有和无外部磁场时的射频击穿
rf Breakdown with and without External Magnetic Fields
摘要：
中微子工厂和μ子对撞机的冷却晶格既需要高梯度rf，也需要强聚焦rf。实验表明，在所需的磁场中运行射频可能会出现严重的问题。使用高压气体，以避免这些问题进行了讨论，包括可能的损失问题，从电子和离子生产的电离束的通道。还应注意，高压气体不能用于μ子对撞机冷却的后期阶段。讨论了真空射频腔在磁场中的实验观测，总结了目前发表的有无磁场击穿模型，并将它们的一些预测与观测进行了比较。提出了一种新的磁场相关击穿理论。提出了腔体一侧的微凸体上的场致发射发射的电子被磁场聚焦到另一侧，在那里它们将腔体表面熔化成小斑点。然后金属被静电从熔融点中抽出，通过剩余损伤的场发射而蒸发和电离，并导致击穿。该理论适合现有的805 MHz的数据和预测的性能在201 MHz。该模型预测的击穿梯度显着低于国际范围研究（ISS）中微子工厂或μ子对撞机的规定。这些问题的可能的解决方案进行了讨论，包括“磁绝缘射频”的设计，其中腔壁被设计成平行于一个选定的磁场轮廓线，因此从场发射的损害被抑制。一个实验方案来研究这些问题和他们可能的解决方案的概述。
英文摘要：
Neutrino Factories and Muon Colliders' cooling lattices require both high gradient rf and strong focusing solenoids. Experiments have shown that there may be serious problems operating rf in the required magnetic fields. The use of high pressure gas to avoid these problems is discussed, including possible loss problems from electron and ion production by the passage of an ionizing beam. It is also noted that high pressure gas cannot be used in later stages of cooling for a muon collider. Experimental observations using vacuum rf cavities in magnetic fields are discussed, current published models of breakdown with and without magnetic fields are summarized, and some of their predictions compared with observations. A new theory of magnetic field dependent breakdown is presented. It is proposed that electrons emitted by field emission on asperities on one side of a cavity are focused by the magnetic field to the other side where they melt the cavity surface in small spots. Metal is then electrostatically drawn from the molten spots, becomes vaporized and ionized by field emission from the remaining damage and cause breakdown. The theory is fitted to existing 805 MHz data and predictions are made for performance at 201 MHz. The model predicts breakdown gradients significantly below those specified for either the International Scoping Study (ISS) Neutrino Factory or a Muon Collider. Possible solutions to these problems are discussed, including designs for `magnetically insulated rf' in which the cavity walls are designed to be parallel to a chosen magnetic field contour line and consequently damage from field emission is suppressed. An experimental program to study these problems and their possible solution is outlined.
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