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 supersonic flow by a pulsed electron beam has been measured by a time-of-flight technique using a Langmuir probe. This velocity is compared with the neutral-species bulk velocity deduced from impact-pressure measurements. This comparison allows a determination of an upper limit of the electron drift velocity to be made, which in turn shows that electrons are well thermalized in the flow. Therefore this kind of flowing supersonic afterglow can be used for electron-attachment studies at very low temperatures.

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