Slow Neutron Resonances in Terbium-159

Abstract

An experiment of neutron resonances in ¹⁵⁹Tb was carried out using the Japan Atomic Energy Research Institute linac time-of-flight facility. Transmission and capture measurements were made on terbium samples of two thicknesses, using ⁶Li-glass and Moxon Rae detectors at the 47 m station; the neutron flux was monitored with a ⁶Li-glass transmission type flux monitor. Transmission data were analyzed with an area program up to 1.2 keV, and capture data with Monte-Carlo program CAFIT, to obtain 2gΓ⁰ _n Γ and Γ_γ Resonance parameters of 209 levels below 1.2 keV are obtained, and 52 levels between 754eV and 1.2keV are new ones. The results are; average level spacing <D>=4.4±0.4eV below 600 eV, s-wave strength function S₀=(1.55 ±0.15)10⁴ below 1.2 keV, and average radiation width <Γ_γ>=107±7 meV for lower 25 levels. Average capture cross section <σ_c> were obtained from 50 eV to 30keV.

KEYWORDS:

• slow neutron resonances
• terbium 159
• energy range 0–1200 eV
• resonance parameters
• level spacing
• strength functions
• average radiation width
• average capture cross sections