The fission cross section of $$^{232}$$ 232 Th has been measured at fast neutron energies, using a setup based on Micromegas detectors. The experiment was performed at the 5.5 MV Van de Graaff Tandem accelerator in the neutron beam facility of the National Centre for Scientific Research “Demokritos”. The quasi-monoenergetic neutron beams were produced via the $$^{3}$$ 3 H(p,n), $$^{2}$$ 2 H(d,n) and $$^{3}$$ 3 H(d,n) reactions, while the $$^{238}$$ 238 U(n,f) and $$^{235}$$ 235 U(n,f) reactions were used as references, in order to acquire cross-section data points in the energy range 2–18 MeV. The characterization of the actinide samples was performed via $$\alpha $$ α -spectroscopy with a Silicon Surface Barrier (SSB) detector, while Monte Carlo simulations with the FLUKA code were used to achieve the deconvolution of the $$^{232}$$ 232 Th $$\alpha $$ α peak from the $$\alpha $$ α background of its daughter nuclei present in the spectrum. Special attention was given to the study of the parasitic neutrons present in the experimental area, produced via charged particle reactions induced by the particle beam and from neutron scattering. Details on the data analysis and results are presented.

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The γ -ray strength function and the nuclear level density of 167 Ho have been extracted using the Oslo method from a 164 Dy(α, pγ ) 167 Ho experiment carried out at the Oslo Cyclotron Laboratory. The level density displays a shape that is compatible with the constant temperature model in the quasicontinuum, while the strength function shows structures indicating the presence of both a scissors resonance and a pygmy dipole resonance. Using our present results as well as data from a previous 163 Dy(α, pγ ) 166 Ho experiment, the 165 Ho(n, γ ) and 166 Ho(n, γ ) eellian-averaged cross section (MACS) uncertainties have been constrained. The possible influence of the low-lying, long-lived 6 keV isomer 166 Ho in the s process is investigated in the context of a 2M , [Fe/H] = −0.5 asymptotic giant branch star. We show that the newly obtained 165 Ho(n, γ ) MACS affects the final 165 Ho abundance, while the 166 Ho(n, γ ) MACS only impacts the enrichment of 166,167 Er to a limited degree due to the relatively rapid β decay of the thermalized 166 Ho at typical s-process temperatures.

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