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This article introduces an optimal design method for a multistage induction coil launcher. Considering the magnetic coupling and the effect of the armature’s resistance, the basic criteria to select the structure of the driving coil and armature are proposed, and the genetic algorithm is introduced to optimize the pending parameters. Based on the principle that the current in the driving coil matches the movement state of the armature, the design method of optimal capacitor parameters is deduced. The results show that the design error is less than 1%. For a multistage induction coil launcher, the optimization is carried out stage by stage. The effect of the stage spacing between driving coils is analyzed, and it is found that changing the direction of the current in driving coils helps to improve the system efficiency. Finally, based on the above optimal design method, a multistage induction coil launcher is designed, and the energy conversion efficiency of the system is close to 40%. [ABSTRACT FROM AUTHOR]

The inductance gradient reflects the armature thrust in the electromagnetic rail launcher (EML). The inductance gradient is separated into two components: one is the armature thrust inductance gradient $L'_{a}$ that affects armature velocity and position and another is the rail inductance gradient $L'_{r}$ that affects the rail’s forward thrust, when combined with armature inductance gradient gives the total time-varying inductive load for the pulsed power. Thus, an accurate estimate of the system current can be created, which feeds back to the armature thrust and velocity calculation. The velocity frequency $f_{v}$ is introduced to interpret the velocity skin effect (VSE). The energy storage inductance gradient $L_{u}$ varying with $f_{v}$ is obtained in the 2-D finite-element model (FEM), which is used to calculate the time-varying inductance, and $L'_{a}$ can be obtained in the 3-D FEM, which is used to calculate the armature thrust. A simulate diagram is introduced to interpret how all the system components are calculated and fit together. Launch simulations reproduce experiments to about 1%. [ABSTRACT FROM AUTHOR]

Reconnection electromagnetic launcher is a kind of electromagnetic launcher, which has excellent performance of launching. The change of projectile width has a great influence on the launching efficiency of reconnection electromagnetic launcher. The influence of the reverse vortex generated on both sides of the projectile on the launch efficiency when the projectile width increases is studied in this article. First, the model and basic principles of the reconnection electromagnetic launcher are introduced, and then the electromagnetic finite-element software is used to carry out a large number of simulations to study the launch model. The results show that when the projectile weight is kept constant by digging out a part of the projectile, and the projectile width increases within a certain range, the launch efficiency will increase as the width of the projectile increases, the increasing trend is smaller and smaller, and finally it will gradually decrease. When the mass of the projectile is determined, there is an optimal width. Finally, the eddy current distribution in the projectile is analyzed, and it is found that when the projectile has a wide width, the eddy current opposite to the eddy current in the middle of the projectile will appear on both sides of the projectile. Through the analysis of electromagnetic force, it can be concluded that the reverse eddy current is beneficial to the launch. Therefore, when keeping the weight of the projectile constant and only increasing the width, the efficiency will gradually increase. When the width of the projectile is highly wide, the excavated part of the projectile is very large, which starts to affect the vortex distribution and reduce the efficiency. This research provides a reference for the design of the projectile of the reconnection electromagnetic launcher. [ABSTRACT FROM AUTHOR]

ASELSAN Inc. has been working on electromagnetic launch technologies since 2014. The first prototype, EMFY-1, has a 25 mm $\times25$ mm square bore and 3-m-length rails. The second prototype, EMFY-2, has a 50 $\times50$ mm square bore and 3-m-length. This article presents a recently developed prototype, EMFY-3, with a 50 $\times75$ mm rectangular bore and 6-m length. The input energy of the pulsed-power supply (PPS) is doubled to 8 MJ, and the 2.91 MJ muzzle energy is obtained. Velocity curves are captured with Doppler radar, enabling us to establish propulsive inductance gradient $L^{\prime }_{\mathrm {pr}}$ transients empirically. The results confirm that $L^{\prime }_{\mathrm {pr}}$ is constant throughout the launch, as no significant breaking mechanism occurs with the non-magnetic containment. However, a slight variation (2% at maximum) happens with different rails’ current magnitudes from one launch to another. The transition phenomenon is a candidate for the drop in the $L^{\prime }_{\mathrm {pr}}$ , as it occurs more likely at launches with higher linear current densities. Moreover, a sensitivity analysis is conducted to show the importance of $L^{\prime }_{\mathrm {pr}}$ calculations. A deviation of 5% from the actual value can cause an error in muzzle velocity up to 6.2%. This fact indicates that simulation models are very susceptible to $L^{\prime }_{\mathrm {pr}}$ calculations. Although $L^{\prime }_{\mathrm {pr}}$ is calculated as 0.515 $\mathrm {\mu H/m}$ with 3-D finite element method (FEM), the Kerrisk formula calculates as if $0.561~\mathrm {\mu H/m}$ ; the experimental measurement gives 0.575 $\mathrm {\mu H/m}$. These methods differ by 8% at maximum, which causes muzzle velocities errors. Regarding empirical findings, the 3-D FEM model calculates $L^{\prime }_{\mathrm {pr}}$ more precisely than analytical formulas, and the contrast between models have grave importance due to the muzzle velocity errors. [ABSTRACT FROM AUTHOR]

This article describes the performance of a multi-gap, multichannel (MGMC) spark gap switch, evaluated numerically and experimentally, to achieve multichanneling using a relatively low-magnitude trigger pulse. First, an electrostatic analysis of the switch geometry was carried out using COMSOL Multiphysics 5.5 to determine the electric field distribution during high-voltage hold-off before triggering and to determine the coupling parameters between trigger and other intermediate electrodes of the switch. Second, a circuit model was developed in PSpice Lite 16.6 for predicting the process of channel formation and its influence on adjacent channels. Based on the simulation results obtained, a six-gap, eight-channel, planar MGMC switch operating in air has been designed and developed. The developed switch was, then, incorporated into a compact experimental setup to experimentally evaluate various switch parameters such as inductance, switching delay, jitter, and closing time when triggered using a negative-polarity trigger pulse of magnitude −40 kV, generated using a compact, in-house developed trigger generator. In contrast to most of the reported MGMC switches that use complicated Marx-based generators to produce ≥120-kV trigger pulses for multichannel formation, the experimental results, thus obtained, report comparable switch performance using a low-magnitude (−40 kV) trigger pulse. In addition, framing and streak camera images taken during the current discharge indicate the presence of ~6 luminous channels. In addition, short-circuit experiments for estimating switch inductance by consecutively shorting one or more channels also indicate multichanneling in the switch using a low-magnitude trigger pulse. [ABSTRACT FROM AUTHOR]

One of the key challenges in the design of gas lasers powered by pulsed power circuits pertains to reducing the flow of current through the electrodes during the filamentary discharge phase. This phase occurs after the lasing period (“volume glow”) is terminated due to discharge instabilities and the current flow during this period is referred to as late currents. Late currents contribute to electrode erosion. The ejected electrode material contaminates the gas, and lowering the service life of the laser. Snubber circuits are an economic solution to reducing late currents in pulsed power circuits that do not employ a magnetic switch. In a simple snubber, which is connected directly across the main storage/drive capacitor $C_{0}$ , it was found that the stray series inductances of both $C_{0}$ and the high voltage snubber diodes significantly reduced the magnitude of current flowing through the snubber. A new coaxial capacitor and snubber assembly was proposed to improve the effectiveness of the snubber in reducing the late currents. The design exploited the high degree of mutual coupling between the concentric coaxial cylinders to reduce the total inductance in the snubber loop. Experimental results showed an almost 40% reduction in the total charge that flows through the discharge in the late currents stage. Although the improvement was significant, it is expected that improvements to the construction quality of the prototype could potentially lower the late currents even further. [ABSTRACT FROM AUTHOR]