Mass composition of cosmic rays with energy above $10^{17}$ eV according to the data of surface detectors of Yakutsk EAS array

In this paper we present our estimation of mass composition of cosmic rays with energy above $10^{17}$ eV. It was obtained from the analysis of the lateral distribution of cascade particles in extensive air showers кegistered at the Yakutsk EAS array over the course of continuous observations from 1974 to 2017. Experimental values were compared to simulation results obtained within the framework of four hadron interaction models. The result of this comparison shows that over the energy range $(1-20) \times 10^{17}$ eV cosmic rays mass composition changes from nuclei with $\left \simeq 2.5$ to protons.