a system and method for maintaining a plasma in a plasma region by supplying rf power at a fundamental frequency to the plasma region together with a gas in order to create an rf electromagnetic field which interacts with the gas to create a plasma that contains electromagnetic energy components at frequencies that are harmonics of the fundamental frequency . the components at frequencies that are harmonics of the fundamental frequency are reduced by placing rf energy absorbing resistive loads in energy receiving communication with the plasma , the resistive loads having a frequency dependent attenuation characteristic such that the resistive loads attenuate electrical energy at frequencies higher than the fundamental frequency more strongly than energy at the fundamental frequency .