In the beam pipe of the positron Main Damping Ring (MDR) of the Next Linear Collider (NLC), ionization of residual gases and secondary electron emission give rise to an electron cloud which can cause the loss of the circulating beam. One path to avoid the

Aniongunisavailableforcleaningthesamplesbysputteringandforionconditioning

surfaces.

Figure2:Experimentalsystemusedforsurfaceanalysis

Afterallsamples(uptotenorso)aretransferredintothemeasurementchamber,onesampleatatimeisloaded,onitsindividualcarrierplate,ontoamanipulatorarm(VacuumGenerators”Omniax”).TheOmniax carrierplateholderdesignisshowninFig.4.Twothermocouplesareinstalledonthisholderplateaswellasheating lamentandsampleconnectionwires.Samplescanbeheatedviaatungstenwire lament,Fig.3,byradiationorbyelectronbombardment.Electronbombardmentisachievedbybiasingthe lamentnegatively.TheOmniaxsampleholderisinsulatedfromgroundviaanaluminaceramicandbyseveralthermalshieldplatesinsulatedviafoursapphireballs,Fig.3andFig.4.

Thesamplecarrierplatesaremadeofmolybdenum(forattainingthehighesttem-peratures)orstainlesssteel,Fig.5.Thisplatewillsupportonesamplewhichisheldbycornerscrewsontoitssurface.ThisdesignallowstheplatetothenslideintotherailsoftheOmniaxplateholder,cfFig.3.AnexampleofanaluminiumprototypecarrierplateisshowninFig.6andFig.7.NotethatonFig.6theholesforthescrewsarenotdrilled.Inthiscon guration,thethermocouplesarenotattacheddirectlytothecarrierplatebutindirectlythroughtheholderplate.Sampletemperaturesarecomparedtothethermocoupletemperaturesbyusingablackbody-calibratedinfraredpyrometer(0.8µm-1.3µmbandpass)whichiscorrectedforabsorptionbythe7056glassviewportofthemeasurementchamberandthesampleemissivity( )of0.2-0.4.

AgoodwaytomonitortheactivationprocessoftheTiZrVnon-evaporablegetter