Empirical formula for (n, f) reaction cross sections of Uranium isotopes at 1-20 MeV neutrons.

This article describes how to calculate neutron-induced fission reaction cross sections using a proposed empirical formula and the EMPIRE 3.2.3 and TALYS 1.95 computer codes for Uranium isotopes up to the third fission plateau. In this study, the excitation functions of 232U (n, f), 233U (n, f), 234U (n, f), 235U (n, f), 236U (n, f), 237U (n, f) and 238U (n, f) nuclear reactions were calculated at 1-20 MeV neutron energies. The results were contrasted to measured values from the Experimental Nuclear Reaction Data (EXFOR) as well as the evaluated data from Evaluated Nuclear Data File (ENDF) such as (EAF-2010, JEFF-3.3, ENDF/B-VIII.0 and TENDL-2019). Overall, the calculated, experimental, and evaluated fission cross-sections are in concordance.

Semi-empirical formula for (n, α) reaction cross sections at 14-15 MeV neutrons.

Semi-empirical formula for calculating the average (n, α) reaction cross-section was derived by using the EXFOR experimental data at 14-15 MeV neutron energies for 133 target nuclei in the mass number range 9≤A≤209. In this new systematic, the non-elastic cross-section portion has been modified by [Formula: see text] , while the asymmetry parameter-dependent term has been maintained. Using EMPIRE 3.2.3 and TALYS 1.95, the (n, α) cross sections for selected nuclei within the same energy range were calculated. The experimental data can be predicted with greater precision when the cross sections derived from the proposed formula are compared to those derived from codes and earlier systematics.

The shallow structure of Mars at the InSight landing site from inversion of ambient vibrations.

Orbital and surface observations can shed light on the internal structure of Mars. NASA's InSight mission allows mapping the shallow subsurface of Elysium Planitia using seismic data. In this work, we apply a classical seismological technique of inverting Rayleigh wave ellipticity curves extracted from ambient seismic vibrations to resolve, for the first time on Mars, the shallow subsurface to around 200 m depth. While our seismic velocity model is largely consistent with the expected layered subsurface consisting of a thin regolith layer above stacks of lava flows, we find a seismic low-velocity zone at about 30 to 75 m depth that we interpret as a sedimentary layer sandwiched somewhere within the underlying Hesperian and Amazonian aged basalt layers. A prominent amplitude peak observed in the seismic data at 2.4 Hz is interpreted as an Airy phase related to surface wave energy trapped in this local low-velocity channel.