PERSPECTIVES OF PERSONNEL EXTERNAL DOSIMETRY AT STANFORD LINEAR-ACCELERATOR CENTER

The need for providing personnel external monitoring for exposure to l ow energy photon (<150 keV) and beta radiation at the Stanford Linear Accelerator Center (SLAG) has been studied. At SLAG, a high energy ele ctron accelerator facility, the major sources of low energy photons an d betas (electrons and positrons) are from the induced activities in a ccelerator parts and components. Shower theory and measurements show t hat these induced activities are generally distributed deep inside the materials. Therefore, the low energy photons and betas will be signif icantly absorbed within the materials. Calculations based on the chara cteristics of the radionuclides produced by photonuclear reactions in several common materials have indicated that the beta doses on the mat erial surface are small fractions of the photon doses. Field measureme nts at SLAG were made using Kodak type 2 films, Panasonic UD810 TLDs a nd a Victoreen 450 survey meter to determine the doses from low energy photons and betas, and then compared them with the doses from high en ergy photons. The X rays from the klystrons and the synchrotron radiat ion are also discussed. The results verify that the doses are small en ough that, from the technical point of view, no personnel monitoring i s needed for low energy photons and betas.