Abstract: A laser arrangement includes an outer envelope and an inner alumina tube between which insulating material is located. The insulating material has a plurality of apertures therein in its transverse end faces, the aperture being arranged at each end on two circle of similar radii. Hydrogen reservoirs are located within the apertures. During operation of the laser arrangement, the reservoirs become heated causing hydrogen to be evolved and diffused through to the laser active medium, improving the efficiency of the laser operation. When laser action ceases, the arrangement cools and hydrogen returns to the reservoirs. Efficiency enhancing gases other than hydrogen may be used in the arrangement.

Abstract: A magnetron anode is manufactured by producing a blank in a sheet of conductive material which is then bent to form an anode vane structure. The structure is then inserted in a cylindrical block and brazed in position to form the magnetron anode. The anode vane structure may be formed from two folded blanks, which are arranged to interengage one another.

Abstract: Laser apparatus includes a gas filled tube and is arranged to act as a switch to trigger, within the tube itself, a discharge. The power dissipated in the discharge is applied to material which forms, or is to form, a laser amplifying medium, to provide pumping power. Thus, no external switch, such as a thyratron, is required, unlike conventional laser arrangements.

Abstract: Laser apparatus includes hydrogen or deuterium buffer gas and dispenser reservoirs which contain a hydride or deuteride as appropriate. As gas molecules from the buffer gas are lost within the discharge tube due to trapping and sputtering processes, hydrogen or deuterium is given off from the surfaces of the reservoirs at a greater rate to maintain the vapor pressure within the discharge tube at a substantially constant level. Thus the laser apparatus may operate in a "sealed-off" mode, that is without requiring that buffer gas be flowed through it.

Abstract: A discharge tube arrangement, for example, a thyratron, in accordance with the invention has a first electrode arranged co-axially about a second electrode. Thus, in a thyratron, the anode may surround the cathode or vice versa. The envelope may be tubular having an aperture at its center. The discharge tube arrangement is constructed such that it is capable of being added to another such arrangement. A plurality of such arrangements may be added together to produce, for example, a thyratron capable of large current conduction.

Abstract: Imaging apparatus includes an image sensor which is connected to a computer, or computer frame store, by an interface. The computer is arranged to generate control signals which are used to control the sequence of signals applied to the image sensor, thereby enabling the interface to be used with a plurality of different image sensor types.

Abstract: A thyratron includes a grid structure in which a grid element has a plurality of apertures therethrough, each of the apertures comprising two arcuate portions at different distances from the center of the grid which are connected by a radial portion. Thus a large grid area may be provided without detrimentally affecting voltage hold-off, jitter or mechanical soundness.

Abstract: Laser apparatus includes an outer envelope which contains a plurality of laser discharge tubes. Each of the laser discharge tubes includes copper pieces which, when vaporised, acts as a laser amplifying medium. Each of the laser discharge tubes is of the maximum volume compatible with good efficiency which, when combined with the output power of the other tubes, enables a very high power output to be achieved compared with previously known tubes.

Abstract: A gas discharge device includes means for injecting electrons into a high field region between an anode and a cathode structure located within a gas filled envelope. This causes ionisation within the region and triggers the device into conduction.

Abstract: A laser arrangement includes electron beam apparatus comprising a plurality of electrodes, each of which having an aperture therethrough. The apertures are aligned along the longitudinal axis of an envelope which surrounds them and contains gas. The electrodes are electrically connected such that, of an adjacent pair, one is at a lower potential than the other. An electron beam is produced between the first electrode and an adjacent electrode, and is accelerated along the axis through the apertures, the electron current increasing in magnitude. The electron beam produced is used to provide pumping powder to the gas contained within the envelope such that it acts as a laser amplifying medium.

Abstract: Apparatus for forming an electron beam sheet includes a cathode member having a slot in a front surface thereof, a grid electrode and the anode of a thyratron. When it is desired to trigger the thyratron into conduction, a suitably large potential difference is applied between the cathode member and the grid, resulting in an electron beam sheet being produced extensive of a slot formed in the front surface of the cathode member. This produces ionisation and a main discharge current is established between the main anode and cathode of the thyratron.

Abstract: A CCD image sensor is operated in an asynchronous mode to enable it to capture short lived events, or to freeze rapid motion. The image is acquired during an integration period which is triggered by a strobe pulse, and the resulting charge is held in a storage section of the CCD sensor until a regularly occuring field read-out period, during which the charge is read-out to constitute a video signal.

Abstract: An ignitron device is provided in which a permanent annular magnet at least partly surrounds the region between the ignitron anode and the surface of a mercury pool connected to the cathode terminal, the magnet being effective to create an axial magnetic field in the aforementioned region which tends to constrain the discharge arc of the device towards the center of the pool and away from the envelope walls of the device.

Abstract: A magnetron includes a cathode and vane type anode structure. The frequency of oscillation of a microwave output signal of the magnetron is tunable by means of a tuning member, which is in the form of an annular plate arranged adjacent resonant cavities of the magnetron. The frequency of oscillation is determined by the position of the tuning member relative to the resonant cavities. When it is wished to tune the magnetron output frequency a current is passed along a path defined by the tuning member. This causes axial forces to be exerted on the tuning member so that it moves. Since the current is arranged to pass through the tuning member itself, the device is particularly simple, no actuating mechanisms or drive coils, for example, being necessary.

Abstract: Laser apparatus includes a ceramic tube within which is contained a gas and a cylindrical cathode having a plurality of holes therethrough. An anode is located along the axis of the tube. During operation of the apparatus, a large potential difference is applied between the anode and cathode, causing a plurality of electron beams to be formed extensive of the holes. Vapor is emitted from the electron bombarded cylindrical rod and becomes excited, and laser action occurs.

Abstract: Hydrogen Sulphide is a toxic gas present in many environments. It is necessary for a detector to be highly sensitive and not to respond to other common gases. The sensor is made up of electrodes (5) coated with a thin layer (6) of material comprising the oxides of molybdenum and tungsten and in the presence of hydrogen sulphide gas, changes its resistance. The layer is formed in such a way that a bronze-like ordered lattice is formed, containing molybdenum, tungsten and oxygen ions.

Abstract: An amplifying arrangement includes a klystron in which an electron beam interacts with a high frequency signal to produce a modulated amplified signal. The high frequency signal is maintained at a substantially constant amplitude and modulation of the amplified signal is provided by controlling the electron beam current.

Abstract: A directly heated cathode comprises a metal tube having a filling of powdered metal which extends beyond the tube and in which is embedded an electrical wire which is coaxial and extensive with said the outer tube over part of its length. The electrical wire is coated with insulating material which is normally alumina. The tube, the metal powder filling and the wire are sintered together, giving a relatively robust structure.

Abstract: Discharge tube apparatus includes an outer containing vessel and a structure comprising for example five metal cylinders located co-axially within it. Each of the metal cylinders includes projecting spacers on its outer surface which serve to space it from adjacent ones. Such a structure is thermally insulating and may be arranged to enable a large temperature difference to be maintained between the interior of the discharge tube and the outer containing vessel. In other embodiments, a plurality of structures are included disposed along the axis of the tube. Also, dispenser segments for dispensing part of the active medium of a metal vapor laser may be included and arranged to shield vulnerable surfaces in the tube from direct exposure to the discharge.

Abstract: A shielded faceplate for use in an image intensifier having a photocathode which comprises an inner core of glass transparent to light to which the photocathode is sensitive and an outer shielding region of glass which absorbs light to which the photocathode is sensitive. The outer shielding region surrounds and is adjacent to the inner core. The inner core has a transverse dimension which decreases along its length, the transverse dimension being smallest at the photocathode surface. The shielded faceplate is manufactured by arranging in a mold to which glass does not bond a first type of glass transparent to light to which the photocathode is sensitive and a second type of glass which absorbs light to which the photocathode is sensitive, heating the glass members so that they fuse to produce a block having an inner core of the first type of glass and an outer region of the second type of glass and removing the block from the mold.