Fabrication and cold test of dielectric assist accelerating structure
Fabrication and cold test of dielectric assist accelerating structure
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介电辅助加速结构的制作及冷态试验
DOI：
10.1103/physrevaccelbeams.20.091302
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发表时间：
2017
影响因子：
1.7
通讯作者：
N. Hayashizaki
中科院分区：
文献类型：
--
作者：
D. Satoh;M. Yoshida;N. Hayashizaki
详细介绍了介质辅助加速（DAA）结构的成功设计和冷态测试。DAA结构由周期性排列在金属外壳中的超低损耗介质圆柱体和具有虹膜的圆盘组成。DAA结构的优点是在室温下具有极高的品质因数和极高的分流阻抗，因为加速模的电磁场分布可以由介质部件控制，从而大大降低了金属表面的壁损。在C波段（5.712 GHz）设计并制造了五单元DAA结构的原型，并进行了冷测试。采用烧结高纯氧化镁的方法制备了“规则”、"端部“和"混合”三种类型的电介质电池结构。原型是通过将这些电池堆叠在中空的铜圆柱体中组装而成的，铜圆柱体的两端由铜板封闭。通过仅加工端部铜板，将原型的谐振频率调谐到所需频率。加速模式的无负载品质因数测量值为119，314，并且根据珠拉测量的实验结果估计原型的每单位长度的分流阻抗为${Z}_{\mathrm{sh}}= 617\text {}\mathrm{\ensuremath{\Omega}}/\mathrm{m}$，其在设计值的2%以内。采用拉珠法测量了加速模式下的场分布，其结果与模拟结果吻合较好。
We present the detailed description of a successful design and cold testing of the dielectric assist accelerating (DAA) structure. The DAA structure consists of ultralow-loss dielectric cylinders and disks with irises which are periodically arranged in a metallic enclosure. The advantage of the DAA structure is that it has an extremely high quality factor and a very high shunt impedance at room temperature since the electromagnetic field distribution of accelerating mode can be controlled by dielectric parts so that the wall loss on the metallic surface is greatly reduced. A prototype of the five-cell DAA structure was designed and built at C-band (5.712 GHz), and cold tested. Three types of dielectric cell structure, ``regular,'' ``end,'' and ``hybrid'' dielectric cells, are fabricated by sintering high-purity magnesia. The prototype was assembled by stacking these cells in the hollow copper cylinder, whose two ends are closed by copper plates. The resonant frequency of the prototype was tuned to the desired frequency by machining only end copper plates. The unloaded quality factor of the accelerating mode was measured at 119,314 and the shunt impedance per unit length of the prototype was estimated from the experimental results of the bead pull measurement as ${Z}_{\mathrm{sh}}=617\text{ }\text{ }\mathrm{M}\mathrm{\ensuremath{\Omega}}/\mathrm{m}$, which were within 2 percent of the design values. The field distribution of accelerating mode was also measured by the bead pull method, and its results agreed well with simulation results.