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

采用大通径双煎饼线圈在强磁场中输运大电流的方法，实现了高电磁应力状态。我们专注于采用高强度Cu-50 Ag带或哈氏合金带增强的宽孔线圈，使用反应Ag包覆Bi221 2带的共绕组技术，以克服30 t级超导磁体产生的约300 MPa应力。利用应变片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Cu-50 Ag胶带和哈氏合金胶带加固两种测试线圈，制作成双煎饼形状，11个X2匝，直径280 mm。在4.2 K和10 t的液氦条件下，对测试线圈施加超过350 A临界电流500 A的输运电流，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时的环向应力为262 MPa。发现临界电流在0.16%的应变范围内不退化。这一结果表明，哈氏合金增强ag护套Bi2212线圈克服电磁应力高达150mpa。

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.