'r PrProcaadng田崎dinga s ofof 世帽民削白川町田信副首..itw Fourth Intamtional 5"Symposiu暗闘..... m 。oan ADVANCEDADVANCE D 鈍NUCLEAUCLEAII R ENERGYENERG Y RESTRESEARC由CHH ROLES ASDAXO DIRECTIO.... DIRECTIOX OF 且MATERIALrA TE RlA ι SCISCIEXCE E. ... CE 1: IX、.. .w' SVCLEARc. ιEAR TECHXOLOGYTECH I'> OLOG1' POSITRONPOSITRO N ANNIBIANNIHILATIOL& TION N STUDYSTUD Y OFO P GlUlGRAPHITEPIUTE ,， GGLASSLIlS SYY CaRBONCARBO N JUQ)AN D C60/C70Cfi0 /C7o FULLDEFULLEREN蜘EE 阿Masayukasa 抑制i HHasegawa管記~gawa,， MasahirMas_a~iro.K~noo Ka^no,，_ T~da?Tadao lwataIwata合 EiichiEiich i KuraKuramot皿oto-- o ，, MinoruMinor u Takenaka--Takenaka andan d SadaeSada e YaYamaguch皿aguchi i InstituteInstitut e forfo r MaterialsMaterial s Research ,， TohokuTohok u University ,， SendaiSenda i 980 ,， JapanJapa n _. * _. PhonePhon e 022-227-6200022-227-620 0 eext.2454.認 t.2454 ， FaxFa x 022-215-2061022-215-206 1 PhysicsPhysic s DeDepartmentpartment ,， JapanJapa n AtomicAtoni c EnEnergergy y ResearchResearc h lnstituteInstitute,， TOkaiTokai,， IbarakiIbarak i 319319-11・11 ,， JapanJapa n 合会 PhonePhon e 0292-82-5470 ,， FaxFa x 0292-820292-82-529・5297 7 * ResearchResearc h InstituteInstitut e forfo r App1iedApplie d MeMechanicschanics ,， Kyusyu Kyusy u UniversityUniversity,， Kasuga ,， FukuokaFukuok a 816 ,， JapanJapa n PhonePhon e 092-573092-573-961・9611 1 ext.ext . 566 ,， FaxFa x 092-582092-582-420・4201 1 且ABSTRACTBSTR 且.CT: : ACARACA R ( AnAngulagular r CoCorrelatior. relation n ofo f AnnihilationAnnihilatio n Radiation)Radiation ) andan d positronpositro n Keyword*K~yword.:: PositronPositro n AnnAnnihilationihilation ,， lifetimelifetim e measurementsmeasurement s havehav e beenbeen 皿madade e on,， Graphite, Glassy Carbon, C , Fullerene, Graphite ， G1assy Carbon ， C 6600' Fu11erene ， HOPGHOP G (High1y(Highl y OrientedOriente d PyrPyrolytio1ytic c Graph-Graph­ Void ,， Pore ,， VoidVoi d TrappingTrapping~-Soccer, Soccer 8a11Bal l ite) ,， isotropicisotropi c fine-grainedfine-graine d graphite ,， VacancyVacanc y glassyglass y carbonscarbon s andan d C60/C70C50/C7 Q P?wder._powder . HOPGHOP G showedshowe d markedmarke d bimodalitybimodalit y a10ngalon g theth e c-c- axisaxi s andan d anisotropyanisotrop y ini n ACARACA R momentummomentu m 1.1.INTRODUCTIOlM'l'R ODUCT l: ONN distribution ,， whichwhic h stemste m fromfro m character-character­ isticisti c annihi1ationannihilatio n betweenbetwee n "inter1ayer""interlayer " GraphiteGraphit e hasha s beenbee n emp10yedemploye d asa s theth e posipositron trons s andan d 1[T-electron -e1ectrons s ini n graphigraphite te. 圃moderatooderator r andan d structura1structura l cocomponent岨lponents s ofo f ACARACA R curvescurve s ofo f theth e isotropicisotropi c graphitegraphit e fissionfissio n reactors ,， suchsuc h asa s gas-cooledgas-coole d andan d glassyglass y carbonscarbon s arear e eveneve n narrowernarrowe r one ,， becausebecaus e ofo f 10wlo w neutronneutro n crosscros s sec-sec­ thantha n tDattf^a t ofo f HOPGHOP G perpendicu1arperpendicula r tot o theth e tion ,， chemica1chemica l stabi1itystabilit y andan d highhig h melt-melt­ c-axis.c-axis . PositronPositro n 1ifetimeslifetime s ofo f 42042 0and and ingin g point.point . FurtherFurthe r recentlyrecentl y carboncarbo n 39039 0 - 48048 0 psec ,， muchmuc h longerlonge r thantha n thattha t ofo f materia1smaterials,， forfo r exampleexampl e graphitegraphit e andan d 22122 1 psecpse c ini n HOPG ,， werewer e observedobserve d forfo r theth e cabon-carboncabon-carbo n composites ,， havehav beco e becom圃e oneon e isotropicisotropi c graphitegraphit e andan d g1assyglass y carbonscarbon s ofo f theth e keyke y materialsmaterial s ini n theth e fie1dfiel d ofo f respective1yrespectively,， which whic h arear e duedu e tot o positronpositro n plasma-wa11plasma-wal l lnteractioninteractio n ini n fusionfusio n reac-reac­ trappingtrappin g ini n structura1structura l voidsvoid s ini n them.them . torstor s becausebecaus e ofo f itsit s 10wlo w atomicatomi number c number PositroPositron n 1ifetimelifetim e anand d ACAACAR R widtwidth h (FWHM)(FWHM ) anand d high-temperaturehigh-temperatur e characteristics.characteristics . canca n beb e we11wel l correlatedcorrelate d tot o voidvoi d sizessize s ForFo r fusionfusio n reactorreacto r app1icationapplication,， absorp-absorp­ (1.7(1. 7 tot o 5.05. 0 nm)nm ) oro f g1assyglass y carbonscarbon s whichwhic h tiontio n andan d desorptiondesorptio n ofo f hydrogenhydroge n isotopeisotop e havenav e beenbee n determineddetermine d byb y sma11smal l ang1eangl e atomsatom s arear e veryver y iimportan田lportant t andan d sensensitivel!l!:t- tive1y y neutronneutro n (SAN)(SAN ) scatteringscatterin g measuremeasur e .-唖 •intsnts. affectedaffecte d byb y structuralstructura l voids..void s J' andan d ACARACA R ..:urves curves andan d posipositro tron n 1ifetilifetiml' .e e ofo f radiation-inducedradiation-induce d vacanciesvacancie s andan d voidsvoids. C60/C70CCQ/C7 0 powderpowde r ag~eagree we11wel l withwit h thosethos e ofo f Consequent1yConsequentl y atomisticatomisti c informationinformatio n andan d gIassy-carbons.glass y carbons. ThisThi s showsshow s thattha t positronpositro n characterizationcharacterizatio n ofo f structuralstructura l voidsvoid s andan d wavewav e functionsfunction s extend ,， asa s ini n theth e voidsvoid s radiation-inducedradiation-induce d defectsdefect s isi s veryver y necesneces- ­ ofo f glassyglass y carbons ,， muchmuc h widerwide r thantha n openope n sary.sary . PositronPositro n annihi1ationannihilatio n hasha s beenbee n spacesspace s ofo f theth e octahedraloctahedra l intersticesinterstice s ofo f successivelysuccessivel y useduse d forfo r studiesstudie s ofo f vacan-vacan­ theth e face-centeredface-centere d cubiccubi c (FCC)(FCC ) structurestructur e ciescie s andan d voidsvoid s ini n meta1smetal s 【[1]1]. ForFo r ofo f C60C 60 crysta1crysta l andan d stro~g1ystrongly suggest~suggests carboncarbo n materia1smaterial s theth e usefu1nessusefulnes s ofo f thisthi s positionpositro n trappingtrappin g ini n thethe 町"soccesoccer r ballba11" " techniquetechniqu e hasha s beenbee n demonstrateddemonstrate d byb y vacancy.vacancy . Possib1ePossibl positron e positron statesstate s ini n theth e severa1severa l workersworker s [2[2-6]・6]. carboncarbo n materialsmaterial s arear e discusseddiscusse d withwit h a simp1esimpl e modelmode l ofo f voidvoi d volume-trapping.volume-trapping . *) ' sometimessometime s ca1ladcal l 3d asa s cavitiescavitie s oro r Pre1iminaryPreliminar y resu1tsresult s ono n neutronneutro n irradia-irradia­ pores.pores . tiontio n damagedamag e ini n HOPGHOP G arear e a1soals o presented.presented . - 119-119 • --， RecenRecent t excitinexciting g reporreport t oof f methomethod d merit国 ents s oon n HOPG,， glassg1assy y carboncarbons s anand d fofor r preparinpreparing g larglarge e quantitiequantities s oof f ththe e CCQ/C~~0/C707Q _powderpowde r wilwi11 l bbee compareco 園 ipared d anand d "socce"soccer r ballball" " CC60 60 moleculemolecules s [7[7] ] anand d ththe e discussediscussed d witwith h a simplsimple e void-trappingvoid-trappin g followinfollowing g discoverdiscovery y oof f superconductivitsUp'~rconductivityy modelmode1. iin n potassium-dopepotassium-doped d C民6nQ [8[&] ] havhave e raiseraised d greagreat t interesinterest t iin n ththe e structurstructure e anand d 2 2. DPEXPERIMENTAEIUMEN'1' AL L propertieproperties s oof f thithis s allotropia11otropic c forform m oof f carbocarbon n [9,10][9 ，10]. BecausBecause e oof f ththe e weaweak k FigurFigure e 1 showshows s crystacrysta1 l structuresstructure s intermoleculaintermo1ecu1ar r interaction,， ththe e solisolid d oof f diamondiamond d (a)(a )， , graphitgraphi te e (b )】 anand d ththe e C60 hahas s larg1arge e opeopen n spaces, fofor r example , (100(100) ) facface e oof f ththe e FCFCC C C - SampleSamples s useused d 6 ， ， 60 ・ aat- t ththe e octahedraoctahedral l intersticeinterstices s wherwhere e i:L n thi悦1I s studstudy y arare e listelisted d iin n Tab.lTab.1. A potassiupotassiurn m atomatorns s cacan n bbee accommodateaccornrnodated d iin n singlsingle e crystacrystal l platp1ate e oof f synthetisynthetic c diadia- ­ itits s structurestructure. ConsequentlConsequently y iit t iis s ververy y mon皿ond d witwith h (111(111) ) crystacrysta1 l facface e wawas s used.used . interestininteresting g tto o investigatinvestigate e positronpositro n HighlHighly y orienteoriented d pyrolytipyr01ytic c graphitegraphit e statestates s iin n soliso1id d CgC60 andQ and tto o comparcompare e thethern m (HOPG(HOPG) ) (2Y(ZYA A anand d ZYZYH H grade.， Unio Union n CarbideCarbid e witwith h thosthose e iin n graphitgraphite e anand d glassg1assy y ( Co.Co.) ) slabslabs s havhave e mosaimosaic c structurstructure e witwith h glass-likglass-like e ) carboncarbon. ththe e well-orientewe11-oriented d c-axic-axis s bubut t witwith h randorandom m orientatioorientation n oof f ththe e crystallitecrysta11ites s iin n ththe e RecentlRecent1y positron y positron lifetimlifetime e measuremeasure- ­ basabasal l planeplane. ThThe e averagaverage e crysta11itecrystallit e mentments s havhave e beebeen n carriecarried d ouout t bby y severasevera1 l sizsize e alona10ng g ththe e a-axia-axis s iis s abouabout t 225μm5 a m groupgroups s [11-13](11-13] ,， includininc1uding g uus s [6][6]. whilwhi1e e Turn7μ 皿 alona10ng g ththe e c-axic-axis s [3][3]. H0PGHOPG- - FurtheFurther r theoreticatheoretica1 l calculationca1cu1ations s shoshow w ZYZYA A wawas s subjectesubjected d tto o fasfast t neutroneutrop_ n irrairra= ; 18 4 positropositron n statestates s anand d lifetime1ifetimes_in_C60 s in C60 anand d diatiodiation n witwith h fluencf1uence e oof-8.3-~-iõI8f 8.3 x 10 n/car~/C;2 potassium-dopepotassium-doped d fullerenefu11erenes s [14,15][14 ， 15]~-. A11Al l aat t abouabout t 150°150 ・C iin n ththe e JMTJMTR R reactorreactor. TheTh e thesthese e experimentae 翠perimenta1 l studiestudies s havhave e reportedreporte d blochl~_ofk of HOPG-ZYHO fG -ZYH H 町wa'as s irradiateirradiated d tto o 1.41. 4 a positronpositro n 1ifetimelifetim e ofo f aboutabou t 40040 0 psecpse c ini n x 1010~u20 n/cmn/cm~2 ata t aboutabou t 6060 ・"CC inin 位田the JRR-2JRR- 2 C powders.powders .