> because fusion reactor plasma is optically thin, it doesn't radiate following blackbody radiation law.
It still follows the laws of blackbody radiation - it's just that the emissivity of the body is part of the equation.
A classical blackbody has a emissivity of 1. This means not only that it absorbs radiation really well, it also means it's really good at radiating energy away.
Things that have low emissivity (all things transparent and all things reflective) are also really bad at radiating energy away. This is used for solar-thermal collectors today: you make them from an engineered material that is completely black at in the visible range, but highly reflective in the infra-red. That way, they absorb sunlight and get hot, but they don't lose heat energy because they can't radiate it away as heat radiation.
And yes, fusion plasma is extremely, extremely transparent. Not only is it extremely thin (ITER or Wendeltstein 7-X contain only 1-2g of hydrogen during operation), hydrogen is also extremely bad at absorbing gamma-rays (black body radiation at 1e8 K).
It still follows the laws of blackbody radiation - it's just that the emissivity of the body is part of the equation.
A classical blackbody has a emissivity of 1. This means not only that it absorbs radiation really well, it also means it's really good at radiating energy away.
Things that have low emissivity (all things transparent and all things reflective) are also really bad at radiating energy away. This is used for solar-thermal collectors today: you make them from an engineered material that is completely black at in the visible range, but highly reflective in the infra-red. That way, they absorb sunlight and get hot, but they don't lose heat energy because they can't radiate it away as heat radiation.
And yes, fusion plasma is extremely, extremely transparent. Not only is it extremely thin (ITER or Wendeltstein 7-X contain only 1-2g of hydrogen during operation), hydrogen is also extremely bad at absorbing gamma-rays (black body radiation at 1e8 K).