Charge-Exchange Neutral Hydrogen Measurements in TFTR Using Pd-Mos Microsensors

J. Nucl. Mater., 176-177, 1038-1043 (1990).

Bastasz, R., Kilpatrick, S. J., Ruzic, D. N.

An array of Pd-metal-oxide semiconductor (Pd-MOS) diodes has been used to monitor the fluence and energy of charge-exchange neutral hydrogen isotopes striking the wall of the Tokamak Fusion Test Reactor (TFTR). The array was positioned 4 cm behind the graphite-tiled wall at the toroidal midplane and exposed to several hundred plasma discharges. Hydrogen isotopes striking the Pd-MOS diodes were detected by measuring the leakage current, which is affected by the presence of these species at the Pd/SiO₂ interface. It was found that the midplane flux strongly increased for neutral-beam heated plasmas and correlated with co-injected neutral beam power. The majority of the neutral flux was < 50 eV in energy but its energy distribution extended to above 500 eV.