Patent Number: 
Section: claims

1. An assembly for a fixed-energy cyclotron, wherein the cyclotron is configured to produce a particle beam, the assembly comprising:a target holder assembly comprising a target body that includes:a first region configured to hold a target material;a second region with a receiving slot; anda third region including a receiving section for receiving the particle beam from the cyclotron; anda removable degrader comprising an attenuation disc;wherein:the receiving slot is configured to receive the removable degrader;the removable degrader is configured for removable insertion into the receiving slot such that, when (a) the removable degrader is in the receiving slot, (b) the target material is held in the first region of the target body, and (c) the particle beam travels into the receiving section, the attenuation disc is positioned in a path of the particle beam that extends from the receiving section to the target material; andthe attenuation disc is configured to reduce an energy level of the particle beam prior to the particle beam reaching the target material. 2. The assembly of claim 1, wherein the target holder assembly and the removable degrader are configured to allow for removal of the removable degrader without removal of the target holder assembly from the cyclotron. 3. The assembly of claim 1, wherein:the target body includes a first target body in which the first region is located, a second target body in which the second region is located, and a third target body in which the third region is located; andthe second target body and the third target body are configured to attach to the cyclotron independently from the first target body, to allow a pressure between the first target body and the second target body to be adjusted independently from a pressure between the second target body and the third target body, and from a pressure between the third target body and the cyclotron. 4. The assembly of claim 3, wherein the first target body is configured to shift towards the second target body when the removable degrader is inserted into the receiving slot to form an air tight seal around the attenuation disc. 5. The assembly of claim 3, wherein the target holder assembly further comprises a vacuum foil between the second target body and the third target body, and wherein the attenuation disc is positioned between the vacuum foil and the target material when the removable degrader is inserted into the receiving slot. 6. The assembly of claim 1, wherein:the removable degrader further comprises:a frame;an inner ring;a first circular channel formed by the inner ring and the frame at a first side of the attenuation disc;a second circular channel formed by the inner ring and the frame at a second side of the attenuation disc;a first O-ring within the first circular channel; anda second O-ring within the second circular channel; andthe first and second circular channels circumscribe the attenuation disc. 7. The assembly of claim 1, wherein the removable degrader is made from a single piece of aluminum. 8. The assembly of claim 1, wherein a thickness of the attenuation disc is about 0.6 to 0.9 mm. 9. The assembly of claim 8, wherein the thickness of the attenuation disc is uniform. 10. A method of adjusting an energy level of a particle beam of a fixed-energy cyclotron prior to the particle beam reaching a target material, the method comprising:inserting a removable degrader with an attenuation disc into a receiving slot of a target holder assembly, wherein:the removable degrader is configured for removable insertion into the receiving slot such that, when inserted, the attenuation disc is positioned in a path of the particle beam that extends from the cyclotron to the target material, andthe attenuation disc is configured to adjust the energy level of the particle beam prior to the particle beam reaching the target material. 11. The method of claim 10, wherein the target holder assembly and the removable degrader are configured to allow for removal of the removable degrader without removal of the target holder assembly from the cyclotron. 12. The method of claim 11, wherein the attenuation disc is configured to reduce the energy level of the particle beam. 13. The method of claim 12, further comprising:removing the removable degrader from the receiving slot without removing the target holder assembly from the cyclotron; andinserting a second removable degrader with a second attenuation disc into the receiving slot;wherein:the second removable degrader is configured for removable insertion into the receiving slot such that, when inserted, the second attenuation disc is positioned in the path of the particle beam, andthe second attenuation disc has a thickness that is different than a thickness of the attenuation disc. 14. A method of independently adjusting energy levels of first and second particle beams of a cyclotron prior to the particle beams reaching their respective first and second target materials, the method comprising:(a) inserting a first removable degrader with a first attenuation disc into a first receiving slot of a first target holder assembly; and(b) inserting a second removable degrader with a second attenuation disc into a second receiving slot of a second target holder assembly;wherein the first and second removable degraders are configured for removable insertion into the respective first and second receiving slots such that, when inserted, the respective first and second attenuation discs are positioned in respective paths of the first and second particle beams that extend from the cyclotron to the respective first and second target materials. 15. The method of claim 14, wherein the first attenuation disc has a first thickness and the second attenuation disc has a second thickness, and wherein the first thickness and second thickness are different. 16. The method of claim 14, wherein the first and second target holder assemblies and the first and second removable degraders are configured to allow for removal of the first and second removable degraders without removal of the first and second target holder assemblies from the cyclotron.