Effect of plasma physics on choices of first wall materials and structures for a thermonuclear reactor

nWI T HIM Mil Tnh report «u prepared ai an iccoum ol work •ponlorol by the United Sum Goveriun.nl.Neither tfw United Slatei no. the United ~MM Enc.gy Kaeaicn and Development Administration, noi any of tneir employee!, nor .ny or Ihtli contracloii aibconnaciori, or thd, employee,, "»"".">warranty, eipreu 01 implied, or amirnei any kol HibiBli.«,rwpomftimy for the accvm-y, comply™* 01 uKfulneaa of any Information, apparalui, moduci or pncxu diKtaKd, or repreienti thai iu use would noi infnnjr pnultly owned r|ihu.Impurity ions adversely affect the behavior of present-dny tokamaks, and control of impurities is expected to be a key element in determining the feasibility of thermonuclear fusion reactors.In this paper, we describe the plasma-surface interactions for tokamaks and several techniques for controlling impurities.The plasma-surface problem of next generation devices PLT.PDX, Dill and TFTR is expected to be similar to those encountered in a reactor.For these devices calculations indicate that most of the particle energy efflux will be in the 1 keV region.Ironically this energy region has not yet been investigated thoroughly by the surface physicists.