Interaction of a spherical high voltage probe with the space environment: electron trapping, current drain and collective process

The effects of electron trapping and plasma turbulence on the current-voltage relationship for a positively charged high-voltage spherical probe in a magnetized plasma are studied. The results of a study conducted prior to the launch of SPEAR I (Space Power Experiment Aboard Rockets) are summarized and analyzed. A primary goal of the SPEAR I experiment was to obtain quantitative measures of the effects of an ambient magnetic field on electron collection by a high-voltage spherical probe. Analysis indicates that the structure of the sheath and the I-V relation for a high-voltage probe configured as in the originally planned SPEAR I experiment (with a working plasma contactor) would be substantially influenced by the combined action of trapped electrons and wave-particle scattering processes.<>