Patent Number: 
Section: claims

1. A particle accelerator comprising:a conductive housing including a cell, the cell defining a cavity, the cell having a substantially monolithic structure that has no seams or joints internal to the cell;a charged particle source for emitting charged particles into the cavity;a wave guide coupled to the housing for guiding a micro wave into the cavity;an opening disposed in a wall of the conductive housing for guiding the charged particles emitted into the cavity out from the cavity to form an electron beam; anda flow path through which coolant flows to forcibly cool the conductive housing;wherein the conductive housing comprises a cylinder having an inner circumferential surface and a toroid like protrusion from the inner circumferential surface toward a center axis of the conductive housing;wherein the flow path enters an external wall of the conductive housing from an outer circumferential surface, the flow path circulates around a through hole defined in a central area of the protrusion, and then returns to the outer circumferential surface of the conductive housing; andwherein the flow path comprises a portion following a curved path. 2. The accelerator of claim 1, wherein the curved path includes at least a semi-circle. 3. The accelerator of claim 1, wherein the flow path is configured to conform to the external geometry of the housing, such that a substantially constant thickness of housing material separates the flow path from an external surface of the housing over a length of the flow path. 4. The accelerator of claim 1, wherein the flow path has no discontinuities in gradient over its length within the housing. 5. The accelerator of claim 4, wherein the flow path has a cross sectional shape that is elongate. 6. The accelerator of claim 1, wherein the flow path is not circular in cross section. 7. The accelerator of claim 6, wherein the flow path has a cross sectional elongate axis that extends outwardly along a radius of the housing. 8. The accelerator of claim 1, wherein the cell is fabricated by a metal additive manufacturing technique, wherein a metal is deposited in layers using a directed material fabrication process controlled by a computer. 9. The accelerator of claim 1, wherein the metal additive manufacturing technique uses an electron beam to melt the metal feedstock in order to build up the layers of material. 10. The accelerator of claim 1, wherein the cell has an internal surface and the internal surface is subjected to machining after fabrication to achieve surface roughness of less than 63 micro inches. 11. The accelerator of claim 1, wherein the conducting material is copper or an alloy of copper. 12. A particle accelerator comprising:a conductive housing including a cell, the cell defining a cavity, the cell having a substantially monolithic structure that has no seams or joints internal to the cell;a charged particle source for emitting charged particles into the cavity;a wave guide coupled to the housing for guiding a micro wave into the cavity;an opening disposed in a wall of the conductive housing for guiding the charged particles emitted into the cavity out from the cavity to form an electron beam; anda flow path through which coolant flows to forcibly cool the conductive housing;wherein the conductive housing comprises a cylinder having an inner circumferential surface and an opening for connection between the cavity and the wave guide, whereby micro waves may be admitted into the cavity;wherein the flow path enters an external wall of the conductive housing from an outer circumferential surface, the flow path circulates around the opening, and then returns to the outer circumferential surface of the conductive housing; andwherein the flow path comprises a portion following a curved path. 13. The accelerator of claim 12, wherein the flow path has no discontinuities in flow gradient. 14. The accelerator of claim 13, wherein the flow path includes a semi circle. 15. The accelerator of claim 14, wherein a substantially constant thickness of housing material separates the flow path from the opening over the length of the semicircle.