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SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 1 of Lecture II
Superconductivity
Ramesh GuptaSuperconducting Magnet Division Brookhaven National Laboratory
Lecture II
US Particle Accelerator SchoolUniversity of California – Santa Barbara
June 23-27, 2003
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 2 of Lecture II
Basic Superconductivity
An Introduction to Superconductivity
• It will not be a general course onsuperconductivity
•The purpose of this lecture is to give you abrief introduction to the parts that are relevantto designing superconducting acceleratormagnets
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 3 of Lecture II
The SuperconductivityR
RR
=ρ(2
73K
)/ρ(~
4K)
Hig
h pu
rity
copp
er h
as la
rger
RR
R
Resistivity of Cu as a function of Temperature Resistance of Mercury falls suddenly below
measurement accuracy at very low temperature
First observation of “Superconductivity” by Onnes (1911)
Temperature (K)
Res
ista
nce
(Ohm
s)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 4 of Lecture II
Superconducting Accelerator MagnetsA Brief History
1908 Heinke Kemerlingh Onnes achieves very low temperature (<4.2 K)1911 Onnes and Holst observe sudden drop in resistivity to essentially zero
Superconductivity is born !1914 Persistent current experiments1933 Meissner-Ochsenfeld effect observed1935 Fritz and London theory1950 Ginsburg - Landau theory1957 BCS Theory1967 Observation of Flux Tubes in Type II superconductors1980 Tevatron: The first accelerator using superconducting magnets1986 First observation of High Temperature SuperconductorsIt took ~70 years to get first accelerator from conventional superconductors.How long will it take for HTS to get to accelerator magnets? Have patience!
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 5 of Lecture II
Critical Surface of Nb-Ti
What a magnet designer always dreams for ?: A material that remains superconducting at higher temperatures and at higher fields.
Critical SurfaceThe surface on 3-d (J,T,B) volume within which the material remain superconducting.
Operating point of the magnet must stay within this volume with a suitable margin.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 6 of Lecture II
Meissner Effect
A remarkable observation in superconductors:They exclude the magnet flux lines from going through it.
Attenuation of magnetic field andshielding currents in Type I superconductors
Normal Conductor Superconductor
Courtesy: Wilson
Courtesy: Schmuser
Meissner and Ochsenfeld (1933)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 7 of Lecture II
Type I and Type II Superconductors
Type I: Also known as the
“soft superconductors”. Completely exclude the flux lines. Allow only small field (< 0.1 T). Not good for accelerator magnets.
Type II: Also known as the “hard superconductors”. Completely exclude flux lines up to Bc1 but then part of the flux enters till Bc2 Important plus: Allow much higher fields. Examples: NbTi, Nb3Sn
Courtesy: Schmuser
Normal phase
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 8 of Lecture II
Critical Surface ofType I Superconductors
Critical Temperature (K)
Crit
ical
Fie
ld B
c (T)
0.0
0.3
0.6
0.9
Type Isuperconductorsare obviouslyNOT suitable forhigh field magnetapplications.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 9 of Lecture II
Critical Surface of Type II LowTemperature Superconductors (LTS)
• Conductors that are currently being used in building accelerator magnets are Type IILow Temperature Superconductors.• NbTi, a ductile material, has been the conductor of choice so far. All acceleratormachine magnets have been and are being built with this superconductor.• For future high field magnet applications one must turn to Nb3Sn, etc.(higher Bc2).However, Nb3Sn is brittle nature, and presents many challenge in building magnets.
Not shown here: MgB2 (39 K)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 10 of Lecture II
Magnesium Diboride (MgB2)
Magnesium Diboride (MgB2) Discovered in January 2001 (Akimitsu) LTS with Tc: ~39 KA low temperature superconductor with high Tc
The basic powder is very cheap, andabundantly available. The championperformance is continuously improvingin terms of Jc and Bc. However, it is stillnot available in sufficient lengths formaking little test coils.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 11 of Lecture II
London Penetration Depthand Coherence Length
• “London Penetration Depth” tells how field falls• “Coherence Length” tells how does cooper pair density increases
Courtesy: Schmuser
κ = λL/ξGinzburg-Landau Parameter
Nb is type II superconductor
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 12 of Lecture II
Current Transport inBulk Superconductors
Courtesy: Schmuser
Motion of these fluxoids generates heat.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 13 of Lecture II
Nb-Ti Microstructure
A high critical current density microstructure in a conventionally processed Nb-Ti microstructure (UW strand). Courtesy: P.J. Lee (University of Wisconsin-Madison)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 14 of Lecture II
Difference Between the SuperconductorRequirements for Superconducting RF Cavities andSuperconducting Magnets for Particle Accelerators
• For superconducting RF cavities, one needs veryhigh purity materials, with no defects.
• For superconducting magnets, the presence ofcertain defects is essential, as without those defects,it can not stand those high fields.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 15 of Lecture II
Flux Jumping
Initially, when the field is raised, large screening current are generated to oppose thechanges. These current densities may be much larger than Jc which will create Jouleheating. However, these large currents soon die and attenuate to Jc, which persist.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 16 of Lecture II
Instability from Flux Jumping
Courtesy: Wilson
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 17 of Lecture II
Stability Criteria Against Flux Jumping
aC T T
Jc
c
o
o<
−32
( )µ
∆Q heat increases temperature ∆T and reduces Jc by ∆Jc
Calculate if this creates an unstable (runaway) situation?B(x) = Bo - µo Jc (a-x) hφ(x)= Bo x - µo Jc (ax-x2/2) hChange in flux due to change in Jc: ∆φ(x)= µo ∆J (ax-x2/2)hAdditional heat due to flux motion: ∆q = = µo Jc ∆Jc a2/3To first order ∆Jc = Jc ∆T / (Tc-To), thus ∆q = µo J2
c a2 /[3(Tc-To)] ∆T
Total heat to raise the temperature: ∆Q + ∆q = C ∆Twhere C is specific heat per unit volume∆Q = C ∆T - ∆q = {C- µo J2
c a2 /[3(Tc-To)] }∆T = C’ ∆Twhere C’ = {C- µo J2
c a2 /[3(Tc-To)] } is the effective specific heat.For stability condition, the effective specific heat must be positive.This determines the maximum slab thickness “a” for stabilitySimilarly determine condition for filament of diameter r.The computed filament diameter for flux stability in NbTi is < 40 µ; for safety margin use ~ 20 µ.
rC T T
Jc
c
o
o<
−πµ4
32
( )
∫ ∆φ(x) J dx c0
x
Assignment:Go through theexpressions.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 18 of Lecture II
Magnetization Effects inSuperconducting Filaments
Courtesy: Schmuser
The abovemagnetization createspersistent current, amajor issue in SCmagnets.
Persistent current induced magnetization:
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 19 of Lecture II
Persistent Current-induced Harmonicsin High Field (Nb3Sn Magnets)
Courtesy: Ghosh
Measured magnetization (NbTi)Persistent current induced magnetization :
Problem in Nb3Sn Magnets because(a) Jc is higher by several times(b) Filament size is big and gets biggerafter reaction due to sintering
In most Nb3Sn available today, the effective filament diameter is an order of magnitude larger than thatin NbTi. The obvious solution is to reduce filament diameter; however, in some cases it also reduces Jc.
A small filament diameter is important for :• increasing stability• reducing persistent currents
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 20 of Lecture II
Persistent Current-induced Harmonics(may be a problem in Nb3Sn magnets, if done nothing)
Nb3Sn superconductor, with the technology under use now, is expected to generate persistent current-induced harmonics which are a factor of 10-100 worse than those measured in Nb-Ti magnets.
In addition, a snap-back problem is observed when the acceleration starts (ramp-up) after injection atsteady state (constant field).
Measured sextupole harmonicin a Nb-Ti magnet
Measured sextupole harmonicin a Nb3Sn magnet
Snap back
Either reduce the effective filament diameter or come up with a magnetic designthat minimizes the effect of magnetization in the magnets (LBL, FNAL, TAMU).
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 21 of Lecture II
Manufacturing of Nb-Ti Wires
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 22 of Lecture II
A Typical Superconducting Cable
Filaments in an actual cable(Filament size in SSC/RHIC magnets: 6 micron)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 23 of Lecture II
Stability of Superconducting Wire(Wire is Made of Many Filaments)
Filaments not coupled Coupled filaments
A wire composed of twisted filaments
Courtesy: Wilson
Rutherford cable
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 24 of Lecture II
Interstrand Coupling
Courtesy: Devred
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 25 of Lecture II
Influence of Interstrand Coupling
Courtesy: Devred
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 26 of Lecture II
Nb-Ti Alloys at 4.2 K and 1.8 K
Courtesy: P. Lee (U Of W-M)
A Reasonable Assumption:3 T increase between4.2 K and 1.8 K
LHC will operate at 1.8 K; all current accelerators operate at ~4.5 K. All use Nb-Ti.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 27 of Lecture II
Courtesy: Ghosh
Cable Measurement Set-up
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 28 of Lecture II
-20
-10
0
10
20
30
40
2000 3000 4000 5000 6000 7000 8000Is (A)
Vs (µ
V)
LOCALLY DAMAGED CABLE.
SMOOTH CABLE
Nb3Sn Cable in Cu- Channel
Courtesy: Ghosh
n-value:A good indicator ofthe quality of cable.
A lower “n-value” meansa slow transition fromsuperconducting tonormal phase, whichgenerally indicates somesort of damage in thecable.
V ∝ (I/Ic)n
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 29 of Lecture II
The Conventional Low Temperature Superconductors (LTS)and the New High Temperature Superconductors (HTS)
Resistance of Mercury falls suddenly belowmeas. accuracy at very low (4.2) temperature
Low Temperature Superconductor Onnes (1911)
Temperature (K)
Res
ista
nce
(Ohm
s)
New materials (ceramics) loose their resistanceat NOT so low temperature (Liquid Nitrogen)!High Temperature Superconductors (HTS)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 30 of Lecture II
Critical Surface of HighTemperature Superconductors (HTS)
HTS (this example, BSCCO2212) can operate at a temperature much higher than ~4 Krequired for conventional LTS; say 20K (or even more).
Fiel
d pe
rpen
dicu
lar
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 31 of Lecture II
Critical Surface of HighTemperature Superconductors (HTS)
HTS (this example, BSCCO2212) can operate at a temperature much higher than ~4 Krequired for conventional LTS; say 20K (or even more).
Fiel
d pa
ralle
l cas
e is
bet
ter (
low
er d
rop
in J
c)C
.M. F
riend
et a
l., P
hysi
ca C
(199
6)
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 32 of Lecture II
Popular HTS Materials of Today
•BSCCO 2223 (Bi,Pb)2Sr2Ca2Cu3Ox
•BSCCO 2212•YBCCO
•MgB2 is technically a low temperature superconductor (LTS) withcritical temperature ~39 K.
Of these only BSCCO2212 and BSCCO2223 are now available insufficient quantity to make accelerator magnets.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 33 of Lecture II
Applied Field, T
Univers ity of Wis co ns in-Madis o nApplied S uperco nductivity CenterUnivers ity of Wis co ns in-Madis o nApplied S uperco nductivity Center
De ce mbe r 12th 2002 - Compiled by Pe te r J. Lee - jcprog_02bl.ppt, jcprog_02.xlsDe ce mbe r 12th 2002 - Compiled by Pe te r J. Lee - jcprog_02bl.ppt, jcprog_02.xlsSuperconductor Critical CurrentsSuperconductor Critical CurrentsLegend on next s lide
Crit
ical
Cur
rent
Den
sity
, A/m
m²
10
100
1,000
10,000
100,000
0 5 10 15 20 25 30Applied Field, T
YBCO75 K H||a-b
YBCO75 K H||c
Nb3Al RQHT+Cu
Nb3SnITER
Nb-Ti APC
2223Tape B|_
At 4.2 K UnlessOtherwise Stated
1.8 KNb-Ti-Ta
PbSnMo6S8
1.8 KNb-Ti
Nb3Sn Tapefrom (Nb,Ta) 6Sn5
2212 Round wire
YBCOµbridge H||c
MgB2Film Nb3Sn
1.8 K Bronze
Nb-Ti HT
Nb3Sn Internal Sn
Nb3AlITER
2223Tape B||
2212 Tape
Nb-Ti Multilayer
J c,
A/m
m2
Some Remarkable Properties of HTS(High Temperature Superconductors)
Also compare the highfield performance of“High TemperatureSuperconductors (HTS)”as compared to that of“Low TemperatureSuperconductors (LTS)”.
R vs. T
ASC
HTS retainsuperconductivity tohigher temperature
HTS
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 34 of Lecture II
High Field Superconductors
Differences between Low field and high field superconductors:
Low field superconductors (NbTi) are ductile.The coils can be wound without significantly damaging the conductors.
High field superconductors (Nb3Sn and HTS) are brittle!
One has to be very careful in winding coil with these brittle materialor use alternate design to minimize the damage on conductors.
One can also wind the coil before they become brittle (& superconducting) andreact the material after winding to make them superconductor.This is referred to as “Wind and React” technique and it requires everything in thecoil to go through the high temperature (650 C or more) reaction process. One hasto be careful in choosing material, etc.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 35 of Lecture II
Usable Current Densities in Coils
Even though the superconductor may be capable ofcarrying a current density of 3000 A/mm2 or so, only afraction of that is available to power the magnet.
Here is why?• There should be enough copper within the wire to providestability against transient heat loads and to carry the currentin the event superconductor turns normal. Usually coppercontent is more than superconductor. In most NbTi mediumfield production magnets, the maximum current density incopper is 1000 A/mm2 or less at the design field. In high fieldNb3Sn R&D magnets, we are allowing it to be twice that.
• The trapezoidal “Rutherford cable” is made of several roundwire. The fill factor may be 90% or so.
• The coil is consisted of many turns. There must be a turn-to-turn insulation taking ~15% of the volume.
Jc Vs. B curve in NbTi
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 36 of Lecture II
Usable Current Densities in Coils
The example on the right is for aNb3Sn superconducting cablewith Cu/Sc ratio fixed at 1.7.Note that overall current densityin the coil is only ¼ of thesuperconductor current density.
In the example on the right, theoverall current density iscomputed to keep currentdensity in copper at a givenvalue. 0.0
0.10.20.30.40.50.60.70.80.91.01.11.2
0 1 2 3 4 5 6 7 8 9 10
Jsc(kA/mm2)
Jove
rall(
kA/m
m2)
1.01.21.41.61.82.0
Joverall for various Jcu
Jcu=
010002000300040005000600070008000
5 6 7 8 9 10 11 12 13 14 15B(T)
Jc, J
w, J
o (A
/mm
2) Jc (A/mm2)JwireJoverall
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 37 of Lecture II
Usable Current Density in Magnet Design(A case study of Nb3Sn for fix Jcu at quench)
Jsc(12T,4.3K) Jcu(A/mm2)
2500 1500
Cu/Sc Ratio B(T) Jc(A/mm2) J wire (A/mm 2) Joverall6.30 5 9454 1295 9115.18 6 7766 1257 8854.29 7 6431 1216 8563.56 8 5347 1171 8252.96 9 4446 1122 7902.46 10 3689 1066 7512.03 11 3048 1005 7081.67 12 2500 938 6601.35 13 2031 863 6071.09 14 1631 781 5500.86 15 1289 693 488
Scaled from TWCA Insulated
y = -74.64x + 1824.1R2 = 0.9956
700
750
800
850
900
950
1000
1050
1100
10 11 12 13 14 15B(T)
Jove
rall
(A/m
m2 )
A Good "Linear Fit"
Critical Current Density in Superconductor: Jsc(at 4.3 K) Also Wire & Overall Current Densities Normalized for a Given Jcu
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
5500
6000
6500
7000
7500
8000
5 6 7 8 9 10 11 12 13 14 15
B(T)
Jsc,
Jw
ire, J
over
all (
A/m
m2 )
Jsc
Jwire
Joverall
Assignment: Obtain Jwire and Joverall curves for magnet designs at various short sample fields.Assume the (Bc,Jc) relationship above and Jcu to be 1500 A/mm2 at quench.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 38 of Lecture II
A Guide to Choosing the MaximumField in Superconducting Magnets
0.0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
3.6
4.0
0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2 3.6 4.0Coil thickness(dipole),
coil thickness/coil radius [quadrupole]
Rel
ativ
e Fi
eld
(dip
), R
elat
ive
Gra
d (q
uad)
Dipole Field
Quadrupole Gradient
Dipole: B=-muo Jo/2 *tQuad: G=-muo jo/2 ln(1+t/a)t = coil thicknessa = coil radius
To get maximum field keep increasing coil thickness (within practical limit) till you reach themaximum field in the coil where magnet quenches
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 39 of Lecture II
Quadrupole Gradient for various coilradius
0
100
200
300
400
500
600
700
800
900
1000
0 5 10 15 20 25 30 35 40 45 50 55 60
Coil thickness mm
Gra
dien
t (T/
m)
40
35
30
25
20
15
10
Dipole: B=-muo Jo/2 *tQuad: G=-muo Jo/2 ln(1+t/a)t = coil thicknessa = coil radius
Jo=700 A/mm2 at the given field.Need Jc ~ 2000 or more.
Not
e: L
egen
ds a
re c
oil r
adiu
s, n
ot a
pertu
reTh
e pl
ot s
cale
line
arly
with
Jo
(cur
rent
den
sity
in c
oil).
A re
ason
able
rang
e of
Jc
is 4
00-1
000
A/m
m2
Important number is pole-tip field = Gradient * coil radiusIn large aperture magnets, forces become large.
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 40 of Lecture II
Assignment
Assume that a rectangular cable (Non-Keystone, Rutherford cable) ismade of 30 wires (strands). The diameter of each wire is 1 mm. Thewidth of the insulated cable is 17 mm and thickness is 2 mm. Theinsulation on each side of the cable is 0.2 mm. The critical currentdensity of superconductor at 12 T is 2500 A/mm2. The wire has 40 %superconductor and you can assume that the rest is copper.
The magnet made with this cable operates at 12 T. Compute thecurrent density in wire, in insulated cable and bare cable (cablewithout insulation) at 12 T. What will be the current density in copperif the magnet quenches (looses its superconductivity) at 12 T?
SuperconductingMagnet Division
Ramesh Gupta, BNLUSPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 41 of Lecture II
Why Use SuperconductingMagnets in Accelerators?
Use of superconductors in accelerator magnets generate field much higherthan what can be achieved from the normal conductors.
Two major reasons for using superconductingmagnets in the accelerators: Cost advantage
In high energy circular hadron colliders, thesuperconducting magnets reduce the size ofa machine. This usually translate in to areduction in the overall machine cost.Superconducting magnets also lower thepower consumption and hence the cost ofoperating a high energy machine.
Performance advantageIn interaction regions, a few high field andhigh field quality magnets may significantlyenhance the luminosity of the machine. Inthis case magnet costs may be large but theoverall returns to experimentalists are high.
Courtesy: Martin Wilson
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