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.
Slanted conducting boundaries and field emission of particles in an electromagnetic particle simulation code
Abstract A method to handle slanted perfectly conducting boundaries in electromagnetic particle simulation codes is described. Modifications to standard algorithms for the electromagnetic field advance, charge and current densities, particle destruction, and field averaging are discussed. In addition, a new model for field emission from conducting boundary surfaces is described. Particles can be emitted from conformal or slanted surfaces, and also from certain types of corners. Results of the new models on several problems involving slanted surfaces are presented.
Impedance of an annular‐cathode indented‐anode electron diode terminating a coaxial magnetically insulated transmission line
The impedance of a diode having an annular cathode and indented anode that terminates a coaxial MITL (magnetically insulated transmission line) is measured and compared with a semiempirical model developed from calculations made using the magic code. The measurements were made on the 16‐Ω electron accelerator HELIA (high‐energy linear induction accelerator) operating at 3 MV. The model agrees with the measurements within the 10% measuring error and shows that the diode operates in either a load‐ or line‐dominated regime depending on AK (anode‐cathode) gap spacing. In the load‐dominated regime, which corresponds to small AK gaps, the diode impedance is controlled by an effective anode‐cathode gap, and the flow is approximately axial. In the line‐dominated regime, which corresponds to large AK gaps, the impedance is independent of the AK gap and corresponds to the impedance associated with the minimum current solution of the MITL, with the flow becoming more radial as the AK gap is increased.