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Spectrophotometric Observations of Hydrogen Arc-Jets

  • R. L. Fox
Conference paper
Part of the Developments in Applied Spectroscopy book series (DAIS, volume 3)

Abstract

The object of the work reported herein was to study the applicability of spectrophotometric methods for determining the physical and chemical characteristics of hydrogen arc-jets operating in the power range of 20 to 42 kW. The spectrum was observed from 2500 to 7000 A. No molecular spectra were detected in these spectral scans, nor were there any measurable impurities present in the plume. The visible plasma radiation was emitted at the wavelengths of the hydrogen Balmer lines, but the continuum beyond the series limit was not detectable. The excitation temperatures at various points ranged from 2000 to 15,000 K, with the hottest temperature being in the arc region of the engine. The experimental temperatures were higher than the calculated bulk average temperatures. Electron densities in the plume were less than 1013 electrons/cm3 and in the arc about 1016 electrons/cm3. The results of this investigation indicate that (1) the population of excited states obeys Boltzmann’s law; (2) the plasma is optically thin in the visible region; and (3) apparently the plasma is not in chemical equilibrium.

Keywords

Exit Nozzle Local Thermodynamic Equilibrium Nonrelativistic Quantum Mechanic Plume Region Maxwellian Velocity Distribution 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Abbreviations

Notation

Anm

Einstein probability for pure emission

Bλ(T)

Blackbody function

Cp

Specific heat at constant pressure

Cv

Specific heat at constant volume

d

Diameter of particle

e

Electronic charge

Enm

Energy of proton emitted in nm transition

fe(\(\vec v\))

Non-normalized Maxwellian distribution of the electrons

f(v)dv

Probability of a particle having a velocity between v and v + dv

fnm

Oscillator strength of nm transition

F(x)

Spectrometer observation at position x

gn

Statistical weight of the n th quantum state

h

Planck’s constant

Iline

Intensity of spectrum line

Inm

Spectral intensity in an nm transition

I (r)

Actual radiation from plasma cyclinder of radius r

k

Boltzmarm constant

m

Mass of particle

N

Number density of particles

\(\hat N\)

Number density of particles which could cause excitation

N0

Electron population of ground state

Nn

Electron population of the n th quantum state

P

Pressure

Rlamp

Phototube responses to standard lamp

Rline

Phototube responses to spectrum line

RA

Radius of nozzle in arc region

Rp

Radius of the plume exit

T

Thermodynamic temperature

VA

Plasma velocity in the arc region

VP

Plasma velocity at the plume exit

v

Velocity of particle

Z(r), Z(r+1)

Partition function of neutral and ionized hydrogen, respectively

ε(λ, T)

Emissivity of tungsten

λmn

Wavelength of radiation resulting from n→m transition

ve,a

Collision frequency between and electron and an atom having energy greater than the excitation energy

X(r)

Ionization potential

Subscripts

a

Atom

A

Arc

e

Electron

H

Hydrogen atom

P

Plume

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References

  1. 1.
    L. H. Aller, The Atmospheres of the Stars and Sun, Ronald Press, New York, (1953).Google Scholar
  2. 2.
    Van Camp. W. M., McVey, F. D., Merrifield, S. E., Painter, J. H., Brock, F. J., Fox, R. L., “Hydrogen Arc Jet Exhaust Diagnostics,”. McDonnell Report No. 9621, (1963).Google Scholar
  3. 3.
    Dickerman, P. J., Optical Spectrometric Measurements of High Temperatures, University of Chicago Press, (1961).Google Scholar
  4. 4.
    Poland, D. E., Green, J. W., and Margrave, J. L., “Corrected Optical Pyrometer Readings,” NBS Monograph 30, (1961).Google Scholar
  5. 5.
    Present, R. D., Kinetic Theory of Gases, McGraw-Hill Book Co. Inc., (1958).Google Scholar

Copyright information

© Chicago Section of the Society for Applied Spectroscopy 1964

Authors and Affiliations

  • R. L. Fox
    • 1
  1. 1.McDonnell Aircraft Corp.St. LouisUSA

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