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In this paper, the measurement of the in-bore position and velocity of the armature is performed using B-dot probes. Nine B-dot probes are installed in the rail-to-rail insulator at different distances from the breech. Based on some simplifications of the current flowing in the armature, the magnetic flux formula of the probe is derived. It is found that when the armature passes by the probe, the ratio of magnetic flux of the probe and armature current reaches to its peak value. Thus, using the integrated B-dot probe signals and armature current, we can obtain the armature's position as a function of time, and then the velocity can be obtained. Compared with zero-crossing method, this method considers the influence of di/dt to the signals of B-dot probe, and is more theoretically precise. The B-dot probe signals are also used to analyze the distribution of the armature current in launch process. Index Terms--Electromagnetic launcher, railgun, solid armature, B-dot probe.

A pulsed power supply of a 1.5-MJ capacitor bank has been developed for high-current high-velocity sliding electrical contact studies in railgun launches. The system consists of 8 small modules, each with a capacitance of 15 mF, and one large module with a capacitance of 54mF. All of nine modules use triggered spark gaps as the main switches. Various shapes of high-current pulse can be formed by controlling the charging voltage and firing time of each module. The small module has been designed for the maximum operating voltage of 5 kV, the peak current of 140 kA, the pulse rise time of 0.9 ms, in which semiconducting diode stack is used as crowbar switch. Since the large module has no crowbar switch and relatively small pulse forming inductance, it can supply high-amplitude oscillating current waveform. The effects of the large module are threefold. First, the large module provides a basic current on which the currents of small modules superimpose to form a nearly constant driving current of armature. Second, the oscillating nature of the current can drastically reduce the muzzle arc current; hence suppression of the muzzle arc can be obtained. Third, the crowbar switch can be removed and therefore the cost of the system can be reduced. The experiments were performed to verify the operation performances of the two kinds of modules, where the modules were discharged simultaneously and/or sequentially. The feasibility of large module on the muzzle arc control is also examined. The results of the experiments show that a total current of 400 kA with a 1.5 ms flat-top time can be obtained and all the modules show good performance during the railgun firing. Index Terms--Capacitor bank, electrical sliding contact, pulsed power supply, railgun.

The feasibility and the performance of the armature with resistivity gradient were studied. The current distribution and its improvement by resistance distribution adjustment in C-shaped armature were analyzed by finite-element method. The calculation was performed with a monolithic armature, in which we defined several layers arranged of two different types. With some adjustment of resistivity of the layers, the current density distribution was found more appropriate for EML. The armature of type-I seems more considerable than that of type-II, as it is more sensitive to resistance changes, and the maximum current density appears in head part of the armature instead of corner, which reduces the possibility of armature corner rupture in electromagnetic launch. Index Terms--Armature, finite element method, railgun, resistivity gradient.

The Pseudo-liquid (PSL) armature with air-spring is a novel railgun armature, which has lower mass and more compliance than conventional C-shaped armature. The united research group leaded by Beijing Institute of Special Electromechauical Technology (BISET) has completed a lot of experiments of the PSL armatures with air-spring since 2004. The results of these experiments show this armature can prevent transition with some conditions. This paper presents an overview of PSL armature program including the pulsed power supply, two rail launchers (SRL1 and SRL3), projectiles and some experimental results. As the best result of SRL1 rail launcher tests, it is obtained that muzzle velocity of 1.1 km/s with a 52 g mass. The best performance of SRL3 launcher tests is muzzle velocity of 1.92 km/s with a 45 g mass operating at a stored energy of 1.39 MJ and a flat-top current of 400 kA with about 1.5 ms pulse duration. The further experimental studies are being continued. Index Terms--PSL armature, pulsed power supply, rail launcher, transition.

A new type of capillary with closing switch properties is proposed as a realistic alternative to the conventional capillary in electrothermal (ET) launchers. This capillary is designed as a plasma switch with a trigger electrode (TE) in place of an exploding wire. The capillary plasma switch (CPS) has dual functions of plasma generator or ignition for chemical medium, plus as a switch for the charged circuit, which considerably simplifies the power supply system and meets the requirements of a compact system. The conventional closing switches in the power system for ET launchers can be eliminated. In our work up to now, the special emphasis for CPS has been on the design of the TE. Experiments were carried out to investigate the electrical characteristics of CPS. This paper describes details of experimental testing of devices under a wide range of operating conditions and example waveforms are illustrated. The experiments proved that the CPS was suitable for ET launchers and can offer several advantages over the conventional capillary such as repetitive operation and compactness. Index Terms--Capillary, electrothermal launchers, plasma switch.