Triangle and concave pentagon electrodes for an improved broadband frequency response of stripline beam position monitors
Triangle and concave pentagon electrodes for an improved broadband frequency response of stripline beam position monitors
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三角形和凹五边形电极可改善带状线束位置监视器的宽带频率响应
DOI：
10.1103/physrevaccelbeams.19.021003
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
Keigo Nakamura
中科院分区：
文献类型：
--
作者：
Yoshihiro Shobuda;Yong Ho Chin;Koji Takata;Takeshi Toyama;Keigo Nakamura
带状线束流位置监测器的频域性能在很大程度上取决于其电极的纵向形状。已经提出并测试了除常规矩形之外的一些形状。为了获得沿电极的良好阻抗匹配沿着，它们需要与它们的宽度成比例地朝向它们的下游精确地向下弯曲。这是一项相当艰巨的任务，如果不遵守，将导致频域传递函数由于不需要的信号反射而与理想传递函数发生大的失真。在这份报告中，我们首先提出了一个三角形电极，易于制造和设置：它只需要一个三角形切割的平面电极将被放置在一个腔室，同时倾斜向下游端口。理论和仿真结果表明，简单三角形电极比矩形电极具有更平坦的频率响应。频率响应，特别是在高频下，可以通过垂直于电极上游边缘连接“裙板”来进一步改善。通过用三点折线代替三角形的直边，可以消除低频下频率响应的过冲（结果三角形被变换为凹五边形）。凹五边形电极只需要在折线的中点处弯曲一次，以获得良好的阻抗匹配，因此其制造和设置仍然很容易。已进行了各种电极形状的射频测量。我们发现，凹五边形电极实现了宽而平坦的频率响应高达约4 GHz的J-PARC主环（MR）。
The frequency domain performance of a stripline beam position monitor depends largely on the longitudinal shape of its electrode. Some shapes other than a conventional rectangle have been proposed and tested. To attain a good impedance matching along the electrode, they need to be precisely bent down toward their downstream in proportion to their width. This is a considerable task, and a failure to comply with it will result in a large distortion of the frequency-domain transfer function from the ideal one due to unwanted signal reflections. In this report, we first propose a triangle electrode for easy fabrication and setup: it only requires that a triangularly cut flat electrode will be placed in a chamber while being obliquely inclined toward the downstream port. Theoretical and simulation results show that the simple triangle electrode has a remarkably flatter frequency response than the rectangle one. The frequency response, in particular at high frequencies, can be further improved by attaching an “apron” plate, perpendicular to the upstream edge of the electrode. The overshooting of the frequency response at low frequency can be eliminated by replacing the straight sidelines of the triangle by three-point polylines (with a result that the triangle is transformed to a concave pentagon). The concave pentagon electrode needs to be bent only once at the middle point of the polylines for a good impedance matching and thus its fabrication and setup remain to be easy. Rf measurements for the various electrode shapes have been carried out. We found that the concave pentagon electrode achieves a wide and flat frequency response up to about 4 GHz for the J-PARC Main Ring (MR).