Investigation of activation behind a beryllium slab under irradiation with 14 MeV neutrons

axis of the deuteron beam. The absolute error in measuring the source did not exceed 3 %. The reaction rate was determined from the 3,-ray spectrum, measured with a germanium-lithium detector with a working volume of 60 cm 3. The spectra were processed using the KATOK program [9]. The program algorithm includes the use of self-regularizing iteration processes in approximating the spectrum with Gaussian functions and fitting parameters for the 7-ray peak. The experimental errors in the reaction rate, which consist of the statistical error of measurement, the error of absolute monitoring of the source, and the correction errors are as follows: the statistical error in the area of the "y-ray peak, the error in the detector efficiency, and the error in monitoring of the neutron source are 2.5-7 %, 2 %, and 3 %, respectively; the self-absorption correction is 0.5 %; the uncertainty of the constants is 2%; and, the fluctuation of the neutron flux is 0.5%. Computational Procedure. The experimental data were analyzed theoretically using the MCNP program based on the Monte-Carlo method in a three-dimensional geometry. Estimated data from the Los Alamos file were used for 9Be, and the reaction cross sections of the threshold detectors (response functions) were taken from the ENDF/B IV or ENDL libraries. Since the intensity and energy of the neutron source vary insignificantly within the solid angle determined by the geometry of the tritium target and the beryllium slab, the source was assumed to be isotropic and monoenergetic with neutron energy in the range 14.75-14.95 MeV. The estimated maximum error of the computed reaction rate does not exceed 4 %. Experimental Results. The measured reaction rate is presented in Table 1 as the reaction rate per detector nucleus and one source neutron. The table also gives the ratio of the computed value to the experimental value (C/E) for each reaction rate.