A comparison of flow velocities measured using an impact-pressure probe and electron time of flight in a supersonic flow. Implications for electron thermalization

The bulk velocity of electrons in a burst of plasma created in a uniform su personic how by a pulsed electron beam has been measured by a time-of-fligh t technique using a Langmuir probe. This velocity is compared with the neut ral-species bulk velocity deduced from impact-pressure measurements. This c omparison allows a determination of an upper limit of the electron drift ve locity to be made, which in turn shows that electrons are well thermalized in the how. Therefore this kind of flowing supersonic afterglow can be used for electron-attachment studies at very low temperatures.