Аннотация:Experimental data on the optimization of linac injector operational modes are presented. Injection energy spread of no more than ±1.5% is allowed by the results of calculating the particle dynamics in the accelerator, the normalized beam emittance in the region of the accelerator inlet diaphragm of 6 mm in-diameter should not exceed 0.15 π cmхmrad under the value of injected proton beam current of about 50 mA. The main factors effecting the duoplasmatron-type source beam parameters are considered. To analyse the source operating modes diagrams are plotted in coordinates: discharge current -magnetic field induction, where lines corresponding to the fixed level of the parameter selected are presented. Source operating modes under which calculated requirements to the beam are achieved are determined.