Patent Number: 062158511
Section: claims

1. A proton beam target for generating gamma rays which are generated therefrom in response to an impinging proton beam, the proton beam target comprising: a .sup.13 C gamma reaction layer for generating the gamma rays therefrom; and  a stopping layer for mitigating transmission of the proton beam therethrough, the stopping layer being formed of a refractory metal which has a relatively high hydrogen solubility for dissolving implanted hydrogen atoms therewithin as a result of the impingement of the proton beam and which is chemically reactive with the .sup.13 C gamma reaction layer for chemically bonding therewith.  (a) forming a stopping layer of a refractory metal for mitigating transmission of the proton beam therethrough, the stopping layer having a relatively high hydrogen solubility for dissolving implanted hydrogen atoms therewithin as a result of the impingement of the proton bean and being chemically reactive with .sup.13 C; and  (b) attaching a .sup.13 C gamma reaction layer for generating gamma rays therefrom in response to the impinging proton beam.  (c) attaching the stopping layer onto a cooling support for dissipating heat energy away from the stopping layer.  (d) cooling the stopping layer to a temperature less than the braze temperature; and  (e) reliving any residual thermal stress developed within the stopping layer through the movement of the stopping layer relative to the cooling support. 2. The proton beam target of claim 1 wherein the refractory metal is chosen from the group consisting of Tantalum, Zirconium, Niobium and Hafnium. 3. The proton beam target of claim 1 wherein the stopping layer is formed of a metal foil. 4. The proton beam target of claim 1 wherein the stopping layer has a thickness of approximately between 20 to 130 microns. 5. The proton beam target of claim 1 wherein the stopping layer has a hydrogen solubility greater than that of gold. 6. The proton beam target of claim 1 wherein the stopping layer is chemically reactive with the .sup.13 C gamma reaction layer to form carbide atoms therebetween. 7. The proton beam target of claim 1 wherein the .sup.13 C gamma reaction layer is sputter deposited onto the stopping layer. 8. The proton beam target of claim 1 further comprises a cooling support for dissipating heat energy away from the stopping layer, wherein the stopping layer is attached to the cooling support and the stopping layer is interposed between the .sup.13 C gamma reaction layer and the cooling support. 9. The proton beam target of claim 8 wherein the cooling support is formed of Copper. 10. The proton beam target of claim 8 wherein the cooling support is formed of Beryllium. 11. The proton beam target of claim 8 further comprises a braze layer which is interposed between stopping layer and the cooling support for attaching the stopping layer to the cooling support. 12. The proton beam target of claim 11 wherein the braze layer is formed of Silver based braze alloy. 13. A method of fabricating a proton beam target for generating gamma rays which are reflected therefrom in response to an impinging proton beam, the method comprising the steps of: 14. The method of claim 13 wherein the .sup.13 C gamma reaction layer is attached to the stopping layer via sputter deposition. 15. The method of claim 13 wherein step (a) further comprises chemically reacting the .sup.13 C gamma reaction with the stopping layer to form a carbide phase therebetween. 16. The method of claim 13 further comprising the step of: 17. The method of claim 16 wherein the stopping layer is attached to the cooling support via brazing. 18. The method of claim 17 wherein the brazing is effectuated at a braze temperature greater than 500.degree. C. 19. The method of claim 18 further comprising the steps of: