Flux trapping in superconducting accelerating cavities during cooling down with a spatial temperature gradient
Flux trapping in superconducting accelerating cavities during cooling down with a spatial temperature gradient
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空间温度梯度冷却过程中超导加速腔中的通量捕获
DOI：
10.1093/ptep/ptw049
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发表时间：
2016
影响因子：
3.5
通讯作者：
Takayuki Kubo
中科院分区：
文献类型：
--
作者：
Shichun Huang;Takayuki Kubo;and R. L.Geng;Takayuki Kubo
在超导加速腔冷却过程中，磁通量被捕获为量子化的涡旋，产生额外的耗散并产生剩余电阻。近年来，随着大空间温度梯度的冷却，成功地减少了被困涡的数量引起了人们的广泛关注。本文的目的是提出一个模型来解释所观察到的有效通量驱逐和空间温度梯度的作用，在腔冷却。在温度接近临界温度的区域附近，临界场被强烈抑制，并且可以小于环境磁场。具有小于环境场的低临界场的区域处于涡旋状态。当材料冷却下来时，一个温度接近的区域与涡旋态畴相关，扫过并穿过材料。在这个过程中，包含在涡旋状态域中的涡旋被随机分布在材料中的钉扎中心捕获。捕获的涡流的数量可以通过与光束-目标碰撞事件类比来简单地估计。基于该结果，评估残余电阻。我们发现，被捕获的旋涡和剩余电阻的数量成正比的环境磁场的强度和温度梯度的倒数。得到的剩余电阻与实验结果吻合较好。被困涡的数量的材料属性的依赖关系也进行了讨论。
During the cool-down of a superconducting accelerating cavity, a magnetic flux is trapped as quantized vortices, which yield additional dissipation and contribute to the residual resistance. Recently, cooling down with a large spatial temperature gradient has attracted much attention for successfully reducing the number of trapped vortices. The purpose of the present paper is to propose a model to explain the observed efficient flux expulsions and the role of spatial temperature gradient during the cool-down of the cavity. In the vicinity of a region with a temperature close to the critical temperature, the critical fields are strongly suppressed and can be smaller than the ambient magnetic field. A region with a lower critical field smaller than the ambient field is in the vortex state. As the material is cooled down, a region with a temperature close toassociated with the vortex state domain sweeps and passes through the material. In this process, vortices contained in the vortex state domain are trapped by pinning centers that randomly distribute in the material. The number of trapped vortices can be naively estimated by analogy with a beam–target collision event. Based on this result, the residual resistance is evaluated. We find that the number of trapped vortices and the residual resistance are proportional to the strength of the ambient magnetic field and the inverse of the temperature gradient. The residual resistance obtained agrees well with experimental results. A material property dependence of the number of trapped vortices is also discussed.
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DOI：
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