The article presents the results of finite element modeling of a pyroelectric accelerator based on a single crystal of lithium tantalate. The influence of the charge distribution on the crystal surface on the characteristics of the electron flow is considered. A model using an axially symmetric charge distribution obtained by interpolating the experimental dependence leads to the expected effects of self-focusing and monoenergicity of the flow. Attention is also paid to the model "triangular"\; distribution. This distribution can be caused by the structure of the lithium tantalate domain walls when its temperature changes. Simulation results for both distributions are discussed.
77.22.-d Dielectric properties of solids and liquids
77.70.+a Pyroelectric and electrocaloric effects
78.20.-e Optical properties of bulk materials and thin films
$^3$P.N. Lebedev Physical Institute of the Russian Academy of Sciences