Patent Number: 
Section: claims

1. A linear accelerator head comprising:an electron generator configured to emit electrons along a beam path;a microwave generation assembly comprising:a microwave generator configured to emit microwaves in a first direction along a primary wave path; andan isolator configured to prevent microwaves from propagating in a second direction opposite the first direction along the primary wave path;a waveguide configured to contain a standing or travelling microwave and accelerate electrons to between about 3 MeV and about 9 MeV, the waveguide comprising a plurality of cells each defining an aperture configured to receive electrons therethrough; anda converter disposed within the electron beam path and configured to receive incident electrons and convert the incident electrons into photons, the converter including a disc comprising:a first layer of a first material; anda second layer of a second material. 2. The linear accelerator head of claim 1, wherein the first material comprises a chemical element having an atomic number greater than about 57. 3. The linear accelerator head of claim 1, wherein the second material comprises a chemical element having an atomic number greater than about 57. 4. The linear accelerator head of claim 1, wherein the first material comprises tungsten. 5. The linear accelerator head of claim 1, wherein the second material comprises aluminum. 6. The linear accelerator head of claim 1, wherein the second material comprises copper. 7. The linear accelerator head of claim 1, wherein the disc has a thickness of between about 1 mm and 8 mm. 8. The linear accelerator head of claim 1, wherein the first layer has a thickness of between about 0.5 mm and 4 mm. 9. The linear accelerator head of claim 1, wherein the second layer has a thickness of between about 0.5 mm and 4 mm. 10. A linear accelerator head comprising:an electron generator configured to emit electrons along a beam path;a microwave generation assembly comprising:a microwave generator configured to emit microwaves in a first direction along a primary wave path; andan isolator configured to prevent microwaves from propagating in a second direction opposite the first direction along the primary wave path;a waveguide configured to contain a standing or travelling microwave and accelerate electrons to between about 3 MeV and about 9 MeV, the waveguide comprising a plurality of cells, each of the plurality of cells defining an aperture having a diameter and configured to receive electrons therethrough, the apertures of the cells defining a beam axis of the waveguide along the beam path;a cooling system in thermal communication with the waveguide, the cooling system comprising a block having a channel configured to guide fluid therethrough; anda converter disposed within the electron beam path, the converter configured to receive incident electrons and convert the incident electrons into photons. 11. The linear accelerator head of claim 10, wherein the waveguide comprises a first exterior surface parallel to the beam axis. 12. The linear accelerator head of claim 11, wherein the waveguide comprises a second exterior surface parallel to the first exterior surface. 13. The linear accelerator head of claim 12, wherein the block defines a surface coplanar with the first exterior surface of the waveguide. 14. The linear accelerator head of claim 10, wherein the block comprises an opening configured to allow a user access to at least one of the tuners of the plurality of cells. 15. A linear accelerator head comprising:an electron generator configured to emit electrons along a beam path;a microwave generation assembly comprising:a magnetron configured to emit microwaves in a first direction along a primary wave path; andan isolator configured to prevent microwaves from propagating in a second direction opposite the first direction along the primary wave path;a waveguide configured to contain a standing or travelling microwave and accelerate electrons to between about 3 MeV and about 9 MeV, the waveguide comprising a plurality of cells each defining an aperture configured to receive electrons therethrough; anda converter disposed within the electron beam path, the converter configured to receive incident electrons and convert the incident electrons into photons. 16. The linear accelerator head of claim 15, wherein the magnetron is configured to emit microwaves at a frequency in a range of between about 7.0 GHz and 11.2 GHz. 17. The linear accelerator head of claim 15, wherein the magnetron is configured to emit microwaves at a power greater than 1 MW. 18. The linear accelerator head of claim 15, configured to deliver between about 300 cGy/min and 1800 cGy/min. 19. The linear accelerator head of claim 15, wherein the waveguide further comprises a coupler cell configured to couple microwaves from the isolator into the waveguide and to provide fluid communication between a vacuum pump and an interior of the waveguide. 20. The linear accelerator head of claim 15, wherein the plurality of cells comprises fewer than 24 cells.