ИСТИНА

This work presents the spectrum of Nickel nuclei in the cosmic rays as measured by the NUCLEON experiment. The Nickel spectrum is measured for the first time in a wide energy range from 10^3 to 2*10^4 GeV. The algorithm of heavy cosmic ray elements spectra reconstruction is presented, which includes shower axis, charge, energy determination procedures, calculation of trigger efficiency and algorithm efficiency. The inclination of the experimental nickel spectra is -2.87+-0.05, which differs significantly from the iron nuclei spectra inclination - -2.69+-0.01. The problem of obtaining source spectra from the measured spectra is solved. Statistical significance of the obtained difference between source spectra indexes of iron and nickel is 3.2 standard deviations. Possible causes of the observed difference are discussed.