HIGH-C

M.Kor

Abstract At each in

low-resistancsuperconductcurrent path surrounding [1]. About extensive caand map thsuperconductno splices wNon-invasivemade at 300sectors. Morsuspect intercwere repaireimperfect ststatistical anremaining wmaximum opextensive int

Types of spThe main

two quadrupsplices in tosplices (Figu

Magnet spdiodes and incurrent decayare not protewith the timwhich is mucircuit – betwat 7 TeV). Tabout 300 pΩresistance of 17 μΩ for the

Individual methods. Unmeasured is taps. A typicor 3 splices, bus containssuperconductthe splices bBusbar excesbusbar minsuperconduct

CURREN

ratzinos, F. R.ScR.H.

nterconnectionce solder joting cables inthrough the copper stabil10,000 such mpaign has b

he resistancesting cable spliere found wite measuremen0 K in 5 of thre precise locaconnects that ed. Howevertabilizer jointnalysis is us

worst-case resiperating energtervention [2].

SP

plices circuits of th

pole (RQ) perotal. Out of

ure 1) and the rplices are pron case of a quys in less than

ected by diodeme constant ouch larger (anween 10 s for The nominal iΩ at 1.9 K, wf 16cm of coppe RB and RQ

splices are nder non-inva busbar seg

cal busbar segwhereas a typ

s 8 splices. Nting temperat

but also the ress resistance nus its noting temperatu

NT BUS STHE OPE

Bertinelli, Zchmidt, A.S.Flora, H.Pf

n between LHoint must bn order to prosuperconductizer in case tjoints exist

been undertaks of these jices were meath a resistancents of the stahe 8 sectors, al measuremewere opened

r, it is likelts still exist sed to placeistances. Thisgy of the LHC

PLICES

he LHC – oner sector – conthese 10,170

rest are magnotected by thuench, heatern a second. Ines and have toof the energynd depends oRQ at 3.5 TeVinterconnect s

whereas at rooper stabilizer ibuses respectmeasurable oasive conditi

gment betweengment for the pical busbar sNon-invasive tures measureesistance of th

(REXC,BB) is tominal resiures.

PLICE RERATIN

Z.CharifoulSiemko, A.feffer, J.Str

HC main magne made betovide a contintor and also tthe cable quen

in the LHCken to charactoints. All of

asured at 1.9 Ke larger than 3abilizer joints

and at 80 Kents were madup, and poor jly that addit

in the LHe bounds on sets limits oC, prior to a

e dipole (RBntain about 240 are intercoet splices. he magnet byrs are fired annterconnect spo withstand cuy extraction con the energyV and 100 s fosplice resistanom temperaturis about 10 μΩtively. only with invions what can adjacent voRB bus contaegment for th

methods at e the resistanhe busbar segmthe resistancestance at

RESISTANG ENER

lline, K.DahVerweij, CE

rait, Fermila

nets a tween nuous to the nches

C. An terize f the K and 3 nΩ. were

K in 3 de on joints tional C. A

n the on the

more

) and 4,000 nnect

ypass nd the plices urrent circuit y and or RB nce is re the Ω and

vasive an be oltage ains 2 he RQ

non-ce of ment.

e of a non-

Figupoor

MeaM

the analyaccidresisprobnommeasvarie

Capropcapathe Resi(16 detec1 mKusing

Elmeaswhic10 m

Ussplicthe m

Thoperseriethe segmRega

NCES ANGY OF T

hlerup-PeterERN, Genevab, Batavia I

ure 1: (a) An inr copper stabil

asurements Motivation for m

19 Septembysis of a circudent yields thestance at 1.9blem. This is

minal splice ressure the resistety of ways: alorimetry [4

perties of heliacity of the syresistive heatstive power amagnets, 350cted using thK/hour/W. REg this methodlectrical: Wsurements usich covers 6 ou

magnet splicessing both metces were foundmagnets were he enhancedrational in 20es of accurate above metho

ment REXC,SC warding magne

ND IMPLTHE LHC

rsen, R.Denva, SwitzerIL 60510 U

nterconnect splizer continuit

at cold measuring splber 2008 acuit test performe value of 2349 K (REXC,SC)

orders of msistance and htance of as ma

4]: taking bium, together ystem at 1.9 Kt released by

as low as 1 W 0 t of cold mhis method.

EXC,SC as low .

We have aling the quencut of 7 magne (RQ). thods, two sigd, one 100 nΩreplaced.

d QPS (nQP009/2010. Opvoltmeters, itds, especiallywhere the accet splice res

LICATIONC

nz, C. Scheuland.

U.S.A.

plice and (b) aty (2D projecti

lice resistanceccident. The med a few da4±15 nΩ [3] f) in the vic

magnitude highas prompted aany splices as

benefit of thwith the ver

K, it is possiby a high-resisin one cryoge

mass, 250 m The temper

as 40 nΩ can

lso performeh protection s

et splices (RB)

gnificant REXCΩ and the othe

PS) system perateed esset has a better ay when meascuracy is bettesistances no

NS FOR

uerlein,

an example of ion).

es comes fromcalorimetric

ays before thefor the excesscinity of thegher than thea campaign tos possible in a

he superfluidry small heatle to measurestance splice.enic subsectorlong) can be

rature rise isn be detected

ed (ad-hoc)system (QPS)) and 6 out of

C,SC in magneter 50 nΩ, and

[5] becameentially as aaccuracy thansuring busbarer than 1 nΩ.value above

f

m c e s e e o a

d t e . r e s d

) ) f

t d

e a n r . e

Proceedings of IPAC’10, Kyoto, Japan MOPEB044

07 Accelerator Technology

T10 Superconducting Magnets 373

25 nΩ has resistances, anywhere inseen is 2.99±couple of REX

REXC,SC ofoperation; hoor a problemresult in a hig

Measuremetemperatur

A copper superconduct(Figure 1) lim[6]. Such a higher than nresistance is 300 K for thethe RB busbgood knowlecopper stabilon the limit 80 K is very the resistanceresistance ofto measure. change in theof an increasby increasing50 μΩ, wherRRRCS incre

Table 1: Fa

Busbar segment

Typre(μ

RB@ 300K 20

RQ@ 300K 11

RB@ 80K 2

RQ@ 80K 15

A substa

resistances w2009 [1]. measurementhand-held de

The overaon the sectorRQ at roorespectively)4-5.5 μΩ for

been found, no REXC,SC

n the machine±0.02 nΩ (RQXC,SC above 2

f a few nΩ poowever it migm with the sgh REXC,BB.

ents at non-res – non-in

stabilizer witing cable bamits the maxim

bad joint mnominal resist

challenging, e RB bus beinar segment reedge of the telizer (RRRCS)of accuracy, difficult. Tab

e measured atf a segment anColumn 4 she segment by se in the crossg the width areas the last casing from 10

actors affectin

pical esis. μΩ)

Typical defect (μΩ)

000 50 (2.5%)

000 50 (0.5%)

270 7 (2.5%)

500 7 (0.5%)

antial effort was undertaken

Measurements) were take

evice in the tunall analysis acr) of 9-17 μΩ om temperatu) whereas at 8r the RB and

whereas forabove 3 nΩ

e. The highesQ circuit, secto

nΩ. oses no problght suggest a soldering pro

-supercondunvasive ith no continadly solderedmum safe eneanifests itselfance at warmwith only th

ng relatively eaesistances at 8emperature an. Measuring twhereas mea

ble 1 shows tht warm, togethnd of a defectows the effec1 K. Column

s section of thand the heightcolumn show00 to 150.

ng segment res

Temp. change +1 K

Xc

7 (0.4%)

40 (0.4%)

8 (2.9%)

44 (2.9%)

to map all n during the pnts (referreden manually nnel in all sec

chieved an acfor the RB anure (about 80 K the accud 6-12 μΩ for

r busbar segΩ has been st splice resisor 23), with o

lems under nostructural pro

ocedure that c

uctive

nuity coupled d to the stabergy of the maf as a splice . Measuring s

he measuremeasy. For meas80 K we neednd the RRR othe RQ at 300asuring the Rhe factors affeher with the tyt that we are tct of a temper

5 shows the ehe copper stabt of the copps the effect o

sistance at wa

Xsection change

RRcha

12 (0.6%) (0.3

85 (0.8%)

4(0.3

2 (0.6%) (2.6

11 (0.8%)

4(2.6

busbar segperiod April tod to as Busing an acc

ctors. curacy (depen

nd 25-36 μΩ fo0.7% and

uracy was betr the RQ (2%

gment seen

stance only a

ormal oblem could

to a bilizer chine with

uch a ent at suring d very of the 0 K is RQ at ecting ypical trying rature effect

biliser er by

of the

arm

RRCS ange

7 3%)

40 3%)

7 6%)

40 6%)

gment o July Biddle curate

nding or the 0.3%

tween % and

0.7%300 80 Kand tsectoin th(whecolumsectocolum10-1

T

CircuSecto

A12 A34 A45 A56 A67

MeaIn

indivinvatheseafterBiddwas contihigh

Thsplic

Figuresis42 μ

WorSin

exist

% respectivelyK but was m

K. Five sectothe worst spliors were meashe RB of the ere accuracy mn shows theor at the 90%mn 4, as the m7 μΩ.

Table 2: recap

uit/ or

Temperatspread (K

RB 1.1 RB 1.9 RB 0.9 RB 0.4 RB 0.6

asurements addition to tvidual interconsively (referre were made fr an indicatiodle measureme70μΩ, whereinuous RB b

hest R16 exceshe gamma-rayce interconnec

ure 2: The intestance. The siμΩ (the other s

rst remaininnce reliable ints only for par

y). This was smarginal for tors were measices were opensured at 80K. T

sectors measis good) af

e estimated hig% confidence measurement

of RB Biddle

ture K)

REXC,BB spread (μΩ)

13 10 17 9 14

at warm – ithe Biddle mnnect splices w

red to as R16following an on of a high ents. The wor

e the average busbar is aboss resistance (Ry picture of

ct can be seen

erconnect witide seen has side measured

ng splice nformation abort of the mach

ufficient for tthe RQ and isured at roomned up and reTable 2 showssured at roomfter the repaghest excess rlevel. This isaccuracy is o

measurement

Highest remaining REXC,BB( μΩ

37 35 53 20 31

invasive measurements,

were opened a6 measuremenopening of an

excess resisst R16 resistaresistance of out 10 μΩ. TREXC,R16) is 60one side of in Figure 2.

th the worst man absolute

d at 28 μΩ).

out the resistahine, a statisti

the RB bus atinsufficient at

m temperatureepaired. Threes the situation

m temperatureairs. The lastresistance in as higher than

of the order of

ts at 300 K

Ω)

REXC,BB 90%CL (μΩ)

51 47 78 34 48

a number ofand measurednts). Most ofn interconnectstance by thence measureda 16 cm-long

Therefore the0 μΩ. that specific

measured R16resistance of

ance of splicesical method is

t t e e n e t a n f

f d f t e d g e

c

6 f

s s

MOPEB044 Proceedings of IPAC’10, Kyoto, Japan

374

07 Accelerator Technology

T10 Superconducting Magnets

needed to estLHC, Rmax. the RB meameasured RE

(sector A45)repairs 53±1is 60±1 μΩmeasurementexponential fnumber of saThis fit predwhich these 0.8 joints abois REXC,R16 >

The next limits on whsample contain the machindication ofsufficient resthey provideand for decidsectors for thmeasurementthe high-currsampling framaximum ex90% confidsystematic efof the form ogiving an ovfrom this anderived, howworst identifsuperconductbusbar segmwas used forthe LHC was

CONSTRThe safe e

worst splice concentratedof the energycalculations can be toler=100) give [τEE=15 s):

• RB: • RQ:

For 3.5 TeV • RB: • RQ:

If the RRRthe above va

However, the 3.5 TeV lsuch large d

timate the woThe only rel

asurements atEXC,BB before r), whereas the5 μΩ (again s

Ω. The cumults can be seenfunction, is camples abovedicts that thedata are a sa

ove 60 μΩ. T82 (106) μΩ. question is hhat remains iains about 2.3hine, they wef the non-invasolution in teed a meaningfding which inthe RB bus. ts represents rent joints in action leads xcess resistandence level: ffects were coof the distribuverall uncertanalysis of thewever, is still fied failure moting cable re

ment). Thereforr subsequent ds Rmax ≈ 90 μΩ

RAINTS Oenergy limit oin the machin

d on one side oy extraction (τof what is th

rated as a fun[6]: For 5.0 Te

43 μΩ 41 μΩ operation (RB76 μΩ 80 μΩ

RCS is 200 inslues increase bif the defect ilimits becomedefects canno

orst possible spiable Biddle

t 300 K (5 serepairs for thee worst remasector A45). Tlative distribun in Figure 3.onstrained to

e 20 μΩ, and e underlying ample, would,The limit for 0

how to use thin the machin3% of the totaere selectivelyasive measure

erms of REXC,Rful basis for lterconnects toIn this case tabout (1/3) xthe machine.to the follow

nce for all mRmax,R16 =

onsidered bothution and the ainty to the ce order of ±1larger than thode (it would emained unsre, a more rea

discussions onΩ.

ON THE LHof the LHC isne and dependof a splice, onτEE ) and on thhe worst singnction of eneeV operation

B τEE=50 s, RQ

stead of the (by 10 μΩ for is split on bote 120 μΩ and t be concentr

plice present ameasurement

ectors). The we RB is 74±1

aining REXC,BB

The worst REution of the The red curvgive the obsefits the data distribution,

, on average, .1 (0.01) bad j

hese data to ne. Althoughal number of jy chosen afteements. TheseR16 (~15 μΩ)locating bad j

o open in 5 outhe sample ofx (5/8) =~ 20 This value o

wing value omain circuits a

98 μΩ. Vah in the estimsampling frac

confidence bo10 μΩ. The he resistance omean that 10coldered fromalistic value w

n the safe ener

HC ENERGs a function os on if the defn the time conhe RRRCS. Detgle-side defectergy (using R

(RB τEE=75 s

Q τEE=10 s):

(conservative)both RB and th sides of a s140 μΩ. In re

rated only on

at the ts are worst

15 μΩ after

EXC,R16 R16

ve, an erved well. from have

joints

place h the joints er an e had , that joints

ut of 8 f R16 0% of of the of the at the arious

mation ction, ounds value of the cm of

m the which rgy of

GY of the fect is nstant tailed t that

RRRCS s, RQ

) 100, RQ. splice eality n one

side comp

Figusplic

Thinterhas bof thwhicof mtargewerestatisin thaccuthe Lposs

[1]

[2]

[3]

[4]

[5]

[6]

of the splicpatible with 3

ure 3: The cumce excess resis

he splice rerconnect splicbeen seen. Th

he high currench the LHC cameasuring splieted repairs e performed istical methodhe sectors thauracy. This defLHC can opeibly, repairs) c

M. Koratzinoof main circwarm”, ATS rF. Bertinelli eSuperconductproceedings.M. Koratzinomain circuitLHC using caL. Tavian etdetection of Sectors”, PAC2009-006. F. Formenti eSystems for thMachine at CFirst OperatioA. Verweij, splices for 7Chamonix 20

ce, therefore .5TeV operati

mulative distristance data.

CONCLUsistance has es and no exc

he quality of tnt circuits of than safely operices in a nonand accurate n part of the

d to estimate tat were not mfines the maxierate before can take place

REFEREos et al., “Meacuit busbar sreport in prepaet al., “Towardting Splices fo

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ured for alle above 3 nΩabilizer jointsthe energy at

ded campaignay as well asmeasurementse have used amaining spliceh the requiredergy at whichrements (and,

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nch Protectionts of the LHCDesign to the

oceedings. for the 13kAdings of the-2010-026.

s

6

l Ω s t n s s a e d h ,

e t

C e

y e

e C -

n C e

A e

Proceedings of IPAC’10, Kyoto, Japan MOPEB044

07 Accelerator Technology

T10 Superconducting Magnets 375