REMOTE X-RAY MEASUREMENTS OF THE ELECTRON-BEAM FROM THE EXCEDE-III EXPERIMENT

The EXCEDE III rocket experiment successfully produced an artificial a urora on April 27, 1990, with an injected approximately 18-A beam of a pproximately 2.5-keV electrons. The experiment consisted of an acceler ator module and a sensor module in a mother-daughter configuration. Th e beam was fired along the Earth's magnetic field lines between the al titudes of approximately 62 and 115 km during the flight. A major conc ern prior to the flight was that the injection of such an overdense el ectron beam into the lower ionosphere would charge the accelerator mod ule to a significant fraction of the beam potential. To monitor the pr imary electrons remote from the rocket, two X ray proportional counter s were included as part of the sensor module. X ray spectra from brems strahlung emission yield a direct measure of the primary electron beam energy outside the plasma sheath surrounding the accelerator module. Analysis of these spectra yields a beam energy of 2.2 +/- 0.5 keV whic h indicates no substantial charging of the accelerator module for the entire time that the beam was on. We also find that the X ray intensit y was modulated at the few percent level by firings of the attitude co ntrol jets.