Production of 45Ti using a low-energy accelerator

Abstract: The purpose of this study was to obtain more knowledge of the parameters affecting the production of 45Ti utilizing the nuclear reaction 45Sc(p,n) 45Ti. Titanium-45 decays by +-decay and E.C. to 45Sc with a half-life of 3,08 h. These properties make the radionuclide suitable for positron emission tomography (PET).The work was carried out at the Department of Physics in Lund using the Van de Graaf tandem accelerator, known as the Pelletron accelerator. The theoretical part of the work consisted of studies of the different parts involved in production of radionuclides. This included; calculation of the thick target yield for the nuclear reaction 45Sc(p,n) 45Ti, a study of how the thick target yield depends of energy of the bombarding particles and a calculation of cooling-water efficiency.Practical work included operating the accelerator and its components and covered different areas of physics, such as vacuum technique, electronics and radiation physics. Measurements of target current were performed as function of cooling-water flow and a radiation dosimetry study was done.A new target holder was constructed and adapted to fit the existing beam line at the electrostatic accelerator. Target foils were produced from pieces of scandium using a rolling mill. Preparations for irradiation contained of preparing the Pelletron accelerator and the target. The length of the bombardments varied between ten minutes up to about three hours. After irradiation the titanium was separated from the rest of the scandium target material using solvent extraction. Using the steering devices the beam could be controlled and directed to the target. Target foils were fabricated by hand and this was a lengthy process. The thickness of the foil was the one parameter that could be best controlled. The manufactured target holder worked well and was easy to handle. It could be kept at a low temperature by water-cooling. The yield of the bombardment compared to the theoretical yield is low, the ratio is about 0.35-0.45 and is highly dependent on energy. Solvent extraction can be performed with an exchange of up to 70 %. In the separation process the fingers receive an absorbed dose of about 3 mSv.This study showed that 45Ti can be produced with a low energy accelerator and that the activity produced is high enough to be useful for future diagnostic imaging. The purity of the produced radionuclide has to be examined and its chemistry should be studied. To get good yields good practical skills and experience are required in solvent extraction and especially in operation of the accelerator and its components.