Radiation generated by a charge moving through a vacuum channel in a dielectric cone is analyzed. It is assumed that the charge moves through the cone from the apex side to the base side (the case of inverted cone). The cone size is supposed to be much larger than the wavelengths under consideration. We calculate the wave field outside the target using the aperture method developed in our previous papers. Contrary to the problems considered earlier, here the wave which incidences directly on the aperture is not the main wave, while the wave once reflected from the lateral surface is much more important. The general formulas for the radiation field are obtained, and the particular cases of the ray-optics area and the Fraunhofer area are analyzed. Significant physical effects including the phenomenon of “Cherenkov spotlight” are discussed. In particular it is shown that the Cherenkov spotlight regime allows for reaching the most efficient radiation for the given target with the largest intensity and smallest divergence in the far-field region. Moreover, owing to the inverted cone geometry, this effect can be realized for arbitrary charge velocity, including the ultrarelativistic case, by proper selection of the cone material and the apex angle. Typical radiation patterns in the far-field area are demonstrated.

中文翻译：

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通过倒置圆锥形靶飞行的电荷的Cherenkov辐射

分析了电荷通过介电锥中真空通道移动所产生的辐射。假设电荷从顶侧通过圆锥移动到基部（圆锥倒置的情况）。锥体的大小应该比所考虑的波长大得多。我们使用先前论文中开发的孔径方法计算目标外部的波场。与先前考虑的问题相反，这里直接入射在孔径上的波不是主波，而一次从侧面反射回来的波则更为重要。获得了辐射场的一般公式，并分析了射线光学区域和弗劳恩霍夫区域的特殊情况。讨论了包括“切伦科夫聚光灯”现象在内的重大物理影响。特别地，表明切伦科夫聚光体制允许以远场区域中最大的强度和最小的发散来达到给定目标的最有效辐射。此外，由于在倒置锥体几何形状，可以实现对任意电荷速度这样的效果，其中包括超相对论情况下，由锥形材料的适当选择和顶角。演示了远场区域的典型辐射图。由锥形材料的适当选择和顶角。演示了远场区域的典型辐射图。由锥形材料的适当选择和顶角。演示了远场区域的典型辐射图。