Distribution of arc tracks on the T-10 liner Evidence for the existence of an m = 1, q = 1 instability at the plasma boundary

After more than five years of operation of the T-10 tokamak a visual inspection of the internal liner surface was made and many arc tracks were found and photographed. Both the distribution and the direction of the tracks suggest the existence of an m = 1, n = 1 plasma mode lasting for at least 1 ms. A simple model is proposed to match the observed structures and to yield information about the plasma column.