Evaluation of the gamma-quanta fraction in the primary cosmic ray flux with energy about 1017eV according to the EAS MSU array data

Using the data of the EAS MSU array and model calculations we have performed the search of events with abnormally small fraction of muons with energy above 10 GeV in showers with particle numbers greater than 2.107 and with zenith angles less than 30 degrees. The aim of the work – to estimate a fraction of muon-poor showers in which the underground muon detector registered no muons. These events may be identified as showers generated by primary gamma-quanta of ultrahigh energies. With good statistical accuracy we have confirmed our earlier conclusion that the content of gamma-quanta in the primary cosmic ray flux may be as much as 2 % at energies about 1017 eV.