Abstract

An analysis is made of the errors that arise in line-intensity measurements due to the experimental averaging of the time-varying intensities caused by electron-temperature fluctuations in continuous-plasma sources. These calculations are made both for periodic and for random electron-temperature fluctuations. The errors are dependent on the method of measurement. The possible errors in the monochromator method usually positive and significant for typical spectral lines and electron temperatures. An alternative method, which is shown to be subject to less error, is to use a polychromator and to measure the average of the instantaneous line-intensity ratio. In either method (but more applicable to the monochromator method) the additional measurement of the root-mean-square value of the intensity ratio gives another set of equations and allows the determination of both the mean electron temperature and the oscillation amplitude or standard deviation for gaussian-noise temperature fluctuations.

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  1. D. A. Lee and A. Garscadden, J. opt. Soc. Am. 56, 1698 (1966).
  2. J. Burns, Northwestern University, "Non-Linear Corrections to Spectroscopic Temperature Measurements in Turbulent Arc Plas na," AD 665143 (Natl. Tech. Information Service, Springfield, Va. 22151).
  3. J. S. Bendat and A. G. Piersol, Measurement and Analysis of Random Data (Wiley, New York, 1967).
  4. W. J. Pearce, Plasma-Jet Temperature Measurement in optical Spectrometric Measurement of High Temperatures, edited by P. J. Dickerman (University of Chicago Press, 1960), p. 125.
  5. All of the calculations involving the truncation of a gaussian distribution in this paper have been for an assumed value of L = 3. We find that taking L = 6 makes a difference of less than 1% in the results, and that σ is the important parameter describing the noise properties, provided that L≥3. As the results are functions of several parameters, only representative results are given in this paper. An internal report with more examples will be made available to interested persons.
  6. In principle, it is possible to use the polychromator method also; however, as indicated, for values of ΔE/kT~2, the average intensity ratio is insensitive to the fluctuation amplitude.

Bendat, J. S.

J. S. Bendat and A. G. Piersol, Measurement and Analysis of Random Data (Wiley, New York, 1967).

Burns, J.

J. Burns, Northwestern University, "Non-Linear Corrections to Spectroscopic Temperature Measurements in Turbulent Arc Plas na," AD 665143 (Natl. Tech. Information Service, Springfield, Va. 22151).

Garscadden, A.

D. A. Lee and A. Garscadden, J. opt. Soc. Am. 56, 1698 (1966).

Lee, D. A.

D. A. Lee and A. Garscadden, J. opt. Soc. Am. 56, 1698 (1966).

Pearce, W. J.

W. J. Pearce, Plasma-Jet Temperature Measurement in optical Spectrometric Measurement of High Temperatures, edited by P. J. Dickerman (University of Chicago Press, 1960), p. 125.

Piersol, A. G.

J. S. Bendat and A. G. Piersol, Measurement and Analysis of Random Data (Wiley, New York, 1967).

Other (6)

D. A. Lee and A. Garscadden, J. opt. Soc. Am. 56, 1698 (1966).

J. Burns, Northwestern University, "Non-Linear Corrections to Spectroscopic Temperature Measurements in Turbulent Arc Plas na," AD 665143 (Natl. Tech. Information Service, Springfield, Va. 22151).

J. S. Bendat and A. G. Piersol, Measurement and Analysis of Random Data (Wiley, New York, 1967).

W. J. Pearce, Plasma-Jet Temperature Measurement in optical Spectrometric Measurement of High Temperatures, edited by P. J. Dickerman (University of Chicago Press, 1960), p. 125.

All of the calculations involving the truncation of a gaussian distribution in this paper have been for an assumed value of L = 3. We find that taking L = 6 makes a difference of less than 1% in the results, and that σ is the important parameter describing the noise properties, provided that L≥3. As the results are functions of several parameters, only representative results are given in this paper. An internal report with more examples will be made available to interested persons.

In principle, it is possible to use the polychromator method also; however, as indicated, for values of ΔE/kT~2, the average intensity ratio is insensitive to the fluctuation amplitude.

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