A new discharge is described which is radially contained by a magnetic field and is not sustained by electron emission from any surface. Two positive anodes of arbitrary but similar shape are lined up along the magnetic field. A control electrode, at a lower potential, is placed between them and creates a potential barrier and two positive potential wells in the vicinity of each anode. Electrons are axially trapped in these wells. An rf voltage in the megacycle range is applied, out of phase, to the two anodes and causes the trapped electrons to alternately spill across the barrier and pick up energy from the rf field. During each half‐cycle they make many oscillations in the potential well which is most positive and make ionizing collisions. Every ion pair yields an electron which can gain energy in the same way. The process is very efficient and is characterized by rf breakdown voltages that approach the ionization potential of the gas.