Design of a beam phase cavity and a waveguide coupled eccentric circle structure prebuncher in S-band
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摘要: 设计了工作于S波段的波导耦合型预聚束器和束流相位探测腔。为了增加功率容量,预聚束器采用波导耦合机制代替了传统的同轴耦合环耦合,而偏心圆结构的设计能够补偿因耦合窗口的引入导致的径向电场不对称,进一步改善了强流束流品质。预聚束器设计指标与测试结果:耦合系数1.73,空载品质因数2195,腔体谐振频率的可调范围为2 854.55~2 856.9 MHz。为实现测量束流相对射频脉冲的时间,进行强流输入功率补偿,选择了能够在线进行束流相位实时测量的束流相位探测腔,采用旋转对称结构,并通过两个同轴耦合环提取束流通过时激发的感应信号,作为直线相控系统的参考信号。束流相位探测腔设计与测试结果:空载品质因数2392,3 dB带宽为2.05 MHz,腔体谐振频率的可调范围为2 805.45~2 809.45 MHz。所有器件的仿真设计与测试结果基本一致。Abstract: A new waveguide-coupled prebuncher and a new beam phase cavity working at S-band are designed. For increasing the power capacity, the waveguide coupling mechanism is used instead of the traditional coaxial ring coupling for the prebuncher. An eccentric circle structure of the cavity is adopted to solve the problem of an asymmetric electrical field along the radial direction caused by the introduction of the waveguide coupling window, which improves the beam quality on high beam current. The measurement results of a coupling coefficient of 1.73, an unloaded quality factor of 2195 as well as a variable frequency range from 2 854.55 MHz to 2 856.9 MHz are got in the final prototype of prebuncher. For measuring the timing between beam and RF pulse in order to compensate the input power with the high beam current, a beam phase cavity is chosen to be the on-line equipment for the real-time measurement of beam phase. The beam phase cavity has a rotational symmetrical structure, and two coaxial coupling rings are used to extract the inducted signal from the beam, which will be used as the reference signal of the phase-controlling system. The prototype of beam phase cavity has a measurement result of an unloaded quality factor of 2392, a 3 dB bandwidth of 2.05 MHz as well as a variable frequency range from 2 805.45 MHz to 2 809.45 MHz. The measurement results match well with the simulation results.
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Key words:
- prebuncher /
- eccentric circle structure /
- waveguide coupling /
- beam phase cavity /
- S-band
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