Improvement in electrostatic confinement by second‐harmonic electron cyclotron heating in the Phaedrus tandem mirror

One minimum‐B mirror end cell of the Phaedrus tandem mirror was heated with up to 30 kW of electron cyclotron heating at ω=2ω c e . The plug electron temperature was increased from 18 to 23 eV while a smaller temperature increase was measured in the central cell. Changes in ion end loss energy and current were consistent with direct measurements of increases in the east plug plasma potential. Ion confining potential increases of up to 27 V were observed. These increases were much greater than the T e /e increases and in excess of that predicted by the Boltzmann relation.