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

对于大口径双饼线圈，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30 T级超导磁体中产生的约300 MPa的应力，我们采用反应银包覆Bi 221 2带材的共绕技术，用高强度Cu-50 Ag带材或Hastelloy带材增强了大口径线圈。采用应变片测量了高场超导磁体在大电磁应力状态下的力学性能。用Cu-50 Ag带或Hastelloy带增强的两种测试线圈制成双饼形，具有11 × 2匝，直径为280 mm。在4.2 K和10 T的液氦中，对测试线圈施加高达500 A的传输电流，其高于350 A的临界电流。在I =350 A时，对Cu-50 Ag增强线圈和哈氏合金增强线圈分别施加0.25%和0.22%的应变。1=500 A时的环向应力相当于262 MPa。发现在0.16%的应变范围内，临界电流不降低。该结果表明，哈氏合金增强Ag护套Bi 2212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.