Qualitative Analysis of Long-Lived Residual Radioisotopes in 18 MeV Proton Bombarded Enriched Water Target

Residual radioisotope analysis as a result of cyclotron-based ¹⁸F production is of paramount importance since it relates to the radiation safety of patients as well as radiation workers. In this investigation, 18-MeV proton beams were employed to irradiate enriched water (H₂¹⁸O) target for ¹⁸F production while Talys Evaluated Nuclear Data Library (TENDL) 2017 were used to study the origins of the radionuclide impurities. Gamma rays emmitted by the residual radionuclides were detected using a gamma ray spectroscopic system following a month of decay while their origins were analyzed from the TENDL 2017 nuclear cross-section calculations. Experimental results indicated that several long-lived radionuclides such as ¹⁰⁹Cd, ⁵⁷Co, ⁵⁷Ni, ⁵⁸Co and ⁵⁶Co were recorded by the gamma ray spectroscopic system. The long-lived residual radionuclides were presumably due to proton interactions with Havar window and Silver body. Using the TENDL 2017-calculated nuclear cross-sections, it was discovered that several nuclear reactions responsible for the residual radioisotopes include ¹⁰⁹Ag(p,n)¹⁰⁹Cd which corresponded to the generation of ¹⁰⁹Cd radioisotope, ⁶⁰Ni(p,α)⁵⁷Co and ⁵⁸Ni(p,2p)⁵⁷Co reactions for the formation of ⁵⁷Co, ⁵⁸Ni(p,d)⁵⁷Ni reaction for the production of ⁵⁷Ni radioisotope, ⁵⁸Fe(p,n)⁵⁸Co reaction for the generation of ⁵⁸Co, and ⁵⁶Fe(p,n)⁵⁶Co reaction for the formation of ⁵⁶Co. This experimental result can be used as a reference for future production of ¹⁸F and other radioisotopes should Havar window and silver body are used in the target system.