Inductively coupled plasma (ICP) is a common method of ionizing the residual gas in a vacuum chamber. A RF source (commonly 13.56mhz) is connected to a coil (usually outside of the chamber) which induces currents in the nearby gas volume because of the time-varying magnetic fields.
I used a 10 meter (28mhz) 100 watt ham radio transmitter at 60mTorr with multiple coil designs to create an inductively coupled plasma. Even while minimizing the reflected power with a matching network (antenna tuner) the plasma was difficult to ignite. By briefly powering an anode layer ion source in proximity to the ICP coil I was able to ignite and sustain the ICP at lower power levels.
Once the ICP is sustained, the ALIS is powered off and the RF ICP remains on.