On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Benchmarking of thorium-232 evaluations against spherical transmission and (n,xn) reaction experimental data

The neutron leakage spectra from a thorium sphere of 26 cm outer and 6 cm inner diameters with a central T-D and 252Cf neutron sources measured at the Institute of Physics and Power Engineering as well as available in the literature measured differential cross sections for Th(n,xn) reaction at 14 MeV were used for benchmarking of the evaluated cross sections from ENDF (versions B-VII.0 and B-VI.8), JEFF-3.1 and Maslov'07 libraries. It was finally concluded that while it is difficult to prefer any of these libraries relying on spherical benchmarks validation results, Th(n,xn) differential cross sections are certainly better reproduced by ENDF/B-VII