Method of making an annular radioisotope target having a helical coil-shaped foil ribbon between cladding tubes

1. A method for making an annular radioisotope target comprising,

providing an inner cladding tube,

sliding a helical coil-shaped foil ribbon over the inner cladding tube, the helical coil-shaped foil ribbon comprising a target material to be irradiated and having a first end, a second end, a first edge and a second edge,

sliding an outer cladding tube over the helical coil-shaped foil ribbon and inner cladding tube, and

attaching end caps to the outer cladding tube and inner cladding tube to seal the helical coil-shaped foil ribbon between the outer cladding tube and inner cladding tube.

2. The method of claim 1 , wherein the first edge and second edge of the helical coil-shaped foil ribbon are beveled.

3. The method of claim 1 , wherein the first edge of the helical coil-shaped foil ribbon and the second edge of the helical coil-shaped foil ribbon comprise tongue and groove edges.

4. The method of claim 1 , wherein the helical coil-shaped foil ribbon is compressed by the endcaps to eliminate gaps between the first edge and the second edge of the helical coil-shaped foil ribbon.

5. The method of claim 1 , wherein the step of sliding the helical coil-shaped foil ribbon over the inner cladding tube includes stretching the helical coil-shaped foil ribbon, sliding the stretched helical coil-shaped foil ribbon over the inner cladding tube, and contracting the helical coil-shaped foil ribbon over the inner cladding tube.

6. The method of claim 1 , wherein the method includes placing a barrier material between the helical coil-shaped foil ribbon and at least one cladding tube.

7. The method of claim 1 wherein, prior to disposing the helical coil-shaped foil ribbon over the inner cladding tube, the helical coil-shaped foil ribbon has an inner diameter that is less than an outside diameter of the inner cladding tube.

8. The method of claim 7 wherein, the helical coil-shaped foil ribbon includes a resilience feature and the step of disposing the helical coil-shaped foil ribbon over the inner cladding tube includes:

stretching the helical coil-shaped foil ribbon to expand the inner diameter of the helical coil-shaped ribbon to be greater than the outside diameter of the inner cladding tube;

sliding the stretched helical coil-shaped foil ribbon over the inner cladding tube; and

contracting the stretched helical coil-shaped foil ribbon over the inner cladding tube to provide a close fit between the helical coil-shaped foil ribbon and the inner cladding tube.

9. The method of claim 1 wherein

the inner cladding tube includes an outside diameter;

the helical coil-shaped foil ribbon includes an inside diameter that is less than the outside diameter of the inner cladding tube in a non-stretched configuration, the helical coil-shaped foil ribbon operable to be stretched such that the inside diameter of the helical coil-shaped foil ribbon is greater than the outside diameter of the inner cladding tube in a stretched configuration; and

the step of sliding the helical coil-shaped foil ribbon over the inner cladding tube includes applying tension to the helical coil-shaped foil ribbon to stretch the inside diameter of the helical coil from the non-stretched configuration to the stretched configuration to slide the helical coil-shaped foil ribbon over the inner cladding tube and releasing tension to the helical coil-shaped foil ribbon to compress the helical coil-shaped foil ribbon against the inner cladding tube.

10. The method of claim 9 wherein the helical coil-shaped foil ribbon is compressed inwards at the first end and the second end by the end caps to eliminate gaps between the first edge and the second edge of the helical coil-shaped foil ribbon.

11. The method of claim 9 wherein the first edge of the helical coil-shaped foil ribbon and the second edge of the helical coil-shaped foil ribbon are beveled to eliminate gaps between the first edge and the second edge of the helical coil-shaped foil ribbon.

12. The method of claim 9 wherein the first edge and the second edge of the helical coil shaped foil ribbon comprise tongue and groove edges to assist in eliminating gaps between the first edge and the second edge of the helical coil-shaped foil ribbon.

13. The method of claim 9 further comprising placing a barrier material between the helical coil-shaped foil ribbon and at least one of the inner cladding tube and the outer cladding tube.

14. The method of claim 9 , wherein the inner diameter of the helical coil-shaped foil ribbon is 5% to 20% less than the outside diameter of the inner cladding tube in the non-stretched configuration.