Abstract: The invention provides a thermal camera tube having a reticulated pyroelectric target, that is to say a target having a plurality of separate pyroelectric elements arranged in rows and columns and separated by channels. Each of the separate elements has the shape of a cube the vertical sides of which are inclined so that, except for those in one outer column and one outer row, on two of its sides the top of each element overhangs the base of an adjacent element in the same row and the base on an adjacent element in the same column so that the overhanging surface of the element is exposed to radiation in the region of channels separating it from the aforementioned adjacent elements.

Abstract: A mesh electrode for a c.r.t. display device consists of a number of coplanar portions of mesh insulated from each other and secured to a support plate by means of a refractory compound incorporating particles larger than the pitch of the mesh. These particles space the mesh away from the support plate and allow the electrode to be easily fabricated.

Abstract: A gating circuit intended for use with a camera tube having highlight overload protection is designed to prevent excessively large signals reaching a following video amplifier. These large signals arise when highlight overload protection pulses are applied to the camera tube, and large signals are gated to earth by a pair of diodes arranged to minimize out-of-balance signals.

Abstract: This invention provides an inverter circuit in which an output transformer has a tapped primary winding, one portion of which provides a collector load for a first transistor and the other portion of which provides a collector load for a second transistor, with a saturating transformer arranged to provide oscillatory positive feedback from the collectors to the bases of the transistors. The feedback paths from the saturating transformer to the bases of the transistors each includes the base/emitter path of a respective additional transistor and current is supplied to the collectors of the additional transistors in order to maintain operation during saturation.

Abstract: A travelling wave tube is provided with a slow wave structure consisting of clover leaf cavities in which frequency selective attenuators are present in subsidiary cavities formed within the nose of a clover leaf cavity. Each attenuator consists of dielectric material loaded with attenuation material. The use of the invention enables the coupling properties of the clover leaf cavities and their resonant frequencies to be chosen to provide optimum oscillation suppression.

Abstract: A linear beam tube is provided with a gridded electron gun in which a concave cathode surface is provided with concave channels from which electrons are emitted. The channels may be arranged as concentric annuli. In a preferred embodiment the channels extend radially outwards from the center of the cathode to minimize the effects of temperature distortion. The cathode is provided with a shadow grid and a control grid is spaced from and aligned therewith.

Abstract: A thyratron is provided with a baffled structure between its cathode and first control electrode. The baffled structure consists of a series (e.g. three) annular baffle plates, each having a central aperture aligned with the axis of the cathode, mounted on the end of a cylindrical heat shield surrounding the cathode. The final annular baffle plate, adjacent the first control electrode includes a solid disc within its central aperture.

Abstract: The invention provides a combustible gas detector in which a heatable wire filament embedded in a pellet comprising oxidation catalyst material exhibits a change in resistance occasioned by the change in its temperature which occurs due to the oxidation of a combustible gas passing over it.The pellet is provided with an outer layer of inert non-catalytic material which tends to prevent non-volatile residues from reaching catalytically active regions of the detector.

Abstract: The invention relates to a resonant cavity device such as a magnetron oscillator which is tunable by means of a tuning plunger associated with sealing bellows. A volume defined at least in part by the bellows and producing a range of spurious responses as the tuning plunger is moved is isolated from the resonant cavity or cavities of the device by an isolating choke. The choke may take the form of an annulus having a major radius of 1/4 .lambda. (where .lambda. is the mid-frequency of the tuning range) attached either to the plunger or to the main body of the device and between the bellows and the resonant cavity or cavities.

Abstract: An electronic valve includes a shell electrode which is mounted on a support in such a way as to provide a good continuous electrical contact therewith. The base of the shell electrode is flared and mates with a tapered portion of the support, and is held in contact therewith by means of a clamp.

Abstract: In a vane type magnetron oscillator a resonant co-axial transmission line breaks through the wall of the anode block to couple to two adjacent cavities on either side of a vane. Positioned at a point at which a high radio frequency voltage appears in operation approximately an odd multiple of a quarter wavelength (preferably 3.lambda./4) from the end of the transmission line adjacent the cavities is a multipactor discharge arrangement. This latter consists of two co-axial cylinders one connected to the inner conductor and the other to the outer conductor of said transmission line. The transmission line extends beyond the multipactor discharge arrangement to a total length approximately half wavelength or a multiple thereof and is short circuited at its end.

Abstract: A multipactor discharge tuned resonant cavity device, e.g. a magnetron, is arranged with two multipactor discharge electrodes so that in a discharge condition a net current flows from one electrode to the other. The net current is used to create a self-bias voltage on one of the electrodes which affects the operating frequency of the device.

Abstract: A coupled cavity travelling wave tube is disclosed which has a sever including a termination wedge, a sever pole piece with a drift tube and a termination cavity member defining a rectangular waveguide. Disposed in the rectangular waveguide are preformed projections which are provided so as to engage with the termination wedge, the termination wedge thereby being sandwiched between the projections and the sever pole piece.

Abstract: A klystron tube is provided with a long drift tube between the last prebuncher interaction gap and the first buncher interaction gap. The length of the long drift tube is such that in a preferred embodiment the ratio of the peak R.F. gap voltage to the D.C. beam voltage is between 1.4 .times. Wq/w and 2Wq/w where Wq is the reduced plasma frequency in radians per second and w = 2.pi. .times. signal frequency. By this means the distribution of the electrons in the beam is improved.

Abstract: This invention relates to a co-axial magnetron in which a separate resonator incorporating a multipactor discharge arrangement is used to tune the operating frequency of the magnetron. The separate resonator is symmetrically coupled via couplers into the main resonator cavity of the magnetron. More than one separate resonant can be provided, in which case they are symmetrically coupled into the main resonant cavity to achieve correct tuning.

Abstract: This invention provides a klystron amplifier arrangement having means for producing a radial component of magnetic field tending to direct beam electrons out of their path from the electron gun to the collector electrode of the kylstron. By suitably choosing the strength of the radial component of magnetic field generated undesired slow electrons in the beam will tend to be deflected, while the relatively fast electrons will be substantially unaffected.The radial component of magnetic field may be axially asymmetrical or symmetrical and may be generated in a variety of ways, for example, by means of magnetic material introduced into the field region of the normally provided main solenoid or by the use of an auxiliary winding. The magnetic material may form at least part of a cylinder or cylinders surrounding the beam path, for example, if provided as at least part of a drift tube or a water jacket. Any auxiliary solenoid may for example, be wound around a cooling jacket surrounding the beam path.

Abstract: The input surface of a photocathode consisting of a membrane of p-type silicon is modified to improve it's sensitivity. The p-type concentration is locally increased and the surface is coated with silicon nitride.

Abstract: A circuit interrupting device for providing protection against surge currents is constructed to operate very rapidly. A surge current generates a magnetic field in coils which deflects an electron beam which normally travels from a cathode to an anode to complete an electric circuit.

Abstract: The invention provides a double ended thyratron arrangement in which at each end of the thyratron there is a cathode, at least one intermediate grid and a final grid which borders a high voltage withstanding gap. At each end of the thyratron the final grid which borders a high voltage gap is connected to act as a screen electrode, usually by connecting this grid directly to the cathode. At the same time, at one or both ends of the thyratron means are provided for applying triggering input pulses to one of the intermediate grids between the respective cathode and final grid. The thyratron may be of the pentode type, in which case, at each end the final grid is connected to act as a screen, the intermediate grid adjacent the cathode is subject to bias and the triggering signals are applied to the intermediate grid adjacent the final grid.

Abstract: A method of operating a pyroelectric camera tube having a normally provided electron beam emitting cathode and control grid G.sub.1 controlling the electron beam, and a gas in the interior space of the tube by applying positively-going pulses to the grid G.sub.1 during the period of the normally applied line blanking pulses. A circuit for producing the positively-going pulses is also disclosed which have the effect of increasing the target pedestal potential.