flow, ultra high vacuum, etc. that are required for the test. It is possible to use a miniature model based on a similarity law in the laboratory. One advantage of the scale experiment is the useful recognition of unknown phenomena due to the dense plasma. One objective in the present work is to reveal the dependence upon arrangement of the solar cells on the 2D array for the 2D/HV experiment by way of our ground experimental technique. An explanation of the discharge and the luminosity observed on the electrode and the insulator is attempted. 2. Similarity Law The plasma parameters in LEO at 500 km altitude where the space station is designed are summarized in Table I [8]. In this condition the electron thermal velocity ve, the satellite orbital velocity U and the ion thermal velocity v, satisfy the following relation: so that ions are approximated to impinge on the satellite with U while the electron is with vc. The characteristic length LA, assumed 5 m HVSA span, is shorter than the mean free path /, whereas longer than the plasma Debye length ad. These conditions permit the particles to be regarded as plasma moving without collision near the HVSA. The ion kinetic energy K, is smaller than the maximum array voltage VA, but larger than the electron thermal energy kT^. where the voltage applied to the HVSA is assumed 500 V. The Larmor radii of ion 7?id and 7?, for the drift and thermal velocities are larger than La while that of electron Rc with reference to the thermal velocity is smaller. Therefore the geomagnetic field may have little effect on the ion collection by the HVSA in LEO.
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