Estimate of the mass composition of cosmic rays with $E_0\leq10^{18}\,$ eV according to the data from a new muon detector at the Yakutsk EAS array

The lateral distribution function of muons with the threshold $E_\mu\approx0.5sec\theta$ GeV ($\theta$ is the zenith angle) in extensive air showers with energy $E_0\geq10^{17}\,$ eV has been examined using a new detector located at a distance of 180 m from the center of the Yakutsk array. This detector has been operating since autumn 2012 and consists of $27$ autonomous scintillator counters with an area of $2$ m$^2$. The experimental data have been compared to the calculations within the QGSJET-01 model with the CORSIKA air shower simulator. Agreement between the experimental data and calculations is achieved for the mixed composition of cosmic rays with the average atomic number satisfying the condition $\langle \ln A\rangle\approx2.84\pm0.08$.