Формирование двух импульсов тока пучка убегающих электронов

The conditions for the formation of two current pulses of runaway electron beams during the breakdown of a point-to-plane and tube-to-plane gaps in high-pressure air, nitrogen, and helium are studied. It has been shown experimentally that, depending on a pressure and kind of gas, a rise time of voltage pulse with an amplitude of tens of kilovolts, three modes of generation of runaway electron beams are observed. In the first mode, a single current pulse of runaway electron beam is observed at the maximum voltage across the gap, when a streamer appears in the vicinity of the pointed electrode (cathode). Its duration is ≈100 ps. In the second mode, two current pulses of runaway electron beams are observed at a lower pressure. The first pulse is generated as in the first mode. The second pulse is generated after the gap is bridged by the streamer (the first ionization wave). The electron energy in the second pulse is significantly less than in the first one, but the duration and amplitude of second current pulse under optimal conditions are greater. The third mode is implemented at lower pressures than in the second one. The generation of runaway electrons continues after the first pulse without a pause in the quasi-stationary stage. The total current pulse duration is hundreds of picoseconds.

The Influence of Welding Process Parameters on Pore Formation in Pulsed Laser-Welded Vacuum Plate Glazing

To explore the mechanism of the pore formation in the laser-welded vacuum plate glazing sealing layer, a vacuum plate glazing laser side sealing test was carried out. The influence of the pulse current, pulse duration time, pulse frequency and welding speed on the pores of the sealing layer was studied by means of scanning electron microscopy (SEM) and metallographic microscopy, and the cause of the pores is analyzed. The results show that the porosity decreases with the increase of the pulse current. When the pulse current is 160 A, the pores are the fewest and smallest, and the porosity is only 0.1%. The porosity of the sealing layer decreases first and then increases with the increase of the pulse duration time. The porosity decreases first and then increases with the increase of the pulse frequency. When the pulse frequency is 18 Hz, the porosity is the least, at only 0.08%. The porosity of the sealing layer increases with the increase of the welding speed. When the welding speed is 80, 90, 100 and 110 mm/min, the porosity is 0.02, 0.08, 0.63 and 0.89%, respectively. These studies can provide a theoretical basis for laser sealing manufacturing of vacuum plate glazing.

One-dimensional self-consistent kinetic models as Vlasov equation solutions

One-dimensional self-consistent kinetic models may describe some states of intense charged particle beams. In the collisionless approximation, which is appropriate for the short current pulse duration, the kinetic distribution function may be built as a function of the motion integrals. Two situations are considered corresponding to the wide charged particle flux with the sharp front and to the sheet continuous beam freely propagating in space. In both cases, one-dimensional Vlasov equation solutions are shown to exist, which are based on algebraic functions of the motion invariants.

Experiment and Research of EDM Surface Modification of Titanium in Mist Medium

By AF1100-type EDM machine, graphite rod as a tool electrode, misted deionized water mixed with fine-grained C powder as working medium, the strengthening coating was prepared on the surface of TC4 titanium. The surface microstructure of strengthening layer was observed, the hardness and thickness of strengthening layer was tested, under different peak current, pulse duration, pulse interval and polarity. The results show that: At a current of 2.9A to 6.6A when using negative polarity to strengthen can get better strengthening layer organizational.

Investigation of the Relative Gas Volume in the Discharge Gap when Using Water in Oil Emulsion as Dielectric

The gas presented in the discharge gap which was generated by the decomposition and vaporization of the dielectric due to the extremely high temperature in the EDM process plays an important role in the aspect of EDM performance. In this paper, the relative gas volume in the discharge gap is investigated when water-in-oil (W/O) emulsion was used as dielectric. Parameters, such as peak current, pulse duration, water content of the W/O emulsion were researched. Experimental results show that the relative gas volume in the discharge gap was significantly affected by discharge energy. Besides the discharge energy, water content of W/O emulsion is another significant factor that affects the gas volume in the discharge gap.

Electrochemical Micromachining Using Electrostatic Induction Feeding Method

This paper describes micro electrochemical machining (ECM) using the electrostatic induction feeding method. In ECM, electrolytic dissolution can be localized in the area where the gap width is narrow by using pulse durations shorter than several tens of nano-seconds. With the electrostatic induction feeding method which has been developed for micro electrical discharge machining, the current pulse of such short durations can be obtained more easily compared with the conventional pulse generators. In this study, the influences of the pulse voltage of power supply and feeding capacitance on the machining current were investigated theoretically. It was found that the current pulse duration is nearly equal to the rise time and fall time regardless of the pulse-on time of the pulse voltage. Hence, ultra-short pulses can be obtained without a need to use an expensive pulse generator. Micro-hole drilling carried out in a sodium nitrate aqueous solution with current pulse duration of 30ns showed that significantly small side gap of 2μm could be obtained.