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A very stable automatic pressure controller
RESEARCHANDTECHNICALNOTES A very stable automatic pressure controller G. D h a r m a d u r a i
and B.A. Ratnam
The lemperaliJie i~l an apparatus ilrirnersed iii a liquid rPIrngelarll ,'an he r l l i l l r l i l l e d hY nlalrllalrlllll4 a c'illl.~larll vap~liJl pres.~url > i)Vel Ihe hqiJId SlJrlai'e IrE Iheea!.,e ill hqlJid lil'hlJin, hqllld eval'l(llali,~!~ cllilllnlilllJ,~17 a.~ a leSlJII i~l liPill leak.% I r l l ~
lhe
c'~lislal
arid
,~li, In i ) I d e i
hi illalrllaln
c'lln,%lanl
lerllpl£llJIiJle, Ihe vap~liJr has hi hi' puuiped away al lhe saint' tale ,El w h i r h ii is ~,erleraled '|'here are several ,,iinple devlc'e.~i i ~ w h i c h acl'clniphsh lhl.~; hy alJhlm~illcallv adliJ,dlrl~ , Ihe plJil-ipin[. ~, ~rieed .~;ll a,~ hi kl>e[<) Ilie Vllill_ilJl I)iC~l!~lJll* I lin.~,lanl a l ar/ll/ t t e S l l P d V ~ l J e IrE all Ihe.~e devlc~.~, w l m n the pll'S,%lJil > Irl Ihe r[y~lslal ['a.lls I~l iiJ;;l heh~w the liresel relererlce prl..%iJrl `, Ihe operinii[. ~, hi Ihe p u m p is ;~ealed alllt n,, l u l l h e r lire!,slure illii[.i,l.~i ,'ilhlwl>d ill lll'l.'lJI ']"hi ~ rilallli.~ilal dl,!,l.'llheit hi/ K l P i I i l l a n ~ I~r e~,aliiple, l~lliphw.~ a ri.lhhel lhapt-iral.~,[ll , all~,JI I ~ lllnl Ihlck w h i r h , wlleil ll-lt'rt" I!, a plrl'sl, IJle d l i l e l e r i r e ,ll.'rlills II, I;.l(iw~ (ilJI ,iuill I'lhick~ Ihe piJmplrll~ , lirllil.'e
Ilanl..,,es h~rniinT, parl ~1 Ihe nlallll;dal a~senihlv h a w heen inacliirielt Ill hllerance~ b ~ l l e i lharl ± i)I)~ rnm ltlJI I)1 i'llrllrllPll'l,ll b h l w Ill)It ~ Iree bra.~.~ ]"li~ m:illnl.., , .MJrlacl-!, ill Itl~" hip arid rl>lilre Ilari~,e!, ale i'lilll!~lied aller drilhril4, I:ll'tpinll , alid ;;~fldennl..,, and a lhlri l~lllye!ilt'r I'llril ill Ihickne~,~ ah~,ll 2~ Dim i~; applied Ill II-il> t~llislied SUllai'e.~ ill IIle ahllve Ila[il~e.~ II,ilrl),, a l'llrlllrlell.'laJ ,icltiel~ive (kllck I;isl ) al Ihe Idm pl>ril.llie r~ WiIh Iliv diaillira{,,rii valve cipe[i, ~ill Ihal Elicit' i!~ ,l(llne l'lle:~siJrt, ~lrl elllier kllli ~ ~ll the p~lve;dvr Ilhii, Ihe crw_lldal D iliJlrlped d l l w n I~l Ihe item,lied File~.MJre as illdlC;ilt, d hV Ihe ,ib.~,~llule llre~!aJre ~alJl.,,e (L.evhllh:l-Helaeus) arid when Ibis, i!, r~;/ctied, Ilie valvP is rhls~-d ~i Ihal Ihe t'llrrec'l lelelelll e ple,,,,i/[~ ~ i.~ luapp~>d in Ihe sl~ac'e ahovl, Ilie p~lve.~l~r rllnl arid Ilie Ii~hlJin fl~!~P[Vl)l[ 'T'ht' plJiiil~ htlweve[ t'i)illlrllJt'.~ Ii) Ir~ arid reduce Ihe rlres.~ure, hul Ihe p~llve~ler rilrri bt'cau.~e el IIll.~ [.lll.%lllVe dlllererilla] iJlef~.%lJrP al')lwe Ilie lilrri, ~,eal.~ Ihe llrillceS tlirlliJl.,,h w h i c h [_liJniplrl~ lakes plare
Irl Ilil~ paper wl' de~,clilie a ~;Inlph > d e n l ( l u n l a h l e iii.iliql~dal whll.'h w(nk!i lln a Sllnlla[ l-illlic'lple biJl eiilphW.k a lhlrl polve.~ier rilni iiilile'ad ~ll Ihe c'llnVellll(irra] iiJhher diarlliralT, n-i B Y V l l i l J e ' I)l i l k l . ' o r l S l l l J l . ' h o r l , lhere Ill rile t)ercepIihle [.iIC,~ISUle I]iJl'llJalillrl and leniperaiure slahllilie~ ~ll belier Ihan ! (.) I"i, iii lilt" [.'ill~,P i_ll l e l n p e l a i u l l % I ~ K hi ,-I ~ K all ~ rt'adil 7 al'hlPved 'T(ililOrllhtr lilt' lelnperlillJle.Mahllll 7 ill Ihe nlanlt.slah'd balh we have used Ihe l e p e a l a b l h l y ill crlhl'al culreril;~ qll lllril4 .%lperr(~uidiJr llrlT, pr~lXUTIIly el leci h l l d g e , % , 'l III !.;iJl'ceh!,lVe C ' l J r r e r l l ~weeps, as Ihe C i l l e F I l l r l Ilil lelnrlelallJli' s l a b i h i y
N~lw when Ihe rlle.%~ilJle irl the C'l-Vll.~lal [i.~e~ abtlvl, Ihe relererlce pre.s.~ule lhe I'lhn bows liul .llhlwlrig Ihe piJlnll Ill il'diJi,'i' lhe p[essure ~irice Ihe re.~ilirlng I~ircl-;, irivi~lved nri li-le.~e prore.~:le:; are .~rrlaJI [lie rile.~iMJre l'luCllJalllirls are ,'nl:,~l) ,~mall rau:~ui~, a w~ry h i l l !dabnhly ~1 Ihe vapour pr~,,,,:;ure We have ~bsel'ved Iliai there is n~ pelceplible I l u c i u a l l l m irl rlres,',,ure as indll.'aled by Ihe steady leadinl~ ol Ilie p(~mler ,Iri the pres,~iJre J.;aIJge
Experimental
Estimation
detail
The currenl w dta~.~,e (/ I,r) characlermlnc!¢ ~ll ~ u p e r o m d u e l n n g (Ag,-Srl) pr~lxnrriily e l l e c l hridl~;e.~ rei.'~rded llii an v I' p h l l l e r as II'le clJrrerll ihrout.~,h the l,,iJpc-rcondlJ~,'lur i.~ '4wepl h.lr SlJi.'t'es,~ive sweeps al a c¢~nslarll rele[erlce ple.'4,~aJre have been used Io esliniaLe lhe lelnpefature slabnhly ill' lhe inamlslaled halh When llie valves arid c~uplirigs ~ri lhe .~y.~lem are perleelly leak l~ghl, we ,ibserv~ Ella[ the ~.'rille;d rurreri[s I¢ (viz [he nia.ximum 'zero willat~,e currents) (El these hridge,~ ;.iI cormlanl pressure as ubser~ed ~in sueee.~snve I l.'
Fig I ,sli,~ws the irianli.~lal c~ml'~giJratiuri used m uur experirrierll,S hlr auh~rriallc c o n l r , d or Ihe vap¢,Jr pre,~sure llvel a helnuni balh A sc'aied cr~s,~ secliilrial view ,)1 Ihe mariclslal a,~senibly IS '~l.~.i ;dillwn (Fig. I) The dirl'ereril (.3 D h d r m a d u r , . . l l u,~ In Iht-' ,Siillrl S l a l f f Phy,;nc', Sl.'~" h(iri, Bl'iaLih,,,I A l i i m l l " RP~,Pall",l'l C P r l l r P , B~lmb,.ty 4 0 0 ('1['15 a n d B A Ri:lln,:llTI i'; ,:ll Ihl-, ' r ~ l a Irl~JllUlt-, i'll F u n d d m P r i l a l RPsPdrCl'l, H o m l Bl'iall:lha Rilal'l, B O l T i b a y 4 0 0 0(.)5, I n d i a Wi)ll~ rli-iriP ,il ll'l# rall-i I n ~ l l l u l e o l FIJrld,:imtt.lll,.tl Re,,l~artl'l RPl.'L=lvPq~J 7 J l l n e 1978 --~, •
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CRYOGENICS
OCTOBER
1978
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chal,aclerlslleS l,ema.ln consl,a.rit Io wllhirl -~ () 2'~%(le a spread ol less lhan ().'~ mmts ubserved m tlle crll.cal currenl' readm~:4 ¢~n l,ine ~-I' rect~rdel, wilde Ihe cn(~,.",d cul,renl reading ,Iself curresponds Io 200 mm on Ihe l,ec~rder)
= It(n)
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where Ic(o ) ,s the exl~'apolaled zero lernperatul,e cnhcaJ ClJlrelll and T c, L',;lhe bulk Iransilion lemperalul,e ol lhe bridge malerr, d DtflelenlmlJrtg the above equalmn and rearrarl~ng we gel,
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± LIL)8 ~'~,
'T'hu.s, lhe syslern ,..'~mlrols temperature to belier lhari ±1.1 I%
Fur long superctmducLmg proxJmily el lecl bndges, the espenrnenlal]y i~bserved cnhca.I currenl deper~dence or1 leml.'~eralul,e (T) Is of file form ,4
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Conclusion Irl :,;uml,nary, a sunple derliulJrllable alJi~mla[iL' pre~.,;aJre cemlroller nnc(i,rpol,almg u Ibm p,~iyeslel, I'nLrn us a dn,aplira~n and acluevmg a tempel,al,ure sl.',hfl,lv ~I belier lhan +- (.I I% m lhe range or lempel,alures sludled has been SlJt'L'eSSlIJIIy labru.'aled and used l'(~r lemperalure u'onlrul in lhe range I.,~ K l~,4 2 K
'
where (aT~T) is a nalural measul,e ol Ihe lemperalure slabddy
T'he .',ulh~,l,s lharLk J M M~',,..'IIellot l,elplul ¢~rl,eSl.',mdenee ..'rid S (." Agrawal l~r drautdlhng assmlan,,.'e
For a typical ,sample w]lh ~¢ = 3 0 K and a spread in Ihe cnhcaJ c,urrenl ol less titan t 11 25%, m Ihe range of lemperalures sludled (I S K '....,. T ,.., 3 L) K), lhe lemperalure stabdily wfl.l be a ram,mum a[ T = I ';, K 'T'h,,sm,n,mum vaJue is esllmaled iJSln~-~(2)
Reterences Gdmiml, R. ,4null,lwMChem ~?,(Iq~l) 1~'7 Walke., E.J. Rel, .¢,¢'tInstn+m }0 (19'~q) 8 ~14 Kaetlman, Ret, S¢'t Ins/nnn t.~ t 19h,J)Tdq Nolar~s,H.A.,Metcereau, J.E..I.4PldPhrs44 (I~1"t) IN21
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Simple level detectors, depth gauges and demonstrations of superconductivity based on In Pb covered manganin wire D.S. McLachlan Aller a ~..'onslderable amuunl. ~f IpJuble wilh level detechtrs and deplh gauges in me.lal dewars, [he Physics Deparlmenl i~,l lhe W,lwalel,sl,and Lln,vefs, ly has solved all lhelr pr~blems wilh SUTIpIe devlL'es/cUClJltS wluch IlSe In Ph ,,.'(wered marlganm Wll,e, t as lhe level deteclol, Siimlar devt,..'es r~)rnprlsmg manganm wil,e covered wlth l,n lead s~)Ider were found n . l [o perh~nn us well, needmg higher ~.'urrel,tl rlerlstltes (l',~wer d,ss, p.',l,on) and tf ll,e currenl was ri~l o)rreclly sel, file deptl~ gauges were lourld Io be lwslerelic
i
T'he wire ts prepared by stretching fhe requil,ed length ~I ....l~ ~,alJI.~,c( ( ) 12 mm) rnanganm wil,e, slrtppmg l,he insul.',l,~m and coalmg lhe wIl,e wllh a IJ'~in layer ,,d 'Fluxtle' pasle hel~re runn,ng a soldenng mm wilh a small h l . h of nl, dh;'n In Ph (~()% 2()% by welgh[, T,.. -" 4 ~ K'):,,tddel, ahmg ils lenglh SIJrh .', wtl,e wdl be driven rl(irTrl.',l lusl ab~we l,he hehum hy a conslanl L'lJl'l,eril i~l ahoul Ill0 mA or more 'The reslslarwe ol a length t~l such wire is lyptc',..dly h3 £Zm-a al r~,~m lernperalure and 6(J ~"t,m~ al '7'7 K T h e level d e t e c t o r / s u p e r c o n d u c t i v , W
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A ;,u'hemalir dta~arn ~1 Ibis device is,q.~wn in F"tg I 'The wlre is w~lJnd 111a lhreaded (2()lhl,eads per rm) phaslt,..' h~rnler (.)he erld L~I' lhe wil,e ,,.; soldered h~ the slamless sleel slJpp~rl llJbe and lhe (dher h~ a ."I(~gauge copper wire wlm:l'i l.~..,:~.'.,esd~wrl lhe Intddh: ~)I lhe SLil)I.u~rl tuhe ..'rid lhr~,JpJi D B,'h L,:lchl,,;Irl I', A % o ( I d l P Pluh.-'!,!.~r ,Jrll,J Fh-',.q::h-'l III L o w 1"qJrrll'lPrdlUrP Phv,+I4 ,,, I.')Pl:ldr IITIPI'l1411 lll'l~'+ll:'+, L J l l l V l J r ' ; l l y I)l Ihl-, Wll~N, I h ' r ' ) r d r l d , ,hllh}llrlla,,burq, ?:;(llJnl-i AIrlc,..I Rl,-'l't-,ivl,d ~')1} JlJrlt ~ 1,97L'1
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C R Y O G E N I C S . OCTOBER 1978
and B.A. Ratnam
The lemperaliJie i~l an apparatus ilrirnersed iii a liquid rPIrngelarll ,'an he r l l i l l r l i l l e d hY nlalrllalrlllll4 a c'illl.~larll vap~liJl pres.~url > i)Vel Ihe hqiJId SlJrlai'e IrE Iheea!.,e ill hqlJid lil'hlJin, hqllld eval'l(llali,~!~ cllilllnlilllJ,~17 a.~ a leSlJII i~l liPill leak.% I r l l ~
lhe
c'~lislal
arid
,~li, In i ) I d e i
hi illalrllaln
c'lln,%lanl
lerllpl£llJIiJle, Ihe vap~liJr has hi hi' puuiped away al lhe saint' tale ,El w h i r h ii is ~,erleraled '|'here are several ,,iinple devlc'e.~i i ~ w h i c h acl'clniphsh lhl.~; hy alJhlm~illcallv adliJ,dlrl~ , Ihe plJil-ipin[. ~, ~rieed .~;ll a,~ hi kl>e[<) Ilie Vllill_ilJl I)iC~l!~lJll* I lin.~,lanl a l ar/ll/ t t e S l l P d V ~ l J e IrE all Ihe.~e devlc~.~, w l m n the pll'S,%lJil > Irl Ihe r[y~lslal ['a.lls I~l iiJ;;l heh~w the liresel relererlce prl..%iJrl `, Ihe operinii[. ~, hi Ihe p u m p is ;~ealed alllt n,, l u l l h e r lire!,slure illii[.i,l.~i ,'ilhlwl>d ill lll'l.'lJI ']"hi ~ rilallli.~ilal dl,!,l.'llheit hi/ K l P i I i l l a n ~ I~r e~,aliiple, l~lliphw.~ a ri.lhhel lhapt-iral.~,[ll , all~,JI I ~ lllnl Ihlck w h i r h , wlleil ll-lt'rt" I!, a plrl'sl, IJle d l i l e l e r i r e ,ll.'rlills II, I;.l(iw~ (ilJI ,iuill I'lhick~ Ihe piJmplrll~ , lirllil.'e
Ilanl..,,es h~rniinT, parl ~1 Ihe nlallll;dal a~senihlv h a w heen inacliirielt Ill hllerance~ b ~ l l e i lharl ± i)I)~ rnm ltlJI I)1 i'llrllrllPll'l,ll b h l w Ill)It ~ Iree bra.~.~ ]"li~ m:illnl.., , .MJrlacl-!, ill Itl~" hip arid rl>lilre Ilari~,e!, ale i'lilll!~lied aller drilhril4, I:ll'tpinll , alid ;;~fldennl..,, and a lhlri l~lllye!ilt'r I'llril ill Ihickne~,~ ah~,ll 2~ Dim i~; applied Ill II-il> t~llislied SUllai'e.~ ill IIle ahllve Ila[il~e.~ II,ilrl),, a l'llrlllrlell.'laJ ,icltiel~ive (kllck I;isl ) al Ihe Idm pl>ril.llie r~ WiIh Iliv diaillira{,,rii valve cipe[i, ~ill Ihal Elicit' i!~ ,l(llne l'lle:~siJrt, ~lrl elllier kllli ~ ~ll the p~lve;dvr Ilhii, Ihe crw_lldal D iliJlrlped d l l w n I~l Ihe item,lied File~.MJre as illdlC;ilt, d hV Ihe ,ib.~,~llule llre~!aJre ~alJl.,,e (L.evhllh:l-Helaeus) arid when Ibis, i!, r~;/ctied, Ilie valvP is rhls~-d ~i Ihal Ihe t'llrrec'l lelelelll e ple,,,,i/[~ ~ i.~ luapp~>d in Ihe sl~ac'e ahovl, Ilie p~lve.~l~r rllnl arid Ilie Ii~hlJin fl~!~P[Vl)l[ 'T'ht' plJiiil~ htlweve[ t'i)illlrllJt'.~ Ii) Ir~ arid reduce Ihe rlres.~ure, hul Ihe p~llve~ler rilrri bt'cau.~e el IIll.~ [.lll.%lllVe dlllererilla] iJlef~.%lJrP al')lwe Ilie lilrri, ~,eal.~ Ihe llrillceS tlirlliJl.,,h w h i c h [_liJniplrl~ lakes plare
Irl Ilil~ paper wl' de~,clilie a ~;Inlph > d e n l ( l u n l a h l e iii.iliql~dal whll.'h w(nk!i lln a Sllnlla[ l-illlic'lple biJl eiilphW.k a lhlrl polve.~ier rilni iiilile'ad ~ll Ihe c'llnVellll(irra] iiJhher diarlliralT, n-i B Y V l l i l J e ' I)l i l k l . ' o r l S l l l J l . ' h o r l , lhere Ill rile t)ercepIihle [.iIC,~ISUle I]iJl'llJalillrl and leniperaiure slahllilie~ ~ll belier Ihan ! (.) I"i, iii lilt" [.'ill~,P i_ll l e l n p e l a i u l l % I ~ K hi ,-I ~ K all ~ rt'adil 7 al'hlPved 'T(ililOrllhtr lilt' lelnperlillJle.Mahllll 7 ill Ihe nlanlt.slah'd balh we have used Ihe l e p e a l a b l h l y ill crlhl'al culreril;~ qll lllril4 .%lperr(~uidiJr llrlT, pr~lXUTIIly el leci h l l d g e , % , 'l III !.;iJl'ceh!,lVe C ' l J r r e r l l ~weeps, as Ihe C i l l e F I l l r l Ilil lelnrlelallJli' s l a b i h i y
N~lw when Ihe rlle.%~ilJle irl the C'l-Vll.~lal [i.~e~ abtlvl, Ihe relererlce pre.s.~ule lhe I'lhn bows liul .llhlwlrig Ihe piJlnll Ill il'diJi,'i' lhe p[essure ~irice Ihe re.~ilirlng I~ircl-;, irivi~lved nri li-le.~e prore.~:le:; are .~rrlaJI [lie rile.~iMJre l'luCllJalllirls are ,'nl:,~l) ,~mall rau:~ui~, a w~ry h i l l !dabnhly ~1 Ihe vapour pr~,,,,:;ure We have ~bsel'ved Iliai there is n~ pelceplible I l u c i u a l l l m irl rlres,',,ure as indll.'aled by Ihe steady leadinl~ ol Ilie p(~mler ,Iri the pres,~iJre J.;aIJge
Experimental
Estimation
detail
The currenl w dta~.~,e (/ I,r) characlermlnc!¢ ~ll ~ u p e r o m d u e l n n g (Ag,-Srl) pr~lxnrriily e l l e c l hridl~;e.~ rei.'~rded llii an v I' p h l l l e r as II'le clJrrerll ihrout.~,h the l,,iJpc-rcondlJ~,'lur i.~ '4wepl h.lr SlJi.'t'es,~ive sweeps al a c¢~nslarll rele[erlce ple.'4,~aJre have been used Io esliniaLe lhe lelnpefature slabnhly ill' lhe inamlslaled halh When llie valves arid c~uplirigs ~ri lhe .~y.~lem are perleelly leak l~ghl, we ,ibserv~ Ella[ the ~.'rille;d rurreri[s I¢ (viz [he nia.ximum 'zero willat~,e currents) (El these hridge,~ ;.iI cormlanl pressure as ubser~ed ~in sueee.~snve I l.'
Fig I ,sli,~ws the irianli.~lal c~ml'~giJratiuri used m uur experirrierll,S hlr auh~rriallc c o n l r , d or Ihe vap¢,Jr pre,~sure llvel a helnuni balh A sc'aied cr~s,~ secliilrial view ,)1 Ihe mariclslal a,~senibly IS '~l.~.i ;dillwn (Fig. I) The dirl'ereril (.3 D h d r m a d u r , . . l l u,~ In Iht-' ,Siillrl S l a l f f Phy,;nc', Sl.'~" h(iri, Bl'iaLih,,,I A l i i m l l " RP~,Pall",l'l C P r l l r P , B~lmb,.ty 4 0 0 ('1['15 a n d B A Ri:lln,:llTI i'; ,:ll Ihl-, ' r ~ l a Irl~JllUlt-, i'll F u n d d m P r i l a l RPsPdrCl'l, H o m l Bl'iall:lha Rilal'l, B O l T i b a y 4 0 0 0(.)5, I n d i a Wi)ll~ rli-iriP ,il ll'l# rall-i I n ~ l l l u l e o l FIJrld,:imtt.lll,.tl Re,,l~artl'l RPl.'L=lvPq~J 7 J l l n e 1978 --~, •
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CRYOGENICS
OCTOBER
1978
001 '1-2275/78/100617-02
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$02.00
b - rndn(l~=l.~l L ' ( i n l l q u r a l l ¢ l n
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chal,aclerlslleS l,ema.ln consl,a.rit Io wllhirl -~ () 2'~%(le a spread ol less lhan ().'~ mmts ubserved m tlle crll.cal currenl' readm~:4 ¢~n l,ine ~-I' rect~rdel, wilde Ihe cn(~,.",d cul,renl reading ,Iself curresponds Io 200 mm on Ihe l,ec~rder)
= It(n)
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where Ic(o ) ,s the exl~'apolaled zero lernperatul,e cnhcaJ ClJlrelll and T c, L',;lhe bulk Iransilion lemperalul,e ol lhe bridge malerr, d DtflelenlmlJrtg the above equalmn and rearrarl~ng we gel,
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'T'hu.s, lhe syslern ,..'~mlrols temperature to belier lhari ±1.1 I%
Fur long superctmducLmg proxJmily el lecl bndges, the espenrnenlal]y i~bserved cnhca.I currenl deper~dence or1 leml.'~eralul,e (T) Is of file form ,4
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Conclusion Irl :,;uml,nary, a sunple derliulJrllable alJi~mla[iL' pre~.,;aJre cemlroller nnc(i,rpol,almg u Ibm p,~iyeslel, I'nLrn us a dn,aplira~n and acluevmg a tempel,al,ure sl.',hfl,lv ~I belier lhan +- (.I I% m lhe range or lempel,alures sludled has been SlJt'L'eSSlIJIIy labru.'aled and used l'(~r lemperalure u'onlrul in lhe range I.,~ K l~,4 2 K
'
where (aT~T) is a nalural measul,e ol Ihe lemperalure slabddy
T'he .',ulh~,l,s lharLk J M M~',,..'IIellot l,elplul ¢~rl,eSl.',mdenee ..'rid S (." Agrawal l~r drautdlhng assmlan,,.'e
For a typical ,sample w]lh ~¢ = 3 0 K and a spread in Ihe cnhcaJ c,urrenl ol less titan t 11 25%, m Ihe range of lemperalures sludled (I S K '....,. T ,.., 3 L) K), lhe lemperalure stabdily wfl.l be a ram,mum a[ T = I ';, K 'T'h,,sm,n,mum vaJue is esllmaled iJSln~-~(2)
Reterences Gdmiml, R. ,4null,lwMChem ~?,(Iq~l) 1~'7 Walke., E.J. Rel, .¢,¢'tInstn+m }0 (19'~q) 8 ~14 Kaetlman, Ret, S¢'t Ins/nnn t.~ t 19h,J)Tdq Nolar~s,H.A.,Metcereau, J.E..I.4PldPhrs44 (I~1"t) IN21
i 2
4
Simple level detectors, depth gauges and demonstrations of superconductivity based on In Pb covered manganin wire D.S. McLachlan Aller a ~..'onslderable amuunl. ~f IpJuble wilh level detechtrs and deplh gauges in me.lal dewars, [he Physics Deparlmenl i~,l lhe W,lwalel,sl,and Lln,vefs, ly has solved all lhelr pr~blems wilh SUTIpIe devlL'es/cUClJltS wluch IlSe In Ph ,,.'(wered marlganm Wll,e, t as lhe level deteclol, Siimlar devt,..'es r~)rnprlsmg manganm wil,e covered wlth l,n lead s~)Ider were found n . l [o perh~nn us well, needmg higher ~.'urrel,tl rlerlstltes (l',~wer d,ss, p.',l,on) and tf ll,e currenl was ri~l o)rreclly sel, file deptl~ gauges were lourld Io be lwslerelic
i
T'he wire ts prepared by stretching fhe requil,ed length ~I ....l~ ~,alJI.~,c( ( ) 12 mm) rnanganm wil,e, slrtppmg l,he insul.',l,~m and coalmg lhe wIl,e wllh a IJ'~in layer ,,d 'Fluxtle' pasle hel~re runn,ng a soldenng mm wilh a small h l . h of nl, dh;'n In Ph (~()% 2()% by welgh[, T,.. -" 4 ~ K'):,,tddel, ahmg ils lenglh SIJrh .', wtl,e wdl be driven rl(irTrl.',l lusl ab~we l,he hehum hy a conslanl L'lJl'l,eril i~l ahoul Ill0 mA or more 'The reslslarwe ol a length t~l such wire is lyptc',..dly h3 £Zm-a al r~,~m lernperalure and 6(J ~"t,m~ al '7'7 K T h e level d e t e c t o r / s u p e r c o n d u c t i v , W
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A ;,u'hemalir dta~arn ~1 Ibis device is,q.~wn in F"tg I 'The wlre is w~lJnd 111a lhreaded (2()lhl,eads per rm) phaslt,..' h~rnler (.)he erld L~I' lhe wil,e ,,.; soldered h~ the slamless sleel slJpp~rl llJbe and lhe (dher h~ a ."I(~gauge copper wire wlm:l'i l.~..,:~.'.,esd~wrl lhe Intddh: ~)I lhe SLil)I.u~rl tuhe ..'rid lhr~,JpJi D B,'h L,:lchl,,;Irl I', A % o ( I d l P Pluh.-'!,!.~r ,Jrll,J Fh-',.q::h-'l III L o w 1"qJrrll'lPrdlUrP Phv,+I4 ,,, I.')Pl:ldr IITIPI'l1411 lll'l~'+ll:'+, L J l l l V l J r ' ; l l y I)l Ihl-, Wll~N, I h ' r ' ) r d r l d , ,hllh}llrlla,,burq, ?:;(llJnl-i AIrlc,..I Rl,-'l't-,ivl,d ~')1} JlJrlt ~ 1,97L'1
618
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C)OI 1-2275/75/'1006'18-02 $02.00 (C) 1978 IPC Bu!;mes!; P r e , , ; ;
irl I h P IP,~ I d - F l a ~ , h l : q h l ,;IPPI l u h P , rl - I I , J , ; h h g h l h - I')rd,,,, ~,L'[I.-'W, I - 3 b Iri P b L,il~ln{~l,:l iTh..Irl!,:lanlll
C R Y O G E N I C S . OCTOBER 1978