Initiation of gas electrical breakdown in the field of a microwave traveling over the metal surface

Experimental data on electrical breakdown of air in a linearly polarized traveling microwave with a deeply subcritical field are presented. Breakdown is initiated by a linear electromagnetic vibrator or a set of vibrators. They are placed over a metal surface the plane of which contains the wavevector of the microwave and its electrical component. The axes of the vibrators are parallel to this component, and their distances to the metal surface are shorter than the quarter-wavelength of the field. In experiments with the single vibrator, this distance is varied. When the set of vibrators is used, they were placed one after another along the wavevector of the field.