The Effusion of Charged Particles from a Shock Heated Gas

Author: Sturtevant, Bradford

Year: 1960

Degree: Dissertation (Ph.D.)

Advisor: Liepmann, Hans Wolfgang

Committee Member: Unknown, Unknown

Option: Aeronautics

DOI: 10.7907/PCNN-DW03

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document.

An experimental and theoretical investigation is made of the application of a molecular beam type sampling device for studying low density shock tube flows to the case of slowly ionizing argon behind a reflected shock wave. The flux of charged particles from a gas heated to about 10,OOO[degrees]K and 20 mm. Hg. through a small orifice in the shock tube end wall is measured. The processes determining this flux are the initial stages of ionization in argon and the diffusion of charged particles to a cold metallic wall. Providing the diffusion process is understood, the measurements constitute a direct observation of incipient ionization ([...]).

The transient charge diffusion mechanism is studied in detail theoretically, avoiding the assumption of ambipolar diffusion. It is concluded that the major problem lies in the understanding of the wall-gas interaction as represented by boundary conditions at the wall. An approximate relation for charge effusion is derived.

It is concluded from the experimental results that the initial ionization can not be due to a single step, electron-atom collision process but must result from a series of several atom-atom collisions resulting in the ionization of argon atoms.

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