Abstract: A method and apparatus for repairing microcracks in the metal of a railway track. A high power laser, or equivalent energy beam generator, is moved along a track. The high power laser directs an intense beam of energy towards microcracks in the rail, a vapour space is formed in the metal of the rail, and as the laser beam moves on, the metal resolidifies and repairs the microcracks. Fusible metal may be applied to the vapour space to improve the strength and control the microstructure of the solidified metal. Pre-heating and controlled quenching may improve the crystalline microstructure of the metal after the vapour space has been formed, and, if necessary, the rail may be ground to a smooth finish. A plurality of repaired regions having deep roots are locked in the rail using unaffected metal between them.

Abstract: An excitation system for a gas laser featuring a multiplicity of gain channels uses a resonant cavity to provide broad band RF power division and impedance matching to the multiplicity of gain channels. Integral anode and grid resonant tank circuits featuring positive feedback may be employed to provide a self-excited power oscillator having a very high power capability with good efficiency at low cost. A smaller and higher frequency multi-channel excitation system fabricated from stripline resonator elements may be used for driving small scale multi-channel lasers. A common optical extraction system features either a stable, an unstable, or a hybrid optical cavity mode, with phase-locked or non-phase locked output performance, achieved via external or self-injection.

Abstract: The laser system features a plurality of thin solid-state gain channels mounted radially about a common axis. These gain channels may be excited by multiple flashlamps or by extended arrays of light-emitting-diodes. The gain channels are also mounted in a parallel configuration within a single optical resonator and thereby share a common cavity mode. The resonator may be a stable resonator, a conventional unstable resonator, or a toric resonator. Each resonator configuration may be externally phase-locked via external reference oscillator injection or by self-injection via an internally generated master oscillator. When incorporating a very large number of gain channels, the concept provides an efficient and inexpensive means for constructing extremely high powered, optically-pumped, lasers in very small physical packages.

Abstract: Apparatus and method of providing for the excitation of a pulsed laser in which the pulsed excitation energy is provided to the laser plasma volume in a series of bursts, each burst being characterized by containing sufficient pulses to sustain the laser pumping current and by being separated from the previous bursts by sufficient time for the laser plasma to recombine. Application of the burst mode enhancement technique is described with reference to a PIE or photo-initiated, inpulse-enhanced, electrically excited plasma excitation process.

Abstract: A laser system includes three or more narrow-gap laser discharge channels mounted radially about a common axis. The laser discharge volumes may be excited by RF radiation, microwave radiation or by means of the MAGPIE system. The laser discharge channels may be mounted in an optical resonator having a common unstable cavity mode, a toric resonator, with or without feedback, or a retro-reflected toric unstable resonator. A pair of adjacent discharge channels may be coupled to form a ring microwave resonator, and the ring resonator may be formed by a continuous double ridged waveguide. Excitation for the continuous double ridged waveguide is optimally produced by a magnetron.

Abstract: This invention provides a high voltage transient protection unit comprising a recoverable spark gap, an L-C filter, a voltage variable resistor and provision for specified ground connection of these elements; and a method of protecting electrical equipment from damage due to a high voltage transient comprising directing any transient above a predetermined minimum voltage level through a recoverable spark gap to a first grounding circuit; delaying said transient for a sufficient time to allow said spark gap to fire and filtering out through a separate grounding circuit that portion of a transient below said predetermined minimum level and above a predetermined maximum voltage level.

Abstract: There is provided a method and apparatus for determining the power output of a laser for wavelengths which are substantially fully absorbed by water, such as the wavelengths produced by carbon dioxide lasers. A rotary member defines a surface of revolution which widens away from an opening to a free edge, with the opening being located substantially at the axis of the surface. Means are provided for rotating a member about its axis, and water is brought to the surface through the opening, to form a film running to the free edge. Means are provided for collecting water at the free edge, and the water through-put is measured by suitable means. Further means are provided for measuring the water temperature differential arising due to absorbable radiation falling upon the water as it runs over the surface, and on the basis of the throughput and the temperature differential, the absorbed power, and hence the output of the laser in the wavelength region in question, can be calculated. For CO.sub.

Abstract: This invention provides a high voltage transient protection unit comprising a recoverable spark gap, an L-C filter, and a voltage variable resistor; and a method of protecting electrical equipment from damage due to a high voltage transient comprising directing any transient above a predetermined minimum voltage level through a recoverable spark gap to ground; delaying said transient for a sufficient time to allow said spark gap to fire and filtering out to ground that portion of a transient below said predetermined minimum level and above a predetermined maximum voltage level.

Abstract: A cathode structure for gas lasers comprising a flat plate of non-conducting material positioned in the laser in spaced relation to the laser anode to define a discharge region therebetween, a two-dimensional array of metal sub-electrode rods passing through the plate and having their upper ends lying flush with the surface of the plate, a block of dielectric material positioned below the plate and containing a series of transverse channels therein, electric current conductors lying in the channels and adapted for connection to a power supply, the lower ends of the said rods passing through openings in the block into the channels to define a predetermined uniform gap between the ends of the rods and the electrical conductor, and a liquid electrolyte solution filling the channels and electrically connecting the sub-electrode rods and the conductors.