Jersey Nuclear-Avco Isotopes, Inc.

Avco Research Laboratory, Inc.

George Sargent Janes

Richard H Levy

Leonard N Litzenberger

Donald F Twombly

Robert E Schlier

Charles T Pike

Harold K Forsen

Lawrence A Levin

John Philip Dotson

A scanning beam laser pumped laser is disclosed which is capable of producing pulses of 50 or more microsecond duration with a repetition rate of 100 Hz or more and an energy content per pulse of 3 joules or more. Optics focus the output beam of the pumping laser onto the front surface of the pumped laser which may comprise a flowing dye cell. A rotating mirror synchronized with the pulse repetition rate of the pumping laser moves the spot across the dye in the pumped laser in a direction preferably orthogonal to the flow of dye therein. A spherical mirror behind the rear surface of the dye cell reflects radiant energy back toward the rotating mirror. Reflective radiance is turned therefrom to, in part, pass through the aperture of a beam-combining mirror. The small fraction of radiant energy passing through either a partially reflecting surface or a small aperature on the beam combining mirror enters a resonant cavity whose dimensions define the wavelength of the pumped laser.

Scanning beam laser pumped laser

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.

Use of autoionization transition absorption peaks in isotopically

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.

Linear electron beam gun evaporator having uniform electron emission

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. Reducing the flow of electrons from the vapor source is particularly useful where the vapor is ionized with isotopic selectivity because it avoids superenergization of the vapor by the electron current.

Method and apparatus for suppressing electron generation in a vapor

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.

Vapor coated emissive cathode

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.

Multiple particle type interaction isotopically selective ionization

In a technique for isotope enrichment a system for selectively exciting increased amounts of one isotope type in an environment of plural isotope types by the application of excitation energy at a plurality of frequencies which selectively excite the one isotope from its ground energy level and one or more typically low-lying excited levels.

Isotopically selective excitation from plural excited states

A probe for detecting the evaporation rate of an electron beam evaporation source and for monitoring induced ionization of the vapor. A negatively biased electrode responds to ions in the vapor to measure the ion current density. The ions measured may result from the process of vaporization or from laser produced isotopically selective ionization. The probe provides a current output which is detected as an indication of vaporization or laser ionization rate.

Method and apparatus for measuring vapor flow in isotope separation

A system employing multiple, upper excitation levels in a technique for isotopically selective ionization to improve the ionization efficiency. In a technique which employs laser radiation to excite particles with isotopic selectivity, excitation is produced to a plurality of excited states below the ionization level with the result of increasing the number of available excited particles for ionization and thereby increasing the ionization cross-section for improved system efficiency.

Increased ionization rate in laser enrichment

Frequency selective means, particularly for use in uranium enrichment by laser induced isotopically selective ionization to suppress unwanted lasing of the excited uranium medium. The frequency selective means, such as filters, are placed at intervals in a column of laser illuminated uranium vapor and are transmissive to the illuminating laser frequencies but nontransmissive to frequencies at which population inversions exist in the excited uranium. The filters limit the path length and correspondingly the gain in the excited uranium to prevent high intensity lasing by the uranium itself.

Suppression of unwanted lasing in laser isotope separation

An electron beam vapor source for use in laser enrichment of uranium and providing fast response intermittent vaporization to permit interruption of the enrichment process without wasting vapor or requiring long term reheating.

Fast response high temperature evaporation control

In uranium enrichment, an electrode structure of thin, tensioned, parallel wires for use in applying an electric field to a region of a flowing uranium plasma including selectively ionized particles in order to accelerate the ionized particles for separate collection without interfering with the motion of neutral particles.

Wire anode for isotope separation apparatus

A floating mass or matrix for use in the melt of an electron beam vapor source to permit a wide latitude of evaporant level without necessary replenishment while at the same time reducing convective currents in the melt.

Floating convection barrier for evaporation source

In a system for isotope enrichment, method and apparatus for separating particles of one isotope type from an environment containing particles of plural isotope types by ionizing the particles of said one isotope type and imparting to the electrons released from the ionized particles an energy substantially in excess of the thermal or background energy of the environment whereby these super energetic electrons expand away from the environment in the company of the corresponding ionized particles or trajectories substantially different from those of the remaining particles in the environment to permit separate collection of the particles of the one isotope type.

Method and apparatus for the separation of isotopes

In a system for isotope separation, method and apparatus empolying crossed-field MHD particle accelerating techniques for collecting ions of a desired isotope after selective ionization of that isotope. In the plasma of electrons and selectively ionized atoms which results from selective isotope ionization, the ions are collected by inducing a circulation of the plasma electrons to provide a JXB relationship for MHD acceleration of the ions. The electron circulation enhances penetration of the plasma by the accelerating electric field and avoids the generation of large Hall voltages within the system as well as reducing the required magnitude of electrode currents.

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Lincoln, MA, United States of America

George Sargent Janes