Theory: How electron beams heat plasmoid electrons
A recent paper in Physics of Plasmas by S.K. Yanav et al (Phys. Plasmas 16,040701) may shed light on a remaining theoretical puzzle—how the electron beams so rapidly heat the plasmoid electrons.
This heating is much more efficient than can be explained by collisions of individual electrons, so must involve some instability or other collective phenomenon, but we have never been certain exactly what the mechanism is.
Yadav showed that a rapidly oscillating electron beam can produce shock waves in an inhomogenous plasma that efficiently transfers energy to the plasma.
Such a mechanism may operate in the DPF plasmoid, as the electron beam is rapidly pulsed—each pulse lasting only femtoseconds. The relativistic beam travels much faster than the Alfven velocity in the plasmoid, a velocity which is the magnetic equivalent of the speed of sound in a neutral gas, so shock formation is possible.
LPP contractor John Guillory has written a number of papers on such shock heating and he and Lerner will investigate if the mechanism can explain know DPF experimental results.