REVISTA MEXICANA DE FíSICA -15(5) 517-522 OCTUBRE 1999

Promises and realities in tite application or superconductivity to energy issues

Alcx dc LOl.annc[)l'/){Ir'ml'1lt (JJ P¡'ysics. 11llil'('I"silY (JI Tt'xlIJ r\/Istin TX 787/2-/ U8/

Recibido el ~Ode abril de 1999: aceplado l'¡ 15 de junio de 1(1)9

In this papcr we review the recenl progress on lhe ¡¡pplicatioll uf supcrcondlll.:tivily to lhe licld 01"cncrgy conservalion. and follow this wirhcxamples 01'detaileu material s analysis lel.:hniqlles fmm OUT Iaboratory.

KC'YH'tmü: Supcrcondllctivity: power \ines

En este artículo se revisan los aV,mees recientes sohre 1""plicación Je la sllpcreolllJuctiviJaLl al campo de la conservación de energía y se danejemplos detallados de las lécnic"s de an¡ílisis de maleriales usadas en nueslro IahoralOriu

Dl'.Kril'tOrt'S: Supcrconductividad: líneas de pOlcnt."ia

rAes: 74.90.+n

1. Introdllctinn

Sinec its t1iseovcry in 191 I by Kammerling Onnes 111. super-conJuclivity has ocen perecived as the ncxl-generation teeh-nology for the efficienl Jislribulion of eleetrical powcr [2].This is because a primary property nI' the superl'onduetor isth~l il has fCro resistanee lo lhe now of electricity I:~].Un ..fortunatcly il \Vas nol lIntil the middle 01' Ihis centmy thatpractical Illalcrials \Vere found to Illake lhis possihle. alocitwirh suostantial cosl due to lhe HeeJ for refrigeratiol1 he.low 1() Kelvin. The cost \Vas indecd prohihitive el10ugh Ihalthe impressivc delllonslrations done in Illany Iahoral<lries didnol oceoI11e acccpted cOlllmereial prodllCts rOl" po\\'er gen.eratioll or distribution. The úiseovcry in 19X6 by Betlnorl.ami t>.lllel1er [,ll 01' a !lew class of Illalerials lhat heeol1le Sll-perconducting at higher telllperatures. now as high as 150Kelvin [G], was Ihcrefore receivcd with greal exeilelllent andenthusiaslll [fil.

Unforlunalely Ihe !lew malerials. uuooed "high Icmpera-ture supereonduelors" or H1'5. are aU eeramil..:s wilh a p('r-ovskite slructme. which renders (hel11 too brittle lo makewire. Sinee wire is the Iirst ouilding olock for many applica-lions 01"supereonduetors. the progrcss for widespread COIll-Illercial applieations has heen disappointingiy slow. Nevcl'-lheless. lhe sllostantial worldwitle cffort lo make useful wire\Virh Ihese material s is starling to pay off. and delllonslraliollprojccts are now slarting lo go out of lhe lahoratory into lhe'"real world". The besl cxalllplc of lhis is a suprrcollduelingpowcr line lhat will oc installed in lhe power grid 01' DClroilamI should he operalionai in Ihe year 2000. as dcserioeJ he-lo\\'.

2. Al'l'lications of slll'crcondllcti\'ily

The lraditional c1assification of lhe applications of slIper-conulIctivity Illakes a division oelwcen small-scale anu largc

scalc. as follows:

Al Small scale

1) S()UIDs (Supereondueting Quantulll lntcrferencc De-vkes)

- l\lagnelomet('rs- Al1llllelerS

V(llllllctcrsTr¡ll1sduecrs

2) Vollage slandards. oscillators

J) Ampliliers, mixers: oololllelers

4) Analog signal processing (Filtcrs, convolvers.striplincs)

5) Logie

- Slllall: Analog/Digital convertcrs. logic gates- Largl': C01llputers (lnterconnccts. mcmory.

logid

B) Largc seak'

1) Po\\'er lincs (De prckrahly)

2) ~lagllelS lahoralOry (> 20 Tesla) high energy physics

MRI (Magnetic Resonancc Imaging)- Powcr gClleralors. electric motors

Levilalion: trains. cte.- I\)\\:('r slOrage

- Ship propulsionFusi()1l reaclors

1Ishould he notcd that all of Ihe applications lislcd ahove.except for fusiono have oecl1 delllonstrated at least in labora-lory prolotypes anu that muny are eommercially available.SOlTle are aIread)' lIsing high lemperaturc superconductors.

31M ALEX DE LOZANNE

From lhe lisl above une can scc that "small-scalc" rcfcrsIlloslly 10 sizc and involves elcctronic applications and sen-sors. Thcsc dc\'iccs are used hccausc lhey providc hctlcr PCf-fonllancc ¡han other Icchnologics or beca use lhey are lhe onlytlt:\'il:c Ihal can providc a cenain typc 01' mcasurcmcnl. \VhilcIhe dcviccs thcl11sclvcs use very I¡ttle cncrgy, lIsually lhe CI1-crgy cosls associalcd with rcfrigcration make lhe ovcrall CIl-

crgy use highcr than that 01'otiler tcchnologics. For ¡his rca-SOIl slllall-scalc dcviccs will no! he disCllsscd hefe, cxccpt10 ...•ay tha! thcrc has heen rcccnl succcss in lile application01"high Icmpcraturc supcrconductors for COllllJ1crcial ccllularrhollc Iransmiftcr!rcccivcr unils [71.

r\'1an)' of the Iarge seale applications listed ahove provideellergy savings even when one lakes into aü'ollnt Ihe energylIsed for rcl"rigeralion. In some cases superconduclivily pm-vides capahilities thal are not available wilh <lny other tech-nolog)', slIch as magnelic tlelds over scven Tesla. Clearly, su-perc()[l(JlIclors w(lUld have replaced competing Icchnologieshy no\\" excepl for Iheir higher cost and the added complcx-ily of rcfrigcralion. Sincc Ihe gcneration and transmissioll 01"c1eclrical p()\ver wilh slIpcrconducling lechnologies promiscIhe largcst cnergy savings, Ihcsc two lopics will he discllssedin more delail.

3. SlI(lcrc()nducling gcncral()rs

The eh..'clwmcchanical eflicicllcy of generalors currenllyllsed in power planls is ahollt 9XCk, so improving Ihis lo!learl)' I(Xl percenl wilh sllperconducling Icchnology does nolrepresent a \'cry attraclivc gain. On Ihe othe!" hanJ, in applica-lions Slll:h as nuclear power plants, Ihe redllclion in sil.e ami\',:eight provided hy ;¡ superconducling generalor may he at-u.aclive, as weJl as Ihe hetler response lo transients and faultcurrent conditions. A 300 lvlVA generalor was <.lcsigned hyEPRI illld \Veslinghollse as a firsl step lowanls Ihe cOl1slruc-lion of IIJIJIJ-4IJIJIJMVA units [S]. Unl(>rtunatcly the projcctwas suspenJeJ tlue lO decreascd inlerest in nuclear powergenerationl:2l.

4. SlI(lcrc()nducling (l()\\'cr Iincs

A prololype fOl"a !learly losless AC power line hased (lll ImvTe supereonduclors \Vas designed and ollilt al BrookhavenNational Lahoralories [O]. \Vhilc il is clear Ihal this technol-ogy \vOI"ks, Ihe cosl and complexily 01"oolaining amI maill-laining tcmperalurcs hclow 10 Kclvin makes il impractical,specially in Ihe aosence 01"nuclear powcr pl.lnts. The discov-ery 01"supcrconduclors with Iransition lemperalures up lo 132Kelvin (155 Kelvin lInder presslIre) (5) was Ihercfore verye,\ciling because it greatly reduces the rdrigeralion requirc-lllcnts.

Unforlunalely Ihe ncw superconduclor are ceramics.which mealls thal Ihey are loo brillle to make \Virc. Never-Ihcless. Ihe cOlllmcrcial imj10nance of supc!"cont!ucling wirehas resul1ed in inlense world\\'ide efforls to sol\'(' this proh-

lem, and it is cncouraging 10 sec lhe lIrst eommcrcial protluclscoming I"mm these ellons flO]. Thc duelility problcm hashcen addrcsscd hy lIsing silvcr as a matrix whieh is made Sll-perconducting hy a high density of BilSrlCa:zCUjO¡;¡ supcr-conducling ranicles containeJ wilhin il. This has the advan-lage lhat Ihe supcrcontlucting particles ean he cheaply pro-dllccJ hy hulk Il'cl1niqucs, hut the disadvanlage of Ihe higheosl 01' si lver alllllhe rcdllclion 01" supcrconducting propcrtiestlue lo lhe use 01" Ihe non-superconducling Illelal. An alter-native approach, \vhich is not yel cOIlltl1ercially availahlc, islo use a chearer suhslralc such as a nickcl or Haslelloy lapcand lo coal il \Vilh buffer layers and superconducting layershy Ihin-lilm lechnilJlIes. Unfortunately this approach is cur-renlly loo cxpensivc lo produce large quanlilies of wirc.

As pointed oul hy Ciran! [11}, Ihe silver tape lechnology\\'ill have lO comc down h) a cosl 01' about S IO per meter for IkA caracily in onkr lo be I!"uly altractive ror pO\ver Iransmis-sion ove!" long disl;Inces. On Ihe other hJnd. Ih('r(' are specialsituations sllch as Ihe replacelllent of critical scclions 01"apower grid in urhan-cllvirollmenls. In Ihis case Ihe ahility ufsupercollducli ng lechnology to dcliver highcr po\\'cr densiliesin exisling huried dUl'IS may he allractivc despile Ihe highe:rcost ol"lhe wire ilml ils rdrigeralion requirements. A rcal-life:test of this concepl is schct1ule:d lo go online in the year 20(X)hy pulling a sllpercollt1l1cling power line in a downlowll suh-sial ion in Delroil.

The Delroit slIhstaliolllesl willllse Bi1Sr:!Ca:zCu;jOS /sil-ver superconducting lapes wound iJ1lo cahles. The power linewiJl carry 30()O A (rms) in a Ihree-phase conflguration and\\'ill lit into an exisling 10 cm Jiametcr huricd ducl. It \ViIIreplace a 30-year-old copper conductor, yel il will providc2.5 times larger power Glpacity within the sJme constraincd.'.•pace.

As wilh any olher technology, the real impacl wil1 he Je-lennined by lile overall cosls ami Ihe demonslrated perfor.mance. This /irst test is Ihcrclúre crilical for Ihe fulure imple-mcnlalions 01' sllperconducting lecl1nology in Ihe distrihulionof electrical po\l,'er.

5. i\Iagnclic Icvitalioll

Resides I.ero resislance, slIpcrconductnrs have the lInusualpmperty lhal Ihey expcl l1l:lgnctic Hux fmm their interior, asdiscovered hy t\teissller and Oschenfeld in 1933 [12J. Thisproperty can provide a simple e.xplanalion rOl" Ihe populardemonSlration 01"lhe levilalion 01"magnets on IOP of í.Isupcr-conductor: as Ihe superconductor expcls the lIlagnelic flux itrepels Ihe source 01"that lIux, namely Ihe !llagnct [13J. Per-haps the most imprcssivc delllollstralion of this ellect is lhelevilalion 01"a sumo wrcsller wilh a lotallllass of 300 kg [1,11.Ohsel"\'ing [hese kinds (JI"t1ellHlIlstralions immediatcly hringsto mino appticalions sllch as I"rictionless bearings (151 andkvilalcd lraills.

In the case nI" lrains, howcver, Ihe physics 01' lhe levila-tion ctlcCI is Ihe replIlsion duc lo Eddy currcnts in [he nor-mal melal r<Jils; Ihc superconductor only providcs a large

R('\'. M('x. Fú, -15(5) (1999) 517-522

I'ROMISES AND REALlTIES IN THE APPLlCATlON OF SUPERCONDUCTIYITY TO ENERGY ISSUES 519

magnctic nclJ. Very recen tiy an imprcssivc record has heenreponed: a Icvitatcu train (MagLcv) with supcrconductingmagncts has achicvcd a record spccd of 552 kilomctcrs pcr110m (Ihis dClllonstrmion includcs passcngcrs in a 5-caI" train,while lhe previous record was an unmancd train with 1wocars) IIGI. \Vhilc this is a hcautiful and imprcssive tcchnol-ogy. thefe are criticisms fmm lhe cconomic ami practicalpoint 01"vicw lli], arguing thm whcclcd trains are no\V opcr-atillg up lo 300 km/h and that airplanc fafes are going down,so Iha! lhe extra cnsts ortlle supcrconducting tcchnology mayl101makc sen se. As always, Ihis wiIl cventually be dctcnnincdby markct forccs.

(o)

6. Malerials characlerization

The discovcry, optimization, ami commercializalion 01'supcr-conducting matcrials has always uscd a wide array 01'1001stodetermine compositioll, structurc. ami olhcr properties of theIllatcrials hcing dcvclopcd. Thcsc tcchniqucs rangc fmm lhesimple anJ incxpcnsivc. such as the Illcasuremcnt ol' rcsis-tivily. 10 lhe sophisticatcd ami costly, such as <.:hcmical andstruclural analysis by Rutherford back scattcring (RBS). Thcauthor has a spccial ¡nteres! in scanning probc tcchniqucs,wilcre a microscopic probc is scanncd over the supcrcoll-ducling surfacc. thcreforc these tcchniqucs will he briclly rc-v;c\Vcd herc. A more comprchcnsivc re\'icw 01'this family 01'tcchniqucs has heen puhlishcd vcry rcccntly [181.

7. l\Iagnelic force microscope

The magnelic force microscope (Mf-M) is nol the Jlrst of thescannjng pro be tcchniqucs to he applicd lo superconductors,hut it is perhaps lhe easiest lo understanu. The hasic idea isto sean a lllicroscopic magnel over lhe surface 01' the super-conductor. The tiny rnagncl is levitatcd on top of the super-conductor in Illllch the samc way as the Sumo wrestler wasJcvitaled in lhe delllonslration dcseribed ahoye. As the supcr~conducting propcrties change over the surraec, this levitatiollehanges, tllus providing a spatiallllup of the supereonductingpnlpcrtil's.

The Illicroseopic lllagnet used in MF!\.'1 is forllled hy coal-ing the lllicroscopic lip 01' un atomic force microscopc (AFM)Wilh a magnclic lhin film, such as iron. The AFM tip is sup-ported by a microrabrieated cantilever and the interaction nI"the tir with any surracc is measurcd hy Illonitoring Ihe dellec-lion of Ihe canlilever. This is usually done by opticallllcthous,hut in the case 01' low temperature and vaCUUlll el1Vironfllenlsit is prcferable 10 use u stress sensor that is huilt ¡nto lhe tlli+crofahricalcd canlilevcr [ID].

One nI' the most interesting applications 01' MFM on su-pL'rcOndUclors is to imagc vorticcs. Superconducting vonicesare very inlcrcsting hecause they provide a mechanism fortype 11 superconductors lo survive very large applied f1clds,hy Ictting lhe magnetic flux penetrale at one roinl (lhe eenter01' lhe vortex). The resl 01' the superconductor is shielded fmm

A700

360

O

'o

(b)

FIGURE 1. (a) Noncontact LT MFM imagc. 6.1/1 m on a side, ofa YBa2Cu3Ü7-r film showing vonices with an asymmctric shapc.The gray scalc spans 61 nm. (b) 3D display of thc vortex marked in(a). Reproduccd fmm Ref. 19.

this flux by cin:ulating supcrconducling currents, whichhrings to mind [he piclure of a tornado or a vortex. An cx-ample 01' ~1Ff\..1imagcs 01' VOfliccs is shown in Fig. l.

Anolher app1icatiol1 01' MFM lo superconductors is to ob-serve the penclratiol1 of magnetic llux on scales larger thanthat 01' vortices. As shown in Fig. 2, this essentialIy shmvslhe wcakest poinls in a superconducting thin-film. Nol SUf-prisingly, the magnclic llux f1rst penelratcs through the grainhoundarics 01' this 1¡lm.

8. Scanning lunneling microscope

The scanlling lllllllcling microscope (STM) [20] is the mostfamolls 01"lhe scanning probe techniqucs, although it is his-torically nOl lhe tirst o£1e. Ncverthelcss, the grcat success ofthe STM rcsultcd in many other lechniques based on simi-lar ideas, such as tlle AFM and MFM mentioned abovc. ForIhis rcason lhe STM is regardcd as the founding technique for1Il0st 01' lhe scanning pmhe rnicroscopies.

Thc STr,,1 is hased on the quantum mechanical tunneling01"clcctro£1s fmm a sharp conducling lir to the surface 01' aconducting samplc. The tunneling proccss is strongly depcn-dcnt on Ihe tip-samplc distancc, at [he rale of one order of

Rc\'. Ahx. Ft,\'. 45 (5) (1999) 517-522

520 ALEX DE LOZANNE

~~~ 2_ 1

\../ 050 Z nm 1

50 150 258

/-0:..3250 -150

:\ .•••!\ii--c..

4 ,3 .!'o2>"O"-"O

5

.•.....:~.,.-......: ¡

l ~

-50

......•............

0.3

0.1

-0.1

(a) (b) Sample Bias (mV)

Thc STi\1 is wcll-known 1'01'Ihe ol'alltiflll images il hasproduccd on Illany surltlces wilh exqllisile delail t10wn lo Ihealomic scalc. For YBa:!Cu.¡Oj_1' \vc havl' fOllnd Ihal the oeslIllethod to prepare ils surfacc is lo c1cavc single crystals al lo\\"lemperalure and 10 lakc ST~vl dala oclow 30 Kclvin, withoutletting Ihc sample warmup al ;¡ny lime. In this case one ean

F](;URE 3. The so]id curve is Ihe avcrage of 128 [.F curves talenal lhe same localíon. al lO K (4 mY. 9 pA offset suhlracled).The dolled (:UI"\'C ís lile l"tl1H!tll'lanccd JI di". The dashed curve ísR( \ .) = (dI /,1\") / (1/ \ .)1/1: the peak p",itio", givc 0.0 u. Tbcínsel shtlwS Ihe e\pOllClllial llepenl!L'IlCCof the lUnne1 l'llrl"ent (!ogscale) 011heighl (linear scale) ,ISlhe tip lravcrsed Ihe 0.1 11mpalh Xlimes. Rerroduced from Re!". 1X.

FrGllf{E ~ Sp,lli,,1 Illap (;1) nI' Ihe logarithmie dl'rivalivc[dJldF]/[JI\ '] :11\' =- 22.':, mY. ohlaincd hy suhlracling Ihe cur-renl imagc al \ .= - 20 rnV frolll lhc OI1Cal "= - 25 mV ami divid-ing by lhe ,1\'cra~c 01'Ihe [wo. A sJiglu spalial avcraging is done loreduce Ihe noise inlroducl'd hy lakíng differences. The eross seclion(b) is lakefl Ihrollgh lhe diagonal ShOWflin lhe ilT1<lgc.The vcrtil'<11scale inlhe cross-scl"lioll ís arhilrary, so we have normali/.cd il (o J

in lhe normal rt.'gion. Reproduced from RL'fs. 25 am.l 26.

'"'00

(a)

(b)

DIST ANCE (A)"

FI(iIIRI: 2. Thi .•."lIow ••.lhe topog:raphy (right imagc) and the rm!!-IIclil.' ¡Illa!! •..•Ikft) 01"Ihe ••.aml.' 111m x I 11111arCil 01' a YBCO Ihinlilm Tlll' [allt'!" "ho\\", lhe pcnctration 01'maglll'lil' flux lhrough Ihegr;\in nOllllJ;lric •••.Kcproducr.::J from Kd. IX.

llla~Jli1UdL pe!" Angstrom for clcan I11ctals. J1Iaking lhe ini-tial illlp!L'mclltatioll oflhe tcchniquc difficult, huI atll1e ...aml.'tillle giving il 1Illsurpassct.J rcsolution.

The lirsl dClllollstration [21] 01' lhe l'apahilitics of IheSTí\'l (o 111l'<ISurCsupcrconducting surfaccs lIscd stlllle nI" Ihe1110s1sophisticatcd superconductors availahll' al the linlL' lhis

Il'cliniquL' \Vas tlrs! devclopcd. ¡WlIlL'ly Ihe 1\.15 lIIatcrialssudt :1, Nh;¡Sn. Thc 1\-15 superconductors hall lhe highcslIr;lllsilioll 11'lIlperalures, inlhe range 01' IX-2J Kelvin.

As soon as the high tempcrature superconductors \h'rCdiscoyered, lhe STM was used to char;l(lcrize lhelll. particu-Iarly lo lIleasure lhe supcrconducling gap 12:!,:!:~l.This gapi, a forhidden tUlle in lhe eleclmnic dellsily 01' "'¡Hes of lhe,upl'rCllllduClor. and is olle 01" lhe mosl important p;lrame-lers for lhis material. 1'0 Illeasure lhe gap lhe STf\l is lIseJin lhe S¡wclroscopic moJe: lhe tip is lixed over lhe IOGltionof ill1L'resl, the voltage is rampcJ and lhe tUIlllcling currenlis l\'conkd (lhc resulling dala is called ;1l1IV curve). An c.\-alllp!L' is shown in Fig. 3. The /lat region 01"lhe IV curve allo\\' hia, voltage indicales lhal lillle currenl 1100\'s, lhus illl-plying thal there is an energy gap. This is lIlllrc dearly scenin lhein lhe nUlllcrical dcrivalive (dI /(/\", which is lhe dilTer-l'nlial conduclallcc) hy a oig dip al 10\'.' hias voltage.

i\lon.' rccelltly, computers have made il possihlc lo takea Iar~c a1l11H1Il1of spcclJ"Oscnpic data over a regular mcsh nI"poinls llIl thc ,urface [2.1). lhe huge <lmounl 01' dala ohtaincdcan hc sho\\'n as images 01"the current allixed voltages 1211.01' IhL' dirrcrcntial condUClance can he computed amI shownas ;1Il illlage over lhe surl"acc 12:>. :?ó], as ShllWIl in Fig ....•.This is a pm'.'erl"ul lcchnique hecausc Ihe Illap 01"Ihe ditü'r-cntial COlldllclance ohtained at a \'oltage ncar lile gap (22 IllVin Ihis casL') gives a vcry clca¡- visual illlage 01' (hc spalia] dis-trihulion 01"lhc gap. Thc dark rcgions tIlHllhis figure ha\'e nog.lp. cssl'lltially hchaving as a normallllclal, whik the hriglltrc~iolls h;I\'L' a I"ully dcveloped gap. Inlereslingly. the hound-;¡ry hel\\"cen lhc gap and nnn.gap to regions is a slraighl ¡¡nI.';llld Ihe nossover fmm nnc region to lhe olller lakes placc in;¡hOlll ~() nm (Fig ....•h). which is consistent Wilh lhe coherenccknglh 01"lhe sUl'erconductor in the <l-h plane.

Rl'I'. Mn. Fr.\. ~5 (5) (1999) 517-522

PROMISES AND REALlTIES IN THE APPLlCATION OF SUI'ERCO~DlJCTIVITY TO ENERGY ISSUES 521

FIGURE 5. Rcvcrseu-bias ¡mages ofthe CuO chain layer of YBCO.Thc samplc bias is (a) 240 mV and (h) -240 mY: (e) is Ihe aver-age 01"(a) am.! (h), and (ti) is thcir diffcrcnce. Imagcs are JO 11m ona side. and lhe avc~agc tunncling curren! is 40 pA. (e) and (f1 arecross-scclionaJ plols from (a)--{d). takcn along lhe lines markcd Oll(e): plots in (e) wcrc takcn along rhe uppcr line, whereas (hose in(O wcrc lakcn :llong the Jowcr lineo Thc corrcspondencc of curvesto imagcs is: (a) 1 amJ 5: b) 2: (e) 3 and 7: (d) 4and 8. Rcproducedfmm Rcf. 27.

clcarly observe lhe CuO chains of this compound, sccn aslhe diagonal I¡nes in Fig. S. A surprising discovcry from ollrSTM images was the ohscrvation of a superstructure or lIloJ-ulation running along the chains [27.281. This is nol sirnplylopography hecause these 1ll0Julalions reverse when one rc-verses (he tunneling Jirection. Our Jiscovery was contirmeJhy neutron di/Tractíon 129]. which also showcd lhat Ihe samcphenomcnon occurs in the hulk 01'the crystal.

9. Conclllsions

The cOl1lmcrcial impacl 01' superconductivity has hcen suh-stantial, in Ihc ordcr 01' a hillion dollars per year, most ofwhich is hascd on the low Tc supcrconductors. Thercforeone can say that supercolllluctivily has fulfilled many of thepromises that werc made since its discovery in 1911. A gOOLIexample is the use 01'supcrconducling magnets for magneticrcsonan('e imaging (MRI), which is now available in manyhospitals arounJ the world. Ncvertheless, lhe impact woulJhe Illuch higher if high temperature superconductors couldhe malle into practical wires al a rcasonahle cos1. Such wireswould have grcat usefulness in lhe generation, transmission,and slorage of cleclricity, as well as the gcneralion 01' largemagnetic liclds for levitation and many other applicalions.The f1rsl real.lifc demonstralion of a superconducling powerline, to he inslalled in downtown Dctroit nexl yenr, will hope-fully show lhe great potenlial benefits 01' this lcchnology,which will then drive further research inlo reducing the costs01'lhe wire.

A critical componcnl for this fUlure research is a largcvariety 01"materials characterization tools. Within Ihis largefamily Ihe STM antl Ihe MFM holtl a special place hecallscthey can prohe snme 01' lhe most fundamental supercon-ducling propcrties direclly, and with resolution down lo lheatomie scale. Such aJvanced technologics Illay ir.deed makepossihlc the drcam of tinding new superconductors Ihat canopcrale at room lernpcralurc r30).

Acknowlcdgments

The aulhor is pleased lo gralcfully acknowledge lhe fundingagencies and collahoralors who have made this research POS-

sihlc. This work has heen supporleJ over the years hy theNational Scicnce Foundalion, lhe Texas Advanced Researchand Tcchnology Programs, and lhe R.A. Welch Poundation.Many peoplc have collahorated with the aulhor in Ihe workreviewed hcre, Illost notahly (hose al the Universily Di" Texas(atlhe lillle Ihc rescarch was done): Alex llarr, Erwin Batalla,Chun-Che Chell, David Derro, Hal Edwards. Tamolsu Koy-ano. Qingyou Lu. John Markerl, Shuhcng H. Pan. and Cai-wen Yuan. The aUlhor is indehted to Paul Granl (EPRI) amiHill Carter (American Superconductor) for providing exccl-lent malerials rOl" (hc lecLure presentcd at this symposium andrOl" this papeL

Id'¡e)

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1. 11. Kíllllcrlingh Onnes. Leiden C01l1/1l. 120h (1911); Leidi'fICOI/"I/. 122h (1911); Leúll'll Comm. l24c (1911).

:2. PauJ f\.1.Gran!. IE/:"I:" TrWUllctiom 011Applicd SIII,clnmdllcti\'.ily,7(1997)p.112.

:~. Rcatlcrs who wish an introduction to thc propcrties of supcrcon-t1uctors nrc encouragcd to read C. KittcJ. Itllrodlfcfúm (o So/id-SIl/le Physic.l". 71h cdition, (Wilcy, Ncw York, [9(6) ctwp. 12.

4. J.G. BcJnorl. amI K.A. i\-1ucller,Z. Physik 1164(1986) 189.!J. L. Gau el al.. I'hvs. Re\'. n 50 (1994) 4260RC.G. "Discoverics Bring a \Voodstock for Physics", rile Ni'", }()f.k

Times. March 22 19X7, front ragc,

7. ConductllS. Inc., scc i1ttl,://wwu:('(JflduClltS.COllllilollll'.i1(III.

8. EPRI Rcrort. "J()() MVA Surcrconducting Gcncmlor", 19X2.availablc fmm thc EPRI Publications Servicc

Rel'. Mex. Fí.l. ~5 (5) (1999) 517-522

-n~-- AI.EX DE LOZANNE

9. E.B Forsythl'. SIl/len"ml. Sci. Tecllno/. 6 (1993) 699.

10. Scc. for cxamplc. htll,://wlI'U'.am.HlI'l'r.colII/lJI'IJ/iCl/tlolI/Il/.\/

11. Paul t\1. Granl .md Thomas P. Sheahcn. IEEE Tral/.\llCliO/ls 011

AI)pht,tI SIl/ICIHlfUIIICtivity. 10 be publishcd.

1'2. W. t\kissllcr ami R. OschenfeJ, NalUnl'ÍSwlIsc1uifle1121 (19.13)

707.

1:3. Anothcr simple cxplanntion is Ihnt lhe superconductor seIs upshiclding (unenls (o countewct lile liclds due lo Ihe magncLOne can casily l"onclude Ihm (hese shickling (urrcnts opposcIhe cxlt.'rnaJ licld and push away Ihe magncL. A lllore clegant"ir\\' is Iha! Ihe supcrcom..lucting SUfraCC aets ns ¡j magnclic mir-roro so ¡lIat Ihe magnct sces ils rcncction on lhe supcrcondllctingsurf:Kc. Ir lile N(lrth PolI..' oflhe magnct is ciOSCSll(1 thc sllrfaec.lhell Ihe rcl1ection will nlso have the North Pole closest lo sur-f;U.T, hui hehind lhe mirror. Thc two Norlh Pules thcrcforc rcpcl

caeh (llher.

1.1. A piCIUfC can he scen ni

h (tl':/;' /('hall. s{'mIli i.kl ¡1)l1S.co.j p/I srEC/O TlI E RS/c:- fll'WS. h tm l.

I;j Sec, rOl cxamplc,

/¡111'://1\ '\\ 'IV.Uh. l'lllt/re x{'(II"(:1vt es l/Iv res {'ll,.eI vi el 'jfa h'./u 11/ l.

IG. R.eponed hy lhl' Yamanashi Test Linc on April 14, 1l)()9. Scc

1/11P ://11'11 '1\ ~rt ,.j.OI:j p.

Piclures 01' this heallliful train can he secn al

hffld/II'1t'H'. (/.w/¡i-fIl'I.Or. j,¡/.....,=.b2s ./¡s!Jp/¡olo/plwl0llllx I 'l'. hlm

amllhc history 01 !his projccl at

,,(tl,://\\'wlI'. cyher-hp.or..il,/I jrll'atle/fe-2IJ4, IIlml.

17, rjary Stix., ,l,i¡'il'llIijic American, OCL 1997

18. Alex. tl~ LOl<lllnc. SI/pan",. Sci. mltl J(,dlllol. 12 (1999) R-O.

ID. CW. Yuan{'la!.,A"I'I. Phy.\. lA:rr. 65 (1994) 1308;CW. Yuanl't al., 1. \!c/c, Sci. ree/uJO!. IJ 14 (1996) 1210.

20. Gcrtl Binnig, Hcinrich Rohrcr, Christoph Gcrhcr. anLl Eduartl\Vcihel. PltysiCll I091.'\i. IIOB (1982) 2075; Phys. R{'I'. lA'f(. 50

(19X3) 120

21. 1\.1.. de Lozanne, S.A. Elrod_ and CE Qualc, "h-"s. Rl'I'. Ll'I1.5-4 (1985) 2433; S.A. Elrod, A. de LO/.allne, and C. r:. Quale,

AI'I'!. Plry.5. Lt'u. "5 ( 19R-4) 12-40.

2:2. S. f\m el al .• Phy.\'. I<el', IJ 35 (19X7) 7220.

:n. J.R. Kirtlcy ('Ial .• Phys. Re\'. n .'5 (19X7) 7216.

:2-1 II.L. Edwards el al.. "hys. Rl'\'. Lt'fl. 75 (1995) 1387.

2:). II.L. Edwardsel(/!. .. /. Ve/C. Sci. TéclulOl. H 1"(1996) 1217.

2G D.J. Derro el al., "Lo\\' lempcr;ltllrc scanning tonnc!-ing microscnpy and spcclroscopy of Ihe CuO chains in'YBa'2CLl107_~''', in Pme. (~rtl/l' 10th AIlI/II'i'rmry I/rs Uhrk-.\1101' 01/ 1'lrYJics,M(ltalllIJ {//IlI A'1f,licartoll.\, cditcd by B. Bat-logg l'I a/" (\\'orld Scienlílic, Singaporc, 19(6) p. 433.

~7. ILL Ed\\'ards, J.T. ~IJr~ert, and A.L. de LOlannc, 1. \!tu', Sci.T¡:dl/IO!. Ul2 (1994) IXX6.

:28. II.L. Edwards, A.L. B~lfr. J.T. Markert. and A.L. de Lozannc,

I'I/r.\'. l<i'I'. U'U. 73 (1994) 1154

10. II.A. tv100Kel al., Phys. R{,\,.Li'tl. 77 (1996) 370.

:U1. Paul ~1. GranL "Rescarchcrs FinLl Ex.traordinarily lIígh Tem-pcrOltllre Supcn:onduclivity in Bio-Inspired Nanopolyrncr",Physin' rr."/(/y, May 199H. This is a fulurislic slory.

R('I'. Mn. Ft\. 45 (5) (1999) 517-522