Magnetically Insulated Transmission Line Oscillator

The Magnetically Insulated Transmission Line Oscillator (MILO) is a coaxial crossed-field device. There exists great importance in the investigation either into the fundamental physics related to the beam-wave interaction or into the rule of electron movement in this device. Presented in this dissertation are theoretical analysis, particle simulation and experimental studies on the physical mechanism of the MILO. A series of reasonable and valuable results are obtained from this work.Not concerning the influence of electron on field, the theoretical analysis of electron movement in MILO is made under the condition of planar electrode approximation. First the movement track of single electron in the crossed DC electromagnetic field is obtained. Then with the introduction of the expression of radial electric field and azimuth magnetic field, the movement tracks of electrons in the interaction space are modified on account of the azimuth magnetic field decreasing with the decrease of the axial current. Meanwhile the effect of the initial electron velocity on the movement track is also studied. The least load current to realize magnetic insulation in MILO is obtained from the relation between current and azimuth magnetic field and the relation between magnetic field and electron movement track. The results show that the electron mean drift velocity is affected by the cathode radius, the impedance of the load diode, the inner radius of vanes and the input voltage. The interaction process between space charge and slow wave structure is investigated. According to the energy conservation, the maximum electron efficiency is evaluated either with or without the relativistic effect. The result shows that the efficiency to translate the energy from DC field to RF field will increase with the increase of input voltage to some degree.The reported L-band MILO is modeled and verified first by our simulation code. Then the C-band simple MILO is simulated systematically. The physics of electron bunching andmicrowave field growing is investigated in detail. The relations among MILO's frequency, output power and geometry parameters are presented. The results show that the MILO's frequency will decrease with the increase of the size of the resonant cavity and the output power could be optimized by modifying the cavity. The simulation result also shows that the input voltage has start and cutoff values. Because the microwave field in simple MILO is n mode along the axis and the field is of the standing wave structure. The tapered slow wave structure is introduced to make the field in the downstream of interaction space have a travelling wave structure and easily make the microwave energy transport out of the device. The results also show that the tapered slow wave structure does not affect the output frequency obviously and that the maximum output power of the tapered MILO could reach 5.84GW at frequency 4.53GHz when the input voltage is 800kV. The output microwave field is TM mode.The experimental study is performed on the C-band tapered MILO designed with the help of the simulation. The whole system is calibrated separately by parts. From MILO to microwave receiving hom, the special system is simplified to be a two-port network and its S parameter is measured to calculate the attenuation factor a. The attenuators and the sensitivity of detectors are calibrated in varied frequencies. The attenuation of the cable is also calibrated. In the experiments, the typical results show that the microwave is generated in the frequency range from 4.84GHz to 4.89GHz with the output power of 133MW, when the input voltage is 420kV and diode current is 44kA.