Abstract: The present invention refers to a plasmatron as well as to a process for stable operation of plasmatrons with steam as the plasma gas, in the case of which the operational fluctuations which are typical of steam plasmas as well as the increased degree of electrode erosion are to be avoided. In accordance with the present invention, this is achieved on the basis of a limitation of electrode cooling by using hot water as a coolant having a temperature of at least 80.degree. C. If necessary, it is possible to use, on the one hand, hot water cooling and to exclude, on the other hand, a condensation of the steam on the electrodes by admixing a gas which will lower the condensation temperature of the steam.

Abstract: A rotary head drum for a VCR using a fluid dynamic pressure bearing comprising a lower drum fixed to a base plate, a rotary shaft attached to the center of the lower drum, an upper drum fixed to a flange, a rotary head fixed to the upper drum to record and reproduce video signal in and from a magnetic tape, and a shaft housing including a guide groove, an air flowing groove having an air hole, a lubricant containing groove having a lubricant flowing hole, and a guide boss. The rotary shaft includes plurality lubricating grooves and a lubricant guide groove, so that the generation of the vibration and noise of conventional ball bearing when rotating the head drum, as a result it is possible to improve the Jitter and Wow-flutter of the video signal which effect upon the quality of the screen in recording or reproducing the video signal.