ZERO FIELD-DISTORTION MICROWAVE PROBES

Efforts concerned measuring microwave fields. At least four types of probes are required to probe the high intensity microwave fields and the ac companying plasmas. The disturbance of the plasma and the fields due to the volume displacement of the physical presence of the probe and stem, and due to the small amount of energy extraction necessary for the probe readings is unavoidable, but scattering due to the antenna-like configura tion of the probe stem can be minimized to be negligible. The stems which support the probes and which contain the transmission line connec tions should be as small as mechanical and elec trical designs will readily permit, and must be designed in a special way in order to minimize scattering of the microwaves. It is necessary to design a structure upon the surface of the probe ms which has a high wave impedance for the microwaves, compared to the impedance of space. This permits the currents excited in the probe stems by the microwaves to be held to a minimum so that their reradiation scattering will not interfere with the probe measurements or the general course of the experiment. Probes have so far been designed and tested which are essentially responsive to microwave magnetic field, microwave electric field, microwave power, as a function of wave direction, as in a directional coupler, and temperature of a small test object exposed to the microwave and to any plasma which may exist in its vicinity.