A time dependent, bounce-averaged Fokker-Planck code, with quasi-linear diffusion at fundamental and second harmonic frequencies, has been used to study cold plasma trapping and heating of hot electrons in mirror geometry. Both electron-electron and electron-ion Coulomb collisions are included. The code can model either cavity heating (electric field throughout cavity as in EBT) or beam controlled heating (electric field spatially restricted as in the TMX-Upgrade tandem mirror). The heating method has implications for the equilibrium energy and anisotropy of the hot electrons. In TMX-Upgrade, off-midplane heating at the second harmonic in the thermal barrier is planned as a means to control anisotropy (T/sub parallel//T/sub perpendicular/. By spatially limiting (limit in B) the microwave beam and with strong single-pass absorption, the mean hot electron energy may also be controlled since the heating rate decreases at high energy due to the relativistic mass shift of the resonance to higher magnetic field.