Double cusp gyro gun

Abstract

A gyrotron gun that generates gyrating electron beams in a controllable manner suitable for use in a wide range of gyro-amplifiers and gyro-oscillators is disclosed. The gyrotron comprises first and second means for abruptly changing a magnetic field and which means are positioned between first, second and third field coils. The field coils are operated so as to provide for a desired magnetic field profile that allows for the control of the parameters desired to provide for small-orbit, large-orbit, and linear modes of operation of the gyrotron gun. The gyrotron gun further comprises of a pair of bucking coils arranging near the cathode to independently control the axial velocity spread of the gyrating electron beam.

What is claimed and desired to be secured by Letters Patent of the United States is:  
     
       1. A system for generating and forming a beam of electrons comprising: 
       (a) a vacuum envelope forming a tunnel having entrance, intermediate and exit sections with the intermediate having first and second portions;  
       (b) first, second and third field coils with the first being situated at said entrance section and the second and third being situated at said intermediate section;  
       (c) first and second means for establishing an abrupt change in a magnetic field, said first and second abrupt change means being respectively interposed between said first and second field coils and said second and third field coils, said first field coil and said first abrupt change means comprising a first operating region, said second field coil and said first and second abrupt change means comprising a second operating region and said third field coil and said second abrupt change means comprising a third operating region;  
       (d) a cathode located in said entrance section and capable of emitting a beam of electrons when subjected to the presence of a relatively high voltage pulse; and  
       (e) an anode located in said entrance section and spaced apart from said cathode and capable of attracting said beam of electrons.  
     
     
       2. The system for generating and forming an electron beam according to  claim 1  further comprising a pair of bucking coils located near said cathode. 
     
     
       3. The system for generating and forming an electron beam according to  claim 1  further comprising an interaction circuit connected to said exit portion and extracting microwave energy from said beam of electrons. 
     
     
       4. The system for generating and forming an electron beam according to  claim 1 , wherein said cathode is thermionic or comprises other electron emitting devices. 
     
     
       5. The system for generating and forming an electron beam according to  claim 1 , wherein said cathode and said anode both have an annular shape. 
     
     
       6. The system for generating and forming an electron beam according to  claim 1 , wherein said cathode and anode are offset from each other and have protrusions interposed therebetween so that said beam of attractable electrons are diverted away from said anode and directed toward said intermediate section. 
     
     
       7. The system for generating and forming an electron beam according to  claim 1 , wherein said vacuum envelope, said first, second and third field coils and said first and second means for establishing an abrupt change in a magnetic field comprise a gyrotron device having a predetermined operating period with a corresponding predetermined wavelength and said first and second means for establishing an abrupt change are spaced apart from each other by a distance corresponding to one-half of said predetermined wavelength. 
     
     
       8. A method using a gyrotron gun having a cathode that emits a beam of electrons when subjected to the presence of a relatively high voltage pulse and an anode spaced apart from said cathode and energized with respect to said cathode so that said beam of electrons are attractable toward said anode, said gyrotron gun generating and forming a beam of electrons manifesting electron gyrating around a guiding center and having rotational energy, said beam-forming being determined by at least two factors: (1) the transverse-to-axial velocity ratio, α, of the gyrating electron beam; and (2) the position of the electron's mean guiding center, r g , said method comprising the steps of: 
       (a) providing a vacuum envelope that forms a tunnel having entrance, intermediate and exit sections with the intermediate section having first and second portions;  
       (b) arranging first, second and third field coils with the first being situated at said entrance section and the second and third being situated at said intermediate section;  
       (c) interposing first and second means for establishing an abrupt change in a magnetic field, said imposition placing said first means for establishing an electric field between said first and second field coils and said second means for establishing an abrupt change in a magnetic field between said second and third field coils, said first field coil and said first abrupt changing means comprising a first operating region, said second field coil and said first and second abrupt change means comprising a second operating region, and said third field coil and said second abrupt change means comprising a third operating region;  
       (d) adjusting the first field coil to supply the strength of an axial magnetic field corresponding to a first predetermined quantity f 1  in said first operating region;  
       (e) adjusting the second field coil to supply the strength of an axial magnetic field corresponding to a second predetermined quantity f 2  in said second operating region;  
       (f) adjusting the third field coil to supply the strength of an axial magnetic field corresponding to a third predetermined quantity f 3  in said third operating region;  
       (g) adjusting said f 1  and f 2  quantities to one of the following relationships: (1) (f 1 =f 2 ); (2) (|f 1 |=−|f 2 |) and (3) (f 1 ≠f 2 ).  
     
     
       9. The method of using a gyrotron gun according to  claim 8 , wherein said beam-forming is further determined by a third factor: (3) the spread of the axial velocity v z  of said beam and wherein said method further comprises the steps of: 
       (h) arranging a pair of bucking coils near said cathode; and  
       (i) adjusting the level of current in said bucking coils to control said spread of axial velocity of said beam.