| Millimeter-wave locates in the microwave and far-infrared waves overlap position in electromagnetic spectrum, it has important applications in military communications, radar, radio astronomy, aerospace and other areas. With the development of modern high-tech, a millimeter radiation source which can provide high-power, high efficiency and have small volume is urged needed. Compared with cylindrical or ring electron beam, sheet beam has a larger power capacity and can be used in the millimeter devices. Extended Interaction Klystron which has the advantage of traveling-wave tube and klystron is a typical high power, high efficiency and with a certain bandwidth microwave device. Therefore, W-band sheet beam extended interaction Klystron is a perfect millimeter-wave radiation source to meet current demands.This thesis research on beam focusing and beam-wave interaction of a W-band sheet beam extended interaction klystron. The main content of this text is as follows:Firstly, the klystron theory of bunch and distribution cavity is systematically introduced in the text. A dumbbell-shaped rectangular distribution cavity was designed for a W-band extended interaction klystron. By means of CAD technology, the electronic field distribution in distribution cavity is analyzed.Secondly, although the sheet electron beam has obvious advantages compared with the conventional cylindrical or ring electron beam, but the sheet electron beam was difficult to focusing. Theoretical analysis combined with particle-in-cell method was used to investigate the sheet beam focusing effect using the axial uniform magnetic field, PCM system and PCM-PQM system in W-band extended interaction klystron. When the uniform magnetic field amplitude is 0.45 T, sheet beam can stably travel along the drift tunnel, and "Diocotron" instability does not appear; Choosing the proper magnetic amplitude and magnetic period of PCM system and PCM-PQM system, narrow side of the sheet electron beam is stable, but the broadside diffuses in the end of the device.Finally, the method of the equivalent load was used to determine the size of coupling slot of input and output structure in extended interaction klystron. Electronic beam-wave interaction of dual-cavity version and three-cavity version of W-band extended interaction klystron were investigated with 3D PIC software. Simulations indicate that total length of dual-cavity version is about 1.3 cm at 94.55 GHz, it has a small gain > 30 dB, a saturated output power almost 9 kW, an interaction efficiency of 13.2% and a small signal-3 dB bandwidth of approximately 150 MHz; The three-cavity version total length is about 2.2 cm, it has a small gain > 40 dB, a saturated output power almost 8 kW, an interaction efficiency of 11.7% and a small signal-3 dB bandwidth of 150 MHz. |
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