Cavity Cooling of the Pure Electron Plasma

Magnetized electrons in free space emit cyclotron radiation, cooling at the Larmor rate -1/T dT/dt = 0.24 s^-1 * B[T] ² This rate can be enhanced by confining the plasma in a microwave cavity, where the density of EM oscillator states is concentrated at the cavity resonances [A. P. Povilus, PhD thesis: Berkeley 2015]. Here we present data for the cooling of plasmas with 2*10⁶ electrons, held in three different cavities, over a range of magnetic field from 0.15-1.50 T. We explore in detail the cooling enhancement for a variety of magnetic gradient and field-plasma overlap geometries. Optimizing these parameters, we measure the cooling rate and final temperatures achieved for the range 100 < N < 10⁸ plasma electrons.