In the pursuit of viable nuclear fusion powered energy generation via magnetically
confined fusion theory and experimentation, the single most important scientific question
may be energy confinement time in a fusion plasma. In response, a simple theory is presented
for quantitative calculations of the confinement times of plasma thermal energies in
magnetically confined thermonuclear fusion reactors. The theory is based on radiation
reaction associated with spontaneous electron cyclotron radiation as described by the Larmor
formula. Good agreement is found between theory and experiment. An advanced Lawson
criterion for ignition is derived, which is consistent with the latest magnetically confined
fusion energy record achieved experimentally.
