PDX Divertor operation

PDX was brought into operation in January 1980 as a diverted tokamak with typical parameters of B_T = 15–20 kG, a = 38 cm, R₀ = 123–159 cm, I_P = 180–300 kA, q ~ 3.7, n̄_e = 1–3.8 × 10¹³ cm⁻³, Z̄ = 1.1–3, t_es ~ 25 ms, and pulse lengths up to 0.7s. Internal vacuum components that were exposed to the plasma (such as limiters, shields, microwave horns, etc.) were fabricated from 99% pure titanium. Glow discharge cleaning with 3 × 10⁻² Torr H₂ and pulse discharge cleaning were used to condition the vessel for high power discharges. For the divertor studies, work has concentrated on obtaining long, high current stable discharges. Radial position, plasma current, and gas injection control systems have been used to facilitate this effort. Discharges of inside-D, square, and inverse-D cross-section have been produced. Microwave interferometers, spectroscopy, an X-ray pulse height analyzer system, scanning and fixed bolometers, and thermocouple array have been used to determine plasma and impurity densities, temperature, radiation, and power loss to the divertor. A comparison of diverted and undiverted discharges is presented.