The effects of wall temperature on light impurities in Alcator

The effects of wall temperature on light impurity concentrations in the Alcator tokamak were measured spectroscopically. The results show that the temperature reduction decreases the influx of oxygen by a factor of 4–5 in normal tokamak operation when the wall temperature dropped from 450 to 77 K but does not affect the other light impurities (N,C).