Cathode ray tube including variable delay means

Claim 1

A cathode ray tube including variable delay means for a high frequency electrical wave comprising, within a sealed exhausted enclosure: an elongated wafer of piezolectric material having at least one of its sides designed to emit secondary electrons with a secondary emission coefficient greater than unity when said side is bombarded by a primary electron beam, an input transducer positioned on said side of said wafer in the vicinity of one end thereof for converting said high frequency electrical wave into a mechanical one, said mechanical wave propagating along the surface of said side from said one end of said wafer to its other end, an absorbing load positioned on said side of said wafer in the vicinity of said other end for absorbing said mechanical wave after its propagation along said wafer, means including an electron gun for generating a flat electron beam at least equal to the width of said input transducer for bombarding an impact zone on said side of said wafer, controllable deflection means for adjustably positioning said primary electron beam so that said impact zone may be moved along the propagation direction of said mechanical wave along said wafer, and two plane and parallel electrodes between which said wafer is inserted, a first one being a conductive grid which is positively biased with regard to said electron gun and which is fixed sufficiently close to said side of said wafer for collecting the secondary electrons emitted by said side without substantial phase mixing and which consists of conductive wires parallel to the direction of propagation of said mechanical wave, their number, their thickness and their spacing being such that said grid does not obstruct the primary electron beams and that the secondary electrons are yet collected by said grid, and the second one being a conductive plate which is fixed onto a side of said wafer opposite to said side, said two electrodes constituting a two-wire line between two ends of which is collected a high frequency signal reproducing the high frequency electrical wave applied to said input transducer and being delayed with regard to it by a value depending upon the adjustment of said constrollable deflection means.