Continuum radiation from partially ionized argon

Experimental measurements of the total thermal radiation from an argon plasma arc of the wall-stabilized type with Poiseuille flow are compared with theoretical predictions. The magnitude of radiation is of importance both for re-entry calculations and use in the HellerElenbaas energy balance equation when transport properties are to be determined. The experimentally measured radiation (utilizing a carefully calibrated novel radiation meter) has been compared with predictions from semiclassical quantum theory (cum-experimental constants) based on recombination and bremsstrahlung. A simple equation for the total radiated power (in watts per cubic centimeter) as a function of temperature has been developed and corroborated by experiment. Spectrographically determined temperature distributions from a similar arc in the same laboratory were utilized in-making the comparisons. The plasma arc was operated at 1 atm over a range of argon flow rates from 0.02 to 0.415 g/sec and currents from 35 to 500 amp for three different column lengths. Steady-state total radiation as high as 5500 w/cm of column length, representing over 30% of the power input to the arc, was measured.