Radial observations of emission in the vicinity of the electron cyclotron frequency and its harmonics show the radiation to be polarized; ratio of extraordinary to ordinary mode intensity of about 2:1. In the thermal spectra the effects of cold-plasma resonances upon propagation of the radiation from emission layer to observation point are evident: (i) The extraordinary mode first harmonic is always suppressed by the upper hybrid resonance layer; (ii) The ordinary-mode first harmonic is suppressed when the plasma frequency exceeds the cyclotron frequency; (iii) For sufficiently high density the second harmonic is also affected by the hybrid cut-off. In the non-thermal spectrum the broad-band emission is polarized at high frequency but not at lower. The feature in the vicinity of the plasma frequency at intermediate density is broader than previously observed and almost entirely above ωpe. Internal sawtooth relaxations have been observed in the central temperature even up to peak densities of 7 × 1020 m−3. Temperature profiles deduced from second harmonic cyclotron emission and Thompson scattering data are compared.

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Boeing Electron Dynamic Devices, Inc. (EDD) has designed and fabricated a breadboard version of a 6-kW power processing unit (PPU) for gridded ion thrusters. This breadboard PPU will be integrated with an engineering model 40-cm ion engine designed and tested at GRC. The results of our tests using resistive loads are reported in this paper. The PPU demonstrated efficiencies to date are higher than 95% for the beam supply and higher than 92% for the discharge supply at full power. Overall PPU efficiency is greater than 94% at full throttle settings.

A scanning Fabry-Perot interferometer for use in the far ir (100 microm < < 2 mm) has been developed capable of scanning a free spectral range in a few milliseconds. A commercial loudspeaker was used as a drive, and mirrors were fabricated from electroformed copper mesh. Primary limitations of the instrument were due to vibrations of the interferometer frame.

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