Patent Number: 
Section: claims

1. A radiation source including iridium wherein the density of the active insert containing the iridium is in a range of 30 to 85 percent of the density of 100% dense pure iridium. 2. The radiation source of claim 1 wherein the iridium is in a range of 40 to 70 percent of the density of 100% dense pure iridium. 3. The radiation source of claim 1 wherein the iridium is in a range of 50 to 65 percent of the density of 100% dense pure iridium. 4. The radiation source of claim 1 wherein the iridium is in the form of microbeads containing Iridium-192. 5. The radiation source of claim 4 wherein the microbeads of Iridium-192 are in a random or partly random packed configuration. 6. The radiation source of claim 1 wherein the iridium is Iridium-192 contained within and metal, alloy, compound, or composite and formed into a sphere or quasi-sphere. 7. The radiation source of claim 6 wherein the Iridium-192 is contained within a metal, alloy, compound, or composite material and formed or shaped by a capsule cavity into a sphere or quasi-sphere by a method of physical compression or compaction. 8. The radiation source of claim 1 wherein the iridium is in the form of approximately 0.4 mm. diameter microbeads or approximately 0.3 mm diameter microcylinders containing Iridium-191, prior to neutron irradiation. 9. The radiation source of claim 8 wherein the microbeads or microcylinders of Iridium-191 are in a random-packed or partly random configuration. 10. The radiation source of claim 1 wherein the iridium is in the form of microbeads with a diameter of 0.25-0.60 mm. or microcylinders with a diameter of 0.20-0.50 mm, containing Iridium-191, prior to neutron irradiation. 11. The radiation source of claim 1 wherein the iridium is in the form of approximately 0.3 mm diameter wire containing Iridium-191, prior to neutron irradiation, which is then cut after activation to form microcylinders. 12. The radiation source of claim 1 wherein the iridium contains Iridium-191 in the form of a metal, alloy, compound or composite, prior to neutron irradiation. 13. The radiation source of claim 1 wherein the iridium contains Iridium-191 in the form of a metal, alloy, compound or composite, which is formed into a disk, hemi-ellipsoid or other thin flat shape less than 0.75 mm. thick, prior to neutron irradiation so that it can be activated in conventional activation target canisters and formed into a sphere or quasi-sphere after activation. 14. The radiation source of claim 1 further including a spherical or quasi-spherical source cavity in which the iridium is contained. 15. The radiation source of claim 1 wherein the radiation source is comprised of a plurality of disks of iridium in the form of a metal, alloy, compound or composite. 16. An activation target insert formed in a disk-shape and including a plurality of microbeads or microcylinders of iridium. 17. The activation target insert of claim 16 wherein the microbeads are spherical or quasi-spherical in shape or formed as microcylinders. 18. The activation target insert of claim 17 wherein the radiation target insert includes a plurality of at least partially concentric rings which hold the microbeads. 19. The activation target insert of claim 18 wherein the plurality of rings are concentric with respect to a rotational axis of the radiation target insert and are diagonally offset with respect to a direction perpendicular from the rotational axis. 20. The activation target insert of claim 19 further including cone-shaped walls. 21. The activation target insert of claim 20 wherein the cone-shaped walls of successive radiation target inserts nest with each other. 22. The activation target insert of claim 16 wherein the microbeads have a diameter of approximately 0.4 mm or the microcylinders have a diameter of approximately 0.3 mm. 23. The activation target insert of claim 16 wherein the iridium is in the form of microbeads with a diameter of 0.25-0.60 mm. or microcylinders with a diameter of 0.20-0.50 mm. 24. The activation target insert of claim 16 wherein the iridium includes Iridium-192. 25. The activation target insert of claim 16 wherein the iridium includes Iridium-191 and is activated by neutron irradiation.