshellop`csbutwithanorderofmagnitudemorecollec`ngarea
•  Preliminarystructural,thermal,andop#calanalysiscompletedtomaturethesystemdesign–  Shows0.5”missionisfeasible
•  Prototypeloadtes#ngdemonstratesthemeta-shellsarerobust
•  Developmentcon#nues:design,analysis,tes#ng
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MakingtheCasetotheDecadal
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NeedtoconvincetheDecadal!
•  Performance–  Effec`vearea– Angularresolu`on
•  Mass– Massismoney!– AXISmirrorassembly~500kg
•  Cost/Schedule–  Shouldbelessthan$160M+30%=$200MinRY$.(Cf.Chandra’sFY99$600Mfor1,500kgà $0.4M/kg).AXIS’smirrorisalso$0.4M/kg,butwithRY$.
– Mustbedoneinlessthan5years,preferablyin4years.
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BetweenNowandDecadal
•  Empiricallydemonstratethatmirrorsegmentsmee#ng(orclosetomee#ng)requirementscanbemade–  Repeatedly(highyield),–  Quickly(produc`onrate),and–  Costeffec`vely
•  Buildandtestsmallmirrormodules–  Basicalignment&bondingprocedureissound&efficient–  Theymeetperformanceandenvironmentalrequirements
•  Buildandtestreasonably-definedmeta-shells– Meet(orclosetomeet)bothperformanceandenvironmentaltests
–  ReachTRL-5by2020–  ShowaclearpathtoTRL-6oncetheobservatoryisdefinedwithsufficientfidelity
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MirrorAssemblyProduc#on(1/2)
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~15,000mirrorsegmentsĂ ~6meta-shellsĂ 1mirrorassembly
~2-3mirrorfabricatorsĂ ~1-2meta-shellmakersĂ 1integrator/testerDistributedproduc#onĂ Compe##onĂ Cost/Scheduleriskreduc#on
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MirrorAssemblyProduc#on(2/2)
•  OneprimecontractorwithTBDsub-contractors–  Twotofourparallellinesofproduc`onofmirrorsubstrates
–  Twoparallellinesofmeta-shellconstruc`on– Onemirrorassemblyintegratorandtester(I&T)
•  Detailedproduc#onfacilityandschedule– Allneededinforma`oninhandformakingstep-by-steporblow-by-blowschedule
•  Detailedgrass-rootscostes#mate–  Produc`onandengineeringcostsunderstood– Managementcosttobees`matedbasedonpastexperience
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Thisworkhasbeenfunded
byNASAthrough
ROSES/SATandROSES/APRA.
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Acknowledgements
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