US3702973A - Laser or ozone generator in which a broad electron beam with a sustainer field produce a large area, uniform discharge - Google Patents

Laser or ozone generator in which a broad electron beam with a sustainer field produce a large area, uniform discharge Download PDF

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US3702973A
US3702973A US72982A US3702973DA US3702973A US 3702973 A US3702973 A US 3702973A US 72982 A US72982 A US 72982A US 3702973D A US3702973D A US 3702973DA US 3702973 A US3702973 A US 3702973A
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medium
cavity
working region
electron
density
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Jack D Daugherty
Diarmaid H Douglas-Hamilton
Richard M Patrick
Evan R Pugh
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Combustion Engineering Inc
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Avco Corp
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K44/00—Machines in which the dynamo-electric interaction between a plasma or flow of conductive liquid or of fluid-borne conductive or magnetic particles and a coil system or magnetic field converts energy of mass flow into electrical energy or vice versa
    • H02K44/08—Magnetohydrodynamic [MHD] generators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J17/00—Gas-filled discharge tubes with solid cathode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/097—Processes or apparatus for excitation, e.g. pumping by gas discharge of a gas laser
    • H01S3/09707—Processes or apparatus for excitation, e.g. pumping by gas discharge of a gas laser using an electron or ion beam
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2893/00—Discharge tubes and lamps
    • H01J2893/006—Tubes with electron bombarded gas (e.g. with plasma filter)
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S422/00—Chemical apparatus and process disinfecting, deodorizing, preserving, or sterilizing
    • Y10S422/906—Plasma or ion generation means

Definitions

  • the present invention in its broadest sense is directed to the production of and apparatus for providing useful controlled discharges in a gas at pressure levels and volumes such that discharge stabilization by electron pair diffusion to confining walls is negligible, that is, the discharge is not wall dominated.
  • the invention may comprise means for increasing if not providing the desired electrical conductivity of the gaseous working medium in MHD devicessuch as generators and accelerators. It is equally applicable to other devices and the like that require or use electrically conductive or ionized gas.
  • the invention comprises means for producing ozone wherein the working medium may comprise oxygen or air which is passed through a discharge comprising an independent source of electrons and an electric field in accordance with the invention. Since the electric field is decoupled from the production of electrons optimum conditions for ozone formation are attainable without severe requirements on ballasting as present in the use of a Townsend discharge, or on electrode geometry as present in the use of corona discharge. Because uniform conditions are provided in the positive column, the overall energy efficiency is increased and heat dissipation involved in the process is reduced.
  • the invention comprises a high-power gas laser which is volumetric in character and that can be sealed in all three characteristic dimensions as well as in pressure level. A controlled discharge is created where electron-ion diffusion to the walls is negligible. 2
  • While the preferred embodiment of the present invention will be described in connection with an electrically excited nitrogen (N2), carbon dioxide (CO and helium (He) laser, it may, as noted above by way of example, be applied to other systems where a conducting ionized gas is required or useful and including, but not restricted to, gas constituents other than N,, CO, and He as well as other lasing systems. Since the discharge produced by this invention does not require ionization by the discharge electrons, in a lasing environment, a discharge in accordance with the invention can be adjusted to the correct electron temperature for most efficient laser operation. Moreover, a laser in accordance with the invention is volumetric in the sense that the proper gas temperature and lower laser state concentrations are maintained by means other than diffusion through the gas to cooled side walls. Further, apparatus in accordance with the invention may be operated in the flowing gas as well as the static pulse mode.
  • Laser Light amplification by stimulated emission of radiation
  • a laser produces a beam of coherent electromagnetic radiation having a particular well-defined frequency in that region of the spectrum broadly described as optical. This range includes the near ultraviolet, the visible and the infrared.
  • the coherence of the beam is particularly important because it is that property which distinguishes laser radiation from ordinary optical beams. On account of its coherence, a
  • laser beam has remarkable properties which set it apart from ordinary light which is incoherent. While the maser (microwave amplification by stimulated emission of radiation) and the laser are based on the same principles of statistical and quantum mechanics, the problems and the physical embodiments for achieving laser action are completely different from those for masers.
  • a wave is spatially coherent over a time interval if there exists a surface over which the phase of the wave is the same (or is correlated) at all points.
  • a wave is time-coherent at an infinitesimal area on a receiving surface if there exists a periodic relationship between its amplitude at any one instant and its amplitude at later instants of time. Perfect time coherence is an ideal since it implies perfect monochromaticity, something which is forbidden by the uncertainty principle.
  • Laser beams have a number of remarkable properties. Because of their spatial coherence, they generally have an extremely small divergence and are therefore highly directional. For example, a ruby laser beam one inch in diameter at the source will be about four feet across on a surface ten miles away. The very best that could be accomplished over the same distance with an incoherent source, such as an arc lamp at the focus of a six-foot parabolic mirror, would be a beam spread over an area more than one-third of a mile across. Another important feature of lasers is the enormous power that can be generated in a very narrow wave length range. Under certain operating conditions, nearly monochromatic bursts of millions of watts can be produced.
  • a laser beam because it possesses space coherence can be focused to form a spot whose diameter is of the order of one wave length of the laser light itself. Enormous power densities are thus attainable.
  • the focused output of a 50-kilowatt infrared burst from a laser can have a radiant power density of the order of 10 watts/cm; this is about million times the power density at the surface of the sun. Extraordinarily high temperatures, orders of magnitude greater than that at the sun, can be generated at the small area which absorbs this concentrated radiation.
  • the electric field strength of an electromagnetic wave is proportional to the square root of its intensity
  • the field at the focus of the laser beam can be millions of volts per centimeter.
  • a promising potential of lasers comes from time coherence. It is this property which permitted prior art exploitation of radio and microwaves for communications.
  • laser frequencies are millions of times higher than radio frequencies, and hence are capable of carrying up to millions of times more information.
  • one single laser beam has in principle more information-carrying capacity than all the combined radio and microwave frequencies in use at the present time.
  • lasers are useful for communication in space, on earth, and under sea.
  • Military surveillance and weapons systems, mapping, medical, mining, manufacturing, and computer technology may also include lasers.
  • Population inversion can, for example, be accomplished if (I) the atomic system has at least three levels (one ground and at least two excited levels) which can be involved in the excitation and emission processes and (2) the lifetime of one of the most energetic of the excited states is much longer than that of the other or others.
  • laser action can be achieved by providing l means for stimulating photon emission from the long-lived state, and (2) means for causing photon amplification to build up to extremely high values.
  • this is accomplished by fashioning the medium containing the active atoms into a cylinder with perfectly (as far as possible) parallel ends polished so highly that the surface roughness is measured in terms of the wave length of the laser.
  • the ends may be simply polished metal or they may be silvered or dielectric coated so that they behave as mirrors which reflect photons coming toward them from the interior of the cylinder.
  • Such a structure, whether the mirrors are within or outside the container, is called an optical cavity.
  • Such a high-power laser typically includes two reflectors forming a suitable resonator or cavity, a tube forming the side walls of the laser, suitable pumping apparatus including a cathode, anode and directcurrent sources connected in appropriate polarity between the anode and the cathode; inlet apparatus; a source of carbon dioxide, helium, and nitrogen connected to the inlet apparatus; and equipment for exhausting the spent gases from the laser or for cooling and separating them for reuse.
  • a laser output may be generated in various media (i.e., crystals, semiconductors and gases) by pumping or introducing energy to create an inversion where a large number of the atoms are in high energy levels to support photon emission.
  • the lasers were pumped or excited by using a diffusion controlled electrical discharge in a small tube maintained at a low pressure.
  • the ambipolar diffusion time is generally proportional to the product of the gas pressure and the tube diameter squared for large diameters, this ambipolar diffusion time can, under some circumstances, become long compared to the ionization time in the tube, especially for high ionization rates, large diameter tubes and high pressures.
  • the discharge is no longer ballasted by the presence of the tube walls, i.e., local increases in the electron density are not immediately diffused to the walls where they are reduced by wall recombination, etc. Accordingly, local nonuniformities can be produced by these higher electron densities and the fast-growing non-uniformities can become worse.
  • the result is that the previously uniform glow discharge turns into arcs, streamers or current spokes. This latter condition often is a plasma that is very inefficient, and often useless for certain purposes.
  • a controlled discharge provided in accordance with the invention has a characteristic time which is substantially the duration of the time that sustainer current flows in the gaseous medium as a result of the motion of secondaryelectrons generated in the gaseous medium under the influence of an electric field termed herein a sustainer electric field more fully described hereinafter.
  • the characteristic time is the flow time through the cavity.
  • a still further object of the invention is to provide apparatus for and a method of producing controlled, large, volumetric discharges without the inherent ionization instability that occurs when the discharge current itself produces the ionization.
  • a still further object of the present invention is to provide a method of and apparatus for producing laser action in a flowing gas by generating free electrons, and an electrical discharge to maintain the optimum electron environment to produce the lasing action.
  • a still further object of the present invention is to provide a method of and apparatus for producing laser action in a flowing gas by electrical excitation comprising an electron beam to create electrons and a DC voltage to produce a discharge which maintains the optimum electron environment to produce lasing action.
  • FIG. 1 is a perspective view with parts broken away of the apparatus in accordance with the invention.
  • FIG. 2 is a sectional view taken on lines 2-2 of the apparatus shown in FIG. 1;
  • FIG. 3 is a sectional end view taken on lines 33 of the apparatus shown in FIG. 2;
  • FIG. 4 is a perspective view with parts broken away showing details of the electron source
  • FIG. 6 is a block diagram of the circuitry associated with the electron gun and sustainer electrodes.
  • the aforementioned components other than electrode 52 defining the working region 10 are preferably comprised of an electrical nonconductive material, such as, for example, Lucite, Melamine, Fiberglass Epoxy, and the like.
  • a conventional pulse circuit 40 (see FIG. 6) coupled to grid 35 via supports 33 and 34 and enclosure 26 provides the necessary potential to control the amount of high energy electrons released by the electron gun.
  • the pulse circuit 40 is triggered or actuated by a timing circuit 41. Actuation and control of the electron gun is more fully described hereinafter.
  • the electron emitter or gun provides an abundance of high energy electrons which are defocused and directed toward the working region 10 through the screen grid 35 (see FIG. 5).
  • the volume surrounding the electron gun within wall 36 is evacuated by a vacuum pump (not shown) in conventional manner and the electron gun maintained at a low pressure to provide an optimal environment for the free electrons generated therein to pass unhampered through screen grid 35 and be attracted and accelerated toward a reticulated electrical conducting plate 45.
  • Plate 45 made of stainless steel or the like, is maintained at a potential high compared to that of screen grid 35. Electrons generated at the filaments 27 are strongly accelerated toward plate 45 and a portion passthrough the plurality ofholes 46 provided in plate 45.
  • a thin sheet of material or diaphragm 47 is disposed between the working region 10 and the electron gun to permit the existence of separate pressure regimes.
  • a reticulated cathode 50 which may be constructed of a wire mesh and insulated, if desired, from .the electron gun 25 by a ring of non-conducting material 51.
  • a sustainer electric field between oppositely disposed anode plate 52 and previously mentioned cathode 50 which are coupled to the sustainer circuit 53.
  • Cathode 50 which may be comprised of a wire mesh grid as previously noted prevents, for the electron beam and sustainer electric field arrangements as shown, damage to the diaphragm 47 from spurious arcs which may be otherwise inadvertently struck between the anode 52 and/or cathode 50 and diaphragm 47.
  • a high voltage direct current potential is typically maintained between anode 52 and cathode 50 by a conventional sustainer circuit 53 which may comprise capactive discharge means charged by power supply 54 and triggered by timing circuit 41 for pulsed operation.
  • the example hereinbefore given is for a shower head type electron beamwhich covers a broad area, however, the same result may be accomplished by the provision of a rapidly swept beam of electrons over a broad area.
  • a discharge as used herein is, in an ionized medium, the flow of current under the influence of a sustainer electric field or fields. While primarily described herein is the use of DC voltages with inter-cavity electrodes, to provide a sustainer field the invention described herein includes the use of radio frequency electromagnetic fields, inductive electrode structures, capactive electrode structures, movement of an electrically conductive medium in the presence of an applied magnetic field, and the introduction of laser energy into the working cavity to provide the sustaining electric fields.
  • the present invention comprises an improvement over the aforementioned patent application in the provision of ionizing radiation, such as, for example, the provision of highly efficient ionizing radiation through the use of electron gun means rather than high voltage discharge means or the like disclosed in the aforementioned application.
  • a principal feature in providing a volumetrically scalable discharge is the control of gas temperature and discharge uniformity wherein an electrical discharge or the like produces free electrons and ionization of the working medium in a sustainer electric field.
  • Electron temperature which is a function of E/N in any gas mixture, is controlled by adjustment of the sustainer electric field E and control of the gas density N.
  • proper design determines the allowable temperature rises (A1) in the gas and the corresponding density (A N) in the gas.
  • the heat capacity of the gas, the pulse width and the effect of pressure waves must be considered in the proper control of A N.
  • the volumetric discharge can be maintained in a controlled manner to high pressures.
  • controlled discharges in accordance with the invention of up to one atmosphere have been established.
  • the aforementioned patent application disclosed in detail the provision of a short, high voltage pulse substantially inductively spread throughout the volume of the working medium. This is accomplished by the provision of a plurality of electrodes and a short pulse.
  • the discharge is uniformly provided or spread throughout the cavity containing the working medium because the volumetric discharge through all of the electrodes offers the least inductive impedance and thereby makes the current in the short pulse flow reasonably uniform throughout the volume of the cavity containing the working medium.
  • An important criterion for this arrangement to be practically effective is that the inductive impedance of the short pulse discharge circuit be comparable to the resistive impedance of the discharge.
  • the working medium was a mixture of N CO and Re which was used to produce a lasing medium.
  • volumetric ionization in accordance with the aforementioned patent application as well as the present invention is to stabilize the discharge by suppressing the arcing.
  • Much of the arcing which occurs in systems in accordance with the aforementioned patent application occurs due to the electrode configuration and various electrode configurations have been tested in conjunction with that invention and in all cases ionization in accordance with the present invention creates a stabilizing effect which allows the operation in areas that heretofore would have created arcing and breakdown.
  • electron beam ionization can be simply and conveniently controlled by controlling the potential on a grid disposed in front of the electron emitting means.
  • ionization level and, for example, laser output for laser applications may be simply and economically controlled by controlling the grid voltage which may comprise part of a low powered, easily controlled circuit.
  • At least one wall of means defining a working region must transmit or provide high energy electrons which deliver their kinetic energy to the working medium in the form of ionization with a high efficiency.
  • the electron beam voltage i.e., the energy of the electrons in the beam providing the aforementioned high energy electrons must be sufficiently high that the electrons will enter the working region by, for example, penetration of a diaphragm or foil disposed in a wall of the container before passing through and ionizing the working medium.
  • the intensity of the electron beam current is broadly determined by the ionization level requirements such that the volumetric recombination (or attachment) rate equals the production rate of ionization in the electron beam for a particular application.
  • the diaphragm or diaphragms through which the high energy electrons enter the working region need be only such that they transmit the necessary number of electrons and are adequately supported and cooled during transmission of the high energy electrons.
  • the support requirements are such that the diaphragm must withstand the pressure differences between the working gas and the vacuum region where provided on the other side of the diaphragm where the high energy electrons are created and accelerated toward the diaphragm.
  • a suitable geometry is one where there is a high vacuum region exterior of one or more of the walls of the cavity defining the working region.
  • Electrons are generated in the vacuum region by any suitable method such as, for example, plasma emission, thermionic emission, photo emission, electron bombardment and the like. Upon generation of the electrons, they are in conventional manner accelerated through a suitable electrostatic or electromagnetic structure and caused to pass through the diaphragm into the working region.
  • the diaphragm may be disposed over a reticulated member and in certain pulsed applications the foil temperature rise may be limited simply by its intrinsic heat capacity and may be cooled in any suitable manner such as by gas flow or conduction and may be comprised of Al, Be, T,, C, and
  • the diaphragm Since the function of the diaphragm is to separate the working medium in the working region from the vacuum in the electron gun, it typically should be capable of withstanding a pressure difference of one atmosphere. Since the diaphragm is heated by absorbing energy from transmitted electrons in C. W. or numerous rapid pulse applications, it must be cooled. However, any suitable cooling means may be used.
  • the electrons pass directly through one or more of a series of aligned holes in the plates and the gas in the working region will not diffuse rapidly enough through the hole adjacent the electron gun to substantially affect the generation of electrons.
  • Suitable voltages may be applied to the space between plates to obtain maximum focusing of the electrons and the pressure between plates successively decreased in the direction of the electron gun.
  • Electron beam current and ionization level required in a given working medium are determined by the application.
  • many N CO laser applications require only a relatively low level of ionization and low volumetric beam current.
  • the cooling requirements of the diaphragm are modest and can be satisfactorily met by heat conduction to cooled support members.
  • higher ionization levels and higher volumetric beam currents are necessary for practical devices. Accordingly, a greater cooling of the diaphragm will be required for this type of application than with, for example, a laser.
  • the quality of the electron beam i.e., the spread, energy and uniformity of the electron beam throughout the working medium are determined by the application.
  • the intensity of the electron beam must be substantially uniform (with variations not exceeding about a few percent) in order to produce a working medium with the substantially uniform ionization necessary to provide uniform gain and optical properties in the lasing medium.
  • an electron gun produced a stream of electrons which were directed at a thin metallic foil diaphragm supported by a perforated plate with 470 1/1 6 inch holes in an area 2 X 4 inches.
  • the limiting condition on the electron beam current was that the thin metallic foil used not be heated to a temperature at which its structural strength was significantly reduced, since its function is to withstand the pressure difference between the working region and the gun and still transmit electrons. This temperature was arbitrarily set as 200 K, the foil being aluminum having a thickness of cm. Other materials of other thicknesses may be used, and the foil may be cooled by a variety of means, including conduction to cooled supports, or, for example, forced convection with gas blown across its surface in a pulse mode of operation.
  • the production rate, p, of ions in a gas per cm is dn ldt an -lp
  • a is the effective recombination coefiicient
  • p is the production rate
  • n for a typical electron beam and current density 1 mA/cm, in a mixture of Helium, Nitrogen and CO in the proportions 3:2:1 are given immediately below, with characteristic decay time T l/om and range R at E 50 kv, using E, 50 volts.
  • Thermionic electrons from a tungsten filament were modulated by a grid whose potential could be varied with respect to the filament and the electrons were accelerated through a potential V
  • V was chosen by optimizing the ionization produced in the gas. For higher energies Aluminum foil is more transparent and more electrons are transmitted, but the ionization density produced is lower. Accordingly, in Eq. (2) it may be shown that 8 E/8 m z C 1n E/E, where C is a constant,
  • V used was approximately 50 kv and the electron gun was maintained at a vacuum (p 0.1 micron) and separated from the laser chamber by a thin foil of aluminum of thickness 10 cm. Aluminum was chosen simply because of its ready availability.
  • the laser chamber may be at any pressure from below 1p. up to about one atmosphere or more.
  • the electron beam After passing through the foil, the electron beam entered the working region through a relatively wide mesh grid of stainless steel.
  • This grid constituted a cathode and a gold plated disk constituted an anode, between which a sustainer voltage V l0kv) was applied.
  • the grid was provided to prevent damage to the foil, and the gold plate on the anode served to reflect a proportion of the incident primary electrons, thus increasing the ionization of the gas.
  • the filaments in the electron gun were maintained at 50 kv with respect to the foil (which was at or near ground potential) by a 5 micro farad capacitor which supplied the pulsed electron beam current.
  • the filaments were pulsed negative 500 V with respect to the grid.
  • Many other schemes for projecting a beam of electrons into a gas are possible such as photoelectric, field emission, electron bombardment and ion bombardment.
  • the sustainer current was supplied by a 250 p. F capacitor at voltages up to about 10 kv. Either the anode or the cathode can be grounded.
  • the velocity of gas comprising the working medium which flowed through the laser chamber normal to the electron beam can be varied up to about Mach 1. In preliminary tests velocities of about one meter per second were used in order to ensure that the gas was uncontaminated through leaks.
  • Two mirrors in the laser chamber whose axis was normal to both the gas flow and the electron beam, were positioned vertically in the apparatus.
  • One mirror was copper and concave and the otherone was IRtran 98 percent reflecting at a wavelength of l0.6p..
  • the mirrors were spaced 18 cm apart and were supported in a tube whose orientation could be adjusted by means of screws.
  • the mirrors were aligned using standard techniques and the output from laser action between the mirrors passed through a 10.6 1. filter into a germanium crystal infrared detector, the output of which was fed into an oscilloscope triggered by the electron beam current.
  • the sustainer current was measured as well as the infrared detector signal and the infrared detector was calibrated with a thermocouple calorimeter.
  • This time lag represents the time required to achieve a population inversion by pumping the CO molecules into their upper state and is sensitive to the temperature dependence of the electron pumping rate. Increasing the sustainer voltage, and, therefore, the electron temperature in the lasing medium decreased this time lag.
  • gases and gas mixtures may be employed to support laser action although a 3:2:1 ratio of He:N CO is discussed herein, any gas or combination of gases such as CO, E 0, S0 HCN, NO, H Ar, N0 N 0, HF and the like may be handled in the manner discussed hereinabove and other gases may be added if required or desired.
  • the present invention is applicable to substantially any useful laser gas mixture, the principal advantage of the invention being that it is applicable to suitable gas mixtures at high pressures, producing a controllable volumetrically scalable gas discharge over a wide range 16 of operating conditions and electrode configurations.
  • the present invention permits the production of a stable and controlled discharge when the gas mixture constituents and electron temperature T, are selected so that the rate of one or more of the variety of available recombination process (atom recombination, molecular recombination, attachment, etc.) exceeds the rate of ionization. When this is established, the discharge will not be self-sustaining, i.e., it will not run without the ionizing means being actuated and it is this feature that permits the ionizing means to control the discharge characteristics.
  • (T.,),,,,, is defined as the condition for a specific gas mixture wherein ionization equals recombination
  • viable laser apparatus will be provided if an inversion is produced by electronic excitation (and/or appropriate gas kinetic de-activation of states related to the laser transition) at some electron temperature or temperatures T such that T (T A specific example is the N -CO laser mixture. lonizations become significant when T is of the order of 1.5 ev or higher. However, a net preferential excitation (producing an inversion) can be made to occur for electron temperatures of less than 1.5 ev in both N and C0
  • the prior art teaches a large number of atoms and molecules that can be excited electronically by a discharge.
  • Any lasing species which may be inverted by direct electronic excitation or by excitation via an auxiliary species (as in the N CO system) at T (T may be expected to be susceptible to the ionizersustainer concept and especially the electron beam ionizer-sustainer concept of the present invention.
  • the present ionizer-sustainer concept may be expected to be applicable to use of a gas mixture containing a gas which has a high net attachment rate (producing an effective recombination) at high electron temperatures which occur, for example, in 0 for values of T up to about 3 ev.
  • Use of such a gas mixture may be expected to permit operation at higher than usual electron temperatures wherein significant ionization of one of the lasing mixture constituents occurs. This may make lasing transitions acceptable which are not otherwise stably available (C.W.N
  • the energy is put into the upper laser state of CO and into Nitrogen vibration, the optimum electron temperature assuring optimum laser efficiency.
  • the cloud stays uniform during the time of the electric field provided by the sustainer voltage as long as the sustainer voltage does not result in a rapid creation of electrons. If the level of the sustainer voltage or field is raised to the point where it too produces a rapid ionization, then discharge non-uniformities may be created.
  • provision of a sustainer field selected to create negligible electrons results in maintenance of stable, uniform and controlled discharge for several flow times through the working region.
  • the present invention permits the provision in a flowing gas laser of a spatially uniform discharge at the optimum electron temperature required for efficient laser operation at arbitrary pressure levels and physical sizes. While the invention is not so limited, this may be accomplished by utilization of the aforementioned two-step process comprising preferably, first an electron beam which creates in the gas a non-spoking predetermined spatial distribution (preferably uniform) electron density or ionization which would ordinarily, if left on its own, disappear by volumetric processes and/or flowing out of the channel and be incapable of producing efficient high power laser action.
  • the second step or sustainer discharge is provided which gives the electrons produced by the first step the necessary electron temperature for preferably optimum laser (or other) excitation, with no significant increase in electron density.
  • the invention is not limited to the apparatus shown and described and that, for example, other methods of an apparatus for creating the initial electron density can be used such as ultraviolet radiation, electrical discharge, protons and the like provided by electron beam means for introducing one or more electron beams to produce ionization of the gaseous medium as and for the purposes set forth hereinabove. Irrespective of whether the electrons are generated in the above described manner or any other suitable manner, they must be heated to the correct electron temperature by the E/N applied by the sustainer discharge.
  • the Townsend discharge process is characterized by two significant operating characteristics that are at least somewhat interdependent the requirement of a low current density in the discharge and a low overall energy efficiency.
  • the production of ozone requires high levels of activation energy even with low conversion rates of the order of one mole percent of the working medium; hence cooling is essential if an undesirable change in chemical kinetics due to temperature rise is to be prevented.
  • the aforementioned low current density and low overall energy efficiency characteristic of the Townsend process has not only resulted in high production costs but has severely limited the application of processes incorporating the Townsend discharge.
  • the glow discharge process is not subject to the two basic deficiencies of the Townsend discharge of low current density and high cathode drop.
  • the current density is about 2-3 orders of magnitude higher than that of the Townsend discharge and the cathode drop is generally less than about 1,000 volts.
  • the positive column energy efficiency of the glow discharge process is significantly lower.
  • Glow discharge processes are generally conducted under low pressure and with walls cooled to liquid air temperature.
  • the high pressure discharge, or corona discharge is subject to a more limited stability range than the low pressure glow discharge.
  • electrode geometry is generally a critical factor in achieving stabilization of a corona discharge.
  • Ozone may be more easily and efficiently produced than heretofore by utilizing, in accordance with the present invention, an independent source of electrodes in the form of an electron beam or, alternately, repeated short electron beam pulses superimposed on a sustaining electric field as and for the purposes hereinbefore described.
  • the electric field in the active volume is also decoupled from the requirement of the electron emmission, whereby optimum conditions for ozone formation may be provided without for example, severe requirements on ballasting as required for a Townsend discharge or severe requirements on electrode geometry as in the case of a corona discharge.
  • ozone in accordance with the present invention is a truly volumetric process; hence for large scale applications, not only are scaling problems simpler than with prior art processes, but overall equipment size can be drastically reduced. Furthermore, the uniform conditions provided in the active column in accordance with the present invention provides an improvement in the overall energy efficiency and minimizes heat dissipation involved in the process as compared to that of the prior art. Accordingly, ozone may be produced in accordance with the present invention in higher concentrations than that heretofore available without the necessity of cooling.
  • Ozone may be produced with apparatus substantially as shown and described hereinabove with the exception that the mirror means defining the optical cavity are not required.
  • the working medium for the production of ozone may be air or preferably pure oxygen. Electrons are generated by the electron gun in the manner previously described, enter the working region, and collide with oxygen molecules to form secondary electrons and ions. The electron temperature in the working region must be maintained at a level which is favorable to ozone production.
  • a secondary electron temperature in the range of approximately 2-3 electron volts is provided, a large percentage of the energy lost in elastic collision goes into dissociation of oxygen which is essential to the production of ozone in high concentrations.
  • the electron temperature range suitable for the production of ozone is higher by about a factor of 2 than the range necessary to produce laser action. Further, since a low ambient temperature may be easily provided in the working region, this permits the production of higher concentration of ozone with much greater efficiency than heretofore possible.
  • MHD magnetohydrodynamic power generation
  • Electric power can be extracted from an electrically conductive stream of plasma by passing the plasma through a magnetic field transverse to the direction of flow.
  • the magnetic field creates an electric field perpendicular to the magnetic field and to the direction of flow, and suitably constructed electrodes arranged parallel to the electric field permit the kinetic energy of the plasma to be coupled out as electrical energy.
  • an electron beam in accordance with the invention is injected into the plasma to maintain the required level of ionization independent of the electron temperature.
  • a stable plasma discharge may be usefully produced in the plasma wherein the ionization is volumetric and stabilized not by ambipolar diffusion of ion pairs to the walls as in a conventional discharge, but by equilibrium between ion recombination and ion production by the electron beam.
  • the electron beam current density required to maintain an equilibrium ionization level n, 10 cm is ob tained by equating production rate and recombination rate.
  • om, IE/eE R(E) approximately where a effective recombination coefficient I EB current density, amp cm E electron energy, volts R(E) range of electrons of energy E, cm
  • E, 50 eV per ion pair e 5/3 X 10' coulombs For E 100 keV, and density N,, 2.6 X 10 cm', then R(E) z cm in helium 7.5 X 10" amps/cm when a l0" cm lsec n
  • An electron beam as set forth above is easily produced as and for the purposes previously described and may include for example using a jet of helium to cool the foil or diaphragm, the beam of electrons being injected into the MHD channel at a suitably chosen angle relative to the direction of the applied magnetic field.
  • a sustainer field for providing substantially uniformly throughout said working region a predetermined electron temperature effective to increase the average energy of said secondary electrons without substantially increasing said predetermined electron density by self-regenerative ionization, said electron temperature producing said controlled discharge substantially uniformly throughout said working region at a predetermined level.
  • apparatus for producing a controlled discharge for providing molecular excitation of a gaseous working medium comprising:
  • said cavity includes gas inlet and gas outlet means, and additionally including fourth means coupled to said gas inlet for flowing said medium through said cavity.
  • said fourth means includes further means for providing a predetermined pressure and velocity of said medium in said working region.
  • diaphragm means separating said first means and said cavity, said ionizing radiation being introduced into said medium through said diaphragm intermediate said gas inlet and said gas outlet and normal to the direction of flow of said medium through said cavity.
  • said third means includes electrode means for providing a sustainer electric field in said cavity normal to the direction of flow of said medium, said electrode means comprising a first electrode adjacent the wall through which said radiation is introduced and through which said radiation passes, and a second electrode oppositely disposed to said first electrode adjacent the opposite wall of said cavity.
  • said second means includes a perforate plate member and a thin diaphragm covering and carried by said plate member, said diaphragm being disposed between said plate member and said medium.
  • said medium has an upper and lower laser state
  • said first and second means provides a density of secondary electrons in said medium sufficient to support a population inversion
  • said third means increases the average energy of said secondary electrons to a level to produce a population inversion in said medium in said cavity.
  • a gaseous active medium at a pressure in a working region disposed in a cavity having imperforate walls for confining the gaseous working medium that upon the production of secondary electrons in said medium said medium has ambipolar and thermal diffusion rates incapable of damping local increases in secondary electron density in said medium, said medium having an upper and lower laser state;
  • a sustainer field for providing substantially uniformly throughout said working region a predetermined electron temperature effective to increase the average energy of said secondary electrons without substantially increasing said predetermined electron density by self-regenerative ionization, said electron temperature producing an average energy level sufficient to support a population inversion in said medium.
  • a. gas supply means for producing a flow of a gaseous medium having a predetermined velocity and pressure and an upper and lower laser state
  • third means for providing a sustainer field for controlling the electron temperature of said secondary electrons in said medium to substantially uniformly throughout said working region increase their average energy without substantially increasing the density thereof by self-regenerative ionization at said velocity and pressure and produce a population inversion in said medium in said working region.
  • said first means adds energy to said medium in an amount that is less than that of said third means.

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  • Electromagnetism (AREA)
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  • Plasma & Fusion (AREA)
  • Optics & Photonics (AREA)
  • Lasers (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
US72982A 1970-09-17 1970-09-17 Laser or ozone generator in which a broad electron beam with a sustainer field produce a large area, uniform discharge Expired - Lifetime US3702973A (en)

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CA (1) CA939796A (de)
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US3748505A (en) * 1971-09-17 1973-07-24 Comp Generale Electricite Mhd generator with laser augmentation
US3781712A (en) * 1972-10-17 1973-12-25 Hughes Aircraft Co Gas laser with discharge conditioning using ultraviolet photons generated in high current density preliminary discharge
US3789321A (en) * 1972-09-14 1974-01-29 Atomic Energy Commission Electron beam-pumped gas laser system
US3789319A (en) * 1972-05-08 1974-01-29 Atomic Energy Commission Hydrogen rotation-vibration oscillator
US3808551A (en) * 1972-11-02 1974-04-30 Avco Corp Secondary foil for apparatus producing a controlled discharge which provides molecular excitation of a gaseous working medium
US3808553A (en) * 1972-11-21 1974-04-30 Avco Corp Thermally stable laser resonator support assembly
US3810043A (en) * 1972-11-15 1974-05-07 Avco Corp Method of operating closed-cycle carbon dioxide lasers in which carbon monoxide is used to prevent degradation of performance
DE2411192A1 (de) * 1973-03-09 1974-09-12 Avco Everett Res Lab Inc Gasstroemungs-lasereinrichtung
US3860887A (en) * 1972-10-20 1975-01-14 Avco Corp Electrically excited high power flowing gas devices such as lasers and the like
US3863163A (en) * 1973-04-20 1975-01-28 Sherman R Farrell Broad beam electron gun
DE2442408A1 (de) * 1973-09-04 1975-03-06 Avco Everett Res Lab Inc Verfahren zur betaetigung eines gaslasers
US3883413A (en) * 1972-09-25 1975-05-13 Avco Corp Ozone generator using pulsed electron beam and decaying electric field
US3883819A (en) * 1972-12-14 1975-05-13 Us Energy Apparatus for uniform pumping of lasing media
US3941670A (en) * 1970-11-12 1976-03-02 Massachusetts Institute Of Technology Method of altering biological and chemical activity of molecular species
US3963994A (en) * 1975-01-15 1976-06-15 The United States Of America As Represented By The United States Energy Research And Development Administration Slit injection device
US4008444A (en) * 1976-01-19 1977-02-15 Avco Everett Research Laboratory, Inc. Feedback control of a laser output
US4010427A (en) * 1976-03-08 1977-03-01 Avco Everett Research Laboratory, Inc. Laser output control system
US4085386A (en) * 1973-05-30 1978-04-18 Westinghouse Electric Corporation Independent initiation technique of glow discharge production in high-pressure gas laser cavities
US4091306A (en) * 1977-02-07 1978-05-23 Northrop Corporation Area electron gun employing focused circular beams
US4095115A (en) * 1976-12-27 1978-06-13 Accelerators, Inc. Ozone generation apparatus and method
US4134034A (en) * 1977-03-09 1979-01-09 Banyaszati Kutato Intezet Magnetohydrodynamic power systems
US4167466A (en) * 1976-12-27 1979-09-11 Accelerators, Inc. Ozone generation apparatus and method
WO1979001086A1 (en) * 1978-05-18 1979-12-13 F Duncan Magnetohydrodynamic method and apparatus for converting solar radiation to electrical energy
US4211983A (en) * 1978-05-01 1980-07-08 Avco Everett Research Laboratory, Inc. High energy electron beam driven laser
US4278950A (en) * 1979-06-06 1981-07-14 The United States Of America As Represented By The Secretary Of The Air Force Electro-dynamic laser with acoustic absorbing electrode
US4283686A (en) * 1979-03-21 1981-08-11 Avco Everett Research Laboratory, Inc. Laser operation with closed gas and tuned duct pulsing
US4320359A (en) * 1979-06-26 1982-03-16 The United States Of America As Represented By The Secretary Of The Air Force Optical beam mode controlled laser system
US4321558A (en) * 1980-03-11 1982-03-23 Avco Everett Research Laboratory, Inc. Recirculating gas laser
US4328443A (en) * 1980-03-11 1982-05-04 Avco Everett Research Laboratory, Inc. Apparatus for providing improved characteristics of a broad area electron beam
US4331937A (en) * 1980-03-20 1982-05-25 United Technologies Corporation Stability enhanced halide lasers
US4350915A (en) * 1976-09-27 1982-09-21 Wyatt William G Radiant energy converter
US4387344A (en) * 1981-01-16 1983-06-07 The United States Of America As Represented By The Secretary Of The Air Force Photon storage tube high power laser system
US4414670A (en) * 1981-09-29 1983-11-08 The United States Of America As Represented By The Secretary Of The Air Force E-Beam maintained plasma discharge elecrodes
DE3330238A1 (de) * 1982-08-23 1984-02-23 Metalworking Lasers International Ltd., Neve Sharett Hochleistungslaser
US4456811A (en) * 1982-06-21 1984-06-26 Avco Everett Research Laboratory, Inc. Method of and apparatus for heat treating axisymmetric surfaces with an annular laser beam
US4500803A (en) * 1981-09-23 1985-02-19 Hayes James C Self induced laser magnetohydrodynamic (MHD) electric generator
US4507266A (en) * 1982-03-10 1985-03-26 Tokyo Shibaura Denki Kabushiki Kaisha Glow discharge generating apparatus
US4596017A (en) * 1971-07-13 1986-06-17 The United States Of America As Represented By The United States Department Of Energy Electron beam method and apparatus for obtaining uniform discharges in electrically pumped gas lasers
US4709373A (en) * 1985-11-08 1987-11-24 Summit Technology, Inc. Laser excitation system
US4719641A (en) * 1985-11-08 1988-01-12 Summit Technology, Inc. Multiple chamber laser containment system
US5141806A (en) * 1989-10-31 1992-08-25 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof
US5304352A (en) * 1992-01-13 1994-04-19 Bellettini Arturo G Atmospheric ultra-violet laser ozonogenesis
US5391962A (en) * 1992-07-13 1995-02-21 The United States Of America As Represented By The Secretary Of The Army Electron beam driven negative ion source
US5612588A (en) * 1993-05-26 1997-03-18 American International Technologies, Inc. Electron beam device with single crystal window and expansion-matched anode
US5756054A (en) * 1995-06-07 1998-05-26 Primex Technologies Inc. Ozone generator with enhanced output
US5798261A (en) * 1989-10-31 1998-08-25 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Distributed pore chemistry in porous organic polymers
US6022456A (en) * 1997-02-20 2000-02-08 Valdosta State University Apparatus and method for generating ozone
US6027616A (en) * 1998-05-01 2000-02-22 Mse Technology Applications, Inc. Extraction of contaminants from a gas
US6080362A (en) * 1995-06-07 2000-06-27 Maxwell Technologies Systems Division, Inc. Porous solid remediation utilizing pulsed alternating current
US6452338B1 (en) 1999-12-13 2002-09-17 Semequip, Inc. Electron beam ion source with integral low-temperature vaporizer
US6603268B2 (en) * 1999-12-24 2003-08-05 Zenion Industries, Inc. Method and apparatus for reducing ozone output from ion wind devices
WO2003075313A1 (en) * 2002-03-05 2003-09-12 Philips Intellectual Property & Standards Gmbh Discharge light source with electron beam excitation
US20050105580A1 (en) * 2003-11-13 2005-05-19 Giapis Konstantinos P. Apparatus for and method of series operation of DC microdischarge stages in a tube geometry for microlaser applications
US20080043895A1 (en) * 2000-07-05 2008-02-21 Shehane Stephen H Electromagnetic radiation-initiated plasma reactor
US20110310922A1 (en) * 2008-12-22 2011-12-22 Ams Research Corporation Laser resonator
US20120106586A1 (en) * 2010-10-29 2012-05-03 Trumpf, Inc. RF-Excited Laser Assembly

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Cited By (62)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3941670A (en) * 1970-11-12 1976-03-02 Massachusetts Institute Of Technology Method of altering biological and chemical activity of molecular species
US4596017A (en) * 1971-07-13 1986-06-17 The United States Of America As Represented By The United States Department Of Energy Electron beam method and apparatus for obtaining uniform discharges in electrically pumped gas lasers
US3748505A (en) * 1971-09-17 1973-07-24 Comp Generale Electricite Mhd generator with laser augmentation
US3789319A (en) * 1972-05-08 1974-01-29 Atomic Energy Commission Hydrogen rotation-vibration oscillator
US3789321A (en) * 1972-09-14 1974-01-29 Atomic Energy Commission Electron beam-pumped gas laser system
US3883413A (en) * 1972-09-25 1975-05-13 Avco Corp Ozone generator using pulsed electron beam and decaying electric field
US3781712A (en) * 1972-10-17 1973-12-25 Hughes Aircraft Co Gas laser with discharge conditioning using ultraviolet photons generated in high current density preliminary discharge
US3860887A (en) * 1972-10-20 1975-01-14 Avco Corp Electrically excited high power flowing gas devices such as lasers and the like
US3808551A (en) * 1972-11-02 1974-04-30 Avco Corp Secondary foil for apparatus producing a controlled discharge which provides molecular excitation of a gaseous working medium
US3810043A (en) * 1972-11-15 1974-05-07 Avco Corp Method of operating closed-cycle carbon dioxide lasers in which carbon monoxide is used to prevent degradation of performance
US3808553A (en) * 1972-11-21 1974-04-30 Avco Corp Thermally stable laser resonator support assembly
US3883819A (en) * 1972-12-14 1975-05-13 Us Energy Apparatus for uniform pumping of lasing media
DE2411192A1 (de) * 1973-03-09 1974-09-12 Avco Everett Res Lab Inc Gasstroemungs-lasereinrichtung
US3863163A (en) * 1973-04-20 1975-01-28 Sherman R Farrell Broad beam electron gun
US4085386A (en) * 1973-05-30 1978-04-18 Westinghouse Electric Corporation Independent initiation technique of glow discharge production in high-pressure gas laser cavities
DE2442408A1 (de) * 1973-09-04 1975-03-06 Avco Everett Res Lab Inc Verfahren zur betaetigung eines gaslasers
US3963994A (en) * 1975-01-15 1976-06-15 The United States Of America As Represented By The United States Energy Research And Development Administration Slit injection device
US4008444A (en) * 1976-01-19 1977-02-15 Avco Everett Research Laboratory, Inc. Feedback control of a laser output
FR2338595A1 (fr) * 1976-01-19 1977-08-12 Avco Everett Res Lab Inc Procede de commande par retroaction, de lasers a faisceau d'electrons
DE2702443A1 (de) * 1976-01-19 1977-07-21 Avco Everett Res Lab Inc Verfahren zur rueckfuehrsteuerung von elektronenstrahllasern
US4010427A (en) * 1976-03-08 1977-03-01 Avco Everett Research Laboratory, Inc. Laser output control system
US4350915A (en) * 1976-09-27 1982-09-21 Wyatt William G Radiant energy converter
US4095115A (en) * 1976-12-27 1978-06-13 Accelerators, Inc. Ozone generation apparatus and method
US4167466A (en) * 1976-12-27 1979-09-11 Accelerators, Inc. Ozone generation apparatus and method
US4091306A (en) * 1977-02-07 1978-05-23 Northrop Corporation Area electron gun employing focused circular beams
US4134034A (en) * 1977-03-09 1979-01-09 Banyaszati Kutato Intezet Magnetohydrodynamic power systems
US4211983A (en) * 1978-05-01 1980-07-08 Avco Everett Research Laboratory, Inc. High energy electron beam driven laser
WO1979001086A1 (en) * 1978-05-18 1979-12-13 F Duncan Magnetohydrodynamic method and apparatus for converting solar radiation to electrical energy
US4283686A (en) * 1979-03-21 1981-08-11 Avco Everett Research Laboratory, Inc. Laser operation with closed gas and tuned duct pulsing
US4278950A (en) * 1979-06-06 1981-07-14 The United States Of America As Represented By The Secretary Of The Air Force Electro-dynamic laser with acoustic absorbing electrode
US4320359A (en) * 1979-06-26 1982-03-16 The United States Of America As Represented By The Secretary Of The Air Force Optical beam mode controlled laser system
US4328443A (en) * 1980-03-11 1982-05-04 Avco Everett Research Laboratory, Inc. Apparatus for providing improved characteristics of a broad area electron beam
US4321558A (en) * 1980-03-11 1982-03-23 Avco Everett Research Laboratory, Inc. Recirculating gas laser
US4331937A (en) * 1980-03-20 1982-05-25 United Technologies Corporation Stability enhanced halide lasers
US4387344A (en) * 1981-01-16 1983-06-07 The United States Of America As Represented By The Secretary Of The Air Force Photon storage tube high power laser system
US4500803A (en) * 1981-09-23 1985-02-19 Hayes James C Self induced laser magnetohydrodynamic (MHD) electric generator
US4414670A (en) * 1981-09-29 1983-11-08 The United States Of America As Represented By The Secretary Of The Air Force E-Beam maintained plasma discharge elecrodes
US4507266A (en) * 1982-03-10 1985-03-26 Tokyo Shibaura Denki Kabushiki Kaisha Glow discharge generating apparatus
US4456811A (en) * 1982-06-21 1984-06-26 Avco Everett Research Laboratory, Inc. Method of and apparatus for heat treating axisymmetric surfaces with an annular laser beam
DE3330238A1 (de) * 1982-08-23 1984-02-23 Metalworking Lasers International Ltd., Neve Sharett Hochleistungslaser
US4709373A (en) * 1985-11-08 1987-11-24 Summit Technology, Inc. Laser excitation system
US4719641A (en) * 1985-11-08 1988-01-12 Summit Technology, Inc. Multiple chamber laser containment system
US5141806A (en) * 1989-10-31 1992-08-25 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof
US5215790A (en) * 1989-10-31 1993-06-01 The United States Of America As Represented By The National Aeronautics And Space Administration Method for preparation of a microporous structure with layered interstitial surface treatment
US5798261A (en) * 1989-10-31 1998-08-25 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Distributed pore chemistry in porous organic polymers
US5304352A (en) * 1992-01-13 1994-04-19 Bellettini Arturo G Atmospheric ultra-violet laser ozonogenesis
US5391962A (en) * 1992-07-13 1995-02-21 The United States Of America As Represented By The Secretary Of The Army Electron beam driven negative ion source
US5612588A (en) * 1993-05-26 1997-03-18 American International Technologies, Inc. Electron beam device with single crystal window and expansion-matched anode
US6080362A (en) * 1995-06-07 2000-06-27 Maxwell Technologies Systems Division, Inc. Porous solid remediation utilizing pulsed alternating current
US5756054A (en) * 1995-06-07 1998-05-26 Primex Technologies Inc. Ozone generator with enhanced output
US6022456A (en) * 1997-02-20 2000-02-08 Valdosta State University Apparatus and method for generating ozone
US6027616A (en) * 1998-05-01 2000-02-22 Mse Technology Applications, Inc. Extraction of contaminants from a gas
US6452338B1 (en) 1999-12-13 2002-09-17 Semequip, Inc. Electron beam ion source with integral low-temperature vaporizer
US6603268B2 (en) * 1999-12-24 2003-08-05 Zenion Industries, Inc. Method and apparatus for reducing ozone output from ion wind devices
US20080043895A1 (en) * 2000-07-05 2008-02-21 Shehane Stephen H Electromagnetic radiation-initiated plasma reactor
WO2003075313A1 (en) * 2002-03-05 2003-09-12 Philips Intellectual Property & Standards Gmbh Discharge light source with electron beam excitation
CN100405528C (zh) * 2002-03-05 2008-07-23 皇家飞利浦电子股份有限公司 利用电子束激励的放电光源
US20050105580A1 (en) * 2003-11-13 2005-05-19 Giapis Konstantinos P. Apparatus for and method of series operation of DC microdischarge stages in a tube geometry for microlaser applications
US20110310922A1 (en) * 2008-12-22 2011-12-22 Ams Research Corporation Laser resonator
US8428095B2 (en) * 2008-12-22 2013-04-23 Ams Research Corporation Laser resonator
US20120106586A1 (en) * 2010-10-29 2012-05-03 Trumpf, Inc. RF-Excited Laser Assembly
US9071031B2 (en) * 2010-10-29 2015-06-30 Trumpf, Inc. RF-excited laser assembly

Also Published As

Publication number Publication date
GB1373402A (en) 1974-11-13
IL37615A0 (en) 1972-01-27
IT944700B (it) 1973-04-20
JPS555717B1 (de) 1980-02-08
FR2106572A1 (de) 1972-05-05
IL37615A (en) 1974-03-14
SE376817B (de) 1975-06-09
DE2145963A1 (de) 1972-03-23
CA939796A (en) 1974-01-08
CH575668A5 (de) 1976-05-14
FR2106572B1 (de) 1977-08-05

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