Superconducting Magnet Division High Temperature Superconductor (HTS) Magnet R&D and Designs
Ramesh Gupta Superconducting Magnet Division Brookhaven National Laboratory
US Particle Accelerator School University of California – Santa Barbara June 23-27, 2003
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 1 of Lecture 11 Ramesh Gupta, BNL The Conventional Low Temperature Superconductors (LTS)
Superconducting and the New High Temperature Superconductors (HTS) Magnet Division Low Temperature Superconductor Onnes (1911) Resistance of Mercury falls suddenly below meas. accuracy at very low (4.2) temperature New materials (ceramics) loose their resistance at NOT so low temperature (Liquid Nitrogen)! High Temperature Superconductors (1986) Resistance (Ohms) Resistance
Temperature (K)
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 2 of Lecture 11 Ramesh Gupta, BNL Popular HTS Materials of Today Superconducting Magnet Division
•BSCCO 2223 (Bi,Pb)2Sr2Ca2Cu3Ox •BSCCO 2212 •YBCCO
•MgB2 is technically a low temperature superconductor (LTS) with critical temperature ~39 K.
Of these only BSCCO2212 and BSCCO2223 are now available in sufficient quantities to make accelerator magnets.
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 3 of Lecture 11 Ramesh Gupta, BNL Another Remarkable Property of HTS Superconducting The High Field Current Carrying Capacity Magnet Division
Superconductor Critical Currents DeDe ce ce mbe mbe r r12 12thth20022002 - - Compiled Compiled by by Peter Peter J.J. LeeLee -- jcprog_02bl.ppt, jcprog_02bl.ppt, jcprog_02.xlsjcprog_02.xls Superconductor Critical Currents Legend on next slide 100,000
At 4.2 K Unless R vs. T Otherwise Stated Compare J Vs. B c Nb-Ti Multilayer YBCO µbridge H||c between the 10,000
conventional Low 2212 Tape YBCO HTS Temperature 75 K H||a-b Nb Sn Internal Sn Nb3Sn 3 2212 Round wire Superconductors 1,000 ITER 2223 Tape B|_ 2223 Nb Al 3 Nb Sn Tape (LTS) and High Tape B|| ITER 3 from (Nb,Ta) 6 Sn 5 2 Temperature Nb-Ti HT 1.8 K Nb3Al RQHT+Cu Critical Current Density, A/mm² Density, Current Critical Nb-Ti-Ta
Superconductors 100 Nb-Ti APC 1.8 K YBCO Nb-Ti
(HTS) , A/mm 75 K H||c
c MgB2 Film J PbSnMo6S8 Nb3Sn 1.8 K Bronze
10 0 5 10 15 20 25 30 University of Wisconsin-Madison Univers ity of Wis co ns in-Madiso n Applied Field, T AppliedApplied SuperconductivitySuperconductivity CenterCenter Applied Field, T
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 4 of Lecture 11 Ramesh Gupta, BNL Advantages of using HTS Superconducting Magnet Division in Accelerator Magnets
As compared to LTS, the critical current density (Jc ) falls slowly • as a function of field • as a function of temperature Translate this to magnet design and accelerator operation: • HTS has a potential to produce very high field magnets • HTS based magnets can work at elevated temperatures • a rise in temperature from, e.g., decay particles can be tolerated • the operating temperature does not have to be controlled precisely • HTS based magnets don’t appear to quench in the normal sense •Weak spots don’t limit the magnet performance, instead the local temperature rises a bit (major difference from LTS magnets). It becomes a question of heat load rather than a weak spot limiting the performance of the entire magnet
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 5 of Lecture 11 Ramesh Gupta, BNL Challenges with HTS Superconducting (and the way they are being addressed) Magnet Division • HTS materials are very brittle Work on magnet designs => make “conductor friendly designs”. • HTS materials are still very expensive Cost/Amp is coming down continuously, primarily because of the improvements in performance. Also for some applications, the performance and not the material cost should be the main consideration. One must consider the overall system and operational cost. • Large quantities are not available Situation has significantly improved. We purchased 1.5 km long wire. The tapes are available in similar length. Now we can make coils and magnets having reasonable length. The technical question is controlling the temperature of reaction furnace to ~1/2 degree at 880o-890oC over the entire reaction volume.
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 6 of Lecture 11 Ramesh Gupta, BNL Possible Applications of HTS Superconducting Magnet Division in Accelerator Magnets High Field, Low Temperature Application Example: Interaction Region (IR) Magnets for large luminosity upgrade or very high field main ring dipoles to achieve highest possible energy in existing given tunnel. • At very high fields (>15 T), no superconductor carries as much critical current density as HTS. Medium Field, Higher Temperature Application Example: Quads for Rare Isotope Accelerator (RIA) • The system design benefits enormously because the HTS offers the possibility of magnets to operate at higher than 4K, say at 20-40 K. Special Benefits of HTS • The HTS can tolerate a large increase in temperature in superconducting coils (caused by the decay particles) with only a small loss in performance. • Moreover, the temperature need not be controlled precisely (Think about an order of magnitude relaxation in temperature variations, as compared to the LTS used in current accelerator magnets).
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 7 of Lecture 11 Ramesh Gupta, BNL Expected Performance of Superconducting HTS-based Magnets Magnet Division
Performance of 0.8 mm dia wire Expected performance of all Nb Sn As of year 2000 3 10000 or all HTS magnets at 4.2 K for the same amount of superconductor: BSCCO2212 (4.2K) Year 2000 Data
All Nb3Sn All HTS 1000 Nb3Sn (4.2K) 12 T 5 T
Jc(A/mm2) NbTi (4.2K) 15 T 13 T 18 T 19 T* NbTi (1.8K) *20 T for Hybrid 100 0 2 4 6 8 10121416182 0 Near Future All Nb3Sn All HTS B(T) (performance in ~100 meter or longer lengths) 12 T 11 T 15 T 16 T Year 2000 data for Jc at 12 T, 4.2 K 2 18 T 22 T Nb3Sn: 2200 A/mm BSCCO-2212: 2000 A/mm2 Cu(Ag)/SC Ratio
Near future assumptions for Jc at 12 T, 4.2 K BSCCO: 3:1 (all cases) 2 Nb Sn: 1:1 or J =1500 A/mm2 Nb3Sn: 3000 A/mm (DOE Goal) 3 cu BSCCO-2212: 4000 A/mm2 (2X today) USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 8 of Lecture 11 Ramesh Gupta, BNL First Likely Application of HTS: Superconducting Interaction Region (IR) Magnets Magnet Division Interaction region magnets for the next generation colliders or luminosity upgrade of existing colliders (LHC is existing collider for this purpose) can benefit a lot from: Very high fields Ability to take large energy deposition without much loss in performance Ability to operate at elevated temperatures that need not be uniform
→ For IR magnets, the performance, not the material cost is the issue. → These magnets can be, and perhaps should be, replaced in a few years. (for LHC, the first installment may be due ~10 years from now)
All of above makes HTS a natural choice for next generation IR magnet R&D.
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 9 of Lecture 11 Ramesh Gupta, BNL Construction and Test Results from HTS Superconducting Technology Development Program at BNL Magnet Division
Next Few Slides will Show:
• Results of HTS Tape and Cable Tests
• Construction and Test Results of HTS Coils and R&D Magnets
Please see the tape and cable being distributed
10+ kA HTS Rutherford Cable HTS Wire HTS Tape BNL/LBL/Industry collaboration
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 10 of Lecture 11 Ramesh Gupta, BNL Superconducting HTS Coil Wound by Hand Magnet Division
Al Bobbin (70 mm radius) (also used, Fe, SS and brass bobbins)
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 11 of Lecture 11 Ramesh Gupta, BNL Measured Performance of HTS Cable and Superconducting Tape As A Function of Field at BNL Magnet Division Measurements of “BSCCO-2212 cable” 500 (Showa/LBL/BNL) at BNL test facility Reported Ic in new wires is ~ 3x 400 better than measured in the cable. 300 This was a narrow (18 strand) cable. (A) c I Wider cable with new conductor 200 should be able to carry 5-10 kA current at high fields! 100 BSCCO 2223 Tape Test (self field correction is applied) 4,000 0 3,500 012345678910111213 3,000 Field (T) 2,500 2,000 Measurements of “BSCCO 2223 1,500 //-Low Ic(1.0uV), A //-High tape” wound at 57 mm diameter 1,000 Perp H with applied field parallel (1µV/cm 500 BSCCO 2212 Cable Test criterion) 0 01234567(field perpendicular value is ~60%) H, T USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 12 of Lecture 11 Ramesh Gupta, BNL Critical Current as a Function of Superconducting Temperature & Field Magnet Division
200 Half Coil #1 4,000 180 Half Coil #2 3,500 160 Half Coil #3 3,000 140 Half Coil #4 2,500 120
V/cm) 2,000 µ 100 1,500 //-Low
80 Ic(1.0uV), A //-High Ic(@1 60 1,000 Perp H 40 500 20 0 0 01234567 5 101520253035404550556065 H, T T(K)
For very high field magnet applications, we are interested in low temperature and high field characteristics of high temperature superconductors. However, these conductors still have significant critical current at higher temperature.
Testing at Liquid Nitrogen (LN2) temperature is much more easier than testing at Liquid Helium (LHe) temperatures. BNL has developed and extensively used LN2 testing in HTS cable, coil and magnet R&D.
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 13 of Lecture 11 Ramesh Gupta, BNL HTS Cable and Coil Test Superconducting Magnet Division at Liquid Nitrogen Testing of HTS cables (or tapes) at LN2 is a powerful method even if the cables are to be used in magnets that would operate at LHe temperatures
•LN2 testing is much easier than LHe testing Boiling Point •Yet LN2 testing gives a good indication of Freezing the cable behavior in Point LHe
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 14 of Lecture 11 Ramesh Gupta, BNL BSCCO-2212 Cable “Pancake Coils” Superconducting Magnet Division HTS cable is carefully wound in large radius pancake coil for testing at liquid nitrogen temperatures
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 15 of Lecture 11 Ramesh Gupta, BNL Ic Tracking Between 4.2 K and 55 K Superconducting Magnet Division
Ic of various 3 m sections at 4.2 K and 55 K 1000
100 V/cm µ
Ic for 1 1 for Ic 10
Mix strand cable test, BNL 12/00 Ic1@55K [email protected] 1 01234567891011 Section No.
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 16 of Lecture 11 Ramesh Gupta, BNL Correlation between T and I Superconducting c c Magnet Division T and I Correlation @ 4.2 K and 55 K 74 c c 73 72 71 70 4.2 K 69 55 K
(K) 68 c
T 67 66 65 64 63 Mix strand cable test, BNL 12/00 62 0 20 40 60 80 100 120 140 160 180 200 220 240 260 Ic (A)
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 17 of Lecture 11 Ramesh Gupta, BNL Ic as a function of Superconducting Magnet Division Temperature
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 18 of Lecture 11 Ramesh Gupta, BNL Correlation between T and I Superconducting c c Magnet Division
Better cables (with
higher Ic) also have better Tc
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 19 of Lecture 11 Ramesh Gupta, BNL BNL Measurements of Various Cables from Showa Superconducting (Note: Continuous progress in cable performance) Magnet Division Extrapolated 4 K performance of 20 strand cable (#5) (wire dia = 1 mm) : ~5 kA at high fields and ~9 kA at zero field 400 Ic as a function of T in various Bi2212 cable from Showa (without self field correction) 350 Cable 5 (1 mm) 300 Cable 4 (1 mm) Cable 3 scaled to 1mm
V/cm) 250 Cable 3 (0.8 mm) µ Cable 1 scaled to 1mm 200 Cable 1(0.8 mm) 150
Ic, Amp (forIc, 1 100 Test Dates: Cable 1: 06/00 50 Cable 3: 01/01 Cable 4: 07/01 0 Cable 5: 11/02 55 60 65 70 75 80 T (K)
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 20 of Lecture 11 Ramesh Gupta, BNL Improvement in Tc of BSCCO-2212 Superconducting Cable from Showa Magnet Division Note the improvements both, in the absolute value and in the spread. 6.0 6.0
5.5 5.5 Cable obtained 10 Cable obtained now (Feb. 03) 5.0 5.0 9 ~2 years ago 4.5 8 4.5 Turn-1 4.0 7 4.0 Turn-2 3.5 6 3.5 Turn-3 V/cm) cm
µ sections 8&9
5 V/ Turn-4 3.0 are the worst 3.0 µ ,
4 V Turn-5 2.5 2.5
Voltage ( Voltage 3 Turn-6 2.0 2.0 2 Turn-12 1.5 1.5 1 1 µV/cm Turn-13 1 µV/cm 1.0 1.0 Turn-14 0.5 sections 4&5 are the best 0.5 0.0 0.0 56 58 60 62 64 66 68 70 72 74 76 78 80 80 84 88 92 96 100 104 108 112 Temperature (K) T, K USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 21 of Lecture 11 Ramesh Gupta, BNL HTS Magnet R&D and Superconducting Test Program at BNL Magnet Division HTS Tape Coil Program: • Started ~ 4 years ago • Six 1-meter long coils built and tested 10-turn HTS Cable R&D Program with rapid turn around • Cost effective with rapid turn around encourages systematic and innovative magnet R&D allows many ideas to be tried in parallel •Started ~2 year ago
20 coils with brittle materials (5 HTS, 15 Nb3Sn) built and tested 12T high background field R&D Program • Will address issues related to high field, high stress performance of HTS
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 22 of Lecture 11 Ramesh Gupta, BNL Common Coil Magnets With HTS Tape Superconducting (Field quality in 74 mm aperture to be measured soon) Magnet Division 2.0 ASC Common-Coil Magnet4.2 K
Magnet Voltage Gradient 1.5 Inner Section of Coil #1 Outer Section of Coil #1 V/cm µ
1.0 1µV/cm
Voltage Gradient, Gradient, Voltage 0.5
Current, A 0.0 210 230 250 270 290 310
10 A coil being wound with 0 HTS tape and insulation. -10 IGC
-20
-30 Status of HTS tape coils at BNL Nb3Sn
-40 Size, mm Turns Status Two HTS tape coils in Nb3Sn 0.2 x 3.2 168 Tested -50 IGC 0.25 x 3.3 147 Tested common coil configuration Gauss Field, Dipole Residual -60 ASC 0.18 x 3.1 221 Tested ASC NST 0.20 x 3.2 220 Under construction -70 0 100 200 300 400 500 600 VAC 0.23 x 3.4 170 Under construction Max. Energizing Current Density, A/mm2 USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 23 of Lecture 11 Ramesh Gupta, BNL HTS Cable Magnet Program Superconducting Magnet Division
BSCCO 2212 cable appears to be the most promising high temperature superconductor option for accelerator magnets
• Higher current for operating accelerator magnets •Plus all standard reasons for using cable
HTS Cable A good and productive collaboration has been established between labs (BNL, LBL) and industries (IGC, Showa).
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 24 of Lecture 11 Ramesh Gupta, BNL BSCCO Wire (Year 2000) Superconducting Magnet Division Ic-B characteristics of new wire Showa Electric 700
600 new data conventional wire 500 Jc(12T,4.2K) 400 at 4.2K ~2000 A/mm2 Ic (A) 300 I c (4.2K 0T) : 640A J c (4.2K 0T) : 490kA/cm 2 Size : 0.81mm d 200 Number of filament : 427 Material of outer sheath 100 : Ag alloy Material of inner sheath : Ag Ag/SC ratio : 3.0 0 0246810 Tensile strength (R.T.) : 120MPa Magnetic field ( T )
T. Hasegawa, “HTS Conductor for Magnets”, MT-17, Geneva. 29/05/00 USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 25 of Lecture 11 Ramesh Gupta, BNL Superconducting Vacuum Impregnation Setup Magnet Division
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 26 of Lecture 11 Ramesh Gupta, BNL HTS Coils in Support Structure Superconducting Magnet Division
Coils are heavily instrumented. There is a voltage tap after each turn. Data were recorded from all 26 voltage taps.
Coils are assembled for the most flexible and extensive testing. Four leads are taken out of the cryostat. During the test the coils were powered separately and together in “common coil” and “split-pair solenoid mode”.
Two Hall probes (between the two coils and at the center of two coils) also recorded the central field.
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 27 of Lecture 11 Ramesh Gupta, BNL Performance of Coil #1 and Coil #2 in Common Superconducting Coil Test Configuration in Magnet (DCC002) Magnet Division
Voltage difference between each consecutive turn and on each coil
Measurements in HTS Magnet DCC004 at 4.2 K
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 28 of Lecture 11 Ramesh Gupta, BNL Magnet DCC006: 2nd HTS Dipole Superconducting (Magnet No. 6 in the common coil cable magnet series) Magnet Division HTS Cable Leads to make high temp measurements
Voltage taps on each turn A versatile structure to test single or A versatile structure various configurations double coils in 74 mm aperture to measure field quality Heaters on the magnet to make controlled change in magnet temp 4 thermometers on the coils USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 29 of Lecture 11 Ramesh Gupta, BNL Critical Current in Mixed Strand Cable Superconducting Magnet Division I in ten 3 m long sections at 4.2 K 300 c (non-destructive test) (1uV/cm) 250 (0.1uV/cm) V/cm
µ 200
150 V/cm and 0.1 µ 100
for 1 1 for Mixed strand cable c I 50 (2 BSCCO 2212, 16 Ag) Mixed strand cable tested at BNL prior to winding coil 0 01234567891011 Section No. USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 30 of Lecture 11 Ramesh Gupta, BNL Measured Ic of Various Turns Superconducting Magnet Division Coil #2 of Mixed Strand Cable Turn #1 Turn #2 Mixed strand cable 3.5 Turn #3 Turn #4 (2 BSCCO 2212, 16 Ag) V/cm)
µ 3.0 Turn #5 Turn #6 2.5 Turn #7 Turn #8 2.0 Turn #9 Turn #10 1.5 1.0 0.5 Turn No. 1-7
Voltage Across Turns (Voltage Turns Across 0.0 0 50 100 150 200 250 I(A)
Turns No. 1-7 show an Ic close to the best measured in cable prior to winding. This suggest a low level of degradation. USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 31 of Lecture 11 Ramesh Gupta, BNL Measured Critical Current as a Superconducting Function of Temperature Magnet Division 45 40 200 Half Coil #1 35 180 Half Coil #2 30 25 Half Coil #3 160 20 140 Half Coil #4 15 10 120 5 0 V/cm)
µ 100 45 50 55 60 65 80
Ic(@1 60 40 20 0 5 101520253035404550556065 Mixed strand cable T(K) 4 coil halves (2 BSCCO 2212, 16 Ag) (2 each of two coils)
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 32 of Lecture 11 Ramesh Gupta, BNL Performance of HTS Coil in the Superconducting Background Field of Nb SN Coils Magnet Division 3 Measured electrical Resistance of HTS coil in the background field provided by various Field in various coils Nb3Sn coils in the magnet DCC008R Nb3Sn HTS Nb3Sn Short sample definition for HTS
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 33 of Lecture 11 Ramesh Gupta, BNL Performance of HTS Coil in the Superconducting Background Field of Nb3SN Coils Magnet Division
Performance of HTS cable in coil (before and after winding)
3.5 DCC008R Ic,kA Iss(kA) I(Nb3Sn)=9kA I(Nb3Sn)=6kA 3.0 I(Nb3Sn)=0kA I(Nb3Sn)=3kA Ic Before Winding 2.5
2.0 I(kA) 1.5 Ic After Winding
1.0
I =0kA Nb3SnI =0kA Nb3SnI =0kA Nb3SnI =0kA 0.5 Nb3Sn
0.0 0 0.5 1 1.5 2 2.5 3 3.5 4 H(T) HTS coil was subjected to various background field by changing current in
“React & Wind” Nb3Sn coils (HTS coil in the middle and Nb3Sn on either side) USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 34 of Lecture 11 Ramesh Gupta, BNL Low Field Magnet Applications Superconducting Magnet Division of HTS in Accelerators Medium Field, Higher Temperature Application Example: Quads for Rare Isotope Accelerator (RIA) • These applications don’t require very high fields. • The system design benefits enormously because the HTS offers the possibility of magnets to operate at higher than 4K, say at 20-40 K. • The HTS can tolerate a large increase in temperature in superconducting coils (caused by the decay particles) with only a small loss in performance. • Moreover, the temperature need not be controlled precisely (Think about an order of magnitude relaxation in temperature variations, as compared to the LTS based accelerator magnets).
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 35 of Lecture 11 Ramesh Gupta, BNL High Temperature Superconductor (HTS) Superconducting Quads in Fragment Separator Region of RIA Magnet Division
RIA from BNL/NSCL Collaboration: NSCL Web Site We propose HTS quadrupoles for the first three magnet elements in the RIA Fragment Separator.
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 36 of Lecture 11 Ramesh Gupta, BNL Basic Requirements of Quadrupoles Superconducting for Fragment Separator in RIA Magnet Division
They are the first magnetic elements in the fragment separator for RIA • Required Gradient: 32 T/m in the first quadrupole of the triplet. • This gradient points to superconducting magnet technology. Quads are exposed to high radiation level of fast neutrons (E > 1 MeV) Beam looses 10-20% of its energy in production target, producing several kW of neutrons. A large fraction of above hit the superconducting quadrupole triplet. • This raises several short tem and long term time scale issues. Room temperature, water cooled copper magnets produce lower gradient and/or lower aperture quads. That will lower acceptance and make inefficient use of beam intensity. Also moving quad back and adding more shielding, requires higher gradient and larger aperture quadrupoles. Basically, we need “radiation resistant” superconducting quads, working in a “hostile environment”, where no known magnet has ever lived so long before!
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 37 of Lecture 11 Ramesh Gupta, BNL Short Time Scale Issues Superconducting Magnet Division
Superconducting magnets will quench if large amount of energy is dumped on superconducting coils (over several mJ/g).
In addition, there is a large constant heat load on the cryogenic system : ~ 1 W/kg to the cold mass.
• The temperature increase must be controlled within the acceptable tolerances of the superconductor used.
• The large amount of heat deposited must be removed economically. • HTS appear to have a potential of offering a good technical and a good economical solution with the critical current densities that are available
today (of course, we can always do better with higher Jc). • However, we need to develop magnet technology and prove that the above potential can be utilized in a real magnet system.
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 38 of Lecture 11 Ramesh Gupta, BNL Long Time Scale Issues Superconducting Magnet Division • One must look at the impact on the material properties of such a radiation dose over the life time (estimated 1019 neutrons/cm2 in the region of 0 to 30 degrees in ~12 years ).
• Iron and copper are expected to be able to withstand about ~100 times the above dose.
Note: The normal water cooled electromagnet can not generate the required field gradient.
The development of the radiation resistant superconducting magnet designs & technologies is highly desirable for RIA.
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 39 of Lecture 11 Ramesh Gupta, BNL Significant Reduction in Neutron Superconducting Magnet Division Fluence at Larger Angle Note: A large (almost exponential) reduction in Neutron Fluence at higher angle.
1000
100
n/sr/p 10
1
0.1 Dose (neutrons/sr/particle) 0 102030405060708090 Solid Angle (degree)
NOTE: The radiation dose on superconducting coils can be significantly reduced by moving them outward (larger solid angle).
T. Kurosawa, et al., Phys Rev C, Vol 62, 044615 USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 40 of Lecture 11 Ramesh Gupta, BNL Proposed Alternate Design for the 1st RIA Superconducting Quad in the Triplet of Fragment Separator Magnet Division A Super-ferric design with yoke making significant contribution to field.
Racetrack Coil is at x = 22 cm and yoke starts at Ryoke = 5.5 cm
RIA T1 • Coils are moved further out to reduce A Warm Iron Design with radiation dose. Racetrack HTS Coils • Field lines are funneled at the pole 40 40 to create larger 35 35
gradient. 30 30
• Warm iron 25 25 (cryostat around the coil), to reduce heat 20 20 load on the system. 15 15
10 10
BNL/NSCL Collaboration 5 5
0 0 0 5 10 15 20 25 30 35 40 45 50 55 60
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 41 of Lecture 11 Ramesh Gupta, BNL Insulation in HTS Coils Built at BNL Superconducting Magnet Division BNL has successfully tested several HTS R&D magnets and test coils made with BSCCO 2212 and BSCCO 2223 tape. A unique and very pertinent feature of these coils is the successful use of stainless steel as the insulation material between turns. This technique was developed to provide a strong mechanical coil package capable of withstanding the large Lorentz forces in a 25T environment, but will also provide a highly radiation resistant coil.
S.S. insulation works well with superconductors
Two double pancake NMR coils, one with kapton insulation and the other with stainless steel. HTS Test Coil for an Accelerator Magnet
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 42 of Lecture 11 Ramesh Gupta, BNL Summary and Status of the Alternate Design st Superconducting of the 1 QUAD in RIA Fragment Separator Magnet Division Apart from providing a good technical solution, this design should bring a large reduction in the operating costs.
• HTS Quads can operate at much a higher temperature (20-40 K instead of 4K). •The iron yoke is warm (or at least at ~80 K, which can be cooled by liquid nitrogen). This brings a major reduction in amount of heat to be removed at lower temperature. • The coils are moved significantly outward to reduce radiation dose by a large amount. • HTS can tolerate an order of magnitude higher temperature variations during operation. • The possibility of stainless steel insulation is highly attractive. • It is shown that the field quality requirements can be met.
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 43 of Lecture 11 Ramesh Gupta, BNL Near Term R&D Program at BNL Superconducting Magnet Division
• Build a series of 10 turn coils with better HTS cable
• Build ~40 turn coils after the technology is reasonably developed
• In parallel build ~12 T magnet with Nb3Sn to provide background field
• Assemble hybrid magnet to study issues related to the performance of HTS coils in high field environment
•Study field quality issues related to HTS magnets
Present the results to accelerator community so it can make an informed decision about the viability of HTS in accelerators to take advantage of exciting benefits it offers.
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 44 of Lecture 11 Ramesh Gupta, BNL Cut-away View of the 12 T Magnet Superconducting Magnet Division
Cut-away view of the 12T Magnet
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 45 of Lecture 11 Ramesh Gupta, BNL 12 T Magnet: The Important Next Superconducting Step in HTS R&D Program Magnet Division • At present, HTS alone can not generate the fields we are interested in. HTS COILS •Nb3Sn coils provides high background fields. The HTS coils will be subjected to high field and high stresses that would be present in an all HTS magnet. Therefore, several technical issues will be addressed.
• Since 12 T Nb3Sn magnet uses similar technology (building high field magnet with brittle material), it also provides a valuable learning experience in building an all HTS high field magnet.
LTS COILS • Important design consideration: Allow a simple mechanism for testing HTS insert coils.
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 46 of Lecture 11 Ramesh Gupta, BNL High Field Magnet Designs with HTS Superconducting Magnet Division
10000 Performance of 0.8 mm dia wire NOTE: High Temperature As of year 2000
Superconductors (HTS) are BSCCO2212 (4.2K) uniquely suitable for generating ) Nb3Sn (4.2K) very high fields since, unlike in 1000
conventional Low Temperature Jc(A/mm2 Superconductors (LTS), the reduction in critical current NbTi (4.2K) NbTi (1.8K) 100 density as a function of field is 0 2 4 6 8 101214161820 much smaller at very high fields. B(T)
Applications Under Considerations • Common Coil 2-in-1 Dipole Design for Hadron Colliders • Neutrino Factory Storage Ring/Muon Collider Dipole (and Quads) Design • Interaction Region Magnets (Dipole and Quadrupoles) for High Luminosity Colliders (e.g. for LHC Luminosity Upgrade)
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 47 of Lecture 11 Ramesh Gupta, BNL Operation of HTS Based Superconducting Accelerator Magnets Magnet Division
• HTS based magnets don’t appear to quench in a normal way.
• One (or even a few) weak spot (s) won’t limit the ultimate performance of the magnet. That would only cause the local temperature to rise a bit but the magnet will continue to operate.
• This becomes more a question of the heat load rather than the weak spot limiting the performance of the whole magnet.
• This is a major difference from the LTS based magnets where a single weak spot limits the performance of the entire magnet.
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 48 of Lecture 11 Ramesh Gupta, BNL Superconducting SUMMARY Magnet Division ¾HTS has potential to make a significant impact on the design and operation of future accelerators •HTS can generate high fields •HTS can work at elevated temperature ¾HTS cable and coil testing at Liquid Nitrogen (LN2) temperatures has been found reliable and productive •Good correlation between higher temperature (LN2) and lower temperature testing •LN2 tests are much easier, faster and cost effective ¾New “conductor friendly designs” allow HTS “React & Wind” technology to be incorporated in accelerator magnets
USPAS Course on Superconducting Accelerator Magnets, June 23-27, 2003 Slide No. 49 of Lecture 11 Ramesh Gupta, BNL