Investigation of Total Cross Section Characteristics in the Region of Unresolved Resonances
Neutron transmission through layers of different materials is measured. The source of neutrons is the uranium target of the electron linac LU-50. As a detector a sectioned fission, chamber, containing 6–7 g of 235U, is used. The chamber is placed at 52.18 m of flight path, the investigated sample at 25 m. The neutron pulse duration is 10–13 ns, the total resolution Lime 18 ns. CAMAC standardized equipment registers the time-of-flight neutron spectra, controls the background components and amplitude spectra of fragments for each chamber section. The whole measurement procedure is automatic, including the periodic sample movements. The transmission measurements are made for 7–8 values of thickness. The results are presented in T(t,ΔEi)-tables for 35–40 energy intervals of ΔEi. The transmission T(t) for ΔE intervals of neutron energy may be presented as Laplace transform of the total cross-section probability density p(α) in a given energy interval with the sample thickness (t) as transformation parameter. An algorithm for estimation of probability density semi-invariants and restoration of the p(α)-function was created to treat measured transmission functions T(t). The measurements of the transmission functions for Al, Pb, Fe and others are carried out. The results of the approximation by the semi invariants of the obtained experimental data are used in the practical work. The experimental data and the results of their approximation for Al and Al2O9 are presented.
Keywordsneutron transmission electron linear accelerator ionization chamber scintillation detector time-of-flight method CAMAC standard total cross-section automation of experiment distribution density moments semi invariants resonance structure
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