Investigations of Various Probe Sheath Materials in the Texas Tech Tokamak

Rods of alumina, Macor [1], quartz, and boron nitride have been inserted into the plasma of the Texas Tech Tokamak to determine the feasibility of using these materials as protective sheaths for magnetic probes. Results indicate, as was earlier reported [2], that alumina, Macor, and quartz are unacceptable as sheath materials. Boron nitride, however, survived the plasma environment without affecting the plasma parameters too seriously and without serious material ablation or damage. Hence, it was used as a protective probe sheath. Several radial scans of the fast Alfvén wave field structure have been made successfully using these boron nitride sheaths for protection of the magnetic probes.