Experiments are reported on the beam-plasma instability at times after saturation when the electron distribution function exhibits a high energy tail. The results show that high energy electrons are produced by a velocity resonant wave-particle interaction. The experiments were formed on quite different devices at Dartmouth College and The University of Texas; however, the results from the two laboratories are consistent.

We have observed the generation of high-energy electrons by longitudinal electrostatic waves in a beam-plasma system. We find a direct correlation between the measured field and particle spectra.

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A multiple -point Thomson scattering device, capable of giving radial electron temperature profiles, has been developed for the ZT -40 reversed field pinch experiment.The measurement is accomplished by observing the Thomson scattered spectrum from along an entire chord of focused ruby -laser light traversing the minor diameter of the plasma. A specially built, nearly diffraction limited laser is focused through the plasma using a long focal length lens.