Abstract: A plasma generator comprises a metallic tube of small diameter inside which can circulate a gas such as argon at a small flow rate, which is discharged at the front end of the tube. The tube is coupled with an energizing structure which can comprise a frequency generator supplying electromagnetic microwave via a coaxial connection, a coupling structure allowing the transfer of the energy of the generator to the front portion of the metallic tube. In the absence of a gas current in the tube, the front portion radiates the energy transmitted to it in the manner of an antenna. When a gas is discharged at the end of the tube, said energy allows maintaining a plasma in front of the latter.This plasma generator device is usable in many applications, such as a blowtorch a light source or torch usable in spectrography, a plasma motor or an ion source.

Abstract: N elementary transducers are distributed regularly along a line of scanning. An ultrasonic frequency generator generates a high frequency signal which is applied to a first set of switches with a phase angle .phi. and to a second set of switches with a phase angle .phi. + .pi.. First and second registers are provided for temporarily energizing selected ones of said first and second set of switches such that the high frequency signal is applied to a set of n transducers with a phase angle of either .phi. or .phi. + .pi.. Third and fourth registers stored a phase distribution signal which is serially clocked into and through the first and second registers such that the high frequency signal is applied to n transducers with a phase distribution determined by said stored distribution signal at each of a plurality of successive times, each time to a set of n transducers which is shifted by one transducer of the array of transducers such that scanning occurs throughout the array.