Partial trapping of a low-density plasma by an rf quasipotential well

A study is made of plasma trapping by the radio frequency (rf) quasipotential well of a cylindrical resonant cavity operating in the TM011 mode. This is done by injecting a plasma into the cavity with continuous rf excitation and observing the subsequent plasma decay. The experiment is conducted in such a way that the potential well appears only during the plasma decay. A significant delay in decay time is observed, and calculations indicate this to be due to partial trapping of the plasma by the quasipotential well. This trapping is observed experimentally at an electron density $n_e{\text{[inverted lazy s]10}}^9{\mathrm{cm}}^{\text{−3}}$ for a plasma with an electron temperature $T_e\text{[inverted lazy s]2.5}\mathrm{eV}$ . Trapping is noted by an increase in decay time for an average rf quasipotential well energy <8 eV. For higher well energy, an anomalous loss of plasma is observed as indicated by a marked decrease in decay time.