Publications

The assumptions involved in the use of Boltzmann's law to describe the electron density variations in ion acoustic waves are discussed. The need for electron collisions to fill the regions of maximum potential with low-energy electrons is pointed out. A direct method for measuring the electron energy distribution at any time during the period of an ion wave is presented. Experimental results show the existence of electrons with energy small enough for their motion to be constrained to the wave potential well. For higher energies, the distribution stays approximately the same. The method provides a direct measure of plasma potential, which is related to density. The Boltzmann law is still seen to be accurate for relative fluctuations of the order of up to 20%.