Design and performance of the Z magnetically-insulated transmission lines
The authors have designed and tested a 10 nH, 1.5 m radius vacuum section for the Z accelerator. The vacuum section consists of four vacuum flares, four conical 1.3 m radius magnetically-insulated transmission lines (MITLs), a 7.6 cm radius 12-post double-post-hole convolute which connects the four outer MITLs in parallel, and a 5 cm long inner MITL which connects the output of the convolute to a z-pinch load. The authors have demonstrated they can deliver a 100 ns rise-time 20 MA current pulse to the baseline z-pinch load. They can reproduce the peak MITL current to within /spl plusmn/1.6%. Power-flow measurements indicate the vacuum section performs as expected until peak current. Afterward, measurements and simulation results diverge.
Design criteria for the Z vacuum insulator stack
The Z (formerly PBFA Z) vacuum insulator system consists of four stacks of Rexolite rings about 11 ft. in diameter, immersed in water, that insulate four biconic vacuum power-flow regions. The power flows are combined by a post-hole convolute just outside the imploding plasma load. Each ring stack is driven by nine similar water transmission lines connected around its perimeter. The different inductances between each stack of insulators and the load lead to a different voltage magnitude and waveform across each stack; therefore two stacks consist of five 2.25 inch high insulators, and two stacks consist of six such insulators. The design criteria for the insulator stacks were developed using the analysis described by I.D Smith (Proc. 10th IEEE Int. Pulsed Power Conf., 1995). This treats the case of multiple stack modules each composed of a number of series insulators and each having a large circumferential transit time. The analysis tries to take account of the fact that when one flashover occurs at a particular location in one insulator stage, or even a number of flashovers at various locations, effective breakdown may not have occurred, because it takes time for series stages to flash locally in the same stack, while other parts of the stack are transit-time-isolated. To develop criteria for Z the analysis was first applied to Saturn, and was normalized by assuming a safe level for Saturn based on experience; it was then applied to Z. The analysis is presented, and results to date for the Z stack are described.
Microwave source with enhanced radiation power based on orbitron MASERs
We have proposed the design of high power microwave source in a vacuum tube based on the theory of negative mass instability. The proposed source does not operate based on a slow-wave structure but instead makes use of accelerated charged particles. In our structure, an electron emitter injects the charged particles into to the cavity. Emitted particles move around the anode, which leads to electron acceleration and emission of electromagnetic waves with a specific frequency. In this paper, we have enhanced the output power and frequency of microwave source by variation of particles initial energy and the number of anodes incorporating their specific arrangement and applied voltages. Working at room temperature, compactness, wide bandwidth, and tunability of output frequency are among the advantages of the proposed source.