Abstract: A system for providing a single pulse of laser oscillator radiation of broad spectral range operative to excite a plurality of modes of a ring laser operating as an injection locked oscillator. In order to provide injection locking of the ring oscillator at multiple modes, a pump laser for the laser oscillator has its cavity length substantially similar to that of the laser oscillator thereby producing partial mode locking of the laser oscillator by amplitude modulation of the pump laser. In this manner the laser oscillator provides a single pulse of mode rich frequencies which are chosen within the band desired in the ring laser. This pulse continuously circulates within the cavity of the laser oscillator. The output of the laser oscillator through an output mirror thus forms a series of pulses separated in time by the roundtrip delay of the laser oscillator cavity. A single such pulse is selected by Pockels cell gating for injection into the ring oscillator.

Abstract: A vaporizer and extractor apparatus for a laser isotope separation process is arranged as an assemblage of modular components in which equipment subject to maintenance is replaceable via vacuum casks while the apparatus is operational or briefly shut down without loss of vacuum. A vacuum transfer cask is provided for modular extractor substrate assemblies. The substrate assemblies are nestable and are mounted on extensible probes which permit them to be nested in the vacuum transfer cask for transport. During use the substrates extend from the cask, through a vacuum lock and are placed side by side in the vacuum chamber. A vacuum transfer cask is also provided for the vaporizer assembly which is mounted on an extensible arm which in turn positions the assembly in the chamber or retraces the vaporizer assembly from the chamber into the transfer cask, rotating it during the process in order to permit it to fit into the cask.

Abstract: A vaporizer and extractor apparatus for a laser isotope separation process is arranged as an assemblage of modular components in which equipment subject to maintenance is replaceable via vacuum casks while the apparatus is operational or briefly shut down without loss of vacuum. A vacuum transfer cask is provided for modular extractor substrate assemblies. The substrate assemblies are nestable and are mounted on extensible probes which permit them to be nested in the vacuum transfer cask for transport. During use the substrates extend from the cask, through a vacuum lock and are placed side by side in the vacuum chamber. A vacuum transfer cask is also provided for the vaporizer assembly which is mounted on an extensible arm which in turn positions the assembly in the chamber or retraces the vaporizer assembly from the chamber into the transfer cask, rotating it during the process in order to permit it to fit into the cask.

Abstract: In an isotope separation system in which hot, isotopically separated vapor is deposited on enriched product and depleted tails plates, deposit adherence is improved and plate cooling simplified. The tails plate is liquid-cooled to a lower temperature which permits the product plate to be radiatively cooled by it simplifying product plate cooling and lowering its temperature to reduce the tendency for the product plate deposit to separate during temperature cycling. In one embodiment plate surfaces are cleaned of impurities in a vacuum by allowing the temperature of the tails plates to reach the relatively low operating temperature prior to proceeding with the deposition. In another embodiment plate surfaces are provided with rough surfaces to promote air penetration during deposit stripping, which permits the formation of a brittle, more easily severed bond between plate and deposit.

Abstract: Method and apparatus for exciting particles in an environment in which a selected isotope, of broadened spectral absorption bandwidth, is exposed to laser radiation having a frequency bandwidth substantially narrower than the spectral width. The laser radiation is frequency swept entirely across the broadened spectral width of the absorption band of the selected isotope type particles to provide spectral matching with substantially all of these particles. A laser system is provided having the capability of sweeping a narrow spectral emission entirely across a broadened spectral absorption band.

Abstract: In an electron beam evaporation system utilizing a grid to control electron flow, non-uniformities in vapor density caused by periodic trapping of electrons near the filament due to the magnetic field produced by alternating heater current are substantially reduced either (1) by out-of-phase grid modulation which increases electron flow from the filament at times when the alternating magnetic field operates to trap electrons, (2) by using a high frequency a.c. source for heating the filament thereby to smooth out the effects of the a.c.-produced magnetic field, or (3) by using an auxiliary cathode heated by the bombardment of electrons from a filament spaced from the cathode by a distance which removes the cathode from the magnetic field produced by the a.c. heating of the filament. In one emobodiment, demodulation of vapor density is employed in laser isotope separation to provide a temporally uniform atomic uranium vapor.

Abstract: A flashlamp system is described which permits the use of flashlamp tubes of increased diameter for higher average power capability while retaining the desirable characteristics of a small diameter, wall stabilized tube which includes small image size, short pulse duration and high ionization level. A series of low level pre-pulses are applied to the flashlamp prior to a main pulse to form a low density region along the flashlamp discharge axis for the main pulse for generating radially directed acoustic waves, thereby to confine the main discharge to a small low density region near the tube center. When Xenon flashlamps are used, this results in a higher ionization level of the molecules along the axis of the flashlamp which increases the ratio of the short-lived XeII emission to long-lived continuum, thereby effectively reducing pulse duration.

Abstract: A level sensor for measurement of the level of molten metal in an electron beam evaporator which operates to sense directly the position of the point or line source of evaporant by detection of radiation such as light emitted therefrom. Compensation is provided for variations in electron beam deflecting magnetic field to avoid interpreting lateral movement of the point or line source from field variations as level changes. Compensation is also provided in the detection circuit for variations in detected light intensity that would otherwise provide an erroneous indication of level change. Detection of further conditions that produce unreliable level sensing and system inhibition in response thereto is provided as a safety feature.

Abstract: A hybrid laser resonator for use with a transverse flow waveguide laser includes cylindrical optical elements for coupling together regions of a thin slab-shaped laser medium operating in the waveguide mode through a set of reflectors which define the ends of the laser cavity. Separate waveguide cylindrical optics which focus in the thin dimension of the slab are combined with a negative cylindrical lens which diverges in the thick dimension of the slab. The negative lens causes an unstable resonator condition to exist in the thick or fluid flow direction so as to prevent narrow isolated horizontal lasing bands and thus provide a nearly diffraction limited beam quality in both thick and thin dimensions.

Abstract: Apparatus and process for isotopically selective multi-step photoionization in which the final or ionizing step is tuned to produce a specific transition to an excited state above ionization for which the ionization cross-section is substantially greater than for ionization transitions in general. The autoionization transition to an ionized state is typically made from a highly excited bound state which is reached in one or two isotopically selective energy jumps from the ground state or other low-lying levels. The isotope shift for the ionization transition is typically small compared to the bandwidth of the ionization transition and relatively broad band photoionization radiation covering the entire absorption line can be employed. Broad band radiation is more economic and is preferable for use wherever possible. A technique is also shown for identifying the ionization transitions of augmented cross-section.

Abstract: A single element interposed in a laser resonator cavity provides for AM mode-locking, Q-switching and dumping in a sequential operation in which a Pockels cell or like polarization rotation device is first energized to prevent build-up of radiation in a laser cavity, is then switched to provide for mode-locking by energization with a periodically varying signal, and is finally energized to dump a single mode-locked pulse. The sequential operation permits the use of a single electro-optic element and a single pair of electrodes. Q-switching, mode-locking and dumping are accomplished utilizing the same physical effect in the crystal, e.g., polarization rotation.

Abstract: A dye solution reservoir system for a dye laser comprises a dye solution reservoir, main fluid circuit means for circulating dye solution between the reservoir and a dye laser, and a by-pass dye replenishment loop between the reservoir and the laser for (1) diverting a portion of the solution from the main circuit, (2) filtering substantially all solute, including the dye and other particles from that portion of the solution, (3) replenishing the solution by adding fresh dye solute, and (4) returning the replenished solution to the main circuit. In a preferred embodiment, the solution is filtered by a first filter for removing the dye solute and a second filter for removing degradation by-products and particulate matter. Reverse osmosis may be advantageously used as a part of this filtrate system. The advantage of such systems is a substantial reduction in the required reservoir capacity and enhanced dye recoverability.

Abstract: Method and apparatus for inducing isotopically selective photoexcitation of atoms in at least first and second energy steps. The total energy change accomplished by the two energy steps is provided with isotopic selectivity at precise resonance for the two steps. In an isotope separation system in which an environment of particles of plural isotope types is created, isotopically selective photoexcitation from laser radiation is shown to produce a great improvement in excitation efficiency where the radiation is controlled in the aggregate of plural photons to achieve precise resonance over the plurality of the degenerate energy steps. Even with multimode excitation, precise resonance is only achieved for isolated atoms, and a chirp or frequency sweep is applied to one of several excitation frequencies to insure precise resonance at least once for each atom.

Abstract: A coaxial flashlamp for pulsed operation at high repetition rates having an annular, light emitting discharge path between fluid cooled coaxially disposed, inner and outer optically transparent tubes. Electrodes are provided at opposite ends of the discharge paths and a gas such as Xenon is provided between the electrodes. The gas is discharged by confinement between the two tubes, forced to assume a dispersed shape which permits more efficient cooling at the discharge borders by fluid coolant inside the inner tube and around the outer tube.

Abstract: A system for generating pulses of laser radiation which vary in frequency with time to achieve a chirp or frequency sweep in which single or multiple laser spectra in the form of mode lines are displaced or shifted in frequency during the generation of the laser pulse. The system provides for the mode line shift through the use of an optical wedge which moves tranversely through one of the optical paths utilized in the optical loop to generate the laser pulse. This provides a linear increase with time in the optical path length so as to perturb the wavelength of oscillation of the laser output, which results in a linear chirp. In a preferred embodiment a number of prisms of optically dense material with a wedge-like profile are mounted on a rotating disc. When the disc with the prisms is interposed in the optical loop of an injection locked laser oscillator, successive prisms traverse the laser's optical loop.

Abstract: A single electro-optic device is provided for simultaneously mode-locking and chirping the output of a laser by simultaneously applying to the electrodes of the electro-optic device a periodic signal superimposed on a voltage ramp. The electro-optic device in general utilizes a crystal of the type which changes refractive index in accordance with an applied voltage. As a result, FM mode-locking is achieved through the use of the periodic signal, whereas mode lines are displaced or shifted in frequency during the generation of the laser output by virtue of the changing bias supplied by the voltage ramp.

Abstract: A fluid laser having a flow channel between fluid inlet and active lasing regions and in which medium heating and resulting medium disturbances are reduced by minimizing channel wall and window heating in the area of the channel bordering the window seal. The channel wall includes a bevelled portion exterior of the channel and having a highly reflective surface immediately adjacent a window. The resulting thinning of the channel wall immediately adjacent the window reduces the absorption in the window seal region of reflected flashlamp light and of dye fluorescence light originating from within the flow channel, and the highly reflective surface reflects away from the window seal region the dye fluorescent light and reflected lamp light. Polished edge surfaces on the window also refract away from the window seal region the dye fluorescent light and reflected light passing through the window/air interface.

Abstract: The problems of collimating, synchronizing and combining a plurality of laser beams to generate a composite beam are substantially reduced by the use of one or more lasers especially adapted to lase in two or more separate wavelengths. Specifically, a composite beam generating system comprises at least one multiwavelength laser for emitting a multiwavelength beam having at least two separated wavelength components, one or more additional lasers for generating respective additional beams, and means for combining the multiwavelength beam with one or more additional beams. In a preferred embodiment, a four-component multiwavelength composite beam is generated by polarization combination of the outputs of a pair of orthogonally polarized two-component multiwavelength lasers.

Abstract: Apparatus for mounting and aligning an optical element on a support structure comprises pivot means for mounting the element so that it can rotate about axes in two orthogonal directions and a pair of alignment means, each comprising a plunger and an inclined guide groove, for rotating the element about the two respective axes. Adjustment means, such as threaded screws, are provided for urging the plunger along the inclined grooves. The grooves are inclined at a sufficiently small angle to permit precision alignment. In order to reduce temperature sensitivity, the path of plunger motion is directed towards the pivotal centers and axes of the mount, and the optical element is placed on the axis between the pivot and the plunger.

Abstract: A flashlamp excited dye laser capable of high amplification and high pulse repetition rate. An active region of laser amplification is defined in a flowing dye by a long narrow channel created between confronting tube-shaped chambers. Laser excitation is directed into the channel through the transmissive walls of the chambers from flashlamps contained in each of the chambers, but which are thermally isolated from the dye channel. A specific geometry of the chambers provides a structural rigidity for long amplification channels.