Eric’s term “plasmoid” actually refers to the tiny ball made of plasma filaments.
Plasma, except perhaps for jets. must be electrically neutral. That is it must contain a roughly equivalent number on protons in its constituent nuclei, and electrons either bound or free. At these high energies they are all free.
The beam is not a direct result of the fusion reactions. It is a result of the collapsing magnetic field which is confining the plasma which makes the plasmoid. This collapsing field accelerates the electrons in the plasma in the opposite direction as the nuclei. The fusion reactions in turn fuel the magnetic field. I’m not sure we understand how exactly. Eric might.
As to the electron’s energy, Eric believes that in the process of spiraling around in the filaments which make up the plasmoid; they will transfer most of their momentum to the helium nuclei.