This paper reports the detection and measurement of neutron-induced isotopes in the vault wall of the CS-30 cyclotron located at King Faisal Specialist Hospital and Research Centre (KFSHRC). The aim was to avoid the harmful effects of radiation on employees working with the cyclotron and on faculty members and students using it for nuclear physics research and industrial applications. In addition, emitted radioactivity values are essential in future experiments, as background levels to be subtracted from collected data. Detection was performed using a portable gamma ray spectroscopy system consisting of a NaI(Tl) detector (CANBERRA, model: 802-4) coupled with a digitizer (CAEN, model: N6730) at a counting time of 10 minutes for each point on the wall. The points were at the orientation of 0° with respect to the incoming proton beams and all at 1.5 m above the floor. The results indicate that Co-60, Co-56, Mn-56, Fe-53 are the major radionuclides contributing to the gamma radiation emitted from the wall of cyclotron vault. The link between these isotopes and their corresponding elements was established using the branching index technique. It was found that some isotopes detected were the daughters of elements constituting a very small proportion of the concrete structure such as iron (0.50%), while the elements representing the bulk of the concrete showed no radioactivity. No other significant radioactive sources were detected in the wall. The maximum exposure measured on the wall surface was much less than the permissible occupational exposure for radiation workers.
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