Adiabatic Acceleration of Ions by Electrons

The velocities and angular distributions of different plasmas ejected from pulsed low-voltage (37 v) discharges have been measured. Velocities of metal plasmas greater than 106 cm/sec have been observed. Probe measurements of the initial electron temperature (≈25 ev) in the discharge and measurements of the final electron temperature (≈1 ev) in the drifting plasma are taken as evidence for an acceleration of the ions by the space charge set up by the initially more energetic electrons. The angular distribution of the ejected plasma was isotropic and the plasma velocity was inversely proportional to the square root of the ion mass, in agreement with the theoretical explanation.