Experimental Observations of Strong Double Layers

Strong electric potential double layers ($\frac{e\ensuremath{\phi}}{k{T}_{e}}\ensuremath{\simeq}14$) are produced in a triple plasma device. The upper bound to $\frac{e\ensuremath{\phi}}{k{T}_{e}}$ reported in earlier experiments is not found. The electron beam which results from acceleration by the double layer maintains its identity with little heating until it reaches the end of the device. Results of a computer simulation are presented which are in qualitative agreement with the experiment and which indicate that the stability of the double layer depends on the length of the system.