本文描述了一个4mm回旋管用的超导磁体,它可在谐振腔区提供3T的均匀磁场,均匀区长6cm,均匀度优于±0.16%,均匀磁场又可调节成梯度场,梯度ΔB/Bo≥8.5%。阴极区磁场均匀区长4cm,均匀度±(1.0～1.8)%,压缩比B_k/Bo可在1/6～1/15范围内调节。采用四台电源串联供电。磁场位形调节好后,磁体可实现闭环运行。磁体将与回旋管配合在HL—1装置上进行ECRH物理实验。 This paper describes a 4mm gyrotron with a superconducting magnet that provides a uniform magnetic field of 3T in the resonator area with a uniform area of ​​6cm and a uniformity of better than ± 0.16%. A uniform magnetic field can be adjusted to a gradient field with a gradient of ΔB / Bo ≥8.5%. The uniformity of the magnetic field in the cathode region is 4cm, the uniformity is ± (1.0 ~ 1.8)%, and the compression ratio B_k / Bo can be adjusted from 1/6 to 1/15. Using four power supplies in series. After adjusting the magnetic field profile, the magnet can achieve closed-loop operation. The magnet will be fitted with a gyrotron to conduct an ECRH physical experiment on the HL-1 device.