Abstract
In order to reduce light impurities in hot plasmas in nuclear fusion devices, we have two techniques established, bake-out and discharge cleaning. Here is given a short lecture on these techniques. We are confronting increase in engineering complexity to construct fusion machines. This trend led the author to take a view point searching possibility of “decrease in baking temperature, or rather room-temperature-pumping”. Concerning the discharge cleaning, description is focused on utilization of hydrogen plasma of low electron temperature.
