Investigation Of Marx-PFN

Pulse-Forming Network (PFN) is one of the main technologies to obtain long pulses with microsecond level. Besides typical single-stage PFNs often used in laboratory, in order to meet different requirements, there are two kinds of combined PFNs made from single-stage PFNs in different connection manner, which are Blumlein-PFN and Marx-PFN. Based on the discussion and analysis of typical single-PFN, this thesis mainly investigates the principle and the characteristics of Marx-PFN, and examines the influences of relative parameter changes on the output pulse. The design procedure of Marx-PFN is given and a four-stage Marx-PFN has been built and tested. The experimental results are accordant with the design.The basic characteristics of singe-stage PFNs, especially the transmission line simulating networks, are studied, and the relations between the network impedance, pulse duration and the capacitance, inductance, mesh number are clarified. The comparison of the different output features on the match loads with different PFN structures is made. The principles, characteristics and main structures of Guillemin networks are presented briefly, which are useful for the design of our pulse power source.The simulation of single-stage PFN verifies some basic characteristics of PFN in theoretical analyses. A five-mesh PFN with equal capacitances is simulated in detail. The influences of inductance changes on the output pulse are obtained. A satisfactory output pulse on the match resistance is obtained by optimizing the values of each mesh inductance. The influences of the load capacitance and inductance on the output are also analyzed. A four-stage Marx-PFN is designed and simulated and the effects of related parameter changes on the output pulse are analyzed.In experiment, the design and test of the gas spark switch are introduced, which show that the gas spark switches are of good coincidence, can be triggered or break down itself normally and satisfy the requests of our system. The low-voltage experiments of single-stage PFN testify that each single-stage PFN can generate a pulse with a rise-time of 500ns, an FWHM (Full Wave at Half Maximum) of about 3μs and a flat-top of 2μs. In the high-voltage experiments on the four-stage Marx FPN, a 30kV output with 500ns rise-time, 2μs flat-top, 3μs FWHM is obtained on the matched CuSO₄ water resistance of 17Ωwhen the Marx-PFN is charged to 20kV, and the output pulse is basically in agreement with the simulated result. Finally the reason of the oscillation on the rise section of the output pulse is analyzed.