Abstract: An electron gun comprises a cathode made of an emissive material with an active face emitting electrons through a control grid that is placed before the active face but has no contact with it. The active face has emissive zones and non-emissive zones. The non-emissive zones are formed by grooves hollowed out of the emissive material. The control grid has solid parts that directly face the grooves. Application to electron guns with reduced heating of the control grid. FIG. 5 .

Abstract: Disclosed is a travelling-wave tube with helix. The helix is mounted in a metal sleeve and is held in a centered position by at least three dielectric rods. Parts of the helix are in contact with the rods. The helix is made out of a thin strip of a metal that is a good conductor of heat and electricity. Instead of having a rectangular cross-section, the thin strip now has a T-shaped cross-section, at least at all the parts of the helix that are in contact with the rods. The base of the T is brazed to the rods. This structure prevents the risk of electric arcs at the facing brazing beads on two consecutive turns of the helix. The disclosure can be applied to travelling-wave tubes operating in wide bandwidth and at high peak power and/or mean power values.

Abstract: A wide band device is provided for coupling between the delay line of a travelling wave tube and the external circuit transmitting the energy of the tube, comprising a coupling wave guide having a single ridge, connected on one side to the delay line and on the other being extended by one of the two ridges of the output guide, the section of the coupling guide increasing progressively, with constant impedance from the line to the output guide whereas this latter has an impedance transformer providing impedance matching between its standard guide part and the coupling guide.