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Present status and future plan of the Tsukuba Magnet Laboratories
Physica B 216 (1996) 141 145
ELSEVIER
Present status and future plan of the Tsukuba Magnet Laboratories H. Maeda*, K. Inoue, T. Kiyoshi, T. Asano, Y. Sakai, T. Takeuchi, K. Itoh, H. Aoki, G. Kido Tsukuba Magnet Laboratories, ,National Research Institute.tbr Metals, Sengen, Tsukuba 305, Japan
Abstract We have been developing and installing several high field magnets, i.e. long pulsed magnets, a 40 T class hybrid magnet, a 21 T superconducting magnet, several high resolution magnets, etc. The 40 T class hybrid magnet is composed of a 15 T superconducting magnet with a room temperature clear bore of 400 mm and a 25 T polyhelix-type water-cooled magnet with a 30 mm bore. The 21 T superconducting magnet with a clear bore of 61 mm, operated at 1.8 K, is now being used. Inside the magnet small Bi-2212 coils have been installed and excited to generate a total field up to 21.8 T in a clear bore of 13 mm. Using the high resolution magnet systems, Fermi surface properties of many materials have been revealed. Furthermore, we have fabricated two types of pulsed magnet coils to generate 73.4 T in a short pulse duration of 5 ms and 64.5 T in a long 100 ms duration, using newly developed Cu-Ag alloy composite wires with high strength and high conductivity.
1. Introduction Several kinds of high field magnets, i.e. long pulsed magnets, a 40T class hybrid magnet (40THM) [1], a 21 T superconducting magnet (21 TSM) [2], several high resolution superconducting magnet systems, etc., are installed in a newly constructed building of the Tsukuba Magnet Laboratories (TML). The 40 T HM is progressing in test operations to be ready for operation in May 1995. The other magnets are now being used for some experiments; for instance, high-T~ oxide superconducting coil test, NMR and dHvA measurements in heavy fermion and organic conductors, etc. All the magnet systems will be opened for world-wide cooperative research works from next year, 1996. Furthermore, we have a plan to develop and install several high field
*Corresponding author.
magnets, such as superconducting magnets (a 15 T split and a 20T magnet/dilution system), a 1 GHz NMR system, and several 20-27 T water-cooled resistive magnets in the near future.
2. 21 T superconducting magnet (21 T SM) The 21 T SM can supply several kinds of experimental spaces by changing the combination of three component coils (outer, middle and inner coils), as shown in Fig. 1. The specifications of the coils are listed in Table 1. The 21 TSM is operated at 1.8K in saturated superfluid helium, and by three power supplies. The middle and inner coils are isolated thermally from the outer coils by another coaxial cryostat or chamber. When the middle and inner coils are removed out of the inner chamber, the magnet can supply a large temperature-variable bore of 314 mm with a field up to 15 T. The middle coil generates
0921-4526/96/S15.00 ~" 1996 Elsevier Science B.V. All rights reserved SSDI 0 9 2 1 - 4 5 2 6 ( 9 5 1 0 0 4 5 9 - 9
142
H. Maeda et al. / Phvsica B 216 (1996) 141 145 25
"lmmr
~, 20 '~
v
.~I.IT
I
w , "--t~ ¢Sambe~
!
700 ,,.,,
I
600
? Xt2,6 ,,
500
15
10
~1850
800
!
,~
,00
"i5¢,I1:' ~b~l: ,~1 o~zau:~ro~,mani .,~[llI[Ilcl ~@~.'=
300~
g,
200 .~ o 100 r,.)
0 0
100
200
300
400 500 600 R a d i u s in c o i l m i d - p l a n e (ram)
0
Fig. 1. Magnetic field distribution and bore sizes in the middle plane of 21 T superconducting magnet. 18 T in a 160 mm bore. We have already fabricated two kinds of inner coils to generate a field above 21 T; one is No. 3 coil with a 50 mm bore, made of a newly developed (Nb, Ti, Ta)3Sn conductor I-3], and the other is No. 4 coil with a 6 1 m m bore, listed in Table 1, wound by (Nb, TihSn conductor with an extremely reduced Cu ratio of 0.25. The maximum field generated so far is 21.16 T [4]. Recently, a double pancake Bi-2212 oxide coil with a 13 mm clear bore, fabricated by a dip-coating process, was installed in the 21 T S M and excited at 1.8 K to generate 21.8 T under a back-up field of 20.9 T, which is the highest field in a full superconducting system [5].
3. 40 T class hybrid magnet (40 THM) The 40 T H M is composed of a 15 T superconducting magnet (15 T SM) with a room-temperature clear bore of
Cool
Cool
Fig. 2. Whole view of 40T class hybrid magnet.
400 mm and a 25 T polyhelix-type water-cooled magnet (25 T WM) with a 30 mm bore (Fig. 2). The 40 T H M system has a 15 M W DC power supply (the maximum of 430 V and 35 kA) and a 15 M W water-cooling system (an inlet temperature of 10°C, a flow rate of 700 t/h and
Table 1 Parameters for 21 T superconducting magnet Coil parameter
Inner coil (No. 4)
Middle coil
Outer-1 coil
Outer-2 coil
Inner winding diameter (mmi Outer winding diameter tmm) Winding height (mm) No. of double pancakes No. of turns Superconducting material Conductor type Whole conductor size Copper ( + AI) ratio Operation current (M Maximum field (T) Stored energy (M J)
64.5 153. I 219.9
180 285.2 463.5 31 1364 (Nb, Ti)sSn Monolith 2x6 1.5 883 18.1 0.052
380 717.7 1230 40 1520 (Nb, Ti)3Sn Cu-housing + A1 8.15 x 13.4 5.15 4717 15.3 4.0
801 1165.8 1293.6 41 2296 Nb-Ti Cu-housing + AI 6 x 13.8 7.31 4717 8.4 27.0
1901 (Nb, Ti)sSn Monolith 1.5 x 2.8 0.25 360 21.49
143
H. Maeda et al. /Physica B 216 (1996) 141-145
Table 2 Parameters for 15 T superconducting magnet of 40 T hybrid magnet Central field (T) Operation temperature (K) Operation current (A) Spacer ratio between turns (%) Spacer ratio between pancakes (%) Inductance (H) Stored energy (M J) Net weight of winding part (t) No. of pancakes
15 4.2 1476.1 30 50 58.17 63.37 9.42 116
Conductor grade
G1
G2
G3
G4
Inner diameter (mm) Outer diameter (mm) Winding height (mm) No. of turns Superconducting material Conductor type Copper ratio Coil current density (MA/m 2) Maximum field (T) Joule heat flux (kW/m 2)
471.56 663.50 1020.80 16 (Nb, Ti)3Sn Cu-housing 4.39 27.96 15.52 3.13
669.80 918.20 1020.80 23 (Nb, TibSn Cu-housing 6.87 31.06 12.63 2.58
922.28 1150.16 1020.80 27 Nb-Ti Monolith 5.70 39.75 8.55 3.01
1152.96 1391.00 1020.80 32 Nb-Ti Monolith 9.60 45.09 6.47 2.80
Table 3 Parameters for polyhelix coils of 40 T and 35 T hybrid magnets Coil
25 TWM
20 TWM
Material Total field (T) Incremental field (T) Clear bore diameter (mm) Outer coil diameter (mm) Coil height (mm) No. of helix Maximum current (kA) Maximum voltage (V) Flow rate of water (t/hr) Flow velocity of water (m/s)
Cu AI20 3 40 25 30 340 490 18 33.3 13.3 646 18.5
Cu Cr 35 20 50 340 490 15 31.7 10.8 700 17.9
a pressure loss of 147 MPa), and a helium refrigerator (150 I/h or 450 W at 4.4 K). The 15 T S M is composed of 58 double pancake coils; each pancake is made of four kinds of superconductors (G1, G2, G3 and G4). The specifications of the 15 T S M and conductors are listed in Table 2. The magnet is cryogenically stabilized to operate at 4.2 K under the maximum current of 1476 A and a stored energy of 63.37MJ. We fabricated new structural Cu-housing (Nb, Ti)3Sn conductors used in high field regions (GI and
G2), in order to avoid the stress-induced I¢ degradation of the conductor due to a large compressive transverse stress of 50-70 M P a loaded to the magnet in a full operation. The magnet is cooled down for about 145 h from r o o m temperature to 4.2 K [6]. The 25 T W M is composed of 18 coaxial helical coils with a 30 mm clear bore, as listed in Table 3. The coils are made of Cu AlzO3 alloy. The magnet is designed to generate 25 T at an operating current of 33.3 kA, consuming a power of 13.3 MW, in a back-up field of 15 T. The magnet is cooled directly by flowing deionized water at a flow rate of about 700 t/h through three turborefrigerators; each with a cooling power of 5,2 MW. We have also another 20 T polyhelix-type water-cooled magnet with a 50 mm bore (20 T W M ) , composed of 15 polyhelix coils which are fabricated by C u - C r alloy (Table 3).
4. Pulsed magnets We have been constructing two types of pulsed magnets. One is a small magnet with a pulse duration of 5 ms, matching a small 10 m F capacitor bank of 125 kJ/5 kV. The other is a large magnet with a 100 ms duration for a large 128 m F capacitor bank of 1.6 M J/5 kV. Recently, we have developed a new C u - A g alloy wire with high strength ( > 1 GPa) and high conductivity
144
H. Maeda et al. ; Phvsica B 216 (1996) 141 145
Table 4 Parameters of Cu Ag multilayered pulsed coils
5. High resolution magnet systems
Coils
SPM
LPM
Outer/inner wind diameter tmm) Wind length (mm) No. of turns/layer No. of layers Cu Ag wire size (mm) Inter layer material
57/10 55 16 8 2x3 Stycasl
149/16 130 19 12 4 ×6 Epoxy
80~r
'
'
I
I
'
'
'
!
.
.
.
.
.
.
Using several installed superconducting magnet systems including a solid state N M R system with a 15.5 T magnet, a 500 MHz high resolution solid state N M R system and a 16 T magnet/dilution refrigerator system for detecting q u a n t u m oscillations, cooperative studies, particularly, on Fermi surface properties of many materials, have been carried out, and some interesting results are obtained in heavy fermion compounds and organic conductors [9].
6. Future plan
--
A Mel 49 10~ Cu-Ag3x 2 (SPM) t //~T°n2!6tpCuiAg6-x4(LPM~
60 i
li / ' / / ~ T o n l
16~ Cu 6X4 (LPM)
,01 !//
I
20
-20
~
-20
'
'
'
. 0
- . ~ 20
,
I 40
,
,
,
~
,
60
,
J 80
,
,
i 1 O0
. . . .
J 120
Time (ms) Fig. 3. Pulsed magnetic field generated by Cu Ag multilayered coils of SPM and LPM. Ton 1 coil is the same size magnet as LPM, made of pure Cu wire.
( > 80% IACS), sufficiently useful for pulsed magnets [7]. Using the 2 x 3 mm rectangular C u - 1 6 % A g alloy wires we have fabricated small multilayered pulsed magnets (SPM) with a short pulse duration of 5 ms, as listed in Table 4. Internally, reinforcements by glass fiber windings are carried out between the layers. The maximum field achieved by the SPM so far is 73.4 T in a 10 mm bore, as shown in Fig. 3 [8]. For long pulsed magnets, on the other hand, using the large size, 4 × 6 mm C u - A g wire, we have fabricated large multilayered pulsed magnets (LPM) and generated 64.5 T in a 16 mm bore in a pulse duration of 100 ms without destruction (Table 4J. The magnets, of course, can generate much higher fields than those made of low strength pure Cu wire, as seen in Fig. 3. Since a higher tensile strength of 1.1-1.2 G P a has been already realized in a laboratory-scale Cu Ag alloy wire, a higher generating field will be expected in the near future. Using these pulsed magnets we have been doing cyclotron resonance, ESR and dHvA measurements for wide-gap semiconductors and heavy fermion compounds.
In addition to the magnets described above, the T M L have several compact solenoid-type and split-type superconducting magnets. The present status of TML, however, seems to be not enough for accepting m a n y nearfuture users. We will soon install some superconducting magnets including a 15 T split magnet with a 35 mm clear gap and a 20 T magnet/dilution refrigerator system. Furthermore, a project to develop a 1 G H z N M R system will start from April 1995. For the project we will have to develop a 24 T superconducting magnet, which will be composed of a 21 T superconducting magnet with a 150 mm clear bore, made of metallic superconductors and a 3 T high-T¢ oxide inner magnet, e.g. Bi-2212 coil with a room temperature bore of 50 mm, inserted in the 21 T magnet. We will also have a plan to install several 23-30 T water-cooled resistive magnets. For the watercooled magnets the Cu Ag alloy sheets, which we have developed recently [10], will be used. The sheets have been used in the innermost part of the Hybrid III magnet at the Francis Bitter National Magnet L a b o r a t o r y - M I T , which succeeded in generating 35.25 T [11], and will also be used in a 30 T water-cooled magnet at Florida National High Magnetic Field Laboratory.
References [1] K. Inoue, T. Takeuchi, T. Kiyoshi, K. ltoh, H. Wada, H. Maeda, T. Fujioka, S. Murase, Y. Wachi, S. Hanai and T. Sasaki, IEEE Trans. Magn. 28 (1992) 493. [2] T. Kiyoshi, K Inoue. K. Itoh, T. Takeuehi, H. Wada, H. Maeda, K. Kuroishi, F. Suzuki, T. Takizawa, N. Tada and H. Mori, IEEE Trans. Appl. Supercond. 3 (1993) 78. [3] K. Takeuchi, H. Sekine and Y. lijima, Japan Patent No. 1378791 (1987). [4] M. Oshikiri, K. Inoue, T. Kiyoshi, T. Takeuchi, K. Itoh, K. Takehana, M. Kosuge, Y. Iijima and H. Maeda, Physica B 201 (1994) 521. [5] N. Tomita, M. Arai, E. Yanagisawa, T. Morimoto, H. Kitaguchi, H Kumakura, K. Togano, T. Kiyoshi, K.
H. Maeda et al. / Phvswa B 216 (1996) 141 145
Inoue, H. Maeda, K. Nomura and J.C. Vallier, IEEE Trans. Appl. Supercond., to be published. [6] K. lnoue, T. Takeucbi, K. Takehana. K. Itoh, T. Kiyoshi. H. Maeda, T. Fujioka, S. Murase, Y. Wachi, S. Hanai, Y. Dozono and T. Kojo, Cryogenics 34 (1995) 717. [7] Y. Sakai, K. lnoue, T. Asano, H. Wada and H. Maeda. Appl. Phys. Lett. 59 (1991) 29656. [8] T. Asano, Y. Sakai, M. Oshikiri, K. Inoue, H. Maeda, G. Heremans, L.v. Bockstal, L. Li and F. Herlach. Physica B 201 (1994) 556.
145
[9] H Aoki, S. Uji, A.K. Albessard and Y. Onuki, Phys. Rev. Lett. 71 {1993) 2110: S. Uji, T. Terashima, H. Aoki, J.S. Brooks, R. Kato, H. Sawa, S. Aonuma, M. Tamura and M. Kinoshita, Phys. Rev. B 50 (1994) 15597. [10] Y. Sakai, K. Inoue and H. Maeda, IEEE Trans. Magn. 30 (1994) 2114. [11] Y. Iwasa, M.J. Leupold, RJ. Weggel and J.E.C. Williams, IEEE Trans. Appl. Supercond. 3 (1993) 58; Y. Iwasa, privale communication (June 1994).
ELSEVIER
Present status and future plan of the Tsukuba Magnet Laboratories H. Maeda*, K. Inoue, T. Kiyoshi, T. Asano, Y. Sakai, T. Takeuchi, K. Itoh, H. Aoki, G. Kido Tsukuba Magnet Laboratories, ,National Research Institute.tbr Metals, Sengen, Tsukuba 305, Japan
Abstract We have been developing and installing several high field magnets, i.e. long pulsed magnets, a 40 T class hybrid magnet, a 21 T superconducting magnet, several high resolution magnets, etc. The 40 T class hybrid magnet is composed of a 15 T superconducting magnet with a room temperature clear bore of 400 mm and a 25 T polyhelix-type water-cooled magnet with a 30 mm bore. The 21 T superconducting magnet with a clear bore of 61 mm, operated at 1.8 K, is now being used. Inside the magnet small Bi-2212 coils have been installed and excited to generate a total field up to 21.8 T in a clear bore of 13 mm. Using the high resolution magnet systems, Fermi surface properties of many materials have been revealed. Furthermore, we have fabricated two types of pulsed magnet coils to generate 73.4 T in a short pulse duration of 5 ms and 64.5 T in a long 100 ms duration, using newly developed Cu-Ag alloy composite wires with high strength and high conductivity.
1. Introduction Several kinds of high field magnets, i.e. long pulsed magnets, a 40T class hybrid magnet (40THM) [1], a 21 T superconducting magnet (21 TSM) [2], several high resolution superconducting magnet systems, etc., are installed in a newly constructed building of the Tsukuba Magnet Laboratories (TML). The 40 T HM is progressing in test operations to be ready for operation in May 1995. The other magnets are now being used for some experiments; for instance, high-T~ oxide superconducting coil test, NMR and dHvA measurements in heavy fermion and organic conductors, etc. All the magnet systems will be opened for world-wide cooperative research works from next year, 1996. Furthermore, we have a plan to develop and install several high field
*Corresponding author.
magnets, such as superconducting magnets (a 15 T split and a 20T magnet/dilution system), a 1 GHz NMR system, and several 20-27 T water-cooled resistive magnets in the near future.
2. 21 T superconducting magnet (21 T SM) The 21 T SM can supply several kinds of experimental spaces by changing the combination of three component coils (outer, middle and inner coils), as shown in Fig. 1. The specifications of the coils are listed in Table 1. The 21 TSM is operated at 1.8K in saturated superfluid helium, and by three power supplies. The middle and inner coils are isolated thermally from the outer coils by another coaxial cryostat or chamber. When the middle and inner coils are removed out of the inner chamber, the magnet can supply a large temperature-variable bore of 314 mm with a field up to 15 T. The middle coil generates
0921-4526/96/S15.00 ~" 1996 Elsevier Science B.V. All rights reserved SSDI 0 9 2 1 - 4 5 2 6 ( 9 5 1 0 0 4 5 9 - 9
142
H. Maeda et al. / Phvsica B 216 (1996) 141 145 25
"lmmr
~, 20 '~
v
.~I.IT
I
w , "--t~ ¢Sambe~
!
700 ,,.,,
I
600
? Xt2,6 ,,
500
15
10
~1850
800
!
,~
,00
"i5¢,I1:' ~b~l: ,~1 o~zau:~ro~,mani .,~[llI[Ilcl ~@~.'=
300~
g,
200 .~ o 100 r,.)
0 0
100
200
300
400 500 600 R a d i u s in c o i l m i d - p l a n e (ram)
0
Fig. 1. Magnetic field distribution and bore sizes in the middle plane of 21 T superconducting magnet. 18 T in a 160 mm bore. We have already fabricated two kinds of inner coils to generate a field above 21 T; one is No. 3 coil with a 50 mm bore, made of a newly developed (Nb, Ti, Ta)3Sn conductor I-3], and the other is No. 4 coil with a 6 1 m m bore, listed in Table 1, wound by (Nb, TihSn conductor with an extremely reduced Cu ratio of 0.25. The maximum field generated so far is 21.16 T [4]. Recently, a double pancake Bi-2212 oxide coil with a 13 mm clear bore, fabricated by a dip-coating process, was installed in the 21 T S M and excited at 1.8 K to generate 21.8 T under a back-up field of 20.9 T, which is the highest field in a full superconducting system [5].
3. 40 T class hybrid magnet (40 THM) The 40 T H M is composed of a 15 T superconducting magnet (15 T SM) with a room-temperature clear bore of
Cool
Cool
Fig. 2. Whole view of 40T class hybrid magnet.
400 mm and a 25 T polyhelix-type water-cooled magnet (25 T WM) with a 30 mm bore (Fig. 2). The 40 T H M system has a 15 M W DC power supply (the maximum of 430 V and 35 kA) and a 15 M W water-cooling system (an inlet temperature of 10°C, a flow rate of 700 t/h and
Table 1 Parameters for 21 T superconducting magnet Coil parameter
Inner coil (No. 4)
Middle coil
Outer-1 coil
Outer-2 coil
Inner winding diameter (mmi Outer winding diameter tmm) Winding height (mm) No. of double pancakes No. of turns Superconducting material Conductor type Whole conductor size Copper ( + AI) ratio Operation current (M Maximum field (T) Stored energy (M J)
64.5 153. I 219.9
180 285.2 463.5 31 1364 (Nb, Ti)sSn Monolith 2x6 1.5 883 18.1 0.052
380 717.7 1230 40 1520 (Nb, Ti)3Sn Cu-housing + A1 8.15 x 13.4 5.15 4717 15.3 4.0
801 1165.8 1293.6 41 2296 Nb-Ti Cu-housing + AI 6 x 13.8 7.31 4717 8.4 27.0
1901 (Nb, Ti)sSn Monolith 1.5 x 2.8 0.25 360 21.49
143
H. Maeda et al. /Physica B 216 (1996) 141-145
Table 2 Parameters for 15 T superconducting magnet of 40 T hybrid magnet Central field (T) Operation temperature (K) Operation current (A) Spacer ratio between turns (%) Spacer ratio between pancakes (%) Inductance (H) Stored energy (M J) Net weight of winding part (t) No. of pancakes
15 4.2 1476.1 30 50 58.17 63.37 9.42 116
Conductor grade
G1
G2
G3
G4
Inner diameter (mm) Outer diameter (mm) Winding height (mm) No. of turns Superconducting material Conductor type Copper ratio Coil current density (MA/m 2) Maximum field (T) Joule heat flux (kW/m 2)
471.56 663.50 1020.80 16 (Nb, Ti)3Sn Cu-housing 4.39 27.96 15.52 3.13
669.80 918.20 1020.80 23 (Nb, TibSn Cu-housing 6.87 31.06 12.63 2.58
922.28 1150.16 1020.80 27 Nb-Ti Monolith 5.70 39.75 8.55 3.01
1152.96 1391.00 1020.80 32 Nb-Ti Monolith 9.60 45.09 6.47 2.80
Table 3 Parameters for polyhelix coils of 40 T and 35 T hybrid magnets Coil
25 TWM
20 TWM
Material Total field (T) Incremental field (T) Clear bore diameter (mm) Outer coil diameter (mm) Coil height (mm) No. of helix Maximum current (kA) Maximum voltage (V) Flow rate of water (t/hr) Flow velocity of water (m/s)
Cu AI20 3 40 25 30 340 490 18 33.3 13.3 646 18.5
Cu Cr 35 20 50 340 490 15 31.7 10.8 700 17.9
a pressure loss of 147 MPa), and a helium refrigerator (150 I/h or 450 W at 4.4 K). The 15 T S M is composed of 58 double pancake coils; each pancake is made of four kinds of superconductors (G1, G2, G3 and G4). The specifications of the 15 T S M and conductors are listed in Table 2. The magnet is cryogenically stabilized to operate at 4.2 K under the maximum current of 1476 A and a stored energy of 63.37MJ. We fabricated new structural Cu-housing (Nb, Ti)3Sn conductors used in high field regions (GI and
G2), in order to avoid the stress-induced I¢ degradation of the conductor due to a large compressive transverse stress of 50-70 M P a loaded to the magnet in a full operation. The magnet is cooled down for about 145 h from r o o m temperature to 4.2 K [6]. The 25 T W M is composed of 18 coaxial helical coils with a 30 mm clear bore, as listed in Table 3. The coils are made of Cu AlzO3 alloy. The magnet is designed to generate 25 T at an operating current of 33.3 kA, consuming a power of 13.3 MW, in a back-up field of 15 T. The magnet is cooled directly by flowing deionized water at a flow rate of about 700 t/h through three turborefrigerators; each with a cooling power of 5,2 MW. We have also another 20 T polyhelix-type water-cooled magnet with a 50 mm bore (20 T W M ) , composed of 15 polyhelix coils which are fabricated by C u - C r alloy (Table 3).
4. Pulsed magnets We have been constructing two types of pulsed magnets. One is a small magnet with a pulse duration of 5 ms, matching a small 10 m F capacitor bank of 125 kJ/5 kV. The other is a large magnet with a 100 ms duration for a large 128 m F capacitor bank of 1.6 M J/5 kV. Recently, we have developed a new C u - A g alloy wire with high strength ( > 1 GPa) and high conductivity
144
H. Maeda et al. ; Phvsica B 216 (1996) 141 145
Table 4 Parameters of Cu Ag multilayered pulsed coils
5. High resolution magnet systems
Coils
SPM
LPM
Outer/inner wind diameter tmm) Wind length (mm) No. of turns/layer No. of layers Cu Ag wire size (mm) Inter layer material
57/10 55 16 8 2x3 Stycasl
149/16 130 19 12 4 ×6 Epoxy
80~r
'
'
I
I
'
'
'
!
.
.
.
.
.
.
Using several installed superconducting magnet systems including a solid state N M R system with a 15.5 T magnet, a 500 MHz high resolution solid state N M R system and a 16 T magnet/dilution refrigerator system for detecting q u a n t u m oscillations, cooperative studies, particularly, on Fermi surface properties of many materials, have been carried out, and some interesting results are obtained in heavy fermion compounds and organic conductors [9].
6. Future plan
--
A Mel 49 10~ Cu-Ag3x 2 (SPM) t //~T°n2!6tpCuiAg6-x4(LPM~
60 i
li / ' / / ~ T o n l
16~ Cu 6X4 (LPM)
,01 !//
I
20
-20
~
-20
'
'
'
. 0
- . ~ 20
,
I 40
,
,
,
~
,
60
,
J 80
,
,
i 1 O0
. . . .
J 120
Time (ms) Fig. 3. Pulsed magnetic field generated by Cu Ag multilayered coils of SPM and LPM. Ton 1 coil is the same size magnet as LPM, made of pure Cu wire.
( > 80% IACS), sufficiently useful for pulsed magnets [7]. Using the 2 x 3 mm rectangular C u - 1 6 % A g alloy wires we have fabricated small multilayered pulsed magnets (SPM) with a short pulse duration of 5 ms, as listed in Table 4. Internally, reinforcements by glass fiber windings are carried out between the layers. The maximum field achieved by the SPM so far is 73.4 T in a 10 mm bore, as shown in Fig. 3 [8]. For long pulsed magnets, on the other hand, using the large size, 4 × 6 mm C u - A g wire, we have fabricated large multilayered pulsed magnets (LPM) and generated 64.5 T in a 16 mm bore in a pulse duration of 100 ms without destruction (Table 4J. The magnets, of course, can generate much higher fields than those made of low strength pure Cu wire, as seen in Fig. 3. Since a higher tensile strength of 1.1-1.2 G P a has been already realized in a laboratory-scale Cu Ag alloy wire, a higher generating field will be expected in the near future. Using these pulsed magnets we have been doing cyclotron resonance, ESR and dHvA measurements for wide-gap semiconductors and heavy fermion compounds.
In addition to the magnets described above, the T M L have several compact solenoid-type and split-type superconducting magnets. The present status of TML, however, seems to be not enough for accepting m a n y nearfuture users. We will soon install some superconducting magnets including a 15 T split magnet with a 35 mm clear gap and a 20 T magnet/dilution refrigerator system. Furthermore, a project to develop a 1 G H z N M R system will start from April 1995. For the project we will have to develop a 24 T superconducting magnet, which will be composed of a 21 T superconducting magnet with a 150 mm clear bore, made of metallic superconductors and a 3 T high-T¢ oxide inner magnet, e.g. Bi-2212 coil with a room temperature bore of 50 mm, inserted in the 21 T magnet. We will also have a plan to install several 23-30 T water-cooled resistive magnets. For the watercooled magnets the Cu Ag alloy sheets, which we have developed recently [10], will be used. The sheets have been used in the innermost part of the Hybrid III magnet at the Francis Bitter National Magnet L a b o r a t o r y - M I T , which succeeded in generating 35.25 T [11], and will also be used in a 30 T water-cooled magnet at Florida National High Magnetic Field Laboratory.
References [1] K. Inoue, T. Takeuchi, T. Kiyoshi, K. ltoh, H. Wada, H. Maeda, T. Fujioka, S. Murase, Y. Wachi, S. Hanai and T. Sasaki, IEEE Trans. Magn. 28 (1992) 493. [2] T. Kiyoshi, K Inoue. K. Itoh, T. Takeuehi, H. Wada, H. Maeda, K. Kuroishi, F. Suzuki, T. Takizawa, N. Tada and H. Mori, IEEE Trans. Appl. Supercond. 3 (1993) 78. [3] K. Takeuchi, H. Sekine and Y. lijima, Japan Patent No. 1378791 (1987). [4] M. Oshikiri, K. Inoue, T. Kiyoshi, T. Takeuchi, K. Itoh, K. Takehana, M. Kosuge, Y. Iijima and H. Maeda, Physica B 201 (1994) 521. [5] N. Tomita, M. Arai, E. Yanagisawa, T. Morimoto, H. Kitaguchi, H Kumakura, K. Togano, T. Kiyoshi, K.
H. Maeda et al. / Phvswa B 216 (1996) 141 145
Inoue, H. Maeda, K. Nomura and J.C. Vallier, IEEE Trans. Appl. Supercond., to be published. [6] K. lnoue, T. Takeucbi, K. Takehana. K. Itoh, T. Kiyoshi. H. Maeda, T. Fujioka, S. Murase, Y. Wachi, S. Hanai, Y. Dozono and T. Kojo, Cryogenics 34 (1995) 717. [7] Y. Sakai, K. lnoue, T. Asano, H. Wada and H. Maeda. Appl. Phys. Lett. 59 (1991) 29656. [8] T. Asano, Y. Sakai, M. Oshikiri, K. Inoue, H. Maeda, G. Heremans, L.v. Bockstal, L. Li and F. Herlach. Physica B 201 (1994) 556.
145
[9] H Aoki, S. Uji, A.K. Albessard and Y. Onuki, Phys. Rev. Lett. 71 {1993) 2110: S. Uji, T. Terashima, H. Aoki, J.S. Brooks, R. Kato, H. Sawa, S. Aonuma, M. Tamura and M. Kinoshita, Phys. Rev. B 50 (1994) 15597. [10] Y. Sakai, K. Inoue and H. Maeda, IEEE Trans. Magn. 30 (1994) 2114. [11] Y. Iwasa, M.J. Leupold, RJ. Weggel and J.E.C. Williams, IEEE Trans. Appl. Supercond. 3 (1993) 58; Y. Iwasa, privale communication (June 1994).