Abstract:
An improved Klystron device is disclosed which has opposed electrostatic (ES) magnetic field generating members which are uniformly spaced along a longitudinal axis to form an electron beam chamber. The ES magnetic field generating members produce a magnetic flux which confines an electron beam passing through the chamber when an alternating current (AC) is imposed upon the magnetic field generating members. An additional improvement includes a chamber formed from a single sheet of electron conductive metal having a ladder-like structure symmetrical about a longitudinal hinge which permits the structure to be folded about the hinge to form a suitable electron beam chamber.

Description:
PRIORITY CLAIM 
   This application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 60/446,831, filed Feb. 11, 2003. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to Klystron and TWT devices which have a magnetically focused electron beam, including electrostatically focused beams. 
   2. State of the Art 
   Klystron devices, for example, with electrostatically focused beams have been constructed with focusing lenses rather than permanent magnets such as that illustrated in  FIG. 1 . 
   U.S. Pat. No. 5,821,693 illustrates and describes a recent improvement in Klystron construction. Magnets, either permanent or electrostatic are brazed to the external surface of a tube. These magnets must be placed by hand in a precise manner and then brazed in place. Precise placement by hand is difficult and brazing limits the temperature at which the Klystron may be operated. 
   BRIEF SUMMARY OF THE INVENTION 
   Improved infrastructures for electron beam containing cavities has been invented. Ladder-like structures made by photolithographic/micromachining processes to form miniature ladder-like structures capable of being nested provide significant improvement in weight and power amplification for Klystron and TWT devices. 
   The precise structures are made by applying a precise mask by photolithographic technique and etching the substrate, generally an electroconductive metal, to form ladder-like structures of precise dimensions. The unremoved portions of the sheet form a ladder with spaced rungs and parallel rails. The spacing between rungs has micron-rigid tolerances and the spacing is such that rungs form an elongated ladder-like structure may superposed and interspersed with sufficient air gaps to prevent arcing or shorting. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     In the drawings, which illustrate what is currently considered to be the best mode for carrying out the invention: 
       FIG. 1  is an illustration of a prior art Klystron device with electrostatic focusing lenses; 
       FIG. 2  is a perspective view of a single ladder-like structure made by micromachining techniques; 
       FIG. 3  illustrates two ladder-like structures in a face-to-face relationship, whereby a precise tunnel may be formed by folding one ladder over the other along the hinge axis; 
       FIG. 4  illustrates schematically a second set of ladders shaped and structured to nest between rungs of a first pair of opposed ladders forming an elongated tunnel; and 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Improvements in the fabrication and structure of electrostatically (ES) focused Klystrons have been achieved by employing microfabrication techniques. Unique, precise infrastructures for Klystron and TWT devices may be readily fabricated to have low, micron-sized tolerances. The infrastructures further permit multi-cavity devices of miniature dimensions to be made thereby providing high amplification devices which are small in size and light in weight. 
   Unique, elongated ladder-type structures which are formed as identical pairs are placed together to form an elongated tunnel (electron cavity). The ladder-like structure is illustrated in  FIGS. 2 and 3 . 
     FIG. 2  is a perspective view of a single ladder-like electroconductive structure wherein the cross-members (rungs) are recessed from the plane of the elongated ladder rails. 
     FIG. 3  shows two ladder-like structures positioned in a face-to-face relationship to create an elongated tunnel having a hexagonal, cross-sectional shape. 
   A second set of ladder-like structures of a similar shape to the structure shown in  FIG. 2  is superposed on the opposed structures of  FIG. 3  whereby the rungs are sized and shaped to fit between the rungs of the structures in  FIG. 3 . The gaps between rungs of the  FIG. 2  structure must be sufficiently wide to accommodate rungs of a second superimposed ladder so that the rungs of the second ladder are interspersed between the rungs of the first ladder with sufficient space on either side of adjacent rungs to prevent arcing or shorting between rungs. 
   The rails of the second superposed “ladder” are preferably separated from the rails of the first “ladder” by an electrical insulating material. The rungs of the first and second ladders may be of the same or slightly different dimensions. Each set of ladders will preferably have substantially the same geometric shape for its rungs. Opposed rungs forming a hexagonally shaped, elongated cavity are readily formed although the rungs could be half circles, e.g., so that a cylindrically shaped tunnel could be formed. Also, a tunnel with square or rectangular cross-sectional shape can be readily constructed. A hexagonally or octagonally shaped tunnel is preferred since a more uniform magnetic field can be created where the tunnel cross-section more closely approximates a circle. 
   Thus, a compact precise tunnel may be formed from four ladder-like structures of an electro-conductive material, e.g. copper, moly and similar conductive metals as well as conductive ceramics, silicon and the like. 
   One pair of ladders, top and bottom, with rungs directly opposed to one another is connected to an alternating current of RF frequency to create an electrostatically field (magnetic field) within the tunnel to maintain a beam of electrons flowing from an electron gun cathode in a tightly confined beam. The other pair of ladders, top and bottom are connected to a slow wave source of a.c. The slow wave current, in a simusoidal wave preferably, creates a field which causes bunching of the electrons, causing the electrons to slow. 
   The energy lost by the slowing electrons is captured by an RF field projected by a transmitting antenna located near the front end of the tunnel with a receiver antenna located near the beam discharge end of the tunnel. Thus, as shown in the attached tables, significant amplification of the RF field results from a Klystron having the ladder-type structures forming an electron beam tunnel. 
   The construction of a pair of opposed ladder-type structures is facilitated by forming such a pair from a single sheet of material having an elongated hinge whereby the axis of rotation of said hinge is parallel with the central longitudinal axis of the tunnel formed by folding one ladder-like structure over its twin along the hinge joint to form a structure such as that shown in  FIG. 5 . This novel structure facilitates ready alignment of one ladder with an opposed ladder to form an electron beam tunnel. A hinged structure is illustrated in  FIG. 5 . The pair of interlacing, superposed ladders may also be made from a single sheet of material with a hinge joint. 
   Design of TWTA with Electrical Focusing System 
   Structure Instruction 
   1. Dimensions 
   All dimensions are scaled from Kory&#39;s structure according to pitch ratio except the following: 
   Short position given in the table; 
   Dielectric constant of cube 4.1; 
   Inserted electrical focusing system:
         a. Thick of plate: 0.09807 mm;   b. Distance to waveguide side wall: 0.09807 mm;   c. Distance to waveguide bottom: 0.09807 mm.       

   2. The Electrical Focusing Structure 
   The two plates are connected together by ladders and in the same positive potential, and the waveguide are grounded. We have another version in which the two plates are separated and not in same potential as well as waveguide not grounded, which will be released in the future if necessary. 
   In the electrical focusing structure, the original ladders are cut every another required by the focusing voltage. The functions of the plates provide a big capacitance for the compensation of displacement current as well as the supporting mechanism. The outlet of the electrical plates are through the two small cubes, which can be found under the plates. The simulations show that there is no significant RF performance influence from the two ports, largely because of the plate capacitance function. 
   3. RF Performance Influenced by Electrical Focusing Structure 
   It is noticed there is significant influence by the introduction of electrical focusing structure. The significant influences include the increased dispersive, increased wave length or wave speed (resulting in a higher required anode voltage), increased attenuation, as well as increased deformation of waveform in space (or space spectrum). Efforts have been made to reduce the side effect as small as possible. However, up to date the performance can not be thought as optimum. The future work will be needed depending the feedback from other engineer who performs the process. 
   The structure is intended for the design of V band, however in principal this design can be extended to Ka band by the structure scaling according to frequency ratio. We can evaluate the feasibility roughly, and then move further if necessary. 
   
     
       
             
           
             
             
             
           
         
             
               TABLE 1 
             
           
           
             
                 
             
             
               Performance Table 
             
             
               Pitch = 0.190221978 mm 
             
           
        
         
             
               Frequency 
               51 GHz 
               52 GHz 
             
             
                 
             
             
               Slow wavelength λc 
               1.3319 mm 
               1.1463 mm 
             
             
               Phase shift per cavity 
               51.41° 
               59.73° 
             
             
               Slow wave velocity Vp 
               0.679 E8 m/s 
               0.596 E8 m/s 
             
             
               Attenuation per cavity 
               0.18 dB/per cavity 
               0.29 dB/per cavity 
             
             
               Interaction impedance Zc 
               165 Ω 
               152 Ω 
             
             
               Required anode voltage to 
               13,000 v 
               10,000 v 
             
             
               match wave speed 
             
             
               Gain parameter C @ ia = 60 
               0.0575 
               0.061 
             
             
               mA 
             
             
               Gain of 64 cavities 
               3.78 dB 
               2.58 dB 
             
             
               Gain of 70 cavities 
               5.03 dB 
               3.71 dB 
             
             
               Gain of 80 cavities 
               7.11 dB 
               5.61 dB 
             
             
               Gain of 90 cavities 
               9.19 dB 
               7.50 dB 
             
             
               Gain of 100 cavities 
               11.28 dB 
               9.4 dB 
             
             
               Gain parameter C @ ia = 80 
               0.0672 
             
             
               mA 
             
             
               Gain of 64 cavities 
               6.28 dB 
               5.67 dB 
             
             
               Gain of 70 cavities 
               7.77 dB 
               7.09 dB 
             
             
               Gain of 80 cavities 
               10.24 dB 
               9.47 dB 
             
             
               Gain of 90 cavities 
               12.71 dB 
               11.89 dB 
             
             
               Gain of 100 cavities 
               15.18 dB 
               14.22 dB 
             
             
               VSWR at input port 
               1.38 
               1.29 
             
             
               Short position from axis 
               2.888 mm 
               2.888 mm 
             
             
                 
             
           
        
       
     
   
   Magnetic Field Focusing in TWT Slow Wave Structure 
   The simulations of beam current profile as a function of static focusing magnetic field are shown in the following tables for both Ka band and V band. The simulations are conducted under a slow wave structure of 16 ladder, with given injected beam current and observed current after 16 ladders. A perfect focusing profile is no difference between input and output beam current. From the following results, we can clearly see that the required magnetic field intensity to maintain a perfect beam focusing is increased as the beam radius decreases and current intensity increases. 
   
     
       
             
             
             
           
             
             
             
             
             
           
         
             
                 
               TABLE 2 
             
           
           
             
                 
                 
             
             
                 
               Ka Band (30 GHz) 
               V Band (50 GHz) 
             
             
                 
               Pitch = 0.31797 mm 
               Pitch = 0.19022 mm 
             
             
                 
               Beam radius = 
               Beam radius = 
             
             
                 
               0.2459 mm 
               0.147 mm 
             
           
        
         
             
               Injected beam 
               60 mA 
               80 mA 
               60 mA 
               80 mA 
             
             
                 
             
             
               Beam current after 16 
                 
                 
                 
                 
             
             
               ladders 
             
             
               B = 0.1 Tesla 
               38.2 mA 
             
             
               B = 0.2 Tesla 
               55.7 mA 
             
             
               B = 0.3 Tesla 
               58.3 mA 
               74.1 mA 
               55.7 mA 
             
             
               B = 0.5 Tesla 
               60.0 mA 
               77.9 mA 
               58.3 mA 
               74.0 mA 
             
             
               B = 0.7 Tesla 
                 
               78.0 mA 
               58.9 mA 
               77.8 mA 
             
             
               B = 0.9 Tesla 
                 
               80.0 mA 
               60.0 mA 
               78.3 mA 
             
             
               B = 1.2 Tesla 
                 
                 
                 
               80. mA 
             
             
                 
             
           
        
       
     
   
   Although the following results show a big difference among different applied magnetic field, no significant differences are observed from beam image trajectories. So the final design should be always based on the detailed numerical results, not the qualitative image pictures.