Measurement of Gas Density by Electron Scattering
Measurement of Gas Density by Electron Scattering

Author: J. W. Cunningham

Publisher:

Published: 1967

Total Pages: 113

ISBN-13:

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It is theoretically possible to infer the density of a gas from the rate at which particles are scattered out of a beam of subatomic particles which is passed through the gas. This technique offers the possibility of a probeless density measurement which is independent of the state of the gas. Previous research verified that this technique could be implemented using a gamma ray beam, but that the best spatial resolution and measuring time which could be achieved were inadequate to allow the technique to be applied to a low density test facility. In the research reported, the technique was applied using a 50,000-v electron beam. It was found that excellent spatial resolution and measuring time could be achieved at densities as low as 6 x 10 to the -8th power gm/cc. Density profiles were measured in a low density wind tunnel with a nozzle exit diameter of 18 in. and an open jet test section. A spatial resolution of about 1 cm was achieved, and measurements required 10 sec per point. This measuring time can probably be reduced by several orders of magnitude if necessary. The densities measured were repeatable within 1 percent. Accuracy, spatial resolution, and measuring time are found to be interrelated. The constraint on the combination is discussed in detail. The design of equipment is discussed. (Author).

A Technique for Measuring a Local Gas Density Using Scattered Gamma Radiation
A Technique for Measuring a Local Gas Density Using Scattered Gamma Radiation

Author: J. E. Shepard

Publisher:

Published: 1963

Total Pages: 33

ISBN-13:

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A method for direct density measurement of a gas without the use of material probes is proposed and the experimental investigation summarized. The operation of the gas density measuring instrument is based upon the interaction between a gamma-ray beam and the electrons in the gas as described by the Compton scattering principle. Experimental results indicate the practicability of this instrument for use in low density, high temperature wind tunnels and other high temperature gas flows such as rocket exhausts. (Author).

Flow Visualization and Quantitative Gas Density Measurements in Rarefied Gas Flows
Flow Visualization and Quantitative Gas Density Measurements in Rarefied Gas Flows

Author: Robert C. MacArthur

Publisher:

Published: 1962

Total Pages: 50

ISBN-13:

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The use of an electron beam to stimulate emission from a gas with the resultant beam intensity providing a measure of point-by-point gas density has been investigated. The tests have been conducted in the 1 to 200 micron pressure range, at standard temperature, employing a 5 to 20 kev electron beam. Analysis was performed by photographing the beam at conditions of varying density, and examining the film by means of a microdensitometer. A low-cost electron gun capable of projecting a 20 kev, Soomicroampere beam across a 24-inch test charnber was successfully developed. The results of the program indicate that at the beam voltages employed. scattering of the electrons by the atoms of the gas severely limits the particular technique used. The analytical and experimental results of the program indicate that gas density measurement and flow visualization may be possible by employing a more energetic electron beam. By observation of the beam-excited emission spectra, it is possible to measure the rotational and vibrational temperature of the nitrogen molecules as well as the number density of nitrogen molecules in the gas. Further investigation of this latter electron beam technique as a diagnostic technique in hypervelocity flows is recommended.

Electron Scattering
Electron Scattering

Author: Colm T. Whelan

Publisher: Springer Science & Business Media

Published: 2006-01-17

Total Pages: 342

ISBN-13: 0387275673

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There is a unity to physics; it is a discipline which provides the most fundamental understanding of the dynamics of matter and energy. To understand anything about a physical system you have to interact with it and one of the best ways to learn something is to use electrons as probes. This book is the result of a meeting, which took place in Magdalene College Cambridge in December 2001. Atomic, nuclear, cluster, soHd state, chemical and even bio- physicists got together to consider scattering electrons to explore matter in all its forms. Theory and experiment were represented in about equal measure. It was meeting marked by the most lively of discussions and the free exchange of ideas. We all learnt a lot. The Editors are grateful to EPSRC through its Collaborative Computational Project program (CCP2), lOPP, the Division of Atomic, Molecular, Optical and Plasma Physics (DAMOPP) and the Atomic Molecular Interactions group (AMIG) of the Institute of Physics for financial support. The smooth running of the meeting was enormously facilitated by the efficiency and helpfulness of the staff of Magdalene College, for which we are extremely grateful. This meeting marked the end for one of us (CTW) of a ten-year period as a fellow of the College and he would like to take this opportunity to thank the fellows and staff for the privilege of working with them.

Flow Visualization and Quantitative Gas Density Measurements in Rarefield Gas Flows
Flow Visualization and Quantitative Gas Density Measurements in Rarefield Gas Flows

Author: ROBERT C. MACARTHUR

Publisher:

Published: 1962

Total Pages: 48

ISBN-13:

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The use of an electron beam to stimulate emission from a gas with the resultant beam intensity providing a measure of point-by-point gas density has been investigated. The tests have been conducted in the 1 to 200 micron pressure range, at standard temperature, employing a 5 to 20 kev electron beam. Analysis was performed by photographing the beam at conditions of varying density, and examining the film by means of a microdensitometer. A low-cost electron gun capable of projecting a 20 kev, Soomicroampere beam across a 24-inch test charnber was successfully developed. The results of the program indicate that at the beam voltages employed. scattering of the electrons by the atoms of the gas severely limits the particular technique used. The analytical and experimental results of the program indicate that gas density measurement and flow visualization may be possible by employing a more energetic electron beam. By observation of the beam-excited emission spectra, it is possible to measure the rotational and vibrational temperature of the nitrogen molecules as well as the number density of nitrogen molecules in the gas. Further investigation of this latter electron beam technique as a diagnostic technique in hypervelocity flows is recommended.

Scientific and Technical Aerospace Reports
Scientific and Technical Aerospace Reports

Author:

Publisher:

Published: 1987

Total Pages: 1390

ISBN-13:

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Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.