GB639983A - Improvements in or relating to electron discharge apparatus - Google Patents

Abstract

639,983. Velocity - modulated tubes. STEVENS, A. H. (Leland Stanford Junior University, Board of Trustees of). May 13, 1942, No. 6521/44. Divided out of 639,981. [A Specification was laid open to inspection under Sect. 91 of the Acts, Aug. 14, 1946.] [Class 39 (i)] A velocity-modulated tube is modified by the introduction of a non-linear admittance so as to exhibit a constant mutual conductance over a range of amplitudes appreciably above zero. The tube is particularly adapted for use as a combined transmitter-detector in a regenerative system for detecting distant objects, for example as described in Specification 639,981, and in which the stated condition is shown to be necessary to combine high-power as a transmitter with sensitivity as a detector. The non-linear admittance may be introduced (1) in the feed-back path, Fig. 1, (2) across the buncher gap, Fig. 2, or (3) across the catcher gap, Fig. 3 (not shown). The buncher resonator 1, Fig. 1, is connected to the catcher 2 by a conventional feed-back line 13 and also by an overbunched klystron system 3, 4 excited by beam from cathode 32. The normal characteristic A, Fig. 4, and over-bunched characteristic B combine to give a curve E having a flat portion F. The detector system 21-27 is that described in Specification 639,982. In the second arrangement, beams from two cathodes 5, 41, Fig. 2, pass through the buncher resonator 1<1>, but the cathodes are so biassed relatively that only the central beam 46 passes on to the catcher, the outer annular beam 48 being reflected by intermediately-biassed grid 45 and passing back in an overbunched condition to the buncher gaps 8, 9. The second cathode 41 carries grids 42, 43 for correctly shaping the fields accelerating the first beam 46. Resonator 1<1> carries a further field-shaping grid 44. In the third arrangement, a third resonator is arranged beyond the catcher resonator and velocity-modulates, with the same signal, an electron beam which passes into the catcher, in the opposite direction to the main beam, in the necessary overbunched condition to produce a constant mutual conductance. To avoid interference by the beams passing on to the opposite bunchers, they may be set at an angle, or deflecting magnetic or electric fields may be employed. The detector consists of a third beam arranged to be fired transversely through the catcher gap and deflected by its field across an apertured electrode to give a rectified signal. Reception is by antennµ or apertures in either the buncher or catcher resonator, preferably the buncher; transmission is similarly preferably by the catcher, but may be by the buncher. A radiation shield 4<1> is provided to prevent direct interaction. Specifications 523,712, 529,771, 530,870 and 531,251 also are referred to.