Abstract: Method and apparatus for inhibiting dimer formation of molecules of a selected isotope type in a cooled flow of gas to enhance the effectiveness of mass difference isotope separation techniques. Molecules in the flow containing atoms of the selected isotope type are selectively excited by infrared radiation in order to inhibit the formation of dimers and larger clusters of such molecules, while the molecules not containing atoms of the selected, excited type are encouraged to form dimers and higher order aggregates by the cooling of the gaseous flow. The molecules with the excited isotope will predominate in monomers and will constitute the enriched product stream, while the aggregated group comprising molecules having the unexcited isotope will predominate in dimers and larger clusters of molecules, forming the tails stream.

Abstract: A fluid laser having a flow channel between fluid inlet and active lasing region which reduces medium heating and resulting medium disturbances. The channel includes a thin optically transparent, thermally insulating layer directly bordering the medium. The thin layer rests upon a metallic heat sink, typically cooled, which receives and removes radiated energy from the active region, preventing it from heating the medium. The thin insulating layer permits the heat sink to be cooler than the medium without causing thermal effects in the medium. The more homogeneous medium resulting from such treatment contributes to better laser beam quality.

Abstract: A flow channel for a dye laser having means for reducing thermal and pressure variations in the flowing laser medium particularly in the vicinity of active lasing in order to permit high power and high pulse rate lasing with a high quality, low divergence output beam. Pressure disturbances and turbulence are minimized with a number of flow design techniques including a configured input conduit for even pressure drop, a set of turbulence reducing screens, as well as a hydraulic pressure damping capacitor on both input and output ends of the flow channel, either side of the excitation window. A porous wall is used to exhaust the medium and isolate the lasing region from downstream effects. In addition, cooling of the conduit just upstream of the region of active lasing reduces temperature disturbances resulting from applied excitation to further minimize its disturbing effect on laser beam quality and lasing efficiency.

Abstract: A system of passive or static optics for combining distinct beams of laser radiation into a number of output beams, each having colinear, superimposed beam components of the original radiation. This system further provides power sharing between the combined beams of the power in the original input beams of laser radiation.

Abstract: A linear electron beam evaporation source for a high vapor temperature material such as uranium, the source being provided with a filamentary emitter and apparatus for controlling the filament electron emission to maintain an approximately constant current per filament unit length. A control structure is provided and operated to create a space charge in the vicinity of the electron emitting filament such that the current density of the electron beam is controlled by the space charge rather than the local electron emissivity along the length of the filament.

Abstract: A flow channel for a fluid laser medium which promotes high pulse rate high power lasing of the medium. The flow channel operates to permit this high efficiency operation by preparing the flowing laser material to stream past a set of windows for the application of transverse pumping radiation with a very smooth laminar flow having thin laminar boundary layers. This flow characteristic is provided by a carefully configured input channel. In addition, high quality flow characteristics are further insured by an exhaust channel which triggers a turbulent flow directly downstream of the windows and provides a controlled expansion without separation of the flowing laser material into an outlet conduit.

Abstract: A system for applying accelerating forces to ionized particles of a vapor in a manner to suppress the flow of electron current from the vapor source. The accelerating forces are applied as an electric field in a configuration orthogonal to a magnetic field. The electric field is applied between one or more anodes in the plasma and one or more cathodes operated as electron emitting surfaces. The circuit for applying the electric field floats the cathodes with respect to the vapor source, thereby removing the vapor source from the circuit of electron flow through the plasma and suppressing the flow of electrons from the vapor source. The potential of other conducting structures contacting the plasma is controlled at or permitted to seek a level which further suppresses the flow of electron currents from the vapor source.

Abstract: A system for producing isotopically selective excitation of particles of a predetermined isotope type in a mixture of isotopes from plural low-lying energy levels to respective, plural excited energy levels. Ionization and separate collection of particles of the predetermined isotope type are then achieved through further excitations through a single, further excited energy state. Decay losses from the second excited energy states are reduced due to distribution of the excited particles among several states and resulting lower cross-sections for self-lasing decay.

Abstract: Method and apparatus for achieving isotopically selective adiabatic inversion, particularly for improved isotope separation efficiency. In a preferred embodiment for practicing the invention, chirped laser radiation induces photoionization of a vapor state material in isotopically selective excitation and ionization energy steps. A frequency sweep or "chirp" is provided in the excitation laser radiation at a controlled rate and over a range of frequencies which is limited to prevent loss of selectivity in the excitation. The frequency swept radiation has a theoretical capability of producing 100% inversion of ground state particles in the vapor. The features of the invention additionally permit excitation of a material to very high energy states useful in producing high frequency, ultraviolet lasing.

Abstract: An optical combiner for combining multiple synchronized, pulsed light beams is disclosed. A pair of planar mirrors are joined, facing each other, along an edge of each, to form a V-shaped assembly rotatable about an axis normal to the line of intersection of these edges, passing through the center of that line and bisecting the center of the angle formed between the two mirrors. A plurality of pulsed laser beams is impinged upon such mirror assembly as it rotates, the lasers each being pulsed at a rate equal to an even integral multiple of the rotational speed of the mirror assembly in synchronism with the rotation of the mirror assembly. The individual incident laser beams are combined by the mirror assembly and emitted as a single pulsed laser beam having a pulse repetition rate equal to the product of the number of incident beams multiplied by the pulse rate of each such beam.

Abstract: A long life, high emission electron source for a plasma environment. The plasma environment is made up of corrosive particles having a lower work function than the exposed material of the electron source. The electron source is operated at an elevated temperature not only to provide free electrons but also to establish and maintain a thin partial monolayer coating of the source's emissive surface with plasma particles in an equilibrium between condensation and evaporation. The equilibrium coating increases the emissivity of the surface without permitting substantial corrosion of the surface or structure from the particles of the plasma environment. The cooler regions of the electron source are shielded from the plasma particles to prevent a build-up of corrosive particles.

Abstract: A system for correcting misalignment and divergence in a long, propagating beam of radiation as is typically applied through a plurality of chambers to produce isotopically selective photoexcitation in a system for isotope separation. The corrective apparatus comprises a reflective relay system placed at predetermined intervals along the path of propagation of the radiation where correction of alignment and/or divergence are required. The reflective relay includes a concave mirror employed to correct divergence and which receives radiation directed at it by a first plane reflective surface which in turn responds to the radiation on the path of propagation. The concave mirror reflects toward a second plane mirror which in turn reflects the radiation back onto the path of beam propagation with correction of alignment and divergence.

Abstract: Method and apparatus for impact ionization of particles excited with isotopic selectivity, particularly for use in a system of uranium isotope separation and enrichment. Efficient impact ionization is achieved by first selectively exciting vaporized particles of the desired isotope in a beam of finely tuned laser radiant energy. The energies of the interacting photons are selected to produce a total energy shift during excitation which is slightly less than the ionization energy for the selected isotope. The excited isotope will thus be raised to an excitation level only slightly below the ionization level. This level is selected to permit efficient ionization, particle collisional ionization, between energetic particles in the uranium vapor environment and the highly excited particles of the desired isotope type.

Abstract: A reflector for a high power laser beam comprising a low absorption, transmitting substrate with a rear reflective coating. The reflector element consisting of the substrate and rear coating is mounted within a housing using low stress supports to prevent deformation of the reflective element and resulting loss in optical beam quality in the reflected laser beam. Coolant is sprayed onto the rear surface of the reflector element preferably in a pattern which modulates the coolant flow volume in accordance with the intensity distribution across the incident laser beam so as to maintain uniform heating in the reflective element and further to prevent distortion in the reflected beam.

Abstract: A free jet dye laser having a sheet of fluent laser material bounded along its edges by a pair of opposed guide members. An orifice injects the sheet of laser fluid into the region between the guide members where it flows towards a transparent portion of the guide members through which a beam of laser radiation to be amplified is directed. Pump excitation in the form of laser energy is applied through an exposed surface of the flowing laser material in the region between the transparent portions.

Abstract: A system for generating pulses of laser radiation which vary in frequency with time to achieve a "chirp" or frequency sweep. In a preferred embodiment, a variable-thickness, rapidly rotating disk of optically-dense material is placed in the optical loop of an injection-locked oscillator. Rotation of the disk in the optical loop of the injection-locked oscillator varies the loop optical path length, resulting in a frequency chirp. By appropriately choosing the shape of the optically dense material, a desired linear output chirp may be obtained.

Abstract: A system of wholly passive or static elements for increasing laser pulse rate by interleaving the pulses of a plurality of beams of pulsed laser radiation. The system of static elements includes an array of beam splitters which are operative to receive a plurality of beams of pulsed laser radiation and provide a plurality of output beams, each sharing the radiation in each of the input beams. The invention includes a methodology for expanding the array of beam splitter elements to combine any number of input beams, of whatever differing characteristics, to provide a corresponding number of output beams, each sharing a portion of the radiation in each of the input beams.

Abstract: A flashlamp for exciting a laser medium having a vortex stabilized continuous low level DC discharge. The stabilized continuous discharge is periodically pulsed with a high energy discharge to provide pulses of excitation radiation that are focused into the laser medium to promote lasing thereof.

Abstract: A linear electron beam evaporation source for a high vapor temperature material such as uranium which is protected against filament degradation from reverse accelerated ions in the generated vapor. Electron beam evaporation is produced by the energy in a focused, cylindrical electron beam emanating from an elongate filament and impinging upon a trough shaped crucible of the material to be evaporated. A set of linear electrodes are provided adjacent to the trajectory of the focused electron beam from the filament to provide a slight deceleration voltage in the electron accelerating potential between the filament and the crucible. The decelerating voltage acts as a potential barrier to the few ions in the generated vapor.

Abstract: A system for isotope separation or enrichment wherein molecules of a selected isotope type in a flow of molecules of plural isotope types are vibrationally excited and collided with a background gas to provide enhanced diffusivity for the molecules of the selected isotope type permitting their separate collection. The system typically is for the enrichment of uranium using a uranium hexafluoride gas in combination with a noble gas such as argon. The uranium hexafluoride molecules having a specific isotope of uranium are vibrationally excited by laser radiation. The vibrational energy is converted to a translation energy upon collision with a particle of the background gas and the added translation energy enhances the diffusivity of the selected hexafluoride molecules facilitating its condensation on collection surfaces provided for that purpose. This process is periodically interrupted and the cryogenic flow halted to permit evaporation of the collected molecules to provide a distinct, enriched flow.