- Email: [email protected]
PLD process
Physica C 463–465 (2007) 751–754 www.elsevier.com/locate/physc
Preparation of conduction-cooled HTS coils using Y-123 coated conductors by IBAD/PLD process H. Fuji *, S. Hanyu, K. Kakimoto, Y. Iijima, T. Saitoh Fujikura Ltd., Material Technology Laboratory, Koto-ku, 1-5-1, Kiba, Tokyo 135-8512, Japan Accepted 5 April 2007 Available online 2 June 2007
Abstract We have developed a long Y-123 coated conductors by ion-beam-assisted deposition (IBAD) and pulsed-laser-deposition (PLD) method. Now, we can routinely obtained 100 m class Y-123 tapes with over 100 A at 77 K. For power applications using Y-123 conductors, coiling and cooling techniques are important elements. From 2004, we have developed and demonstrated a solenoid type coil that is the most suitable for practical application because it has advantage such as (1) uniformity of magnetic field (2) no joint. In this paper, we describe the development of conduction-cooled HTS test coil that has 14 turn · 22 layers using 100 m Y-123 conductors. In order to use the conduction cooling system, the Y-123 conductors were stabilized for 0.1 mm thick Cu tapes and spacers between the layers consisted of aluminum nitride in the coils. In the demonstration of this coil at 30 K, 40 K, 50 K, 60 K and 77 K by cryo-cooling system, the good cooling and superconducting performances were observed. The central magnetic fields of over 1 T were successfully obtained with operating currents of over 400 A and under 40 K. Furthermore, this coil was operated on additional magnetic fields of 3 T by combination of LTS magnets. The central magnetic fields of 0.5 T were generated from the cooled HTS coils with operating current of 190 A on additional magnetic fields of 3 T by LTS magnets at 30 K. Total magnetic fields were exceeded 3.5 T at 30 K. 2007 Published by Elsevier B.V. PACS: 74.72.Bk; 75.47. m; 85.25.Kx Keywords: IBAD; PLD; Y-123; Solenoid coil
1. Introduction The developments of YBCO coated conductors have been performed all over the world. Recently, over 100 m long YBCO coated conductors with the Ic of over 100 A were prepared in several research organizations [1,2]. For the length over 100 m, a large area apparatus of IBAD was successfully developed with long lifetime operation even in oxygen atmosphere [1,3]. The PLD method has been used as a deposition technique of Y-123 films. It is characterized with stable stoichiometry, easy oxygen pressure control, very high growth rate, etc. The combination of IBAD and PLD is so far the most promising to fabricate long YBCO coated conductors. *
Corresponding author. Tel.: +81 3 5606 1064; fax: +81 3 5606 1512. E-mail address: [email protected] (H. Fuji).
0921-4534/$ - see front matter 2007 Published by Elsevier B.V. doi:10.1016/j.physc.2007.04.315
For power applications using Y-123 conductors, coiling and cooling techniques are important elements. Generally pancake type coils were developed using tape conductors, because it was difficult to wind the solenoid coils for mechanical strain of superconducting tape conductors. However, solenoid coil is the most suitable for practical application because it has advantage such as (1) uniformity of magnetic field (2) no joint. In Fujikura, solenoid type coil was developed and tested from 2004. In this paper, we described the fabrication and demonstration of conduction-cooled solenoid coil using Y-123 coated conductors. 2. Experimental Gd2Zr2O7 (GZO) films were deposited on roll-milled Hastelloy C276 with the 10 mm width and the 100 lm
752
H. Fuji et al. / Physica C 463–465 (2007) 751–754
thickness by reel-to-reel, dual-ion-beam sputtering system with two sets of radio frequency (RF) discharged 66 cm · 6 cm square-shaped ion sources. Continuous growth of GZO films was performed with the production speed of 0.5–1.0 m/h under the conventional condition. CeO2 secondary buffer layers and YBCO films were deposited by a reel-to-reel PLD system with Kr-F (l = 248 nm) excimer laser. The estimated production rate per 1 lm thick YBCO film was 1.0–25 m/h. Ag films (20 lm thick) were deposited on YBCO films by RF magnetron sputtering and there after annealed for several hours at 500 C in 760 T oxygen. Before winding coils, we performed the evaluation of the bending strain property. Using these results, we wound the solenoid type coils carefully. A 110 m longAg/Y-123/ CeO2/GZO/Hastelloy tape formed by IBAD/PLD was wound into a 14 turn · 26 layer solenoid type magnet whose inner diameter of 60 mm. Solenoid magnets have many merits as joint free, good thermal and mechanical stability etc., compared to the pancake type magnet. In order to use the conduction cooling system, the Y-123 conductors were stabilized by 0.1 mm thick Cu tapes. In addition, coil spacers between the layers consisted of aluminum nitride for cooling. The coil temperature was monitored by thermocouples and the central magnetic field was monitored by a Hall probe. The coil was cooled by a cycle cryo-cooler. In addition, this coil was operated in back up field of 1–3 T by LTS magnet. Coil currents were defined the transport current with the beginning of generation of voltages of which criterion of current was 2.5 nV/ cm. The transport currents were carried out at about 250 lV of coil voltages and reduced due to avoid the partial burnout of the rapid voltage increase.
pressive bending strain. The degradation of Ic/Ic0 was not observed up to the 0.5% in the over 20 lm thick Ag cap layer. However, in the case of thin Ag cap layer, Ic degradation occurs from low strain. In the case of the strain of compressive side, Ic degradation was not observed up higher bending strain compared with the strain of tensile side. From these results, it was found that the thick Ag cap layer reinforced the Y-123 layer effectively, and inside of Y-123 layer in winding was effective for keeping from Ic degradation. Fig. 2 shows illustration of winding the coil using coated conductor. In order to avoid edgewise strains in Y-123 tape, it was necessary to wind carefully at turning point between layers. Fig. 3 shows cryo-cooled solenoid coil wound for this work. The designed specifications of coil are given in Table 1.
Fig. 2. Illustration of winding the coil using coated conductor.
3. Results and discussion Fig. 1 shows the normalized critical current, the Ic (with the bending strain)/Ic0 (initial Ic) on the tensile and com1.2
compressive
1
Ic /c0
0.8
tensile
0.6 0.4 0.2 0
Ag 20 μm Ag 30 μm
0
0.2
0.4
0.6
0.8
1
Bending strain (%) Fig. 1. Ic (with the bending strain)/Ic0 (initial Ic) on the tensile and compressive bending strain.
Fig. 3. Picture of cryo-cooled solenoid coil.
H. Fuji et al. / Physica C 463–465 (2007) 751–754 Table 1 The designed specification of coil
753
1.5
300
Turn · layer Inner diameter Outer diameter Height Conductor length Width Ic (77 K, 0 T)
14 · 26 60 mm 110 mm 114 mm 110 m 10 mm 100 110 A
250
200
Volt ( μ V)
Solenoid
150
1 9th layer Volt
1st layer Volt
Fig. 4 shows illustration of operation in conductioncooled coil test. Conduction-cooled coil was located in LTS magnet and center of coil was adjusted same position prevent from magnetic force of each coil. In the demonstration of this coil at 30 K, 35 K, 40 K, 50 K, 60 K and 77 K by cryo-cooling system, the good cooling and superconducting properties were observed. Fig. 5 shows the voltage of the 1st and 9th layers in the coil in the solenoid at the temperature of 30 K. The generation of voltage began in the 9th layer first of all and then the generations of voltage were occurred in the layer around the 9th layer. At the center of the 1st and 9th layer, magnetic field was a only perpendicular magnetic field. However, at the top of the 1st and 9th layer, the angle of magnetic field was 25 and 45. Fig. 6 shows the voltage of the 1st and 9th layers in the coil in the solenoid at the temperature of 30 K and additional field of 3 T by LTS magnet. At the center of the 1st and 9th layer, magnetic field was a only perpendicular magnetic field. However, another point of the 1st and 9th layer, the angle of magnetic field was changed every moment by operating current.
0.5
100
50
0 0
100
200
300
400
0 500
I (A) Fig. 5. Voltage of the 1st and 9th layers in the coil in the solenoid at the temperature of 30 K.
Fig. 7 shows the relationship between current of coil and central magnetic field at each temperature on each additional magnetic field by LTS magnet. Load line of central magnetic was linear of 0.27 T/100 A. Over 1 T of central magnetic fields were successfully observed under 40 K. The operating current of coil and central magnetic field were holding at 400 A and 1.1 T during the 10 min at 35 K. During holding time, the rise of the conductor temperature could not be confirmed in the coil. It indicates that cryo-cooling solenoid magnet has high reliability compared to pancake type magnet at least the point of no joint.
Cryo-cooling system
250
200
4.5 1st layer center field 1st layer Top field 9th layer Center field 9th layer Top field
4
Volt (μV)
150
3.5
100
3
2.5
50
0 0
Magnetic field (T)
Cryo-cooled coil
Magnetic Field (T)
Type
θ= 0 0º θ= 25º θ= 0º θ= 45º
11st st layer layercenter centerfield field 1st layer Top field 9th layer Center field 9th layer top field
50
100
150
200
250
300
2 350
I (A)
LTS magnet Fig. 4. Illustration of operation in conduction-cooled coil test.
Fig. 6. Voltage of the 1st and 9th layers in the coil in the solenoid at the temperature of 30 K and additional field of 3 T by LTS magnet.
754
H. Fuji et al. / Physica C 463–465 (2007) 751–754
500
35K
Operating Current (A)
400
30K 300
200
40K 50K
100
Fig. 8. Large-scale coils of the race track type for field magnet of motor using Y-123 coated conductor.
60K 77K 0 0
0.5
1
1.5
2
2.5
3
3.5
4
Center magnetic field of coil (T) Fig. 7. Relationship between current of coil and central magnetic field at each temperature on each additional magnetic field.
4. Conclusions A 14 turn · 26 layer solenoid type magnet whose inner diameter of 60 mm was successfully operated using a 110 m long Ag/Y-123/CeO2/GZO/Hastelloy tape formed by IBAD/PLD. During the demonstrations, the good cooling and superconducting performance were observed. In addition, over 1 T of central magnetic fields were successfully observed under 40 K. It indicates that cryo-cooling solenoid magnet and YBCO conductors have a good performance. Now, using the knowledge of these results, we develop the large-scale coils of the race track type for field magnet of motor using Y-123 coated conductor of the 0.5 cm width with Cu stabilizer (Fig. 8).
Acknowledgements We deeply appreciate Dr. K. Mizuno at Suzuki Shokan Co., Ltd. for the kind collaboration of operating the cryocooled magnets. This work is/was supported by New Energy and Industrial Technology Development Organization (NEDO) as Collaborative Research and Development of Fundamental Technologies for Superconductivity Application. References [1] Y. Iijima, K. Onabe, N. Futaki, N. Tanabe, N. Sadakata, O. Kohno, Y. Ikeno, IEEE Trans. Appl. Supercond. 3 (1993) 1510. [2] S.R. Foltyn, P.N. Arendt, C. Dowden, R.F. DePaula, J.R. Groves, J.Y. Coulter, Q. Jia, M.P. Maley, D.E. Peterson, IEEE Trans. Appl. Supercond. 9 (1999) 1519. [3] K. Kakimoto, Y. Sutoh, N. Kaneko, Y. Iijima, T. Saitoh, Physica C 426–431 (2005) 858, Part 2.
Preparation of conduction-cooled HTS coils using Y-123 coated conductors by IBAD/PLD process H. Fuji *, S. Hanyu, K. Kakimoto, Y. Iijima, T. Saitoh Fujikura Ltd., Material Technology Laboratory, Koto-ku, 1-5-1, Kiba, Tokyo 135-8512, Japan Accepted 5 April 2007 Available online 2 June 2007
Abstract We have developed a long Y-123 coated conductors by ion-beam-assisted deposition (IBAD) and pulsed-laser-deposition (PLD) method. Now, we can routinely obtained 100 m class Y-123 tapes with over 100 A at 77 K. For power applications using Y-123 conductors, coiling and cooling techniques are important elements. From 2004, we have developed and demonstrated a solenoid type coil that is the most suitable for practical application because it has advantage such as (1) uniformity of magnetic field (2) no joint. In this paper, we describe the development of conduction-cooled HTS test coil that has 14 turn · 22 layers using 100 m Y-123 conductors. In order to use the conduction cooling system, the Y-123 conductors were stabilized for 0.1 mm thick Cu tapes and spacers between the layers consisted of aluminum nitride in the coils. In the demonstration of this coil at 30 K, 40 K, 50 K, 60 K and 77 K by cryo-cooling system, the good cooling and superconducting performances were observed. The central magnetic fields of over 1 T were successfully obtained with operating currents of over 400 A and under 40 K. Furthermore, this coil was operated on additional magnetic fields of 3 T by combination of LTS magnets. The central magnetic fields of 0.5 T were generated from the cooled HTS coils with operating current of 190 A on additional magnetic fields of 3 T by LTS magnets at 30 K. Total magnetic fields were exceeded 3.5 T at 30 K. 2007 Published by Elsevier B.V. PACS: 74.72.Bk; 75.47. m; 85.25.Kx Keywords: IBAD; PLD; Y-123; Solenoid coil
1. Introduction The developments of YBCO coated conductors have been performed all over the world. Recently, over 100 m long YBCO coated conductors with the Ic of over 100 A were prepared in several research organizations [1,2]. For the length over 100 m, a large area apparatus of IBAD was successfully developed with long lifetime operation even in oxygen atmosphere [1,3]. The PLD method has been used as a deposition technique of Y-123 films. It is characterized with stable stoichiometry, easy oxygen pressure control, very high growth rate, etc. The combination of IBAD and PLD is so far the most promising to fabricate long YBCO coated conductors. *
Corresponding author. Tel.: +81 3 5606 1064; fax: +81 3 5606 1512. E-mail address: [email protected] (H. Fuji).
0921-4534/$ - see front matter 2007 Published by Elsevier B.V. doi:10.1016/j.physc.2007.04.315
For power applications using Y-123 conductors, coiling and cooling techniques are important elements. Generally pancake type coils were developed using tape conductors, because it was difficult to wind the solenoid coils for mechanical strain of superconducting tape conductors. However, solenoid coil is the most suitable for practical application because it has advantage such as (1) uniformity of magnetic field (2) no joint. In Fujikura, solenoid type coil was developed and tested from 2004. In this paper, we described the fabrication and demonstration of conduction-cooled solenoid coil using Y-123 coated conductors. 2. Experimental Gd2Zr2O7 (GZO) films were deposited on roll-milled Hastelloy C276 with the 10 mm width and the 100 lm
752
H. Fuji et al. / Physica C 463–465 (2007) 751–754
thickness by reel-to-reel, dual-ion-beam sputtering system with two sets of radio frequency (RF) discharged 66 cm · 6 cm square-shaped ion sources. Continuous growth of GZO films was performed with the production speed of 0.5–1.0 m/h under the conventional condition. CeO2 secondary buffer layers and YBCO films were deposited by a reel-to-reel PLD system with Kr-F (l = 248 nm) excimer laser. The estimated production rate per 1 lm thick YBCO film was 1.0–25 m/h. Ag films (20 lm thick) were deposited on YBCO films by RF magnetron sputtering and there after annealed for several hours at 500 C in 760 T oxygen. Before winding coils, we performed the evaluation of the bending strain property. Using these results, we wound the solenoid type coils carefully. A 110 m longAg/Y-123/ CeO2/GZO/Hastelloy tape formed by IBAD/PLD was wound into a 14 turn · 26 layer solenoid type magnet whose inner diameter of 60 mm. Solenoid magnets have many merits as joint free, good thermal and mechanical stability etc., compared to the pancake type magnet. In order to use the conduction cooling system, the Y-123 conductors were stabilized by 0.1 mm thick Cu tapes. In addition, coil spacers between the layers consisted of aluminum nitride for cooling. The coil temperature was monitored by thermocouples and the central magnetic field was monitored by a Hall probe. The coil was cooled by a cycle cryo-cooler. In addition, this coil was operated in back up field of 1–3 T by LTS magnet. Coil currents were defined the transport current with the beginning of generation of voltages of which criterion of current was 2.5 nV/ cm. The transport currents were carried out at about 250 lV of coil voltages and reduced due to avoid the partial burnout of the rapid voltage increase.
pressive bending strain. The degradation of Ic/Ic0 was not observed up to the 0.5% in the over 20 lm thick Ag cap layer. However, in the case of thin Ag cap layer, Ic degradation occurs from low strain. In the case of the strain of compressive side, Ic degradation was not observed up higher bending strain compared with the strain of tensile side. From these results, it was found that the thick Ag cap layer reinforced the Y-123 layer effectively, and inside of Y-123 layer in winding was effective for keeping from Ic degradation. Fig. 2 shows illustration of winding the coil using coated conductor. In order to avoid edgewise strains in Y-123 tape, it was necessary to wind carefully at turning point between layers. Fig. 3 shows cryo-cooled solenoid coil wound for this work. The designed specifications of coil are given in Table 1.
Fig. 2. Illustration of winding the coil using coated conductor.
3. Results and discussion Fig. 1 shows the normalized critical current, the Ic (with the bending strain)/Ic0 (initial Ic) on the tensile and com1.2
compressive
1
Ic /c0
0.8
tensile
0.6 0.4 0.2 0
Ag 20 μm Ag 30 μm
0
0.2
0.4
0.6
0.8
1
Bending strain (%) Fig. 1. Ic (with the bending strain)/Ic0 (initial Ic) on the tensile and compressive bending strain.
Fig. 3. Picture of cryo-cooled solenoid coil.
H. Fuji et al. / Physica C 463–465 (2007) 751–754 Table 1 The designed specification of coil
753
1.5
300
Turn · layer Inner diameter Outer diameter Height Conductor length Width Ic (77 K, 0 T)
14 · 26 60 mm 110 mm 114 mm 110 m 10 mm 100 110 A
250
200
Volt ( μ V)
Solenoid
150
1 9th layer Volt
1st layer Volt
Fig. 4 shows illustration of operation in conductioncooled coil test. Conduction-cooled coil was located in LTS magnet and center of coil was adjusted same position prevent from magnetic force of each coil. In the demonstration of this coil at 30 K, 35 K, 40 K, 50 K, 60 K and 77 K by cryo-cooling system, the good cooling and superconducting properties were observed. Fig. 5 shows the voltage of the 1st and 9th layers in the coil in the solenoid at the temperature of 30 K. The generation of voltage began in the 9th layer first of all and then the generations of voltage were occurred in the layer around the 9th layer. At the center of the 1st and 9th layer, magnetic field was a only perpendicular magnetic field. However, at the top of the 1st and 9th layer, the angle of magnetic field was 25 and 45. Fig. 6 shows the voltage of the 1st and 9th layers in the coil in the solenoid at the temperature of 30 K and additional field of 3 T by LTS magnet. At the center of the 1st and 9th layer, magnetic field was a only perpendicular magnetic field. However, another point of the 1st and 9th layer, the angle of magnetic field was changed every moment by operating current.
0.5
100
50
0 0
100
200
300
400
0 500
I (A) Fig. 5. Voltage of the 1st and 9th layers in the coil in the solenoid at the temperature of 30 K.
Fig. 7 shows the relationship between current of coil and central magnetic field at each temperature on each additional magnetic field by LTS magnet. Load line of central magnetic was linear of 0.27 T/100 A. Over 1 T of central magnetic fields were successfully observed under 40 K. The operating current of coil and central magnetic field were holding at 400 A and 1.1 T during the 10 min at 35 K. During holding time, the rise of the conductor temperature could not be confirmed in the coil. It indicates that cryo-cooling solenoid magnet has high reliability compared to pancake type magnet at least the point of no joint.
Cryo-cooling system
250
200
4.5 1st layer center field 1st layer Top field 9th layer Center field 9th layer Top field
4
Volt (μV)
150
3.5
100
3
2.5
50
0 0
Magnetic field (T)
Cryo-cooled coil
Magnetic Field (T)
Type
θ= 0 0º θ= 25º θ= 0º θ= 45º
11st st layer layercenter centerfield field 1st layer Top field 9th layer Center field 9th layer top field
50
100
150
200
250
300
2 350
I (A)
LTS magnet Fig. 4. Illustration of operation in conduction-cooled coil test.
Fig. 6. Voltage of the 1st and 9th layers in the coil in the solenoid at the temperature of 30 K and additional field of 3 T by LTS magnet.
754
H. Fuji et al. / Physica C 463–465 (2007) 751–754
500
35K
Operating Current (A)
400
30K 300
200
40K 50K
100
Fig. 8. Large-scale coils of the race track type for field magnet of motor using Y-123 coated conductor.
60K 77K 0 0
0.5
1
1.5
2
2.5
3
3.5
4
Center magnetic field of coil (T) Fig. 7. Relationship between current of coil and central magnetic field at each temperature on each additional magnetic field.
4. Conclusions A 14 turn · 26 layer solenoid type magnet whose inner diameter of 60 mm was successfully operated using a 110 m long Ag/Y-123/CeO2/GZO/Hastelloy tape formed by IBAD/PLD. During the demonstrations, the good cooling and superconducting performance were observed. In addition, over 1 T of central magnetic fields were successfully observed under 40 K. It indicates that cryo-cooling solenoid magnet and YBCO conductors have a good performance. Now, using the knowledge of these results, we develop the large-scale coils of the race track type for field magnet of motor using Y-123 coated conductor of the 0.5 cm width with Cu stabilizer (Fig. 8).
Acknowledgements We deeply appreciate Dr. K. Mizuno at Suzuki Shokan Co., Ltd. for the kind collaboration of operating the cryocooled magnets. This work is/was supported by New Energy and Industrial Technology Development Organization (NEDO) as Collaborative Research and Development of Fundamental Technologies for Superconductivity Application. References [1] Y. Iijima, K. Onabe, N. Futaki, N. Tanabe, N. Sadakata, O. Kohno, Y. Ikeno, IEEE Trans. Appl. Supercond. 3 (1993) 1510. [2] S.R. Foltyn, P.N. Arendt, C. Dowden, R.F. DePaula, J.R. Groves, J.Y. Coulter, Q. Jia, M.P. Maley, D.E. Peterson, IEEE Trans. Appl. Supercond. 9 (1999) 1519. [3] K. Kakimoto, Y. Sutoh, N. Kaneko, Y. Iijima, T. Saitoh, Physica C 426–431 (2005) 858, Part 2.