A fluid model was used to study the response of a nonmagnetized plasma to a high-voltage sphere for a time interval up to 20000 plasma periods. Different applied voltages, background plasma densities and voltage rise times were considered. It was found that after the transient response to the applied voltage the system evolves to a steady state. In the steady state, the ion density satisfies the Boltzmann relation. The thicknesses of both the electron sheath and the presheath increase with the applied voltage. The sheath thickness, estimated from the electron and ion density profiles, agrees with the simple Langmuir-Blodgett (LB) theory, but the simulation current is 2-5 times higher. If the voltage is applied according to an exponential law with a rise time tau , only the electron motion at very early times is affected if tau展开▼
