English Electric Valve Company Limited

Hugh Menown

Arthur Maitland

Christopher V Neale

Timothy P Donaldson

Ian A Strudwick

Barry P Newton

Clifford R Weatherup

Robert J Wheldon

Graeme L Clark

Raymond P Knight

Robert J Carman

Leonard R Cullum

Robert E Baker

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.

Laser apparatus

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.

Discharge tubes

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.

Thyratrons

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.

Discharge tube apparatus

A metal vapor discharge tube includes cylindrical dispenser blocks of sintered tungsten which are porous and support metal whose vapor is to form at least part of the active medium of the tube. Thus, the dispenser blocks retain the metal, holding it in position when in its solid and liquid states. Heat shields serve to retain heat within the envelope of the discharge tube and uniformly heat the cylinders.

A thyratron comprises an anode and control grids between which is located a double layer screen grid. Thermionic cathode material is inserted in an aperture in the part of the screen grid furthest from the anode, and in operation this is heated to the required temperature by hot plasma which surrounds it, thus eliminating the need for a cathode heater.

Thyratron having thermionic cathode material between anode and control

A thyratron includes an envelope containing a gas filling, an anode, an intermediate grid, control grids and a cylindrical structure which acts as a cathode heat shield in a conventional thyratron. In operation the intermediate grid is maintained at cathode potential and, when triggering pulses are applied to the control grids, the gas filling ionizes and the thyratron becomes conducting. The main part of the current comes from the intermediate grid which acts as a 'hollow' cathode, and enables the thermionic cathode conventionally used to be dispensed with if desired.

Thyratron having anode and multiple grids

The present invention provides apparatus for forming electron beams, which may be advantageously employed in many applications, for example in display devices or thyratrons. A cathode member has a hole in its front surface. All the surfaces of the cathode member, except for the wall and base of the holes, are covered in an electrically insulating material such as glass. The cathode member and an anode member are contained within an envelope which also contains a gas filling. On application of a suitably high voltage between the cathode and anode members an electron beam is formed extensive in a direction away from the hole. The anode member may be located behind the front surface of the cathode member, and an electron beam still forms in front of the front surface.

Apparatus for forming electron beams

A magnetic thyratron interrupter is provided having between an anode and a cathode a structure having an aperture therein for a discharge presenting a succession of surfaces in the direction of discharge which are contacted when the discharge is moved by applying a magnetic field transversely to the discharge direction. Examples of structure are stacks of discs having concentric holes which are alternately of larger and smaller diameter and a strip of gauze wound into a spiral.

Thyratron interrupters

Thyratrons have an anode and cathode with a control grid lying between them. A primary grid located between the control grid and cathode may be used to maintain a primary discharge between it and the cathode, and improve the operating characteristics of the thyratron. However, the primary discharge may penetrate into the region where the main discharge occurs and hence increase the probability of premature triggering of the thyratron. By employing the invention, the penetration of the primary discharge into the main discharge region is reduced. A primary grid comprises two elements which have apertures. The elements are arranged so that the apertures in one element do not overlap those in the other. Thus the primary discharge which penetrates through the first element is prevented from reaching the main discharge region by the second element.

The invention provides a laser arrangement including in its discharge circuit a switching thyratron which is capable of conduction normally in one direction and protectively in the reverse direction. The thyratron has an anode formed as a hollow body which is adapted to retain plasma generated during a pulse of forward conduction so that the anode is provided to act as a cathode permitting protective reversal of the thyratron when this is subject to reversal of voltage.

Thyratron capable of reverse conduction

Laser arrangements

The invention provides a glass enveloped thyratron having an anode carried by an anode pin extending through a glass neck in the thyratron envelope and forming a pant leg. The anode is surrounded by a screening box operated at cathode potential which has a back plate with a tubular portion extending away from the anode into the interior of said pant leg to surround said anode pin. The outer surface of the extremity of the pant leg is flared outwardly adjacent the back plate into engagement with a mounting collar secured to the rear of the back plate. The tubular portion of the back plate extends within the pant leg for a distance substantially greater than the extent to which the pant leg is enclosed by the mounting collar.

A segmented discharge tube device is provided, particularly for the discharge tube of a laser, in which a number of electrically isolated aluminium segments presenting a passage through which plasma may pass are located within an aluminium tube with heat conductive electrically insulating material in the form of anodization between the outer surfaces of the segments and the adjacent inner surfaces of the tube.

Segmented discharge tube devices

The invention concerns thyratrons and in particular thyratrons which are required to be able to conduct protectively in a reverse direction. In order to assist in such reverse conduction an electrode which at such times acts as a cathode e.g. a conventional anode is formed or includes material of low work function such as tungsten impregnated with barium aluminate. Where the electrode in question is a plate anode the disc or plate is itself formed of the low work function material. Where the anode is a so-called hollow anode material of low work function may be introduced within the interior of the hollow anode. Where the anode electrode is in the well known form of an inverted cup material of low work function may be provided as a layer on the surface thereof facing the cathode.

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Writtle, United Kingdom

Hugh Menown