A currentless plasma has been obtained in a tokamak device using a powerful microwave at electron cyclotron frequency generated by gyrotron systems. Its electron density is up to 8×1012cm-3; the electron temperature is up to 50 eV; the particle confinement time is about. 0.5ms; the heating efficiency is above 25%. The effect of the plasma on the toroidal breakdown and the heating mechanism have been studied.