Positron annihilation techniques have been used to estimate dislocation densities induced in cold rolled f.c.c. polycrystals by plastic deformation. The positrons are assumed to be trapped by defects in the crystal lattice, thus causing the narrowing of the annihilation lineshapes obtained in a Ge(Li) spectrometer. A trapping cross section is derived from the experimental results, using a theoretical model. In plastically deformed polycrystals of Ni, Cu, Ag, and Au a linear strain hardening range is observed up to 15 to 20% deformation. In that range, dislocation densities vary from about 108 to 1010 cm−2 for Ni and Cu, and from about 107 to 109 cm−2 for Ag and Au. The trapping cross section of positrons by dislocations were found to be 6 × 10−16 cm2 for Ni, 9 × 10−16 cm2 for Cu, 5 × 10−15 cm2 for Ag, and 2 × 10−15 cm2 for Au.

The gyrokinetic particle simulation is a powerful tool for studies of transport, nonlinear phenomenon, and energetic particle physics in tokamak plasmas. While most gyrokinetic simulations make use of the scalar and vector potentials, a new model (GK-E&B) has been developed by using the E and B field in a general form and has been implemented in simulating kinetic Alfvén waves in uniform plasma [Chen et al., Sci. China: Phys., Mech. Astron. 64, 245211 (2021)]. In our work, the Chen et al. GK-E&B model has been expressed, in general, tokamak geometry using the local orthogonal coordinates and general tokamak coordinates. Its reduction for uniform plasma is verified, and the numerical results show good agreement with the original work. The theoretical dispersion relation and numerical results in the local model in screw pinch geometry are also in excellent agreement. Numerical results show excellent performance in a realistic parameter regime of burning plasmas with high values of [Formula: see text], which is a challenge for traditional methods due to the “cancellation” problem. As one application, the GK-E&B model is implemented with kinetic electrons in the local single flux surface limit. With the matched International Tokamak Physics Activity-Toroidicity-induced Alfvén Eigenmodes parameters adopted, numerical results show the capability of the GK-E&B in treating the parallel electron Landau damping for realistic tokamak plasma parameters. As another application, the global GK-E&B model has been implemented with the dominant electron contribution in the cold electron limit. Its capability in simulating the finite [Formula: see text] due to the finite electron mass is demonstrated.

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