AlphaindirectconversionradioisotopepowersourceAppliedRadiationandIsotopes66(2021)173–177/locate/apradisoAlphaindirectconversionradioisotopepowersourceMaximSychov,AlexandrKavetsky,GalinaYakubova,GabrielWalter,ShahidYousaf,QianLin,DorisChan,HeatherSocarras,KennethBowerTRACEPhotonicsInc.,1680WestPolk,Charleston,IL61920,USAReceived1October2021;receivedinrevisedform5August2021;accepted3September2021AbstractAdvantagesofradioisotope-poweredelectricgeneratorsincludelongservicelife,widetemperaturerangeoperationandhigh-energydensity.Wereportdevelopmentofalong-lifegeneratorbasedonindirectconversionofalphadecayenergy.Prototypingused300mCiPu-238alphaemitterandAlGaAsphotovoltaiccellsdesignedforlowlightintensityconditions.Thealphaemitter,phosphorscreens,andvoltaicarrayswereassembledintoapowersourcewiththefollowingcharacteristics:Isc14mA;Uoc2.3V;poweroutputingthisprototypewehavepoweredaneight-digitelectroniccalculatorandwristwatch.r2021ElsevierLtd.Allrightsreserved.Keywords:Microbatteries;Plutonium;Phosphor;Indirectconversion;Powergeneration1.IntroductionAnewgenerationofultralowpowerdevicesneedsminiaturelong-lastingelectricsources.Oneoptionistheutilizationofradioisotope-poweredmicrogeneratorsasshownbyOlsen(1992)andSimsetal.(1995).Advantagesofradioisotope-poweredenergysourcesarelongservicelife(over10yearsdependingonisotope),lowweight,smallsize,wideoperatingtemperaturerangeandhighreliability(Boweretal.,2021;Sychovetal.,2021).Amongthemanyradioisotopedecayenergyconversiontechniques,weheredescribealphaindirectconversion.Thekineticenergyofalphaparticlesisconvertedtolightinaphosphorscreen.Thematchedphotonwavelengthsarethenguidedtothephotovoltaic.Thephosphorscreenisopticallycoupledtothephotovoltaicdevice,asshowninFig.1.Indirectconversionusinganalphasourcehasseveraladvantagestobothdirectconversionofalphasandutilizationofbetaemitters:specicpower(powerperunitsurface)comparedtobetaparticles.Therefore,lessphotovoltaicsurfaceareaisneeded,makingthedevicesmallerandcheaper.Forthesamereason,alpharadioluminescence(RL)isbrightercomparedtobeta-excitationandphotovoltaicconversionismoreefcientatbrighterlightlevels.Comparedtodirectconversionofalphas,initialoverallefciencyislower,butthestabilityismuchhighersincephosphorsaremorestablethanvoltaics.Overthelongterm,theindirectpoweroutputsurpassesthatofdirectalphavoltaics.InthispaperwedescribefabricationandtestingofpowersourcesusingPu-238.2.PhosphorscreenfabricationPhosphorwasdepositedonglasssubstratesusingthefollowingprocedure:glassslides2.52.5cm2werewashedwithalkalinesolutionandthenwithasolutionofpotassiumdichromateinsulfuricacid.Phosphorpowderwasmixedwitha5%solutionofphosphoricacidinacetoneandthatmixturewaspouredintoavialinwhichwasplacedtheweighedglassslides.Afterseveralhoursofsedimentation,theslidesweretakenoutofthevial,bakedat2501Candweighedagain.ThedifferencebetweenThehighenergyofalphaparticlesprovideshigherCorrespondingauthor.Tel.:+12173486703;fax:+12173486394/6713.E-mailaddress:msychov@(M.Sychov).0969-8043/$-seefrontmatterr2021ElsevierLtd.Allrightsreserved.doi:10.1016/j.apradiso.2021.09.004Fig.1.Alphaindirectconversionsetup.startingandnalglassweightdividedbysurfaceareaisthesurfacedensityofthephosphorlayer,H(mg/cm2).LayersofdifferentsurfacedensitywerefabricatedfromZnSphosphorandtestedagainstPu-238andSr-90sources.Radioluminescentintensitywasmeasuredwithaphot...