Study On The Folded Plate Blumlein Line And Its Application

The military application of high power microwave requires that the pulsed power technology develops towards the direction of compactness and high average power. As one of the candidates meeting these requirements, the folded plate Blumlein line has attract extensive attention nowadays. In this dissertation, based on the calculation and analysis of the working mechanism and operation properties of folded plate Blumlein lines, a compact folded plate Blumlein line was designed and fabricated, and thereby used to drive a high power microwave source to produce several hundred megawatts high power microwave.This dissertation mainly consists of the following aspects.Based on the detailed investigation of the electric characteristics and other parameters of the solid and liquid dielectrics, the Kapton film has been chosen as the transmitting dielectric and the pure transformer oil as the insulating dielectric in the folded plate Blumlein line. Kapton material is of excellent breakdown voltage (200kV/mm), high endurance to heat, radiance, organic solvent and corona flashover which enables to withstand high voltage with comparably less thickness (thus may reduce the volume of the equipment). Transformer oil is of similar relative dielectric constants as the Kapton film, with high resistivity, high breakdown voltage and minor dielectric loss tangent. Therefore transformer oil of high quality and purity is very suitable to use as filling dielectric for this folded line.Theoretical analysis and electric circuit simulation of the working mechanics of the parallel plate Blumlein line are performed. Parameters such as characteristic resistance, time delay, pulse width, the capacitance, breakdown voltage and overall energy of the plate Blumlein line have been obtained from the non-loss transmission line model; the unit-length resistance R and the unit-length conductance G are involved in the loss transmission line model. By adjusting the parameters, the thickness of folded line dielectric and the copperplate width are optimized as 5mm and 20cm, respectively. And by means of the electromagnetic field distribution simulation, the minimum dielectric edge width is optimized as 3cm.The dispersive property of the folded part of folded Blumlein line is analyzed, calculating results show that dispersion effect of the folded part can be ignored under the present low frequency conditions. Systematic analysis on the characteristic resistance of the folded part of folded Blumlein line is carried out through various methods such as conformal mapping, which leads to the conclusion that there is no much difference between the characteristic resistances of folded part and plane part. Detailed analysis on the influence from characteristic resistance and transmitting voltage wave of the folded part of folded Blumlein line is conducted through the combination of electric circuit analysis and electric field distribution simulation. In consideration of the engineering issues in project realization, the appropriate folding manner with folding angle of 180°and inner radius r = 10mm is determined.Based on theoretical analyses, a folded Blumlein line with Kapton film as dielectric is designed and fabricated; a multi-channel rail switch with the advantage of small volume (Φ60×300mm) and low inductance (40nH), which especially suits for plate Blumlein lines, is developed; An outer-chamber in the size of 120cm×40cm×40cm is made up for holding the folded Blumlein line, liquid filling dielectric and other connection parts. Experiment conducted on this folded Blumlein line has provided a voltage pulse of 600kV and 100ns on a match load. Several water resistances with different constructers have been used for the match loads, but experimental results show that the U-shape resistance is more suitably used as the match load of the folded Blumlein line.Using the folded plate Blumlein line to drive an intense electron beam diode to produce an electron beam of 500kV, 50kA, 100ns when the diode load is matched with the transmission line and then it is used to drive a magnetically insulated line oscillator (MILO) to produce high power microwaves. Experiments have affirmed that with diode parameters of 550kV, 40kA and 80ns, microwave peak power of 350MW with 40ns pulse width can be output from C band MILO.Compared to other transmission lines with the same output power, the folded plate Blumlein line has advantages of small volume and weight, no need of cycle purifying system and other assistant apparatus; these advantages make it possible to develop towards the direction of compactness and integration. Therefore study on the folded plate Blumlein line is of significant application value.