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SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 1
IR Magnets for VLHC
Ramesh GuptaSuperconducting Magnet DivisionBrookhaven National Laboratory
Upton, NY 11973 USA
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 2
Disclaimers
A very limited amount of work has been done on VLHCInteraction Region (IR) magnets.
Consider all designs preliminary and/or conceptual.
All Cosine theta IR quad designs are from Fermilab.
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 3
Design Considerations
There are two classes of magnets:• Main ring magnets
Large numberDesign should be driven by cost
cost is determined by material and labor
• Insertion region magnetsSmall numberDesign should be driven by performance (we can allow bigger cost per magnet)
Material and labor cost does not matterMagnet R&D would determine the cost
♠ Perhaps different design principles should apply to two.
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 4
Energy Deposition Issues
Consider energy deposition issue as an integral part of the magnetdesign. Need feedback before going too far.
Do we need liner? If yes how big?
Does open midplane magnet design help? If yes, how much?
We considered open midplane in an early days of LHC quad design.However, preliminary energy deposition calculations suggested that thesecondary bombardment was also serious. Revisit the issue again.
If open midplane helps then how much do we compromise in gradient(specially if significant number of turns are removed from midplane)?What is the impact of that on IR design (optics, geometry and magnets)?
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 5
IR Magnets for Stage 1 and Stage 2
Stage 1Use present conductor technology for determining magnet design except forsome small projected improvements (for example, 3000 A/mm2 Jc in Nb3Sn).But feel free to be innovative in magnet design.Stage 2Stage 2 is 25 years away!Expect major improvements in superconductor and magnet technology.For example, consider HTS based magnets.
It is not realistic not to assume progress in this period.
Design IR accordingly.But if designs and expected performance are too aggressive;please have a fall back solution, just in case!
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 6
Stage 1 Low ββββ IR Quad
The following information is from VLHC Design Study Report.
Main features/requirements of the quadrupole design:Design gradient: 300 T/mAperture: ~80 mmMaximum beam separation within quad: 12.5 mm
Design gradient: 300 T/m with two layersAperture: 85 mmNb3Sn Jc: 3000 A/mm2Mechanical Design: An upgraded version of LHC IR quad design by FNAL
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 7
IR Magnets for Stage 2
Two type of optics:Flat beam and round beam.IR design depends significantly with the optics chosen.
In round beam optics, the magnetic polarity of the first quad must be the samefor the two counter-rotating beams.
Beam can pass through the same quadrupole, but allow beam to separate.
In flat beam optics, the magnetic polarity of the first quad must be opposite forcounter-rotating beam.
This means that we need separate quadrupoles for the two beams.
Separation between the two magnets is an important parameter•Determines the field in the first beam splitting dipole•Determines the increase in beta function and influences the beam size•Determines the field strength needed for all IR dipoles
�Worthwhile to look for alternate magnet designs
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 8
A Guide to the Maximum Field in the 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 4.0
t(dipole), t/a [quad]
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
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 9
Quadrupole Gradient for various coil radius
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
re
Important number is field: Gradient * coil radius = pole-tip field
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 10
IR Magnets for Round Beam Optics
The following information is from VLHC Design Study Report.
IR quadrupoles are double bore magnets with the same cross section as arc quads.Length of the magnet is adjusted to get the desired integral strength.
Design gradient: 400 T/mAperture: 60 mm
Note: These may not be the final parameters.
First beam splitting dipole (D1) is similar to the second generation IR 80 mmaperture 10 T dipole being built at the University of Twente.
Stage 2 Interaction Region Magnets
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 11
VLHC-2 IR Layout forFlat Beam Optics
• Optics and magnet requirements (field & aperture) depends crucially on theminimum spacing in the first 2-in-1 IR Quadrupole (doublet optics)• 23KW of beam power radiated from the IP makes this a natural for HTS.
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 12
VLHC-2 Interaction RegionMagnet Design Concept
Conventional 2-in-1 cosinetheta design
+
-
+
-
Panofsky 2-in-1 quaddesign
Spacing depends on the conductorand support structure requirements
ModifiedPanofskyQuad with nospacing
(Bo not zero)-
-
-
+
+ +
Support structure and middleconductor is removed/reduced.This reduces spacing betweentwo apertures significantly.
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 13
VLHC-2 Interaction RegionMagnet Design (Preliminary)
Support structure and middle conductor is removed/reduced. This reducesspacing between two apertures significantly.
Conductor friendly and better field quality design
Bore Tubes
Return conductors
++ +
+
+
++
-
-
- -
-
- -
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 14
Variations of the Q1 Design
We have investigated several variations of the design shown inprevious slide. The conductor configuration (consisted of severalblocks) is changed significantly to improve the field quality. Expectsystem optimization between field field strength, field quality andcorrector design.
One design of particular interest is the case when no conductor ispresent at the midpoint of two apertures.
Decay products from IR clearthe superconducting coils
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 15
Fields in the ProposedDouble-Quad Design
Field contours and field lines
Bx o
n Y-
axis
Bx o
n Y-
axis
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 16
Design Parameters of Insertion RegionMagnets for VLHC-2 Flat Beam Optics
1. D1A has higher field and lower aperture. Lower aperture means lessaccumulated forces. Can be built with Nb3Sn or “BSCCO, Nb3Sn hybrid”.2. The gradient in Q1A is lower due to a superimposed non-zero dipole field.
Designs based on the Nb3Sn and other materials available today.
Table Irx1: Design parameters of VLHV-2 interaction region magnetsMagnet Field Gradient Peak Field Aperture Length TypeD1A 16 T --- ~16.7 T 25 mm 12.1 m 1-in-1D1B 12 T --- ~12.5 T 50 mm 6 m 1-in-1D2 12 T --- ~12.5 T 50 mm 11.1 m 2-in-1Q1A 400 T/m ~11 T 30 mm 12.4 m 2-in-1Q1B 600 T/m ~10 T 30 mm 12.4 m 2-in-1Q2A 600 T/m ~10 T 30 mm 7.9 m 2-in-1Q2B 600 T/m ~10 T 30 mm 7.9 m 2-in-1
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 17
Design Parameters of VLHC-2Insertion Region Magnets
For doublet optics
Notes:1. D1A has higher field and lower aperture. Lower aperture means lessaccumulated forces. Can be built with Nb3Sn or “BSCCO, Nb3Sn hybrid”.2. The gradient in Q1A is lower due to a superimposed non-zero dipole field.
Designs based on the Nb3Sn and other materials available today
Table Irx1: Design parameters of VLHV-2 interaction region magnetsMagnet Field Gradient Peak Field Aperture Length TypeD1A 16 T --- ~16.7 T 25 mm 12.1 m 1-in-1D1B 12 T --- ~12.5 T 50 mm 6 m 1-in-1D2 12 T --- ~12.5 T 50 mm 11.1 m 2-in-1Q1A 400 T/m ~11 T 30 mm 12.4 m 2-in-1Q1B 600 T/m ~10 T 30 mm 12.4 m 2-in-1Q2A 600 T/m ~10 T 30 mm 7.9 m 2-in-1Q2B 600 T/m ~10 T 30 mm 7.9 m 2-in-1
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 18
Design Parameters of Insertion RegionMagnets for VLHC-2 Round Beam Optics
One may like to consider alternate designs for round beamoptics as well.
I believe that the magnet parameters can be pushedupward to help beam optics (Please see the maximumfields on the conductor in the previous table).
• Higher field/gradient?• Larger aperture?• Remove a few turns from the midplane?
In particular, a large radiated beam power from IP makesthese magnets a natural candidate for HTS.
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 19
Expected Performance ofHTS-based Magnets
Performance of 0.8 mm dia wire
0
1000
2000
3000
4000
5000
6000
7000
8000
0 2 4 6 8 10 12 14 16 18 20B(T)
Jc(A
/mm
2)
Nb3Sn (4.2K)
BSCCO2212 (4.2K)
NbTi (1.8K)
NbTi (4.2K)
(as of year 2000)
Expected performance of all Nb3Snor all HTS magnets at 4.2 K for thesame amount of superconductor:
All Nb3Sn All HTS12 T 5 T15 T 13 T18 T 19 T*
*20 T for Hybrid
Year 2000 Data
All Nb3Sn All HTS12 T 11 T15 T 16 T18 T 22 T
Near Future
Year 2000 data for Jc at 12 T, 4.2 KNb3Sn: 2200 A/mm2
BSCCO-2212: 2000 A/mm2
Near future assumptions for Jc at 12 T, 4.2 KNb3Sn: 3000 A/mm2 (DOE Goal)BSCCO-2212: 4000 A/mm2 (2X from today)
Cu(Ag)/SC RatioBSCCO: 3:1 (all cases)Nb3Sn: 1:1 or Jcu=1500 A/mm2
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 20
Issues with HTS
Advantages:• Can work at elevated temperature, for example, in IR region wherelarge energy is deposited from the decay products.• Has potential to produce very high magnetic fields.Challenges:•Large quantities are not available yet
But enough to make test coils. The current trends show that longerand longer length are going to be available in future.
• Unknown field quality issuesWe will be measuring them soon.
One point of view: The performance has reached a level that we can doserious R&D. If short coils/magnets are built and results are promising, itwould have a significant impact on IR region design. So far results areencouraging. Consider this option future magnets, but not near future.
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 21
0
100
200
300
400
500
0 1 2 3 4 5 6 7 8 9 10 11 12 13Field (T)
I c(A
)
Measured Performance of HTS Cable andTape As A Function of Field at BNL
Measurement of “BSCCO-2212 cable” atBNL test facility
Ic is better by over a factor of 2 now.This was a narrow (18 strand) cable.Standard cable will carry much more.
HTS-I-00776-1
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
0 1 2 3 4 5 6 7
H, T
Ic(1
.0uV
), A
//-Low//-HighPerp H
Measurement of “BSCCO 2223 tape”wound at 57 mm diameter with appliedfield parallel (1µV/cm criterion)(field perpendicular value is ~60%)
(self field correction is applied)
Note: Tape and wire haveabout the same area.
Cable Test
Tape Test
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 22
Common Coil Magnets With HTS Cable
HTS cable coil prior to vacuum impregnation
A coil cassette made with HTS cable aftervacuum impregnation and instrumentation
Two coils were tested in Liquid Nitrogen
The HTS cables were from two differentbatches. They behaved differently:
• Different Ic• Different Tc
Based on preliminary analysis, no largedegradation has been observed.
10 Turn HTS Coils at 70 K
0.00.10.20.30.40.50.60.70.80.91.01.11.2
0 10 20 30 40 50Current (A)
µµ µµ V/
cm Coil #1
Coil #2
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 23
Performance of Coil #2 inCommon Coil Configuration
Coil #2 in Common Coil Configuration
-0.10
0.10.20.30.40.50.60.70.80.9
11.11.21.31.41.51.61.71.81.9
2
0 100 200 300 400 500 600 700 800 900I(A)
µµ µµV/c
m
Lead-SS Turn#10
Turn#9 Turn#8
Turn#7 Turn#6
Turn#5- Mid-SS
Turn#4- Turn#3
Turn#2 Turn#1
Coil #2
Coil #2 in Common Coil Configuration
0.01
0.1
1
10
100 1000I(A)
µµ µµV/c
m
Lead-SS Turn#10
Turn#9 Turn#8
Turn#7 Turn#6
Turn#5- Mid-SS
Turn#4- Turn#3
Turn#2 Turn#1
Coil #2
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 24
Summary
A conceptual magnet design and layout has been developed.Consider this a classical example of close interactionbetween magnet designers and accelerator physicists.
Most details are yet to be sorted out.
A significant magnet R&D is needed.
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 25
Dipole Field Vs Coil Thickness(for any coil radius)
0
2
4
6
8
10
12
14
16
18
20
0 5 10 15 20 25 30 35 40 45 50 55 60
Coil thickness mm
Cen
tral
Fie
ld (T
)
Dipole: B=-muo Jo/2 *tQuad: G=-muo Jo/2 ln(1+t/a)t = coil thicknessa = coil readius
Jo=700 A/mm2 at the given field.Need Jc ~ 2000 or more.
Required thickness is independent of aperture
In dipoles, conductor amount is proportional to the aperture size (linear).
Note: The coil thickness is proportional to the field, but the conductor amount is notproportional to the field. The conductor amount is computed/optimized differently.
The curve iscomputed forJo=700 A/mm2.However, Jo is afunction of the field.The curve scalesas Jo.
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 26
Usable current Density in Magnet Design
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
850900
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
SuperconductingMagnet Division
Ramesh Gupta, BNL, @SNOWMASS, 7/3/01Slide No. 27
Support Structure ConsumingExpensive Space
Used in early BNL conceptual design.Mechanical designs of other common coil magnetsare different; but this ugly feature did not disappear.
Internal support at midplane
Is th
is a
dequ
ate Investigate alternate mechanical designs.
Do we need it for field quality purpose?See 80% good field aperture in RHIC D0.
-0.0005-0.0004-0.0003-0.0002-0.00010.00000.00010.00020.00030.00040.0005
-80 -60 -40 -20 0 20 40 60 8
Percentage of Coil Radius
dBy/
Bo
Ave
rage
Fie
ld e
rror
s ~10
-4
up to
80%
of t
he c
oil r
adiu
s