Patent Number: 
Section: claims

1. A cylindrical neutron generator, comprising:a cylindrical RF-driven ion source, a cylindrical unintermittent plasma formed in the ion source by a R-F driven antenna;a cylindrically-shaped radial ion extractor system, said extractor system disposed coaxially about the ion source to radially extract ions from the ion source; and,a cylindrical neutron generating solid target having an uninterrupted solid surface that is disposed coaxially as an electrically continuous cylinder inside and spaced from the ion source to receive ions extracted from the ion source by said cylindrical extractor system, whereby said target becomes loaded with impinging ions from the ion source to produce ion induced neutron generating reactions. 2. Apparatus for detecting fissile materials, comprising:a cylindrical neutron generator of claim 1;a moderator surrounding the neutron generator to slow the neutrons to thermal neutrons;a shield surrounding parts of the moderator to prevent neutrons from escaping in undesired directions;an associated neutron detector for detecting neutrons produced by thermal neutron reaction with fissile materials. 3. Apparatus for borehole instrumentation, comprising:a cylindrical neutron generator of claim 1;an associated gamma ray detector for detecting gamma rays produced by neutron reaction with features surrounding the borehole. 4. The cylindrical neutron generator of claim 1 further comprising a RF antenna disposed within the ion source. 5. The cylindrical neutron generator of claim 4 further comprising: a matching network connected to the RF antenna; anda RF power supply connected to the matching network. 6. The cylindrical neutron generator of claim 1 wherein the ion source further comprises a cylindrical extraction system with a plurality of axially extending slots. 7. The cylindrical neutron generator of claim 6 wherein the extraction system comprises a cylindrical extraction electrode disposed in a circumferential portion of the plasma formed in the ion source that is cylindrically positioned toward the target with respect to other portions of the plasma, and the cylindrical extraction electrode having a plurality of axially extending slots. 8. The cylindrical neutron generator of claim 7 wherein the extraction system further comprises a cylindrical plasma electrode outside and spaced apart from the extraction electrode and having a plurality of axially extending slots aligned with the slots in the extraction electrode. 9. The cylindrical neutron generator of claim 1 wherein the plasma ion source is a deuterium ion source or a deuterium and tritium ion source. 10. The cylindrical neutron generator of claim 1 wherein the plasma ion source is a multicusp plasma ion source. 11. The cylindrical neutron generator of claim 1 wherein the target has a titanium surface. 12. The cylindrical neutron generator of claim 1 further comprising a vacuum chamber disposed to contain said target. 13. Apparatus for detecting explosives, comprising:a cylindrical neutron generator of claim 1;a moderator surrounding the neutron generator to slow the neutrons to thermal neutrons;a shield surrounding the moderator except for a front neutron escape portion to prevent neutrons from escaping in undesired directions;an associated gamma ray detector for detecting gamma rays produced by thermal neutron reactions with explosives. 14. A cylindrical neutron generator comprising:a cylindrical RF-driven ion source, a cylindrical unintermittent plasma formed in the ion source by a R-F driven antenna;a cylindrical neutron generating solid target having an uninterrupted solid surface that is disposed coaxially as an electrically continuous cylinder inside and spaced from the ion source; anda means for radially extracting ions from the ion source and impinging the extracted ions upon the target. 15. The cylindrical neutron generator of claim 14 further comprising an RF antenna disposed within the ion source. 16. The cylindrical neutron generator of claim 15 further comprising:a matching network connected to the RF antenna; andan RF power supply connected to the matching network. 17. The cylindrical neutron generator of claim 14 wherein the extracting means comprises a cylindrical extraction system with a plurality of axially extending slots. 18. The cylindrical neutron generator of claim 17 wherein the extracting means comprises a cylindrical extraction electrode disposed in a circumferential portion of the plasma formed in the ion source that is cylindrically positioned toward the target with respect to other portions of the plasma, and the cylindrical extraction electrode having a plurality of axially extending slots. 19. The cylindrical neutron generator of claim 18 wherein the extracting means comprises a cylindrical plasma electrode inside and spaced apart from the extraction electrode and having a plurality of axially extending slots aligned with the slots in the extraction electrode. 20. The cylindrical neutron generator of claim 14 wherein the plasma ion source is a deuterium ion source or a deuterium and tritium ion source. 21. The cylindrical neutron generator claim 14 wherein the plasma ion source is a multicusp plasma ion source. 22. The cylindrical neutron generator of claim 14 wherein the target has a titanium surface. 23. The cylindrical neutron generator of claim 14 further comprising a vacuum chamber disposed to contain the target. 24. Apparatus for detecting explosives, comprising:a cylindrical neutron generator of claim 14;a moderator surrounding the neutron generator to slow the neutrons to thermal neutrons;a shield surrounding the moderator except for a front neutron escape portion to prevent neutrons from escaping in undesired directions; andan associated gamma ray detector for detecting gamma rays produced by thermal neutron reactions with explosives. 25. The cylindrical neutron generator of claim 23, further comprising a detector to detect a neutron reaction produced particles, said detector being disposed outside said vacuum chamber. 26. The cylindrical neutron generator of claim 1 wherein the plasma ion source is a deuterium ion source. 27. The cylindrical neutron generator of claim 14 wherein the plasma ion source is a deuterium ion source.