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.
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Abbreviations
- A nm :
-
Einstein probability for pure emission
- Bλ(T):
-
Blackbody function
- C p :
-
Specific heat at constant pressure
- C v :
-
Specific heat at constant volume
- d :
-
Diameter of particle
- e :
-
Electronic charge
- E nm :
-
Energy of proton emitted in n → m transition
- f e(\(\vec v\)):
-
Non-normalized Maxwellian distribution of the electrons
- f(v)dv :
-
Probability of a particle having a velocity between v and v + dv
- f nm :
-
Oscillator strength of n → m transition
- F(x):
-
Spectrometer observation at position x
- g n :
-
Statistical weight of the n th quantum state
- h :
-
Planck’s constant
- I line :
-
Intensity of spectrum line
- I nm :
-
Spectral intensity in an n → m 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
- N 0 :
-
Electron population of ground state
- N n :
-
Electron population of the n th quantum state
- P :
-
Pressure
- R lamp :
-
Phototube responses to standard lamp
- R line :
-
Phototube responses to spectrum line
- R A :
-
Radius of nozzle in arc region
- R p :
-
Radius of the plume exit
- T :
-
Thermodynamic temperature
- V A :
-
Plasma velocity in the arc region
- V P :
-
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
- λ mn :
-
Wavelength of radiation resulting from n→m transition
- v e,a :
-
Collision frequency between and electron and an atom having energy greater than the excitation energy
- X (r) :
-
Ionization potential
- a :
-
Atom
- A :
-
Arc
- e :
-
Electron
- H :
-
Hydrogen atom
- P :
-
Plume
References
L. H. Aller, The Atmospheres of the Stars and Sun, Ronald Press, New York, (1953).
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).
Dickerman, P. J., Optical Spectrometric Measurements of High Temperatures, University of Chicago Press, (1961).
Poland, D. E., Green, J. W., and Margrave, J. L., “Corrected Optical Pyrometer Readings,” NBS Monograph 30, (1961).
Present, R. D., Kinetic Theory of Gases, McGraw-Hill Book Co. Inc., (1958).
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© 1964 Chicago Section of the Society for Applied Spectroscopy
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Fox, R.L. (1964). Spectrophotometric Observations of Hydrogen Arc-Jets. In: Forrette, J.E., Lanterman, E. (eds) Developments in Applied Spectroscopy. Developments in Applied Spectroscopy, vol 3. Springer, Boston, MA. https://doi.org/10.1007/978-1-4684-8688-9_19
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DOI: https://doi.org/10.1007/978-1-4684-8688-9_19
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