Measurements of Neutron Spectra at the Stanford Linear Accelerator Center

The purpose of the present measurements was to determine neutron spectra outside the shielding of high energy electron accelerators, with a special emphasis on the high energy (>20 MeV) portion of the spectra. The spectrometer system used consists of a standard set of Bonner spheres augmented by a custom made 30.48 cm (12) sphere with a 1 cm inner layer of lead, which increases its response in the high energy region. The system was further complemented by a plastic scintillator used for the measurement of 11 C activation. A pair of rem meters was also used: one standard Anderson-Braun, and one with an inner layer of lead which has an extended high energy response. Measured spectra and relevant dosimetric quantities outside shielding at three different electron beam energies are presented.