A SYSTEM FOR THE MEASUREMENT OF VELOCITY DISTRIBUTIONS OF MOLECULAR BEAMS
Abstract
A system for determining the velocity distributions of molecular beams is described in this report. This system utilizes the time-of-flight technique whereby the velocities are inferred by measuring the flight time of the beam molecules over a known flight distance. A quadrupole mass spectrometer and signal averaging devices are used to improve the signal-to-noise ratio in such a way that the system is applicable to velocity measurements in an environment of a relatively high background gas density. The system is evaluated by comparison of measured distributions of beams obtained from an effusive source with equivalent calculated Maxwellian distributions. Agreement was good enough that the gas temperature could be calculated from the experimental data by using a least squares computer program. Distributions for beam densities down to 2.7 x 10 to the 7th power molecules/cu.cm. in a total background of 3.24 x 10 to the 9th power molecules/cu.cm. were measured. The application of the system to studies involving gas-surface interactions and plume expansion processes from a nozzle is also discussed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1968
- Accession Number
- AD0675306
Entities
People
- H. M. Powell
- J. H. Heald Jr.
Organizations
- Arnold Engineering Development Complex