The Big Bang theory proposes that the Cosmic Microwave Background Radiation (CMBR) is a flash of radiation from a process called recombination which occurred when the temperature of the universe dropped through 3000 degrees Kelvin at a time around 370,000 years after the Big Bang.
It would be good to know if we observe this flash of radiation in a nuclear fusion reactor as the plasma cools through 3000K. I understand that the temperature required for nuclear fusion is around 100 million degrees C so it should be possible to observe this effect as the plasma cools though 3000K. My expectation is that you will not see a flash of radiation at this temperature but it would be good to know for sure from someone working on nuclear fusion.
Richard