PHOSPHATE BASED TARGETS

Abstract

The invention relates to a phosphate based glass target material, wherein said material comprises an isotopically enriched element or monoisotopic element.

Claims

1. A phosphate based glass target material, wherein said material comprises an isotopically enriched element or monoisotopic element.

2. The phosphate based glass target material as claimed in claim 1, wherein the isotopically enriched element or monoisotopic element is selected from the group consisting of metals, metalloids and non-metals.

3. The phosphate based glass target material as claimed in claim 1, wherein the isotopically enriched element or monoisotopic element is selected from the group consisting of Mo, Ra, Y, Ca, Ni, Zn, Ga, 0, Rb, Se, Te, Bi, Th and Yb.

4. The phosphate based glass target material as claimed in claim 1, wherein the isotope is selected from the group consisting of .sup.100Mo, .sup.226Ra, .sup.89Y, .sup.44Ca, .sup.64Ni, .sup.70Zn, .sup.67Zn, .sup.68Zn, .sup.69Ga, .sup.18O, .sup.85Rb, .sup.76Se, .sup.77Se, .sup.124Te, .sup.209Bi and .sup.176Yb.

5. The phosphate based glass target material as claimed in claim 1, wherein said phosphate based material glass has a glass transition temperature in the range 200 C. to 2000 C.

6. The phosphate based glass target material as claimed in claim 1, wherein the phosphate based target has a density in the range 2 to 10 g/cm.sup.3.

7. The phosphate based glass target material as claimed in claim 1, wherein the isotopically enriched element or monoisotopic element is present in an amount of 10 to 50 wt %, relative to the total weight of the material as a whole.

8. A process for preparing the phosphate based glass material of claim 1, said process comprising: i. mixing a metal, metalloid or non-metal oxide with dilute phosphorous acid (H.sub.3PO.sub.4) to form a phosphate compound; and ii. Melting said phosphate compound with phosphorous pentoxide and/or or an oxide of the isotope enriched element to produce the phosphate based glass material.

9. A process for the production of a radionuclide, comprising irradiating a phosphate based glass target material with a high energy particle beam.

10. The process as claimed in claim 9, wherein said phosphate based glass target comprises an isotopically enriched element or monoisotopic element.

11. The process as claimed in claim 9, wherein the high energy particle beam is provided by a particle accelerator.

12. The process as claimed in claim 9, wherein the high energy particle beam is a proton beam, deuteron beam or a beam of alpha-particles.

13. The process as claimed in claim 9, comprising the steps: providing a plate having a recessed portion, the recessed portion having a surface; placing said phosphate based glass target material in the recessed portion; covering the phosphate based glass target material with a foil such that the phosphate based glass target material is encapsulated by the foil and the surface of the recessed portion; securing the foil to the plate such that the phosphate based glass target material is fixed relative to the plate; wherein the foil has a higher melting temperature than the phosphate based glass target material glass transition temperature; and irradiating the encapsulated phosphate based glass target material with a beam of high energy particles.

14. A method of use of a phosphate based glass target in a process for producing radionuclides.

15. The method of claim 14, wherein the phosphate based glass material is used as a target in a process for producing radionuclides.

16. The method of claim 14, wherein said phosphate based glass target comprises an isotopically enriched element or monoisotopic element.

17. The phosphate based glass target material of claim 1, wherein the isotopically enriched element or monoisotopic element is selected from the group consisting of Zn, Y, and Mo.

18. The phosphate based glass target material of claim 1, wherein the isotope is selected from the group consisting of .sup.68Zn, .sup.89Y and .sup.100Mo.

19. The process of claim 9, wherein the high energy particle beam is provided by a cyclotron.

Description

[0101] The invention will now be described with reference to the following non limiting examples and figures.

[0102] FIG. 1: Structural units of phosphate glass materials

[0103] FIG. 2: Platinum crucible with a melt of phosphate and enriched isotope positions in the outer area of a furnace. A mould of steel is placed outside. Also shown is a flat metal spatula that is used to flatten the liquid material after it has been poured into the mould.

[0104] FIG. 3: Plan view of a cover having an aperture in one embodiment of the invention

[0105] FIG. 4: Plan view of a plate having a recessed portion in one embodiment of the invention

[0106] FIG. 5: Side view of the cover of FIG. 3

[0107] FIG. 6: Side view of the plate of FIG. 4

[0108] FIG. 7: Piece of target material and a piece of foil

[0109] FIG. 8: Side view and enlarged side view of the apparatus formed from the cover, plate, target nuclide, and foil in one embodiment of the invention

[0110] FIG. 9: Exploded view of the apparatus formed from the cover, sealing rings, plate, foil, and target nuclide in one embodiment of the invention

[0111] FIG. 10: The ceramic zinc target (mid) is shown between the bottom (left) and top (right) of the target holder

[0112] FIG. 11: The upper part of the graph shows the energy reduction of protons inside material #2 as function of depth, and the linear energy transfer during the traverse. The lower part shows the reaction cross-section (reflecting probability) of the reaction of interest as function of energy at increasing target depth. The production rate reaches maximum and flattens at optimal target thickness.

[0113] FIG. 12: As FIG. 11, but for higher proton energy (13 MeV).

EXAMPLES

Preparation of Glass Material #1 with Zinc

[0114] To a 10 ml platinum crucible was added 2.0 g Zn.sub.3(PO.sub.4).sub.2, 1.47 g P.sub.2O.sub.5 and 0.85 g ZnO. The mixture was homogenized before it was placed in a preheated furnace at 330 C. The temperature was increased to 350 C. over a period of 10 minutes. After this, the temperature was set to reach 1100 C. within 20 min. After holding the temperature at 1100 C. for 30 minutes, the crucible was manipulated and extracted from the furnace by a tong, and the melt was quickly poured into the mold and, essentially simultaneously, the material was flattened into a disc with a spatula. The resulting molded glass disc was subjected to an annealing process, in order to free the material from built in tensions caused by the cold quenching, by heating in a furnace for 15 minutes at 515 C. Finally, the resulting discs were placed in a holder and grained down to the desired thickness, e.g. 400 m.

[0115] For the manufacturing of isotope enriched target discs with Zn.sub.3(PO.sub.4) as a part of the formulation, the [.sup.68Zn]Zn.sub.3(PO.sub.4).sub.2 is prepared by the reaction of [.sup.68Zn]ZnO with dilute phosphoric acid prior to drying the precipitate, followed by graining the material to yield a powder in a mortar. Also the zinc oxide part in the making of glass is substituted by [.sup.68Zn]ZnO.

[0116] Different compositions of zinc phosphate glass were investigated, with and without Zn.sub.3(PO.sub.4).sub.2 and with variable molar ratios of P.sub.2O.sub.5 and ZnO (Table 1).

TABLE-US-00001 TABLE 1 Composition of selected phosphate based glass materials, displaying the weight percentage of zinc and the density of the materials. Zn.sub.3(PO.sub.4).sub.2 P.sub.2O.sub.5 ZnO Zn (Molar (Molar (Molar Weight Density Material # ratio) ratio) ratio) (%) (g/cm.sub.3) 1 1 2 2 39 2 1 3 3 37 2.9 3 1 4 4 36 3.0 4 1 5 5 35 3.1 7 0 1 1.25 33 2.9 8 0 1 1.5 37 3.1

[0117] Heating tests with discs of the different materials (from Table 1) were performed in a furnace with slow increase of temperatures. In the range of the transition temperature, 600-700 C., the material underwent a metamorphic process leading to crystallization. Upon increased temperatures, 800-1100 C., the materials reformed as glass. Upon cold quenching of this discs could be molded.

[0118] To provide target disc materials for production of gallium with the GE cyclotron, MINITrace (accelerating protons up to 9.6 MeV), we molded discs with a diameter of 12 mm that were fitted into a target holder.

[0119] The required target disc thickness was chosen based on the following: i) to capture the part of energy interval from E.sub.proton 9.6. MeV down to the threshold for the nuclear reaction (E.sub.proton<4 MeV), ensuring maximum product yield whilst ii) avoiding deposition (in the target) of the peak-value of energy transfer per unit length of the proton (termed avoiding capture of the Bragg peak; see red line in FIG. 11). The thickness of targets was determined from calculations based on the zinc content and density of each of the materials that were subjected to testing. The upper part of FIG. 11 shows the energy reduction of protons inside material #2 as function of depth, and the linear energy transfer during the traverse. The lower part shows the reaction cross-section (reflecting probability) of the reaction of interest as function of energy at increasing target depth. The production rate reaches maximum and flattens at optimal target thickness. Here, the molded discs of material #2 was grained and polished to a thickness of about 400 m (optimal thickness seen from graph below) by use of a grinding and sanding machine.

[0120] The calculations from FIG. 11 are specific for material #2, with 9.6 MeV protons and taking into account the cross section nuclear data for the reaction .sup.68Zn(p,n).sup.68 Ga. In preparation for runs with a more powerful cyclotron, e.g. GE PETtrace, E.sub.proton, max=16.5 MeV, the same calculations, as above, for the same material have been performed for proton energies first moderated from 16.5 MeV to E.sub.proton=13 MeV (FIG. 12) and revealed an optimal thickness around 800 m with a potential for a doubling of the production rate (GBq/Ah) relative to our hitherto obtained data.