Measurement of the photon flux of 8 MeV microtron by activation analysis

The photon activation reaction 115In(#betta#,#betta#') sup(115m)In has been used to study the bremsstrahlung spectrum of the 8 MeV race-track microtron electron beam. The (#betta#,#betta#') reaction is used in the 8 MeV ener.o.y ran.n.e because reactions of the type (#betta#,p) and (#betta#,n) do not interfere due to their high threshold energies. The In sample of known mass is excited by the bremsstrahlung to produce a nuclear isomer. The photons obtained during de-excitation are counted with a 3'' x 3'' NaI (Tl) crystal. The activation cross-section and the half-life of the isomeric state are well-known. This enables the calculation of the bremsstrahlung intensity. The intensity variation as a function of various parameters such as conversion target thickness, target material and angle with respect to incident beam direction have been measured. The energy of the incident electron beam is measured to an accuracy of 1 percent by using a double-focusing momentum analyzer. (author)