| Ion confining potentials, $varphisb{c}$ in the Phaedrus tandem mirror are shown to be enhanced over Boltzmann relation predicted values by radio-frequency (rf) waves in the ion cyclotron range of frequencies (ICRF). "ICRF enhanced potentials" with $varphisb{c} sim$ T $sb{iparallel}$/ e have their peak values at axial locations where 0.6 $leq omegasb{rf}$/$Omegasb{ci}$ $leq$ 0.9. The ICRF enhanced potential is larger in the end cell with a lower passing density. Peak potential values decrease with increasing ion endloss current (or central cell density) for a constant rf capacitor bank voltage, and increase with increasing rf capacitor bank voltage, for a constant ion endloss value (or central cell density). In fully axisymmetric operation, a potential peak is produced in an end cell by the central cell rf, (without end cell rf) and is found only in the end cell nearer the central cell antenna.;ICRF enhanced potentials are explained as an equilibrium between the electron collisional filling in rate and the electron "pumping out" rate provided by axial time-varying electric fields, E $sb{z}$. Numerical modelling shows predicted values of E $sb{z}$ necessary to pump the well are on the order of E $sb{z}$ values predicted by rf field solving codes, the passing density needs to be low for effective E $sb{z}$ pumping, the collisional filling in rate is fairly independent of trapped density, pumping effectiveness increases with an increasing E $sb{z}$, and larger E $sb{z}$ values are required to pump larger potential peaks. Scaling studies of the E $sb{z}$ electron pumping model show the pumping effectiveness scaling dependence on $mid$ E $sb{z}mid$ and passing density are in qualitative agreement with experimental scaling of potential peaks with rf voltage and ion endloss (or central cell density). The model shows that higher T $sb{e}$ improves pumping by increasing E $sb{z}$ decreasing the collisional filling in rate, and increasing the pumping efficiency.;Thermal barrier-like potential structures with e $Deltavarphi$/ T $sb{e}$ were found in the transition regions between the central cell and end cells, in the fully axisymmetric Phaedrus. Central cell ICRF trapping effects combined with end cell $munabla$ B forces create and pump the barrier potential wells. |
