Multisphere neutron spectra measurements near a high energy medical accelerator

Photoneutron spectral measurements in the vicinity of a high energy medical accelerator have been performed. A LiI (Eu) scintillator and paired thermoluminescent dosimeters were used in conjunction with moderating multispheres to measure the neutron spectra. The photoneutron fluence rate, fluence lethargy, average energy, and quality factors have been calculated using a recursive unfolding algorithm. The dose rates and dose equivalent rates received by the patient and operators due to these neutrons have been estimated from these unfolded spectra. Doses predicted by a semi-empirical dose-equivalent model were compared to the measured values at each point. The dose equivalent rate to operators was found to be 1.9 x 10(-11) Sv MU(-1).