Current driven electrostatic ion-cyclotron waves are excited by drawing a current to an electron-collecting disc (button) in a Q-machine. They are detected in the noise spectrum of the button, the hot plate emission current, and of a probe located at the mid-region of the plasma. By changing the magnetic field locally, the authors show that electrostatic ion-cyclotron waves are excited at frequencies determined by the local button field and the main field of the plasma.
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