Spectra-physics Gmbh

The United States of America As Represented by the United States

Amoco Corporation

The Boeing Company

United States of America As Represented by the Secretary of the Air Force

Sti Optronics, Inc.

William J Thayer, Iii

John F Zumdieck

Chung-Hing Lo

Carmine J Artura

A transverse flow uniform droplet generator and method for its use. The droplet generator, such as is used with a gas laser system, produces singlet oxygen from a flow of droplets of liquid basic hydrogen peroxide (BHP) reacting with a transverse a flow of He/Cl.sub.2 gas mixture. The resulting flow of singlet oxygen travels in the same direction as the He/Cl.sub.2 gas mixture and the unreacted BHP is collected on the opposite of the reaction volume from which it enters. Very uniformly-size BEP droplets are formed by an injector which specific mechanical resonance characteristics and the flow of the BHP and the gas mixture in the generator volume is also carefully controlled.

Transverse flow uniform droplet O.sub.2 (.sup.1 .DELTA.) generator and

The uniform droplet injector assembly is a rigid, low mass injector having a plurality of nozzles therein attached to a manifold. The manifold vibrates by piezoelectric actuators and springs in combination. The droplet injector array allows the process stream to flow through the injector assembly with the droplets uniformly dispersed into this stream. The moving parts such as the injector assembly, springs, and actuators are structurally resonant at a frequency near the droplet formation frequency. The colinear, spring/actuator configuration minimizes internal stresses due to manufacturing tolerances, preloading requirements, temperature changes, and cyclic operation in a large area generator. The linear spring/actuator configuration has low stiffness in the vibration direction and high stiffness in transverse direction to eliminate motions which would cause nonuniformly sized droplets.

Uniform droplet generator

A very compact flow loop for circulating gas through a pulsed laser or other pulsed discharge device is disclosed. An apparatus, having greater resistance to flow and shock wave propagation in the upstream direction, preferentially converts energy from the pulsed discharge residue into flow energy and causes flow through the discharge region in the desired downstream direction. The large available work in the discharge residue lets the efficiency of the conversion apparatus be very low and yet still provide sufficient flow power to circulate gas for purging a conventional flow loop without using a separate input of power to drive the purge flow. Moderate conversion efficiency provides sufficient flow power to allow compact, high loss components to be used for a very compact flow loop with no external flow circulation power and no rotating components.

Ultracompact flow loop with no rotating components

A spark gap switch system is disclosed which is capable of operating at a high pulse rate comprising an insulated switch housing having a purging gas entrance port and a gas exit port, a pair of spaced apart electrodes each having one end thereof within the housing and defining a spark gap therebetween, an easily condensable and preferably low molecular weight insulating gas flowing through the switch housing from the housing, a heat exchanger/condenser for condensing the insulating gas after it exits from the housing, a pump for recirculating the condensed insulating gas as a liquid back to the housing, and a heater exchanger/evaporator to vaporize at least a portion of the condensed insulating gas back into a vapor prior to flowing the insulating gas back into the housing.

Spark gap switch system with condensable dielectric gas

A spark channel purge system for high pulse repetition frequency spark gap switches. A purge fluid having a liquid state and a gaseous state is caused to flow through a spark gap channel, at least a portion of the purge fluid passing through the spark channel being in the gaseous state. The purge fluid is supplied in its liquid state by a purge fluid source. In some embodiments, the purge fluid source is a recirculating flow loop which includes a heat exchanger, while in another embodiment, the purge fluid source is a low-pressure liquid storage vessel. The heat exchanger transfers waste heat from the spark gap switch via the purge fluid flowing from the spark channel into the purge fluid supplied by the purge fluid source. This causes at least a portion of the liquid purge fluid to change to the gaseous state. In some embodiments, the spark channel purge system is suitable for a closed loop system, while other embodiments are suitable for an open loop system. In the two-phase flow loop embodiments, the two-phase purge fluid can be mixed to absorb energy from the spark gap switch.

Spark gap purge system

A spark gap switch apparatus is disclosed which is capable of operating at a high pulse rate which comprises an insulated housing; a pair of spaced apart electrodes each having one end thereof within a first bore formed in the housing and defining a spark gap therebetween; a pressure wave reflector in the first bore in the housing and spaced from the spark gap and capable of admitting purge flow; and a second enlarged bore contiguous with the first bore and spaced from the opposite side of the spark gap; whereby pressure waves generated during discharge of a spark across the spark gap will reflect off the wave reflector and back from the enlarged bore to the spark gap to clear from the spark gap hot gases residues generated during the discharge and simultaneously restore the gas density and pressure in the spark gap to its initial value.

Apparatus and method for tuned unsteady flow purging of high pulse rate

A two-phase fluid is injected into a volume upstream of the spark gap flow channel of a spark switch. The injected two-phase flow can be separated, causing the liquid component of the two-phase fluid to form a layer adjacent the wall of the flow channel and a predominately gas phase region near the spark switch electrodes. This distribution of liquid and gas phases can be achieved by tangential injection of the two-phase fluid. The resulting two-phase flow absorbs the thermal and radiant energy produced by the spark in the spark channel, as well as the energy of the shock wave systems produced by the spark in the spark channel, thereby reducing the temperature that the wall of the spark gap would attain without such two-phase fluid flow injection. Vaporization of the liquid due to this energy absorption generates a substantial gas flow which increases the purge flow and recovery rate of the spark gap switch. The spark gap switch flow channel and the expansion duct to which the spark switch is attached, can be tuned to produce an unsteady purging flow through the spark channel, thereby rapidly removing the hot gas residues caused by the preceding spark from the spark channel and restoring the pressure and density in the spark gap to the initial levels. In one embodiment, the two-phase fluid can be a mixture of water droplets and steam.

Spark gap switch having a two-phase fluid flow

A spark gap chamber to promote mixing and/or translation of hot residue gases into the surrounding gases in an unpurged spark gap chamber. The shock (and expansion) waves are reflected from walls and other structures within the spark gap chamber to cause the hot residue gases formed by a spark between the electrodes in the spark channel to mix with the unheated gases found elsewhere in the spark gap chamber. The spark gap chamber walls can be symmetric and shaped to cause the reflected shock wave to converge simultaneously on the spark channel or to focus on different portions of the spark channel at different appropriate times. Alternatively, the spark gap chamber walls can be asymmetric with respect to the spark channel and can force the hot residue gases away from the spark channel. In another alternative, the spark gap chamber can include structures whose pressure drop depends upon the direction of flow past the structure and, accordingly, can generate a circulation in response to the passing shock (and expansion) waves created by the spark in the spark channel.

Method and apparatus for enhancing spark channel recovery by

An optical assembly isolator and laser system incorporating the same. The isolator attaches to an end of the laser system along the optical axis of the laser system. The isolator includes a flow loop wall, an optical assembly wall, an outer wall connecting the foregoing two walls, and at least one baffle wall included in the volume defined by the outer wall. The flow loop wall and the baffle wall include open first and second apertures, and the optical assembly wall supports an optical assembly. When the isolator is in place on the laser system, the first and second apertures and the optical assembly all align with the optical axis of the laser system. The edges of the first aperture and the flow loop wall can be slanted and oriented with respect to the primary flow through the laser system to induce a small circulation and redirect any entering shock waves and entrained contaminated gas toward the outer wall. The second aperture in the baffle walls can be defined by a surface that extends toward the flow loop wall of the isolator, thereby cancelling shock and expansion waves and dissipating any shock wave energy that enters the isolator from the discharge region of the laser system. This second baffle shape also promotes flow of clean purge gas along the optical axis toward the flow loop and spoils flow of contaminated gas toward the optical assembly. Finally, the isolator can incorporate a purge gas system for tangentially injecting a purge gas adjacent the optical assembly wall and creating a series of circulations that tend to cause the contaminants to be distributed against the inner surface of the outer wall of the optical assembly. If desired, a layer of damping and packing material can be placed against the inner surface of the outer wall for the purpose of damping the shock waves and capturing contaminating particulates.

Isolator for laser optical assemblies

A method and apparatus for tailoring the concentration profiles of reactant and diluent species in the gas stream of a pulsed chemical laser provide a substantially uniform initial chemical reaction rate and index of refraction across the laser cavity. In the preferred embodiment, a gas stream is composed of the two reactant species, molecular hydrogen (or deuterium) and molecular fluorine, diluent species argon and helium, and a trace of oxygen as a preinitiation inhibitor. A substantially uniform initial chemical reaction rate within the laser cavity is obtained by tailoring the concentration profile of the fluorine across the cavity to compensate for the variation in absorption of UV initiation radiation across the cavity along the axis of initiation. The index of refraction of the gas mixture is kept constant within the cavity by varying the concentration of diluent gases to compensate for the variation in the index of refraction that would otherwise result from the tailoring of the fluorine concentration profile. A mathematical model of UV radiation absorption in the laser cavity is developed on the basis of the specific geometry of the laser cavity and its associated source of UV initiation radiation. A radiation absorption analysis is then performed to define the fluorine concentration profile that provides the desired degree of uniformity of the initial chemical reaction rate. An injector/mixer manifold provides a gas stream having the desired reactant gas concentration profile, as well as a diluent gas concentration profile which provides a uniform index of refraction across the reagent stream.

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Kent, WA, United States of America

William J Thayer, Iii