APPLICATION OF HIGH-FIELD SURFACE ANALYTICAL TECHNIQUES TO THE STUDY OF PLASMA-WALL INTERACTIONS IN PLT

The techniques of imaging atom-probe mass spectroscopy, field-ion microscopy, and transmission electron microscopy have been used to analyze the surface and near-surface regions of field-emitter samples exposed to the plasma of the Princeton Large Torus (PLT) tohamak. The experiments were carried out to determine the extent of damage to the emitter surfaces resulting from plasma exposure, the composition and thickness of films deposited on the sample surfaces during irradiation, and the depth distribution of implanted plasma and impurity species in the near-surface region of the specimens. The analyses indicate that very little structural damage occurs to the wall of PLT as a result of impinging particles travelling in a direction perpendicular to the toroidal magnetic field lines within the tokamak, but that a considerable amount of limiter material is deposited on the wall surface during operation. The deposited layer was found only when the sample was directly exposed to the plasma; control specimens which were in the reactor at the same time but shielded from direct plasma exposure remained free of deposits. © 1979.