Research On Dynamic-cascaded Helical Explosively-driven Magnetic Flux Compression Generators

In recent years, dynamic-cascaded helical explosively-driven magnetic flux compression generators (HEMCG) have become the focus due to their capability of outputting high current with short risetime on high impedance loads, and they are suitable to drive vacuum diodes to produce high power microwave and laser after pulsed power modulations. Systematic researches about the dynamic-cascaded HEMCG have been done from theories, equivalent circuit calculations, designs and technological processes to experimental technologies. Their initial energy sources, synchronization system and applications are also systematic studied. Details are listed as follows.For the first time, an initial energy source system for HEMCG was designed and constructed, which includes rechargeable battery, high voltage converter and high energy density (~1J/cm~3) capacitor and can supply more than 10kA current for an inductance load of 60μH. At the same time, it has the characters of small volume, radio telecontrol, and high stability. Additionally, we can fire the detonator in far distance with telecontrol apparatus. Specially, the capacitor used in this system can return to normal after interior partial breakdown. A synchronization system was progressed by using the coaxial switch driven by detonation cord, which is simpler and safer than the old one. The designs and calibrations of the Rogowski coils and resistance dividers are discussed in details. The measurements of the explosive parameters are also discussed.An equivalent circuit MathCAD program called CIRC-206 was written after all kinds of the circuit parameters calculating methods being considered. The inductances and direct current resistances were calculated by using the mirror current model and the magnetic flux coupling between two cascaded classes is decided by using flux capture model which is different from the traditional transformer model. In order to evaluate the non-ohm magnetic flux losses, the magnetic flux losses parameters were used, which can be determined by the related experimental results. CIRC-206 can be run to calculate helical magnetic flux compression generators parameters including inductances, direct current resistances, magnetic flux losses, currents, voltage distribution etc. At the same time, it is easy to be connected with the equivalent circuit calculation programs of the followed pulsed power modulators. The CIRC-206 is a good tool for the design of the dynamic cascaded helical magnetic flux compression generators and a fast program with clear physical pictures.Direct feed and indirect feed are two methods for the capacitor to offer initial magnetic flux to HEMCG, whose advantages and disadvantages are theoretically analyzed in this dissertation.The reasons are given for using the direct feed in ourgenerators.After investigating experiences by international researchers, two kinds of dynamic-cascaded explosively-driven helical magnetic flux compression generators were designed using the CIRC-206. The length of the two generators is 500mm, the diameter is 0160mm, the explosive used is about 1.2kg. The generator whose second class has a conical coil can output more than lOOkA current on 4uH inductance load with a current risetime of 12|a.s, and the other with a cylindrical coil can offer more than 120kA current with risetime of 18us on the same load. The reliability of the two generators is 100%. These results met the requirements of the "863" projects. One of the difficulties is the generators'stability and reliability, which has been overcome by many researches. On one hand, the maching and assembly technologies are perfected. On the other hand the high voltage insulation problems have been resolved by using SF6 and PTFE materials.The voltage waveform of the pulse forming line (PFL) charged by the dynamic-cascaded helical MFCG was analyzed using the CIRC-206, some conclusions about the relations between the charging voltage and the system parameters were achieved. These parameters include connection line inductance between the MFCG and the transformer, the transformer parameters and the PFL parameters. Many experiments have been done and the results demonstrated that the CIRC-206 is helpful for the application research of the dynamic-cascaded HEMCG. The success of the experiments opens a new path for the HEMCG's pulsed power modulationsEspecially, the lOOkA generator and its initial energy source system have been processed in batches and successfully applied to the experiments of the national "863" project with 100% reliability.