Numerical Study of Proton Impact Rates on a Solid Target in Pyroelectric Fusion: Effects of Electrode Geometry and Crystal Heating Temperature

Abstract

Numerical simulations were conducted for a pyroelectric fusion device with three electrode geometries to investigate proton generation, acceleration, and impact with a solid ¹¹B target. Evaluation of the electric field distributions showed that the maximum potential scales with the crystal temperature difference as ϕ_max ≃ 238 ΔT [kV]. Analysis of electron-impact ionization clarified the spatial regions where protons are generated and begin to accelerate, revealing that a considerable fraction of protons is laterally deflected by the electric field structure and fail to reach the target. The proton impact rate was systematically examined by varying the electrode geometry and heating conditions. The results indicate that the impact rate is maximized at moderate temperature differences, whereas excessively strong electric fields shift the ionization region outward and reduce proton delivery to the target. Further analysis suggests that rapid electron acceleration near the electrode shortens the residence time within the energy range favorable for ionization, thereby suppressing proton generation under high heating conditions. These results demonstrate that proton impact efficiency in pyroelectric fusion devices is strongly governed by the interplay between electrode geometry, ionization location, and operating temperature. Appropriate control of these parameters is therefore essential for improving target-directed proton irradiation.