LARGE STRESS STATE IN Bi-SYSTEM HIGH TEMPERATURE SUPERCONDUCTING TAPE FOR A30 T-CLASS SUPERCONDUCTING MAGNET

大口径双饼线圈通过在高场中传输大电流来实现高电磁应力状态。为了克服30T级超导磁体产生的约300 Mpa的应力，我们对反应银护套Bi221 2带采用共绕技术，采用高强度的Cu50Ag带或Hastelloy带增强的大口径线圈。利用应变计对高场超导磁体在大电磁应力状态下的力学性能进行了评价。用铜-50Ag带和Hastelloy带两种增强试验线圈制成双煎饼状，11圈×2圈，直径280 mm。试验线圈在4.2K和10T的液氦中施加了高于350A临界电流的500A的传输电流，在L=350A时分别施加0.25%和0.22%的应变用于铜-50Ag增强线圈和哈氏合金增强线圈。在1=500A时的环向应力相当于262兆帕。结果表明，在0.16%的应变范围内，临界电流不会降低。这一结果表明，Hastelloy增强银套Bi2212线圈克服了高达150 Mpa的电磁应力。

High electromagnetic stress state is realized by transporting a large current in high fields for a double-pancake coil with a wide bore. We concentrate on a wide bore coil reinforced with highly strengthened Cu-50 Ag tape or Hastelloy tape using a co-winding technique for reacted Ag-sheathed Bi221 2 tape, in order to overcome about 300 MPa stress produced in a 30 T-class superconducting magnet. The mechanical properties for a high field superconducting magnet were evaluated in a large electromagnetic stress state using strain gauges. Two kinds of test coils reinforced with Cu-50 Ag tape or Hastelloy tape were made in a double-pancake shape with 11 X2 turns and 280 mm in diameter. Transport currents up to 500 A, which were above the critical current of 350 A, were applied for the test coil in liquid helium at 4.2 K and 10 T.The strains of 0.25 % and 0.22 % were applied at l=350 A for the Cu-50 Ag reinforcement coil and Hastelloy reinforcement coil, respectively. Hoop stress at 1=500 A corresponds to 262 MPa. It is found that the critical current does not degrade within strains of 0.16 %. This result indicates that a Hastelloy reinforcement Ag-sheathed Bi2212 coil overcomes electromagnetic stress up to 150 MPa.