Spectrometry Around Linacs Using Passive Bonner Sphere Spectrometry in Planetary Mode

Authors:   Vega-Carrillo H., Benites-Rengifo J., Gallego E., Lorente A., Guzman-Garcia K., Lacerda M., Mendez R., Hernández-Adame L.
Journal: Modern Neutron Detection. Proceedings of a Technical Meeting
https://www-pub.iaea.org/MTCD/Publications/PDF/TE-1935_web.pdf
Abstract: When linear accelerators operate above 8 MV, neutrons are produced in (g, n) and (e, e´n) reactions in nuclei via the Giant Dipole Resonance. In linear accelerators for medical applications, the neutron contamination is a radiation protection issue where a non-negligible, and non-desired, dose is delivered to the patient. Moreover, neutrons around linear accelerators for medical applications have been associated with the cancer recurrence and the induction of new tumours. In the past decades several efforts to determine the neutron characteristics around linacs have been carried out; novel procedures and innovative measuring devices have been developed to perform such characterizations. The Bonner sphere spectrometer has been largely used to measure the neutron spectra around linacs; however, the time required to perform the measurements in the treatment hall is large, requiring many linac runs due to the number of spheres in the spectrometer. Aiming to reduce the measuring time, a procedure using a Bonner sphere spectrometer has been developed using a single linac exposure. The procedure was used to measure the photoneutron spectrum in a 15 MV linear accelerator.