Strong High-Temperature Superconductor Trapped Field Magnets

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1 Strong High-Temperature Superconductor Trapped Field Magnets M. Muralidhar Superconducting Materials Laboratory Graduate School of Science and Engineering, Shibaura Institute of Technology (SIT) Toyosu, Koto-ku, Tokyo OUT LINE Introduction (importance & improvement of large grain LRE-123) Recent results on critical current density (J c ) (around liquid nitrogen temperature) Summary of Trapped Field Magnets (MMPSC process) Improved Mechanical Performance and its importance for the Industrial Applications Concluding summery

2 Melt-processed high T c bulk superconductor (Large magnetic field (B T ) can be trapped) Permanent magnets : B r 1.5 T under the best condition Superconducting magnets B tr 17 T at about 29 K (Y-123), RTRI B tr 2.6 T at 77 K (Gd-123), SRL B tr 1.5 T at 9 K (NEG-123), SRL B T J c r Trapped magnetic field is proportional to J c and size of the bulk Development of melt-processed high T c bulk superconductor NEG-123 (33 mm) (SRL-ISTEC) Sm-123 (6 mm) (Nagoya University) Gd-123 (14 mm) (SRL-ISTEC)

3 Human Levitation Disk ISTEC-SRL 1991 / 1996 IPHT-JANA 23 RTRI-21 HTS : melt processed YBaCuO melt processed GdBaCuO Cooling : LN 2 LN 2 Processing : in air in air Size : 8% - 4 mm (> 2 pucks) 8% - 25 mm (~ 45 pucks) Performance : >.5 T at 77 K ~ 1 T at 77 K Seeding method : cold seeding cold seeding (batch process)

4 Develop ternary NEG-123 type materials and process to improve the flux pinning capability a 77K (Nd,Eu,Gd)-Ba-Cu-O neodymium, europium, gadolinium mixing ratio (1:1:1) TEM J c [ka/cm 2 ] T=77 K H c-axis H [T] a H irr = 7 T (at 77K, H c-axis) Press Release : July 3 rd, 1998 (SRL-ISTEC) Patent 1998 United States Patent, Patent Number

5 Develop ternary NEG-123 type materials and process to improve the flux pinning capability a 77K (Nd,Eu,Gd)-Ba-Cu-O neodymium, europium, gadolinium mixing ratio (1 : 1.25 :.85) STM Magnetization [emu/cm 3 ] T=77 K H c-axis H a [T] H irr 15 T (at 77K, H c- axis) Press Release : July 17 th, 22 (SRL-ISTEC) Submitted the patent 22

6 DISCOVERY - III Levitation at liquid oxygen (9.2 K)-The new limit for High Temperature Applications (The world first report on magnetic levitation at 9.2 K ) Levitation high-temperature (The world first report liquid applications oxygen magnetic (9.2 levitation K) at the 9.2 new K) limit for (Nd,Eu,Gd)-Ba-Cu-O neodymium, europium, gadolinium with new class of Zr rich nano pinning media Levitation at 9.2 K Press Release : June 27 th, 23 (SRL-ISTEC) Submitted the patent 23 and Submitted the patent 24

7 Develop the critical current density (J c ) around 77.3 K J c (ka cm -2 ) NEG mol% Gd211 (.1% MoO 3 ) H//c-axis 65 K 77 K 87 K 9 K SEM Muralidhar et al., Appl. Phys. Lett., 91 (28) TEM J c (ka cm -2 ) B (T) (.1% Nb 2 O 5 ) H//c-axis 65 K 77 K 87 K 9 K B (T) TEM Elemental ratio note the clouds of < 1 nm sized particles in the NEG-123 matrix NEG/Ba Nd/Ba Eu/Ba Gd/Ba Nb/Ba B1 B2 B3 B4 < 1 nanometer size particles At 65 K tremendous super-currents were achieved, reaching more then 92 ka/cm 2 at and 4.5 T All the J c values presented here are the highest reported so for bulk RE-123 material At the respective temperatures

8 Experiments at liquid oxygen temperature Liquid oxygen is attracted to the magnet due to its paramagnetism Suspension of NEG123 superconductor at 9.2 K The same levitation with large Fe-Nd-B ring magnet

9 Develop the critical current density (Jc) at 77.3 K and higher magnetic field J c [ka cm -2 ] J c (ka cm -2 ) H (T) a T = 77 K H // c-axis H a [T] 3.5 nm STM note the nano-lamellar structure formation with the average spacing around 3 to 4 nm, close to the coherence length (in YBCO (77 K) 4.5 nm) Nanotechnology / Nanopinning can dramatically improve the melt processed LRE-123 material properties at higher magnetic field

10 Research results are covered by front cover picture of Superconductor Science and Technology (Institute of Physics publishing, UK) December 1998 October 21 November 23 March 25 June 26

11 High J c at low / intermediate fields due to secondary phase nanoparticles 2 J c (ka cm -2 ) NEG mol% Gd-211 (1 nm) T = 77 K, H//c-axis Ar-1% O 2 NEG Elemental ratio NEG/Ba Nd/Ba Eu/Ba Gd/Ba Nb/Ba B1 B2 B3 B4 < 1 nanometer size particles J c (ka cm -2 ) H (T) a H//c-axis 65 K 77 K 87 K 9 K note the clouds of < 1 nm sized particles in the NEG-123 matrix Gd-211 Gd H (T) a

12 Development of MgB 2 Superconducting Magnet MgB 2 fabrication Superconducting performance Mg + 2B powder Pressing to disk shape (1, 2, 3 mmφ, 5, 1 mm t ) Heating (in Ar) MgB 2 bulk magnet Railway Technical Research Institute

13 Fabrication of larger MgB 2 bulks 2 mm (~4 g) 6 mm (~36 g) 1 mm (~1 g)

14 Positional dependence of trapped field measured at 3 mm above surface Ideal circle-shape, uniform field distribution with circularity >99%! - suggesting uniform current flow on the whole bulk Weak-link-free uniform current in polycrystal and uniformly distributed natural, nanoscale pinning by GBs. Radial direction Circumferential direction 2 K Trapped field / T y / mm Circularity / % 99% circularity r / mm x / mm T / K

15 Batch I Batch Process: As-Grown Bulk Samples Morphology, and Orientation Batch III 45 mm Batch II 24 mm the four-fold growth facet lines clearly visible on the top surface of all pellets. Which indicate that the crystal growth was perfectly controlled in all positions in the furnace. Railway Technical Research Institute

16 Development of the Train Modal using Bulk LRE-123 Railway Technical Research Institute

17 Development of Permanent Magnet System based on Single Grain Gd-123 Test Result: B z (T) B z (T) x (mm) y (mm) x (mm) y (mm) Magnetized using the Gd-123 annular superconducting PM Magnetized using the 1T superconducting PM Note that both results are almost the same and found that Gd-123 based PM system works very well Railway Technical Research Institute

18 Development of Permanent Magnet System based on Single Grain Gd-123 Summary for the magnetic field strength at center as a function of rings Single bulk Two bulks.75 T 1.32 T Three 1.62 T bulks Four bulks 2.2T magnetic field[t] Layer Note that one can make desired permanent magnet system adjusting the ring magnets. Railway Technical Research Institute

19 Development of Permanent Magnet System based on Single Grain Gd-123 Top cover Sample holder removed from 1 T magnet LN 2 Inner FRP vase Sample holder HTSC annular magnet Magnetizing bulk RE-123 Outer FRP vase Compact, lightweight, movable PM system Based on Gd-123 material M. Tomita et al., J. Appl. Phys 19 (211) Liquid nitrogen feeding HTSC annular magnet Bulk RE-123

20 Importance of new process and formation of plate like crystals Endo T Exoth Normal process 2 REBa 2 Cu 3 O y RE 2 BaO 4 +3BaCu 2 O 2 polycrystalin sc oriented sc P1 melting of 123 phase Endo T Exoth New process reaction and dissolution of RE21 and Ba-Cu-O plate like crystal P1 P2 123 phase formation melting of 123 phase Temperature Er-123 Temperature SEM on MgO substrates

21 Scoring Criterion and I c development Performance High I c 16 Progress in I c 3 grain size & grain coupling density & quality control 2 1 orientation reduction of liquid phases at grain boundary 4 Critical Current I c (A) Jan-6 May-6 T=77.3 K self field 1, 2 Oct-6 Mar-7 3, 4 Aug-7 Jan-8

22 SRL developed pre-annealing, second rolling and two step heating process for high performance tapes Superconducting performance Magnatization (emu) T c (onset) : 92 K Temperature (K) V (x1-6 V) Tape type : Er 1.2 Ba 2 Cu 3 O y + sf3 PA : 8m3_SR : 29% TSHP : 925m1_875h25 77 K, self field I c : 15 A I (A) calculated J c : 48 ka/cm 2 B PASRTSH process is used due to its effectiveness in improving grain coupling and in increasing the film homogeneity in order to obtain good quality long superconducting tapes

23 Development of Prototype 2 meters long Bi-2223 DC Superconducting Cable for Railway System Schematic cross section of the HTS cable structure 2 meter long prototype DC HTS cable Protection (1mmt): 25mm Electric Insulation (2mmt): 22mm(PPLP) Former (Cu): 16mm HTS Conductor: 17mm HTS Shield Layer: 23mm Specifications of the 2 meter long prototype DC HTS cable HTS DC cable system works around 77.3 K HTS cable Part Size Characteristics Former Φ16 mm Filled-core fine-stranded copper HTS tape.35mm (t) 4.5mm (w) Bi-2223, I c = 16 A at 77.3 K HTS conductor Φ17 mm I c = 172 A at 77.3 K, 1 layer with 1 tapes Electrical insulation Φ22 mm Polypropylene Laminated Paper PPLP HTS shield Φ23 mm I c = 243 A at 77.3 K, 1 layer with 14 tapes Power lead Cryostat Railway Technical Research Institute

24 5 m-long Bi-2223 HTS DC cable test setup 5 m Note that the tests were performed in pool boiling nitrogen at 77 K. Inset shows the photograph of a 5 m-long cable.

25 DC voltage-current curves for 5 m-long cable at 77 K 3 Voltage/ V K 73.7K 7.4K 69.K 68.3K 67.55K 67.4K 66.5K 66.12K Current /A

26 3 m-long Bi-2223 HTS DC cable at RTRI