Accession Number : AD0671915

Title :   EXPERIMENTS ON SCATTERING OF MONO-ENERGETIC ARGON BEAMS BY HEATED PLATINUM,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE FLUID DYNAMICS RESEARCH LAB

Personal Author(s) : Moran,James Patrick

Report Date : FEB 1968

Pagination or Media Count : 230

Abstract : Time-of-flight (TOF) measurements were made in both heated and unheated initially mono-energetic argon beams before and after reflection from heated platinum targets. A new and quite simple beam source is described which generates the high intensity, nearly mono-energetic incident beam. Targets were prepared by chemical cleaning. Beams directed at these targets were reflected in directed nonspecular lobes and the molecular TOF distributions in these lobes were investigated. Low order moments of the velocity distribution are obtained directly from the TOF data by integrating the TOF curves after they are weighted by appropriate, derived functions. Relative number flux, momentum flux and energy flux are obtained and ratios of these fluxes yield mean speed and mean energy as a function of angle of reflection. These flux moments are also used to calculate a speed ratio which provides a measure of spread in speed distribution divided by the mean speed. These integrated results are presented for incident beam angles of 20, 40, 55, 65, and 80 degrees, to the target normal and a target temperature of 1000C. In all cases reflected mean momentum and energy show a marked angular dependence, decreasing with increasing angle of reflection from the target normal at a given angle of incidence. The mean tangential velocity is close to the incident beam value over a range of reflection angles which contain most of the reflected particles. The speed ratio at all angles of reflection is appreciably larger than the incident beam value. The differential energy accommodation coefficient increases with increasingly glancing angles and decreases with increasing angle of reflection. (Author)

Descriptors :   (*MOLECULAR BEAMS, SCATTERING), (*ARGON, SCATTERING), KINETIC THEORY, SURFACE PROPERTIES, INTERACTIONS, HEAT TRANSFER, PLATINUM, REFLECTION, TARGETS, VELOCITY, FUNCTIONAL ANALYSIS, MOMENTUM, ENERGY

Subject Categories : Aerodynamics
      Fluid Mechanics
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE