Quench and self-protecting behaviour of an intra-layer no-insulation (LNI) REBCO coil at 31.4 T
Quench and self-protecting behaviour of an intra-layer no-insulation (LNI) REBCO coil at 31.4 T
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DOI：
10.1088/1361-6668/abf54e
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发表时间：
2021-04
影响因子：
3.6
通讯作者：
Y. Suetomi;T. Yoshida;S. Takahashi;T. Takao;G. Nishijima;H. Kitaguchi;Y. Miyoshi;M. Hamada;K. Saito;R. Piao;Y. Takeda;H. Maeda;Y. Yanagisawa
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文献类型：
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作者：
Y. Suetomi;T. Yoshida;S. Takahashi;T. Takao;G. Nishijima;H. Kitaguchi;Y. Miyoshi;M. Hamada;K. Saito;R. Piao;Y. Takeda;H. Maeda;Y. Yanagisawa
本文给出了层内无绝缘(RE：RE)Ba2Cu3O7−δ(REBCO)线圈在31.4T中心磁场中失超的实验结果和失超模拟结果。我们一直在设计一种1.3 GHz(30.5T)永久模核磁共振磁体，该磁体具有层绕的REBCO内线圈。保护REBCO线圈免受失超是一个重要问题，该线圈采用LNI方法来获得自保护特性。我们以1.3 GHz核磁共振磁体为模型，在17.2T的背景磁场下，对与绝缘Bi2Sr2Ca2Cu3Ox(Bi2223)线圈相连的LNI-REBCO线圈进行了高场产生和失超实验。线圈成功地产生了31.4T的中心磁场，虽然LNI-REBCO线圈在31.4T下淬火，但这种淬火没有对线圈造成任何退化。数值模拟表明，由于电流在铜片层间的旁路，失超过程中的电流分布不均匀且随时间变化很快，导致失超传播速度比绝缘REBCO线圈快。在失超传播过程中，峰值温度(T峰)和峰值环向应力BzJR(σθ，峰值)分别为330K和718MPa.这些都低于导致退化的临界值。模拟还表明，线圈绕组中导体与铜片之间的高接触电阻率(ρct)为10000µΩcm~2，在保护中起着重要作用。当ρct低至70µΩcm~2时，失超传播过快，并产生很大的附加电流，导致极高的σθ_1峰，为1398 Mpa，而T峰低至75K。简言之，目前线圈中的高ρ_t引起高T峰，但成功地抑制了σθ_1峰，保护了线圈免受失超。
This paper presents experimental results on a quench of an intra-layer no-insulation (LNI) (RE: rare earth)Ba2Cu3O7−δ (REBCO) coil in a 31.4 T central magnetic field and simulated results on the quench. We have been designing a persistent-mode 1.3 GHz (30.5 T) nuclear magnetic resonance (NMR) magnet with a layer-wound REBCO inner coil. Protection of the REBCO coil from quench is a significant issue and the coil employs the LNI method to obtain self-protecting characteristics. We conducted high-field generation and quench experiments on an LNI-REBCO coil connected to an insulated Bi2Sr2Ca2Cu3O x (Bi-2223) coil under a background magnetic field of 17.2 T as a model of the 1.3 GHz NMR magnet. The coils successfully generated a central magnetic field of 31.4 T. Although the LNI-REBCO coil quenched at 31.4 T, this quench did not cause any degradation to the coil. A numerical simulation showed the current distribution during the quench was non-uniform and changed rapidly over time due to current bypassing through copper sheets between layers, resulting in faster quench propagation than in an insulated REBCO coil. During the quench propagation, the peak temperature (T peak) and the peak hoop stress BzJR (σθ, peak) were calculated to be 330 K and 718 MPa, respectively. These are below critical values that cause degradation. The simulation also showed that the high electrical contact resistivity (ρ ct) of 10 000 µΩ cm2, between REBCO conductors and copper sheets in the LNI-REBCO coil winding, played an important role in protection. When ρ ct was as low as 70 µΩ cm2, the quench propagation became too fast and large additional currents were induced, resulting in an extremely high σθ, peak of 1398 MPa, while the T peak was as low as 75 K. In short, the high ρ ct in the present coil caused a high T peak, but succeeded in suppressing σθ, peak and protecting the coil from the quench.