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不带铁磁屏蔽的超导螺线管可得到场强达100至150千高斯的轴向对称的磁场。在这种螺线管中,可用调整绕组的方法来增加磁场的均匀性。而在许多情况下,例如,对于毫米波行波量子放大器,要求在较大的非轴向对称的空隙中有高均匀度的磁场。将磁体的超导绕组作成拉长了的窄的成对的形式,放在铁磁屏蔽中(见图1),就可以满足以上这些要求。磁体中场的均匀度是由屏蔽材料的磁导率和屏蔽的上下两侧面的平行度来确定的。在μ=∞的屏蔽板内,螺线管的多次反射模拟了一个具有与它相应的高均匀度磁场的无限长螺线管。对于有限的μ值,反射螺线管则为限长。
Superconducting solenoids without ferromagnetic shielding provide axially symmetric magnetic fields with field strengths of 100 to 150 kilo-gauss. In this type of solenoid, the method of adjusting the winding can be used to increase the uniformity of the magnetic field. In many cases, for example, for millimeter-wave traveling-wave quantum amplifiers, it is desirable to have a highly uniform magnetic field in the larger non-axially symmetric gaps. These requirements are met by making the superconducting windings of the magnets elongated elongated pairs in a ferromagnetic shield (see Figure 1). The uniformity of the magnet midfield is determined by the permeability of the shielding material and the parallelism of the upper and lower sides of the shield. In μ = ∞ shields, the multiple reflections of the solenoid simulate an infinitely long solenoid with a correspondingly high uniform magnetic field. For limited μ values, the reflective solenoid is limited length.