A system and method for regulating a gas flow of a plasma arc system. As a result, an antenna device of smaller size and small loss is obtained. A projecting portion is formed in the casing, on which a region of the circuit board in which the heat generating part is installed is seated. The angle of the reflector and end caps is selected such that reflected RF energy dissipates an increasing percentage of the remaining RF energy at each reflection, and the reflected RF energy which returns to the rotating mirror is directed to the back surface of the rotating reflector, and is not coupled to the input waveguide. The groove and the wall of the socket define the flow rate in the dispensing passage.