An atmospheric microplasma is generated by direct-current (dc) discharge in air with a miniature gas flow through a nozzle, which limits plasma volume. Two discharge modes appear in a nozzle-to-mesh electrode system with helium or argon. One is a repetitive pulsed discharge with a current of 10–30 mA and a short pulse width. The fast pulsed current is powered by electric charges stored in the parasitic capacitance, which depends on the spatial arrangement of the electrodes and the power leads. The pulsed discharge makes it possible to develop a discharge scheme for microplasma generation without a high-voltage pulse generator. The other is a sustained dc discharge, which develops with increasing applied voltage. In the case of helium, a glow discharge configuration is observed with a positive column and a layered structure near the cathode. The length of the positive column is affected by electrode separation and gas flow rate.
A way toward a quasicontinuous extreme ultraviolet ͑EUV͒ radiation source is proposed and explored. Tin and lithium vapor discharges with the lateral laser-ablation injection are experimentally studied as possible efficient sources of quasicontinuous emission of EUV radiation at a wavelength of 13.5 nm. It is shown that the time-of-flight control of optimal plasma parameters by means of varying ablating laser pulse parameters provides a considerable elongation of maximal-power EUV emission with an overall efficiency of 0.1% and with an energy output exceeding 1% of the energy deposited in the discharge plasma. Along with a high average power and a stable position, such an emitter may have its size small enough to be used in the projection lithography.
A control algorithm with nonlinear feedback is effective for the precise motion control of robot manipulators. It is usually designed in continuous-time form, although it is digitally implemented. In this paper, a continuous nonlinear control law for a robot manipulator is redesigned for digital implementation. The digital control law is derived so that the response of the digital control system is close to that of the continuous control system. The amount of computation for the redesigned control algorithm is almost the same as the amount of computation for the original nonlinear control algorithm. The redesign method provides satisfactory stable results even for a fairly large sampling interval. The simulation and experimental results illustrate the effectiveness of the proposed redesign method.
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