Accession Number : AD0720833

Title :   Theory of the External Sheath Structure and Ion Collection Characteristics of a Rocket-Borne Mass Spectrometer.

Descriptive Note : Final rept. 2 Sep 69-30 Nov 70,

Corporate Author : MOUNT AUBURN RESEARCH ASSOCIATES INC CAMBRIDGE MASS

Personal Author(s) : Parker,Lee W.

Report Date : 30 NOV 1970

Pagination or Media Count : 84

Abstract : The ion current density at the central point (orifice) of a charged mass-spectrometer plate mounted on a rocket is a function of physical parameters, including the plate voltage, the plate and rocket geometry, the Debye length, and the drift velocity of the ions relative to the plate. Computer calculations are performed to evaluate the current density for chosen values of the physical parameters. It is shown that the current density is a monotonic and linearly increasing function of the plate potential, but may behave non-monotonically with ion drift velocity. For a plate potential 200 kT/e, where T is the electron temperature, and Debye lengths larger than 1/5 the plate radius- the ion current density at unit ion Mach number is more than 100 times the random thermal current density, or more than 27.5 times larger than the value predicted by the 'planar approximation' formula. The current-voltage characteristics and their dependence on Mach number are qualitatively similar to those for a moving sphere. The electric field enhances the current collected, for any ion Mach number. The enhancement becomes negligible only when the Mach number becomes large compared with the square root of the dimensionless plate potential. (Author)

Descriptors :   (*ATMOSPHERIC SOUNDING, MASS SPECTROSCOPY), (*IONOSPHERE, IONIC CURRENT), IONS, SPECTRUM ANALYZERS, PLASMA SHEATHS, SOUNDING ROCKETS, DIFFERENCE EQUATIONS, SAMPLING, ITERATIONS

Subject Categories : Atmospheric Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE