Energy flux measurements in a steady-state discharge at PSI-2

A newly developed heat flux detector for direct measurement of the energy flux to a floating or biased target is presented. The detector has been used to measure the plasma sheath transmission factor (γ) for different gases as a function of the electron temperature. The determined values are in the range of 7<γ<17; they agree roughly with those theoretical predictions [G.A. Emmert, R.M. Wieland, A.T. Mense, J.N. Davidson, Phys. Fluids 23(4) (1980); H. Kimura, H. Maeda, N. Ueda, M. Seki, H. Kawamura, S. Yamamoto, M. Nagami, K. Odajima, S. Sengoku, Y. Shimomura, Nucl. Fusion 18(9) (1978); R.V. Manos, D.M. Budny, S.A. Cohen, J. Vac. Sci. Technol. A 1 (1983); P.C. Stangeby, J. Phys. D 15 (1982); P.C. Stangeby, Phys. Fluids 27(3) 1984] that include the recombination term.