Cyclotron resonance maser system with microwave output window and coupling apparatus

• US 4,604,551 A
• Filed: 06/20/1984
• Issued: 08/05/1986
• Est. Priority Date: 07/27/1983
• Status: Expired due to Fees

• Current Assignee: General Atomics, Inc.
• Original Assignee: GA Technologies Incorporated
• Inventors: Moeller, Charles P.
• Primary Examiner(s): Chatmon, Saxfield
• Application Number:
  US06/622,672
• Time in Patent Office: 776 Days
• Field of Search: 315/3, 315/4, 315/5, 315/5.29, 315/5.31, 315/39, 315/5.32, 372/2, 331/79, 331/81, 330/4.5, 333/230, 333/251, 333/24 R
• US Class Current: 315/4
• CPC Class Codes: H01S 1/005 using a relativistic beam of charged particles, e.g. electron cyclotron maser, gyrotron

Abstract

A cyclotron resonance maser system includes coaxial coupling between coaxial wave guides. Such coupling is provided between an outer coaxial waveguide through which a gyrotron electron beam passes in generating or amplifying microwaves and an inner coaxial waveguide terminating in an annular window. The coupling separates the microwaves from the electron beam before the collector region of the gyrotron so that the collector dimensions are not related to, and hence restricted by, the wavelength of the output microwaves. The particular preferred coupling includes substantially axial slots in the common wall between the respective waveguides which slots provide selective coupling between the waveguides in the desired modes and limiting mode conversion. The coupling is preferably between a TE_On or TE_ml mode in the outer input waveguide and a TE_On'"'"' mode in the inner, output waveguide, n and n'"'"' being integers greater than 1. A preferred resonant cavity limits the generated microwaves to a TE_ml mode. Partial reflection and feedback from the inner waveguide stabilizes the input mode.

Claims

1. A cyclotron resonance maser system comprising:

an assembly of components disposed successively along a common axis and including successively and coaxially an annular source of electrons, tunnel means for defining a beam tunnel symmetrically disposed about said axis, interaction means for defining an electron-microwave interaction region symmetrically disposed about said axis, a first coaxial waveguide coupled to said interaction means, and an annular collector of electrons,

means for forming electrons from said source into an annular beam of electrons having substantial energy transverse of said beam and directing said beam of electrons successively through said beam tunnel, said interaction region and said coaxial waveguide to said collector,

a second coaxial waveguide coaxial with and surrounded by said first coaxial waveguide and extending coaxially through said electron collector, and

symmetric coaxial coupling means for coupling microwave energy between said first and second coaxial waveguides.

2. A cyclotron resonance maser system according to claim 1 wherein said coaxial coupling means includes a common wall between said first and second waveguides, said wall being penetrated by substantially axial elongated slots substantially equally spaced around said axis at a common axial location.

3. A cyclotron resonance maser system according to claim 2 wherein the respective sides of each slot are substantially parallel to one another and each of said slots terminates in a narrowing taper at each end.

4. A cyclotron resonance maser system according to claim 2 wherein said slots have a helical twist for coupling a rotating wave to a symmetric wave.

5. A cyclotron resonance maser system according to claim 1 wherein said coaxial coupling means comprises a mode selective directional coupler for coupling a TE_m1 mode in said first waveguide to a TE_0n mode in said second waveguide, m being an integer large compared to 1 and n being an integer greater than 1, said second waveguide propagating said TE_0n mode and containing means for partially reflecting microwaves in said TE_0n mode back through said coupler for reinforcing the desired TE_m1 mode in said first waveguide.

6. A cyclotron resonance maser system according to claim 5 wherein n is 2.

7. A cyclotron resonance maser system according to claim 5 wherein said directional coupler comprises a common wall between said first and second waveguides, said wall being penetrated by m substantially axial elongated slots.

8. A cyclotron resonance maser system according to claim 5 wherein said common wall has a thickness substantially equal to an odd multiple of one-fourth the cutoff wavelength of the mode going through said coupler.

9. A cyclotron resonance maser system according to claim 1 further comprising an annular window member for hermetically sealing said second waveguide and transmitting microwave energy.

10. A cyclotron resonance maser system according to claim 9 further including means for cooling the inner and outer edges of said annular window member.

11. A cyclotron resonance maser system according to claim 9 wherein said coaxial coupling means includes a common wall between said first and second waveguides, said wall being penetrated by substantially axial elongated slots substantially equally spaced around said axis at a common axial location.

12. A cyclotron resonance maser system according to claim 11 wherein the respective sides of each slot are substantially parallel to one another and each of said slots terminates in a narrowing taper at each end.

13. A cyclotron resonance maser system according to claim 11 wherein said slots have a helical twist for coupling a rotating wave to a symmetric wave.

14. A cyclotron resonance maser system according to claim 9 wherein said coaxial coupling means comprises a mode selective directional coupler for coupling a TE_m1 mode in said first waveguide to a TE_0n mode in said second waveguide, m being an integer large compared to 1 and n being an integer greater than 1, said second waveguide propagating said TE_0n mode and containing means for partially reflecting microwaves in said TE_0n mode back through said coupler for reinforcing the desired TE_m1 mode in said first waveguide.

15. A cyclotron resonance maser system according to claim 14 wherein said means for partially reflecting microwaves comprises said window member.

16. A cyclotron resonance maser system according to claim 14 wherein n is 2.

17. A cyclotron resonance maser system according to claim 14 wherein said directional coupler comprises a common wall between said first and second waveguides, said wall being penetrated by m substantially axial elongated slots.

18. A cyclotron resonance maser system according to claim 14 wherein said common wall has a thickness substantially equal to an odd multiple of one-fourth the cutoff wavelength of the mode going through said coupler.

19. A cyclotron resonance maser system comprising:

an assembly of components disposed successively along a common axis and including successively and coaxially an annular source of electrons, tunnel means for defining a beam tunnel symmetrically disposed about said axis, cutoff means, cavity means for defining a microwave resonant cavity symmetrically disposed about said axis, transition means for defining a transition passage symmetrically disposed about said axis, a first coaxial waveguide coupled to said transition means, and an annular collector of electrons, said cutoff means providing an annular opening between said cavity to said beam tunnel for admitting electrons from said beam tunnel to said resonant cavity while cutting off microwaves resonant in said cavity from entering said beam tunnel,

means for forming electrons from said source into an annular beam of electrons having substantial energy transverse of said beam and directing said beam of electrons successively through said beam tunnel, said cutoff means, said cavity, said transition passage, and said coaxial waveguide to said collector,

a second coaxial waveguide coaxial with and surrounded by said first coaxial waveguide and extending coaxially through said electron collector, and

coaxial coupling means for coupling microwave energy between said first and second waveguides.

20. A cyclotron resonance maser system according to claim 19 wherein said coaxial coupling means includes a common wall between said first and second waveguides, said wall being penetrated by substantially axial elongated slots.

21. A cyclotron resonance maser system according to claim 20 wherein the respective sides of each slot are substantially parallel to one another and each of said slots terminates in a narrowing taper at each end.

22. A cyclotron resonance maser system according to claim 20 wherein said slots have a helical twist for coupling a rotating wave to a symmetric wave.

23. A cyclotron resonance maser system according to claim 19 wherein said coaxial coupling means comprises a mode selective directional coupler for coupling a TE_m1 mode in said first waveguide to a TE_0n mode in said second waveguide, m being an integer large compared to 1 and n being an integer greater than 1, said second waveguide propagating said TE_0n mode and containing means for partially reflecting microwaves in said TE_0n mode back through said coupler for reinforcing the desired TE_m1 mode in said first waveguide.

24. A cyclotron resonance maser system according to claim 23 wherein n is 2.

25. A cyclotron resonance maser system according to claim 23 wherein said directional coupler comprises a common wall between said first and second waveguides, said wall being penetrated by m substantially axial elongated slots.

26. A cyclotron resonance maser system according to claim 23 wherein said common wall has a thickness substantially equal to an odd multiple of one-fourth the cutoff wavelength of the mode going through said coupler.

27. A cyclotron resonance maser system comprising:

an assembly of components disposed successively along a common axis and including successively and coaxially an annular source of electrons, tunnel means for defining a beam tunnel symmetrically disposed about said axis, cutoff means, cavity means for defining a microwave resonant cavity symmetrically disposed about said axis, transition means for defining a transition passage symmetrically disposed about said axis, a first coaxial waveguide coupled to said transition means, and an annular collector of electrons, said cutoff means providing an annular opening between said cavity to said beam tunnel for admitting electrons from said beam tunnel to said resonant cavity while cutting off microwaves resonant in said cavity from entering said beam tunnel,

means for forming electrons from said source into an annular beam of electrons having substantial energy transverse of said beam and directing said beam of electrons successively through said beam tunnel, said cutoff means, said cavity, said transition passage, and said coaxial waveguide to said collector,

a second coaxial waveguide coaxial with and surrounded by said first coaxial waveguide and extending coaxially through said electron collector,

coaxial coupling means for coupling microwave energy between said first and second waveguides, and

an annular window member for hermetically sealing said second waveguide and transmitting microwave energy.

28. A cyclotron resonance maser system according to claim 27 further including means for cooling the inner and outer edges of said annular window member.

29. A cyclotron resonance maser system according to claim 27 wherein said coaxial coupling means includes a common wall between said first and second waveguides, said wall being penetrated by substantially axial elongated slots substantially equally spaced around said axis at a common axial location.

30. A cyclotron resonance maser system according to claim 29 wherein the respective sides of each slot are substantially parallel to one another and each of said slots terminates in a narrowing taper at each end.

31. A cyclotron resonance maser system according to claim 29 wherein said slots have a helical twist for coupling a rotating wave to a symmetric wave.

32. A cyclotron resonance maser system according to claim 27 wherein said coaxial coupling means comprises a mode selective directional coupler for coupling a TE_m1 mode in said first waveguide to a TE_0n mode in said second waveguide, m being an integer large compared to 1 and n being an integer greater than 1, said second waveguide propagating said TE_0n mode and containing means for partially reflecting microwaves in said TE_0n mode back through said coupler for reinforcing the desired TE_m1 mode in said first waveguide.

33. A cyclotron resonance maser system according to claim 32 wherein said means for partially reflecting microwaves comprises said window member.

34. A cyclotron resonance maser system according to claim 32 wherein n is 2.

35. A cyclotron resonance maser system according to claim 32 wherein said directional coupler comprises a common wall between said first and second waveguides, said wall being penetrated by m substantially axial elongated slots.

36. A cyclotron resonance maser system according to claim 32 wherein said common wall has a thickness substantially equal to an odd multiple of one-fourth the cutoff wavelength of the mode going through said coupler.

37. A cyclotron resonance maser system comprising:

an assembly of components disposed successively along a common axis and including successively and coaxially an annular source of electrons, tunnel means for defining a beam tunnel symmetrically disposed about said axis, cutoff means, cavity means for defining a microwave resonant cavity symmetrically disposed about said axis, transition means for defining a transition passage symmetrically disposed about said axis, a first coaxial waveguide coupled to said transition means, and an annular collector of electrons, said cavity being defined by inner and outer walls forming a cavity of transverse cross section monotonically increasing in area in the direction of said transition passage and with substantially constant average radius over the length of the cavity, said cutoff means providing an annular opening between said cavity and said beam tunnel of substantially smaller average radius than that of said cavity for resonating in a TE_m1 mode, wherein m is a predetermined integer substantially greater than 1, said first waveguide having at least a portion of substantially constant transverse cross section of average radius substantially greater than that of said cavity, and said transition passage having transverse cross section of average radius monotonically increasing from that at the output of said cavity to that at the input of said waveguide,

means for forming electrons from said source into an annular beam of electrons having substantial energy transverse of said beam and directing said beam of electrons successively through said beam tunnel, said cutoff means, said cavity, said transition passage, and said coaxial waveguide to said collector,

a second coaxial waveguide coaxial with and surrounded by said first coaxial waveguide and extending coaxially through said electron collector, and

coaxial coupling means for coupling microwave energy between said first and second waveguides,

said coaxial coupling means comprising a mode selective directional coupler for coupling said TE_m1 mode in said first waveguide to a TE_0n mode in said second waveguide, n being an integer greater than 1, said second waveguide propagating said TE_0n mode and containing means for partially reflecting microwaves in said TE_0n mode back through said coupler for reinforcing the desired TE_m1 mode in said first waveguide.

38. A cyclotron resonance maser system according to claim 37 further comprising an annular window member for hermetically sealing said second waveguide and transmitting microwave energy.

39. A cyclotron resonance maser system according to claim 38 wherein said means for partially reflecting microwaves comprises said window member.

40. A cyclotron resonance maser system according to claim 38 further including means for cooling the inner and outer edges of said, annular window member.

41. A cyclotron resonance maser system according to claim 37 wherein n is 2.

42. A cyclotron resonance maser system according to claim 37 wherein said directional coupler comprises a common wall between said first and second waveguides, said wall being penetrated by m substantially axial elongated slots.

43. A cyclotron resonance maser system according to claim 42 wherein said slots have a helical twist.

44. A cyclotron resonance maser system according to claim 37 wherein said common wall has a thickness substantially equal to an odd multiple of one-fourth the cutoff wavelength of the mode going through said coupler.