Design And Performance Of The Induction Cavities System For An Induction Voltage Adder

The induction voltage adder(IVA)is able to produce a very higher voltage output by summing the electric pulses generated by primary pulse generation sections with the aid of induction cavities.This dissertation presents the simulations,design,and test results of the induction cavities for an IVA which aims to produce a peak load voltage of 4.0 MV into a rod-pinch diode(RPD).The main content is as follows:As the induction cavity is connected with the driven section only in a very limited region,there exist two orthogonal directions for the power flow when the electric pulse flows inward the induction cavity.Meanwhile,the rise time of the power flow is usually comparable to the azimuthal transit time of the cell.Two dimensional(2-D)circuit model should be employed to take this 2-D power flow into account.We have proposed a 2-D circuit model of the induction cavity.The transient electromagnetic(EM)simulation is performed to check the 2-D circuit model.It shows that the 2-D circuit model could accurately evaluate the operating voltage of each element in the induction cavity.There are three types of azimuthal transmission lines for the single feed port induction cell.The first one has a constant width in high voltage electrode and the second category is a tapering width.The third one has an azimuthal transmission line network which is composed of two discrete transmission lines.The influences of the three kinds of azimuthal transmission lines on the characteristics of the induction cavity are analyzed with the aid of circuit simulation,electrostatic simulation,and transient EM simulation.The characteristics of the magnetic cores of 2605SA1 manufactured by coating and winding processes are also compared.The remanent induction of the magnetic core fabricated by the winding process is much lower than that of the magnetic core manufactured by the coating process.However,the energy loss of the magnetic core fabricated by the coating process is higher than that of magnetic core manufactured by the winding process when the induced voltage pulse duration of the magnetic cores are about several microseconds.Moreover,the insulation films formed during the coating process are not able to withstand the induced voltage of the induction cavity,and the magnetic core fabricated by the winding process is more suitable to be employed in the induction cell.The detailed design criteria of the azimuthal transmission line,insulation stack,magnetic core,radial feed gap,and output transmission line sections are presented.A full-scale prototype induction cavity is developed.For a typical shot,a maximum voltage about 1.05 MV could be achieved on a water resistor load.The 2-D circuit model is also confirmed by the experiment results.The voltage and current waveforms of the induction cavity obtained during the experiment agree with the circuit simulation results very well.The 2-D circuit simulation results coincide with the experiment results better than that of 1-D circuit model.A full circuit model including the primary energy storage section,pulse forming section,induction cavity,and the load is proposed.The influence of driven timing sequence of the induction cavities on the operating voltages across the cells is analyzed.The six induction cells of the prospective IVA and the corresponding output transmission line impedance profile are designed.We have also conducted preliminary experiments on the IVA.A maximum voltage about 4.2 MV could be obtained on the RPD load.The corresponding X-ray dose and spot size are about 18.0 Rad and 1.5 mm,respectively.The design goal is successfully accomplished.