In order to provide electron beams of powerful gyrotrons, magnetron-injecti
on guns operating in the regime of the temperature limited current are used
. The electron beam quality and gyrotron performances are defined both by t
he cathode emission processes and the processes occurring in the electron b
eam during its formation and transportation, The results of measurements of
the energy spectrum and velocity spread of the gyrotron electron beam in d
ifferent regimes are given. Experimental data on the parameter of efficient
emission inhomogeneity for different regimes are presented, as well as the
dependencies of electron beam parameters on efficient inhomogeneity of the
cathode.