Calculating the energy produced in watts in Alcator C-Mod

Question

I calculated the energy in joules that a deuterium-tritium fusion reaction releases and found 2.81829046e-12J. I then read on some MIT articles that the Alcator C-Mod reactor reached 300 trillions fusion reactions per second. Logically, I multiplied 2.81829046e-12 by 300e12, to find the energy released during one second of runtime. I found approximately 845.48J. And, I know that 1W = 1J/s. So in theory, the reactor should have produced 845.48W of power. But this seems so very very low, considering 4MW were used to heat the plasma. So that's why I came here, where have I made a mistake ?

Answer 1

There is no mistake here. Alcator C-Mod was never meant to be a prototype power plant; rather, it was a research reactor that explored the feasibility of having a high-field, small reactor rather than the huge donuts everyone else was building. So 1 kW is actually pretty reasonable.