Spectroscopic Observations of Impurities in Tokapole Ii Dis Charges

Tokapole II is a tokamak with a four-node poloidal divertor. Impurity concentrations, line radiated power, and impurity behavior have been studied in Tokapole II discharges with two VUV spectrometers, o one of which acquires the VUV spectrum (400-1300 A) with a single discharge. Oxygen (3-5% of the electron density) is the dominant �lpurity, and the measured total radiated power is 15-30% of the ohmic input power. Observed metal impurities cannot be generated by sputtering from the 15-20 eV plasma protons; sheath potentials evidently play a dominant role in the generation of the metal impurities. An impurity doping technlque has been used to measure the impurity concentrations, to estimate the contributions of the various low-Z impurities to the total radiated power, and to study the g�oss effects of impurities on the plasma. A model of impurity behavior in a plasma with � magnetic limiter is presented. SPECTROSCOPIC OBSERVATIONS OF IMPURITIES IN TOKAPOLE II DISCHARGES COO-2387-108 R.J. Groebner J.C. Sprott R.N. Dexter