Cook A M, Tikhoplav R, Tochitsky S Y, Travish G, Williams O B, Rosenzweig J B
Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA.
Phys Rev Lett. 2009 Aug 28;103(9):095003. doi: 10.1103/PhysRevLett.103.095003. Epub 2009 Aug 27.
We report experimental observation of narrow-band coherent Cherenkov radiation driven by a subpicosecond electron bunch traveling along the axis of a hollow cylindrical dielectric-lined waveguide. For an appropriate choice of dielectric wall thickness, a short-pulse beam current profile excites only the fundamental mode of the structure, producing energetic pulses in the terahertz range. We present detailed measurements showing a narrow emission spectrum peaked at 367 + or - 3 GHz from a 1 cm long fused silica capillary tube with submillimeter transverse dimensions, closely matching predictions. We demonstrate a 100 GHz shift in the emitted central frequency when the tube wall thickness is changed by 50 microm. Calibrated measurements of the radiated energy indicate up to 10 microJ per 60 ps pulse for an incident beam charge of 200 pC, corresponding to a peak power of approximately 150 kW.
我们报告了由沿空心圆柱形介质内衬波导轴传播的亚皮秒电子束驱动的窄带相干切伦科夫辐射的实验观测结果。对于介质壁厚度的适当选择，短脉冲束电流分布仅激发结构的基模，在太赫兹范围内产生高能脉冲。我们给出了详细的测量结果，显示从横向尺寸为亚毫米的1厘米长熔融石英毛细管发出的窄发射光谱在367±3吉赫兹处达到峰值，与预测结果紧密匹配。当管壁厚度改变50微米时，我们证明发射中心频率有100吉赫兹的偏移。对辐射能量的校准测量表明，对于200皮库的入射束电荷，每60皮秒脉冲高达10微焦，对应于约150千瓦的峰值功率。
