Abstract: A moisture sensor including in one embodiment a probe formed with a first cylindrical tube extending outward from a base and having a plurality of axially extending slots around the periphery thereof and a second slotted cylindrical tube extending outward from the base separated and insulated from the first tube, and extending coaxially with the first tube. The tubes form an effective coaxial capacitor and are insertable into material to be sensed appear as a ground plane. In a second and third embodiment a member defining flat surfaces extends from a base forming in cross-section a volume with a square center and legs extending from each side thereof to an open peripheral end. An RC bridge circuit, preferably a Wien bridge or a capacitor divider circuit is connected to the tubes to measure the impedance of the material.

Abstract: A radiation source in which a beam of electrons is produced and directed along a path with dielectric material having a constant less than 4 in proximity to the path and an undulator providing oscillatory velocity modulation to the beam along the path for producing millimeter and sub-millimeter wavelength radiation.

Abstract: A moisture sensor including a probe formed with a first ring of spines extending in parallel outward from a base and a second ring of spines extending in parallel outward from the base separated and insulated from the first ring, the spines forming an effective coaxial capacitor and being insertable into material to be sensed and an RC bridge circuit, preferably a Wien bridge connected to the rings to measure the impedance of the material.