Cyclic Activation Method with Bremsstrahlung

Abstract

We intend to make clear the characteristics of cyclic activation method with 16-Me V bremsstrahlung. The experiment was performed with an electron LINAC, using a sample transfer system. A Ge (Li) detector was used for the measurement of γ-ray spectra from activated 16 elements. All the γ-ray peaks detected were due to nuclides formed by (γ, γ') or (γ, n) reaction. Sensitivities were calculated for 27 nuclides with half-lives of 0.8 sec to 32 min.
The experimental parameters were discussed to obtain satisfactory results. (1) In the settings of t_a=t_c=28 sec, t_t=t_t′=2 sec, T=60 sec and nT≤18000 sec, where t_a, t_c, t_t (t_t′) and T are activation, counting, sample transport and cycle period times, respectively, the cyclic activation method is effective, when the half-life of product nuclide T_1/2=5-2600 sec and when the total experiment time nT is changed according to the half-life. Also the relationship nT≥7T_1/2 must be satisfied in this method. (2) For given values of t_t, t_t′ and nT, the optimum number of cycles n must be selected according to the half-life of product nuclide to accumulate the count efficiently. In this case the value of T is also changed. (3) For given values of t_a, t_c, t_t, t_t′ and T, the optimum n value must be determined as in (2), (4) The sensitivity increases by about one order on average for each element, when the value of n is changed from 5 to 300 cycles for the same settings of t_a-t_c=28 sec, t_t-t_t′=2 sec and T=60 sec.