Patent Document

CROSS REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/173,148 filed on Dec. 27, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of Invention 
     This invention relates to a directed energy beam system. 
     BACKGROUND OF THE INVENTION 
     Prior Art 
     From a 1996 press release from Los Alamos National Laboratory titled, “There&#39;s new light at the end of the tunnel for some laser-based technologies”: 
     “Researchers Xin Miao Zhao, David Funk, Charlie Strauss, Toni Taylor and Jason Jones experimenting with a powerful infrared titanium-sapphire laser found that when a light pulse intensity reaches a critical value, the beam focuses itself into a thin filament without the aid of focusing lenses or mirrors and perpetuates itself for long distances. 
     The beam—two to three times the thickness of a human hair—propagates virtually indefinitely through air without spreading, something conventional lasers cannot do.” 
     U.S. Pat. No. 5,726,855 APPARATUS AND METHOD FOR ENABLING THE CREATION OF MULTIPLE EXTENDED CONDUCTION PATHS IN THE ATMOSPHERE, issued Mar. 10, 1998 to Mourou et al. teaches a method for enabling the creation of multiple extended conduction paths in the atmosphere through the use of a chirped-pulse amplification laser system having a high peak-power laser capable of transmitting through the atmosphere a high-peak power ultrashort laser pulse. 
     The creation of the conduction path is described in Column 4, line 50 through Column 5, line 22: 
     “For a high peak-power ultrashort pulse, the peak-power can be strong enough to drive the electrons of the material it is propagating through their linear regime and into a nonlinear regime. In this case, the index of refraction for the material can be written n(r)=n.sub.0+n.sub.2 I(r), where n(r) is the radially varying index of refraction, n.sub.o is the linear (standard) index of refraction, n.sub.2 is the nonlinear refractive index, and I(r) is the radially varying intensity. Since the center of the beam has a higher intensity than the outer edges, the index of refraction varies radially (just as in a regular glass lens), and the pulse experiences a positive lensing effect, even if it is collimated at low powers. This is called self-focusing. The critical peak-power needed to start self-focusing is given by Pcr=.lambda.. sup.2/(2.pi.n.sub.2) which for air is 1.8.times.10.sup.9 W but has been measured to be more like 1.times.10.sup.10 W. With an initially smooth spacial beam, only one filament appears at the center of the beam. Once the beam (or part of it) self-focuses, it will not focus to an arbitrarily small size. It will self-focus until the intensity of the pulse is large enough to ionize the material. This generated plasma reduces the on-axis index of refraction by an amount given by 4.pi.e.sup.2 n.sub.e (I)/(2m.sub.e omega.. sup.2) where n.sub.e (I) is the intensity dependent generated plasma density, e is the electron charge, m.sub.e is the electron mass, and omega. is the laser frequency. Again, the beam experiences a radially varying index of refraction change (because n.sub.e (I) is radially varying) and the change due to the plasma acts as a negative (defocusing) lens. So, through the balance of the continual self-focusing (positive lens) and the plasma defocusing and natural diffraction (negative lens), the pulse stays confined to a high-intensity, small diameter over many meters of propagation while automatically producing free electrons. This is a ‘natural’ way of generating an extended plasma channel. The only preparation needed from the user is to generate the high peak-power laser pulse. 
     Each self-focused “hotspot” creates one electrically conductive ionized channel or plasma column in the atmosphere. The plasma columns can be used for many different applications, one such application being to safely and repetitively control the discharge of lightning strikes before natural breakdown occurs to protect power plants, airports, launch sites, etc.” 
     Hardric Laboratories, Inc. of North Chelmsford, Mass., produces mirrors made of bare-polished beryllium metal that produce a high level of reflectivity. 
     BACKGROUND OF THE INVENTION 
     The world is a hostile place. In recent years there has been a proliferation of countries with strategic and tactical ballistic missiles and cruise missiles capable of delivering nuclear, biological, and chemical weapons. The methods used to combat these threats fall into two categories: Lasers and Anti-Missile Missiles (AMM). 
     An example of the first category is the Airborne Laser (ABL) which uses a high-power chemical laser and is carried in a 747 aircraft. Because it uses a chemical laser it can fire only a limited number of times before the chemicals are used up. In addition, its use in a 747 makes it vulnerable to being shot down. 
     In the category of Anti-Missile Missiles, all systems share the disadvantage that an AMM, however fast, takes time to reach the target. This reduces the time available for finding and identifying it as a threat. It also makes second shots less possible. 
     Accordingly, one of the objects and advantages of my invention is to provide a new method of providing a defense against ballistic missiles and cruise missiles. 
     Further objects and advantages of my invention will become apparant from a consideration of the drawings and ensuing description. 
     SUMMARY OF THE INVENTION 
     A laser system, such as the one taught by Mourou et al. is used to produce a thin ionizing beam through the atmosphere. The thin ionizing beam, or plasma beam, is electrically conducting and is moved in either a circular or rectangular fashion to produce a conductive shell to act as a waveguide for microwave energy. Since the waveguide is composed of a plasma it is called a plasma beam waveguide. 
     In a first embodiment the plasma beam waveguide is formed by physically moving the laser system used to produce the beam. Microwave energy is coupled into the plasma beam waveguide through a hole in the laser assembly. 
     In a second embodiment the laser system is stationary and the beam is moved by using a parabolic mirror with an offset feed. A flat mirror, using a mirror positioner having either one or two degrees of freedom, is mounted at the feedpoint and is used to reflect the laser beam around the periphery of the parabolic mirror, producing a shell. Microwave energy is coupled into the plasma beam waveguide through a hole in the center of the parabolic mirror. This is the reason for using a parabolic mirror with an offset feed. 
     In a third embodiment the laser system is also stationary and the beam is moved by using a parabolic mirror with an offset feed. However, the beam is electrically accelerated and then magnetically deflected by an orthogonal pair of electromagnetic coils at the feedpoint. The plasma beam is electrically accelerated by inducing a current in the plasma beam between two conducting mirrors. To accomplish this, both mirrors are made of a conducting material such as beryllium metal, and a current source is connected between them. 
     In all three embodiments the entire assembly can be mounted on a standard azimuth-elevation mount to allow the system to be aimed. 
     Since microwave energy can be produced more efficiently than laser energy, this system can be used to deliver a directed beam of energy more efficiently than a laser acting alone. 
     At high power levels the directed energy beam system can be used as a weapon. Because the system operates soley from electricity it is easily scaled by adding more units. Therefore its use as a defense weapon has an advantage over its use as an offensive weapon. 
     Another use at high power levels is to power the first stage of a rocket booster. A number of directed energy beam systems are arranged to direct their energy beams at a rocket booster whose fuel consists of water. The microwave energy is used to superheat the water which is then directed through a conventional rocket engine nozzle. The use of water as a fuel eliminates the toxicity problems of conventional rocket fuels. Water is also less expensive and more easily stored than conventional rocket fuels. 
     At moderate power levels the directed energy beam system can be used to provide power to an unmanned aerial vehicle (UAV), enabling the UAV to remain on-station for extended periods of time. 
     Because an object interrupting a waveguide produces a discontinuity in waveguide impedance which is reflected back to the source this system can also be used to track the UAV to maintain beam position. 
     Where it is not necessary to transmit appreciable amounts of power, the directed energy beam system can be used as an ultra-precise radar system. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1A shows the front view of an assembly with two laser systems mounted on a cylindrical disk with a hole in the center of the cylindrical disk. 
     FIG. 1B shows the bottom view of the assembly of FIG.  1 A. 
     FIG. 2A shows the assembly of FIG. 1B with a plasma beam being generated by each laser system. 
     FIG. 2B shows the assembly of FIG. 1A mounted on a cylindrical tube with a counterweight on the opposite end of the cylindrical tube. 
     FIG. 3 shows the assembly of FIG. 2B supported by a bearing mount attached to a base, rotated by a motor, and coupled to a microwave transmitter. 
     FIG. 4 shows an alternate arrangement of two laser systems mounted on a cylindrical disk with a hole in the center of the cylindrical disk. 
     FIG. 5A shows a general method of accelerating a Plasma Beam and affecting its properties with an electromagnetic coil. 
     FIG. 5B shows a general method of accelerating a Plasma Beam and affecting its properties with a set of orthogonal electromagnetic coils. 
     FIG. 6A shows an assembly with an inner cylinder attached to an outer cylinder with four rectangular members to create four cavities. 
     FIG. 6B shows an end view of the assembly of FIG.  6 A. 
     FIG. 7 shows an assembly with a laser system mounted in each of two opposing cavities shown in FIG.  6 A. 
     FIG. 8 shows the assembly of FIG. 7 supported by a bearing mount attached to a base, rotated by a motor, and coupled to a microwave transmitter. 
     FIG. 9A shows the side view of a parabolic reflector with a center feedpoint. 
     FIG. 9B shows the front view of a parabolic reflector shown in FIG.  9 A. 
     FIG. 10A shows the side view of a parabolic reflector with a center feedpoint where two incoming parallel rays are reflected to the feedpoint. 
     FIG. 10B shows the side view of a parabolic reflector with a center feedpoint where two rays coming from the feedpoint are reflected from the parabolic reflector as parallel rays. 
     FIG. 11A shows the side view of a parabolic reflector with a center feedpoint where a different pair of rays coming from the feedpoint are reflected from the parabolic reflector as parallel rays. 
     FIG. 11B shows the side view of the section of the parabolic reflector of FIG. 11A where the pair of rays coming from the feedpoint are reflected from the parabolic reflector as parallel rays. 
     FIG. 12A shows the front view of the parabolic reflector of FIG. 11A where the area of the parabolic reflector used in FIG. 11B is highlighted. 
     FIG. 12B shows the front view of the inside parabolic reflector of FIG. 12A where the center area of the inside parabolic reflector has been removed to form a mirror ring. 
     FIG. 13A shows the mirror ring of FIG. 12B with upper and lower segments marked. 
     FIG. 13B shows the side view of the mirror ring of FIG. 13A with a hard waveguide attached to the center hole area and with rays coming from the offset feedpoint and reflecting off the upper and lower segments of the parabolic mirror ring. 
     FIG. 14 shows the side view of the system of FIG. 13B where a two-axis mirror at the feedpoint directs the beam from a laser in a circular fashion around the periphery of the parabolic mirror ring. 
     FIG. 15 shows the system of FIG. 14 mounted in an azimuth-elevation mount. 
     FIG. 16 shows how the Plasma Beam can be electrically accelerated between the feedpoint mirror and the parabolic mirror. 
     FIG. 17A shows the front view of a parabolic reflector where two areas of the parabolic reflector being used are highlighted. 
     FIG. 17B shows the front view of the two inside areas of FIG. 17A where the center areas of the two inside areas have been removed to form two mirror rings. 
     FIG. 18A shows the two mirror rings of FIG. 18B where each mirror ring is divided into upper and lower halves. 
     FIG. 18B shows a mirror ring formed from the upper half of the lower mirror ring of FIG.  18 A and the lower half of the upper mirror ring of FIG.  18 A. 
     FIG. 19A shows the mirror ring of FIG. 18B with upper and lower segments marked. 
     FIG. 19B shows the side view of a system using the mirror ring of FIG. 19A where a two-axis mirror at each feedpoint directs the beam from its associated laser system around its associated periphery of the parabolic mirror ring. 
     FIG. 20A shows the front view of a parabolic reflector where a rectangular segment of a parabolic reflector is highlighted. 
     FIG. 20B shows a mirror assembly made from four indentical rectangular segments of FIG.  20 A. 
     FIG. 21 shows each rectangular segment of FIG. 20B with its own associated feedpoint and laser system. 
     FIG. 22 shows the side view of a system using the rectangular mirror segments of FIG. 21 where a single-axis mirror at each feedpoint directs the beam from its associated laser system to its associated rectangular mirror segment. Only the upper and lower rectangular mirror segments are shown. 
     FIG. 23 shows the side view of a system where the plasma beam is electrically accelerated and then magnetically deflected in a circular fashion around the periphery of the parabolic mirror ring by a pair of electromagnetic coils located at the feedpoint. 
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it is understood that the invention may be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the invention. 
     A laser system is used to produce a thin ionizing beam through the atmosphere. An example of such a laser system using a titanium-sapphire infrared laser is taught in U.S. Pat. No. 5,726,855 APPARATUS AND METHOD FOR ENABLING THE CREATION OF MULTIPLE EXTENDED CONDUCTION PATHS IN THE ATMOSPHERE, issued Mar. 10, 1998 to Mourou et al. 
     The beam is moved in either a circular or rectangular fashion to produce a conductive shell to act as a waveguide for microwave energy. 
     For the purposes of this application the terms Focal Point, Feedpoint, and FP will mean the same thing. The terms Plasma Beam Waveguide, Plasma Beam Conduit, and Plasma Beam Shell will also all mean the same thing. In addition, the term Laser System means a chirped-pulse amplification laser system having a high peak-power laser capable of transmitting a high-peak power ultrashort laser pulse through the atmosphere. 
     A general method of accelerating a plasma beam is shown in FIG.  5 A. Laser System  51  produces Plasma Beam  52  which is reflected off Flat Mirror  53  and Flat Mirror  54  which are made of an electrically conducting material such as beryllium metal. Current Source  55  is connected between Flat Mirror  53  and Flat Mirror  54 . Current Source  55  may be a direct current, an alternating current, and may also be modulated. Electromagnetic Coil  56  may also be used to modulate Plasma Beam  52 . 
     In FIG. 5B the plasma beam between Flat Mirror  53  and Flat Mirror  54  is deflected by a pair of orthogonally mounted electromagnetic coils, designated as Electromagnetic XY Coils  57 , much as the electron beam in a cathode ray tube is magnetically deflected by a standard set of deflection coils. 
     First Embodiment 
     The following describes a system using two laser systems where the plasma beam conduit is formed using a mechanical system that physically moves the laser systems used to produce the beam. Microwave energy is coupled into the plasma beam conduit through a hole in the laser assembly. The plasma beam conduit has a circular cross-section. 
     In FIG. 1A, Laser Assembly  10  is formed by mounting Laser System  13  and Laser System  15  on Cylindrical Disk  11  which is electrically conductive. Hole  17  is in the center of Cylindrical Disk  11 . Mirror  14  deflects the beam from Laser System  13 . Similarly, Mirror  16  deflects the beam from Laser System  15 . Sleeve  12  is electrically conducting and provides a smooth conducting surface extending from Hole  17 . This is shown in FIG.  1 B. FIG. 2A shows Beam  21  from Laser System  15  being deflected from Mirror  16  to continue the conducting path from Hole  17  and Sleeve  12 . Similarly, Beam  20  from Laser System  13  is deflected from Mirror  14  to continue the conducting path from Hole  17  and Sleeve  12 . 
     In FIG. 2B, Assembly  24  is made by mounting Laser Assembly  10  at one end of Conducting Tube  23 . Counterweight  22  is mounted at the opposite end of Conducting Tube  23  to provide dynamic balancing. 
     In FIG. 3, Assembly  24  (made from Laser Assembly  10 , Conducting Tube  23 , and Counterweight  22 ) is mounted on Bearing Mount  31  to allow Assembly  24  to rotate. Ring Gear  32  is mounted around the circumference of Conducting Tube  23  and engages Gear  33  which is turned by Motor  34 . Motor  34  is supported by Motor Stand  35 . Base  37  supports both Motor Stand  35  and Bearing Mount  31 . Microwave Transmitter  39  is also mounted on Base  37  and is coupled to Conducting Tube  23  through Rotary Coupling  38 , whose design is well known to those in the field of Radar. Power to Laser Assembly  10  is supplied through Slip Ring Assembly  36 . In operation, Laser Assembly  10  rotates, causing the beams from Laser System  13  and Laser System  15  to produce a cylindrical conductive shell to act as a waveguide for the Energy from Microwave Transmitter  39 . Mirror  14  and Mirror  16  are precisely aligned so that only a single conductive shell is produced. 
     Referring to FIG. 1A, the reason for using two laser systems is to dynamically balance Cylindrical Disk  11  and to reduce the speed at which the system must rotate. Alternately, one laser system can be replaced by the appropriate balancing weights. As a further alternative, more than two laser systems may be used as long as they are spaced appropriately in order to preserve the dynamic balance of Laser Assembly  10 . Where more than one laser system is used, they are precisely aligned so that only a single conductive shell is produced. 
     An alternative to the arrangement shown for mounting Laser System  13  and Laser System  15  is shown in FIG.  4 . In this arrangement, Laser System  13  and Laser System  15  are mounted tangentially on Conducting Disk  11 . Mirror  41  directs the beam from Laser System  13  to Mirror  14 , while Mirror  42  directs the beam from Laser System  15  to Mirror  16 . The assembly thus produced (Laser Assembly  40 ) is used in place of Laser Assembly  10  in FIG.  3 . Again, the reason for using two laser systems is to dynamically balance Cylindrical Disk  11  and to reduce the speed at which the system must rotate. Alternately, one laser system can be replaced by the appropriate balancing weights. As a further alternative, more than two laser systems may be used as long as they are spaced appropriately in order to preserve the dynamic balance of Laser Assembly  40 . Where more than one laser system is used, they are precisely aligned so that only a single conductive shell is produced. 
     One advantage of Laser Assembly  40  is to produce a more compact arrangement of its components. Another advantage is that it makes it easy to use an electric current to accelerate the plasma beams produced by Laser System  13  and Laser System  15  by the method previously described in reference to FIG.  5 A and FIG.  5 B. 
     The following describes a different arrangement using two laser systems where the plasma beam conduit is formed using a mechanical system that physically moves the laser systems used to produce the beam. Microwave energy is coupled into the plasma beam conduit through a tube in the laser assembly. The plasma beam conduit has a circular cross-section. 
     In FIG. 6A, Assembly  600  consists of an electrically conducting Inner Cylinder  61  attached to Outer Cylinder  60  through the use of Rectangular Members  62 ,  63 ,  64 , and  65 . Referring to FIG. 6B, this results in the creation of Cavities  66 ,  67 ,  68 , and  69 . 
     Referring to FIG. 7, two opposing cavities (Cavity  67  and Cavity  69 ) each contain a laser system with associated mirrors to produce Laser Assembly  70 . Cavity  67  contains Laser System  75 , Mirror  77 , and Mirror  78 . Laser System  75  produces Beam  76  which is reflected off Mirror  77  and Mirror  78 . Cavity  69  contains Laser System  71 , Mirror  73 , and Mirror  74 . Laser System  71  produces Beam  72  which is reflected off Mirror  73  and Mirror  74 . 
     In FIG. 8, Laser Assembly  70  is mounted on Bearing Mount  81  to allow Laser Assembly  70  to rotate. Ring Gear  83  is mounted around the circumference of Laser Assembly  70  and engages Gear  84  which is turned by Motor  85 . Motor  85  is supported by Motor Stand  86 . Base  82  supports both Motor Stand  86  and Bearing Mount  81 . Microwave Transmitter  89  is also mounted on Base  82  and is coupled to Laser Assembly  70  through Rotary Coupling  88 , whose design is well known to those in the field of Radar. Power to Laser Assembly  70  is supplied through Slip Ring Assembly  87 . In operation, Laser Assembly  70  rotates, causing the beams from Laser System  75  and Laser System  71  to produce a cylindrical conducting shell to act as a waveguide for the energy from Microwave Transmitter  89 . Mirrors  73 ,  74 ,  77 , and  78  are precisely aligned so that only a single conductive shell is produced. 
     Referring to FIG. 7, the reason for using two laser systems is to dynamically balance Laser Assembly  70  and to reduce the speed at which the system must rotate. Alternately, one laser system can be replaced by the appropriate balancing weights. As a further alternative, more than two laser systems may be used as long as they are spaced appropriately in order to preserve the dynamic balance of Laser Assembly  70 . Where more than one laser system is used, they are precisely aligned so that only a single conductive shell is produced. 
     Second Embodiment 
     The following describes a system using a single laser system where the laser system is stationary and the plasma beam conduit is formed by an opto-mechanical system using a parabolic section mirror with an offset feed. Microwave energy is coupled into the plasma beam conduit through a hole in the parabolic mirror section. The plasma beam conduit has a circular cross-section. 
     FIG. 9A shows a side view of parabolic Reflector  91  with Axis  93  and Focal Point  92 . FIG. 9B shows the front view of parabolic Reflector  91  and Focal Point  92 . 
     A parabolic reflector has the property that all rays arriving parallel to the axis will be reflected to the focal point. 
     Referring to FIG. 10A, since Rays  101  and  102  are parallel to Axis  93  they are both reflected off Reflector  91  to Focal Point  92 . 
     Similarly, all rays emanating from the focal point and reflecting off the parabolic reflector will depart parallel to the axis. 
     Referring to FIG. 10B, since Rays  103  and  104  emanate from Focal Point  92  and reflect off Reflector  91 , they will depart parallel to Axis  93 . 
     Similarly, in FIG. 11A, Rays  112  and  113  emanate from Focal Point  92 , reflect off Reflector  91 , and depart parallel to Axis  93 . 
     If we are only interested in Rays  112  and  113 , we do not need all of Reflector  91 . 
     FIG. 11B shows the only part of Reflector  91  that we do need, designated as Reflector  111 . Note that Axis  93  still exists even though there is no physical reflector for it to intercept. 
     FIG. 12A shows the front view of Reflector  111 , which is the part of Reflector  91  needed to produce a cylinder where Rays  112  and  113  represent the boundaries of the cylinder. The part of Reflector  91  not used in Reflector  111  is simply not built. Note that Focal Point  92  is no longer in front of Reflector  111 . This is known as an offset feedpoint. 
     Moving a light source from Focal Point  92  around the outside circumference of Reflector  111  produces a cylinder of light. Since we will only be using the outside of Reflector  111  we can make a hole in the center to produce Mirror Ring  121  as shown in FIG.  12 B. The front view of Mirror Ring  111  is shown in FIG.  12 B. In order to make the following drawings clearer we will designate Mirror Segment  131  and Mirror Segment  132  on Mirror Ring  121  in FIG.  13 A. On drawings where Mirror Segment  131  and Mirror Segment  132  are shown it is to be understood that they are present as part of Mirror Ring  121 . Referring to FIG. 13B, the side view of Mirror Ring  121  showing Mirror Segment  131  and Mirror Segment  132  shows two rays coming from Focal Point  92 . A hole in the center of Mirror Ring  121  allows us to couple microwave energy from Microwave Transmitter  134  through microwave Hard Waveguide  133  to the center of Mirror Ring  121 . 
     In FIG. 14, for clarity only Mirror Segment  131  and Mirror Segment  132  of Mirror Ring  121  are shown. A flat mirror at the Focal Point, shown as FP Mirror  141 , is mounted with two degrees of freedom and Mirror Positioner  142  directs the output from Laser System  143  around Mirror Ring  121  to produce a Plasma Beam Waveguide (PB Waveguide  144 ). Mirror Positioner  142  is of conventional electromechanical design. 
     As shown in FIG. 15, the system can be aimed by mounting it in Azimuth-Elevation Mount  151 , which is of conventional design. 
     FIG. 16 shows how the Plasma Beam can be electrically accelerated between FP Mirror  141  and Mirror Ring  121  of which only Mirror Segment  131  and Mirror Segment  132  are shown. By using an electrically conducting material such as beryllium metal for FP Mirror  141  and Mirror Ring  121 , and by using Current Source  161  to induce an electrical current between the two mirrors, the plasma beam produced by Laser System  143  is electrically accelerated. Normally, for operator safety, Current Source  161  will be grounded at Mirror Ring  121 . Current Source  161  may be a direct current or an alternating current, and may also be modulated. 
     As one example, the transmission of 3 GHz. microwave energy requires a plasma beam waveguide with a diameter of approximately 2.5 inches. Naturally, other dimensions may be used in other applications with other requirements. 
     The following describes an opto-mechanical system using two laser systems where the laser systems are stationary and the plasma beam waveguide is formed by an opto-mechanical system using two parabolic section mirrors, each with an offset feed. The plasma beam conduit has a circular cross-section. This is the preferred embodiment. 
     FIG. 17A shows the front view of Parabolic Reflector  91  with Focal Point  92 , where two inside areas of Parabolic Reflector  91  are highlighted. Area  111  has already been described in conection with FIG.  11 B. Area  171  is a reflection of Area  111  and has the same properties. 
     FIG. 17B shows the front view of Area  111  and Area  171  of FIG. 17A where the center areas of Area  111  and Area  171  have been removed to form Mirror Ring  121  and Mirror Ring  172 . 
     In FIG. 18A Mirror Ring  121  has been divided in half to form Mirror HRing  181  and Mirror HRing  182 . Similarly, Mirror Ring  172  has been divided in half to form Mirror HRing  183  and Mirror HRing  184 . 
     In FIG. 18B Composite Mirror Ring  187  has been formed from the upper half of the lower mirror ring of FIG. 18A (Mirror HRing  183 ) and the lower half of the upper mirror ring of FIG. 18A (Mirror HRing  182 ). In order to distinguish the two focal points derived from Focal Point  92 , the focal point associated with Mirror HRing  182  will be designated as Focal Point  186 , while the focal point associated with Mirror HRing  183  will be designated as Focal Point  185 . 
     In order to make the following drawings clearer we will designate Mirror Segment  190  and Mirror Segment  191  on Composite Mirror Ring  187  as shown in FIG.  19 A. In drawings where Mirror Segment  190  and Mirror Segment  191  are shown it is to be understood that they are present as part of Composite Mirror Ring  187  made of Mirror HRing  183  and Mirror HRing  182 . Referring to FIG. 19B, the side view of Composite Mirror Ring  187  shows Ray  196  from Laser System  194  reflecting off Two-Axis Mirror Positioner  195  located at Focal Point  185  and Ray  199  from Laser System  197  reflecting off Two-Axis Mirror Positioner  198  located at Focal Point  186 . With a full composite mirror Laser System  194 , Mirror Positioner  195 , and Mirror HRing  183  will produce the top half of the plasma beam waveguide, while Laser System  197 , Mirror Positioner  198 , and Mirror HRing  182  will produce the bottom half of the plasma beam waveguide. Hard Waveguide  192  couples the energy from Microwave Transmitter  193  to the center of Composite Mirror Ring  187 . 
     Plasma beam waveguides of other cross-sectional shapes, such as rectangular, may be formed by appropriate mirror design. 
     The following describes a system using four laser systems where the laser systems are stationary and the plasma beam conduit is formed by an opto-mechanical system using four parabolic section mirrors, each with an offset feed. The plasma beam conduit has a rectangular cross-section. 
     FIG. 20A shows the front view of Parabolic Reflector  91  where Rectangular Segment  202  of Area  201  is highlighted. A ray emanating from Focal Point  92  that is directed along the center of the long axis of Rectangular Segment  202  will produce a planar beam. 
     FIG. 20B shows Mirror Assembly  203  made from four indentical pieces, each one consisting of Rectangular Segment  202  in the appropriate position and orientation to form Mirror Assembly  203 . Each rectangular segment has its own focal point. 
     In FIG. 21 the top of the plasma beam waveguide is produced by Laser System  2101 , Single-Axis Mirror Positioner  2102 , and Rectangular Segment  2103 . The right side of the plasma beam waveguide is produced by Laser System  2104 , Single-Axis Mirror Positioner  2105 , and Rectangular Segment  2106 . The bottom of the plasma beam waveguide is produced by Laser System  2107 , Single-Axis Mirror Positioner  2108 , and Rectangular Segment  2109 . The left side of the plasma beam waveguide is produced by Laser System  2110 , Single-Axis Mirror Positioner  2111 , and Rectangular Segment  2112 . Square Section  2113  allows microwave energy to be coupled into the plasma beam waveguide. 
     In FIG. 22, for clarity only the top and bottom parts are shown. The top of the plasma beam waveguide ( 223 ) is produced by Laser System  2101 , Single-Axis Mirror Positioner  2102 , and Rectangular Segment  2103 . The bottom of the plasma beam waveguide ( 224 ) is produced by Laser System  2107 , Single-Axis Mirror Positioner  2108 , and Rectangular Segment  2109 . The two sides not shown (Laser System  2104 , Single-Axis Mirror Positioner  2105 , Rectangular Segment  2106 , Laser System  2110 , Single-Axis Mirror Positioner  2111 , and Rectangular Segment  2112  complete the plasma beam waveguide. Hard Waveguide  222  couples the energy from Microwave Transmitter  221  to the center of Mirror Assembly  203  and into the plasma beam waveguide. 
     Third Embodiment 
     The following describes a system using a single laser system where the laser system is stationary and the plasma beam conduit is formed by an opto-electromagnetic system using a parabolic section mirror with an offset feed. Microwave energy is coupled into the plasma beam conduit through a hole in the parabolic mirror section. The plasma beam conduit has a circular cross-section. 
     FIG. 23 shows Mirror Segment  131 , Mirror Segment  132 , Hard Waveguide  133 , Microwave Transmitter  134 , and Laser System  143  as previously described in connection with FIG.  16 . However, in this embodiment a pair or orthogonal electromagnetic coils (FP Coils  231 ) located at the feedpoint are used to deflect the plasma beam around the periphery of Mirror Ring  121 , of which only Mirror Segment  131  and Mirror Segment  132  are shown. FP Coils  231  are electrically driven to produce a changing magnetic field to deflect the plasma beam in a circular fashion around the periphery of Mirror Ring  121 . Mirror  232  is used for providing a conducting surface in order to provide an electrically path through the plasma beam. As with the Second Embodiment, more than one laser system may be used by choosing the appropriate configuration of parabolic section mirrors. The method taught in the Second Embodiment may also be used to produce a rectangular waveguide. 
     While preferred embodiments of the present invention have been shown, it is to be expressly understood that modifications and changes may be made thereto and that the present invention is set forth in the following claims.

Technology Category: g