I am sorry but I might still not understand your question. I will answer to the best of my ability but if I did in fact misunderstand you please ask again.
The plasma is refered to as the plasma inside a tokamak reactor that will produce energy from fusion reactions. The walls I talk about are the walls of the tokamak reactor which are of course in contact with the plasma inside the tokamak vacuum vessel.
If you want to understand better feel free to read the posts I posted in the Guide to fusion I mention in the post.
Thank you @maticpecovnik.. now I understand a bit, it is not something to cool the reactor.. but the interaction between the plasma and tokamak reactor to producr energy. You really help me to understand it... well, because I'mnot so into science but I like reading something about it.. it make me curious now.
I'll read about the fusion then.. at least I will know about different topic in this world, curiousity won't hurt if it is only for reading, right 😊 this is what I like from steemit, I read and then I can ask the author right away. Thank you for your time to reply my comment too.👋