In magnetic confinement fusion (MCF), the plasma always exhibits an anisotropic temperature distribution, which may impact not only the plasma dynamics but also the nuclear reaction process. Here, through theoretical derivations and self-consistent particle-in-cell simulations with the newly-developed nuclear reaction and alpha particle energy deposition calculation modules, we find that, if considering the plasma has an anisotropic temperature distribution, the fusion energy gain factor ($Q$) of MCF is significantly modified, where both the deuteron-triton nuclear reactivity and the alpha particle energy deposition fraction are heavily influenced. The simulation results show that, under the International Thermonuclear Experimental Reactor (ITER) condition, if the plasma temperature anisotropy ratio can reach 0.1, i.e., the plasma perpendicular temperature component is one-tenth of its parallel component corresponding to the ambient magnetic field direction, the $Q$-value of ITER can be increased from the originally-designed 5 to about 10, with doubled enhancement.

Nuclear reactions in the plasma environment can be substantially different from those in conventional laboratory non-plasma cases, which have attracted considerable attention in the fields of fusion and astrophysics. To self-consistently model the nuclear reaction process during plasma dynamic evolution, an extended nuclear reaction calculation module is developed and included in two-dimensional particle-in-cell simulations. Through the self-consistent simulations, we systematically show that, apart from the plasma screening, the kinetic Weibel instability (WI) occurring in plasmas also results in significant enhancement of nuclear reactions, where the self-generated magnetic fields play a key role. Specifically, the self-generated magnetic fields in WI deflect ion motions, decreasing the relative velocity, and convert plasma kinetic energy to thermal energy, increasing the ion temperature. The simulation results show that, for the t ( d , n ) α reaction with a sharp resonance peak in the cross section, the reaction product yield is enhanced four times due to the WI. For nuclear reactions that have more prominent resonance peaks in the cross section, like 12 C ( p , γ ) 13 N , it is expected that such enhancements can reach up to one or several orders of magnitude.