Abstract

The advantages of the Fabry-Perot interferometer in resolution and luminosity are combined with those of a multichannel spectrometer for the investigation of spectral line shapes and shifts as a rapid function of time. The heart of the instrument is an array of concentric annular mirrors which perform the wavenumber separation, sending the light from each channel into a separate photomultiplier.

© 1965 Optical Society of America

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References

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  1. J. G. Hirschberg, J. Opt. Soc. Am. 50, 514 (1960).
  2. J. G. Hirschberg, R. Chabbal, Princeton Plasma Physics Laboratory Rept. MATT Q-20 (1962), p. 210.
  3. J. Katzenstein, Appl. Opt. 4, 263 (1965).
    [CrossRef]
  4. G. G. Shepherd, C. W. Lake, J. R. Miller, L. L. Cogger, Appl. Opt. 4, 267 (1965).
    [CrossRef]
  5. P. Jacquinot, J. Opt. Soc. Am. 44, 761 (1954).
    [CrossRef]
  6. J. E. Mack, D. P. McNutt, F. L. Roesler, R. Chabbal, Appl. Opt. 2, 873 (1963).
  7. C. R. Burnett, USAEC Rept. TID-7558 (1958), p. 472.
  8. N. Kapany, private communication, 1958.
  9. C. Breton, J. G. Hirschberg, Appl. Opt. 3, 731 (1964).
    [CrossRef]
  10. C. G. Fairclough, Rapport S.R.F.C. No. 31, EURATOMCEA, Fontenay-aux-Roses, Seine, France (1960).
  11. K. E. Weimer, Princeton Plasma Physics Laboratory Rept.TM-42 (1957, revised 1964).
  12. P. Platz, J. G. Hirschberg, Compt. Rend. (to be published).

1965 (2)

1964 (1)

1963 (1)

1960 (1)

J. G. Hirschberg, J. Opt. Soc. Am. 50, 514 (1960).

1954 (1)

Breton, C.

Burnett, C. R.

C. R. Burnett, USAEC Rept. TID-7558 (1958), p. 472.

Chabbal, R.

J. E. Mack, D. P. McNutt, F. L. Roesler, R. Chabbal, Appl. Opt. 2, 873 (1963).

J. G. Hirschberg, R. Chabbal, Princeton Plasma Physics Laboratory Rept. MATT Q-20 (1962), p. 210.

Cogger, L. L.

Fairclough, C. G.

C. G. Fairclough, Rapport S.R.F.C. No. 31, EURATOMCEA, Fontenay-aux-Roses, Seine, France (1960).

Hirschberg, J. G.

C. Breton, J. G. Hirschberg, Appl. Opt. 3, 731 (1964).
[CrossRef]

J. G. Hirschberg, J. Opt. Soc. Am. 50, 514 (1960).

J. G. Hirschberg, R. Chabbal, Princeton Plasma Physics Laboratory Rept. MATT Q-20 (1962), p. 210.

P. Platz, J. G. Hirschberg, Compt. Rend. (to be published).

Jacquinot, P.

Kapany, N.

N. Kapany, private communication, 1958.

Katzenstein, J.

Lake, C. W.

Mack, J. E.

McNutt, D. P.

Miller, J. R.

Platz, P.

P. Platz, J. G. Hirschberg, Compt. Rend. (to be published).

Roesler, F. L.

Shepherd, G. G.

Weimer, K. E.

K. E. Weimer, Princeton Plasma Physics Laboratory Rept.TM-42 (1957, revised 1964).

Appl. Opt. (4)

J. Opt. Soc. Am. (2)

P. Jacquinot, J. Opt. Soc. Am. 44, 761 (1954).
[CrossRef]

J. G. Hirschberg, J. Opt. Soc. Am. 50, 514 (1960).

Other (6)

J. G. Hirschberg, R. Chabbal, Princeton Plasma Physics Laboratory Rept. MATT Q-20 (1962), p. 210.

C. G. Fairclough, Rapport S.R.F.C. No. 31, EURATOMCEA, Fontenay-aux-Roses, Seine, France (1960).

K. E. Weimer, Princeton Plasma Physics Laboratory Rept.TM-42 (1957, revised 1964).

P. Platz, J. G. Hirschberg, Compt. Rend. (to be published).

C. R. Burnett, USAEC Rept. TID-7558 (1958), p. 472.

N. Kapany, private communication, 1958.

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Figures (11)

Fig. 1
Fig. 1

Fringe formation by the Fabry-Perot interferometer. The fringes occur at loci of equal θ = arcosn(2σμt)−1, and for monochromatic light form circles at the focus of the camera lens.

Fig. 2
Fig. 2

Ring separation by the multimirror. For clarity the number of multimirror elements is reduced to three (inclination angle ϕ somewhat exaggerated). Direction of the reflected rays into three directions is indicated, separated from each other by α and from the vertical by 2ϕ.

Fig. 3
Fig. 3

A tubular multimirror section. Twelve telescoping pieces were made and polished together to a mirror finish on the upper faces. The dimensions: ϕ was 5°; α and c, 5 mm and 26 mm, respectively; the extreme height of the kth tube was 90-5k mm (1 ≤ k ≤ 12); and dk−1 and dk are given in Table I.

Fig. 4
Fig. 4

The elements of the multimirror after polishing.

Fig. 5
Fig. 5

The afocal pair of lenses. The magnification, γ, is equal to fa/fb, where fa and fb are the focal lengths of lenses a and b, respectively.

Fig. 6
Fig. 6

Relative wavenumber span ( σ ¯ 12 σ ¯ 1 ) · σ 1 of the instrument as a function of γ.

Fig. 7
Fig. 7

Diagram of the entire instrument. For clarity, only one of the twelve channels is shown. An Ebert monochromator removes interfering orders, if necessary. A field lens and collimator focus the monochromator slit on the Fabry-Perot and the monochromator grating on the multimirror. The afocal pair of lenses a and b are chosen to give the correct value of γ for the line to be studied (see Fig. 8). The field and concentrating lenses serve to direct the light from each annular zone into the end-window photomultiplier.

Fig. 8
Fig. 8

Photograph of the device. The Fabry-Perot is seen at the top left. The twelve photomultipliers are seen just below with their associated cabling. Below them is a light-tight tube which receives the cone at its base containing the multimirror array. For alignment and focusing this is replaced with an identical cone containing a ground glass. On the lower right the Ebert premonochromator appears, and at the extreme right some of the bank of six double-beam oscilloscopes may be seen.

Fig. 9
Fig. 9

Instrumental function measurements. A narrow line of cadmium is used to obtain the instrumental shape, necessary in a line-width determination. Two values of interferometer spacing are used to check the similarity of the channels; the shape and breadth do not change.

Fig. 10
Fig. 10

Apparent ion temperatures, Ti, are shown as a function of time for several plasma events (shots) for each of the two conditions listed in Table II. Ti is shown to rise more steeply where the discharge consists principally of hydrogen with a small percentage of helium than in the reverse case.

Fig. 11
Fig. 11

A comparison between the observed line shape (points) and a Gaussian. The small departures are taken to be within the errors of the experiment.

Tables (2)

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Table I Diameters of the Twelve Mirrors Used in the Fontenay-aux-Roses Instrument

Tables Icon

Table II Gas Filling Conditions

Equations (14)

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n = 2 σ μ t cos θ ,
σ σ 0 = 1 2 σ θ 2 ,
Δ σ = Δ S σ ( 2 π f 2 ) 1 ,
d ¯ k = [ 1 2 ( d k 2 + d k 1 2 ) ] ½ .
δ σ = σ ( d ¯ N 2 d ¯ 1 2 ) / 8 f 2 ,
δ σ = σ ( d ¯ N 2 d ¯ 1 2 ) / 8 f 0 2 γ 2 .
U ( σ ) = 0 G ( σ ) S ( σ σ ) d σ ,
U k ( σ ) = 0 H ( σ ) S k ( σ σ ) d σ .
U ( σ ¯ 1 ) = 0 S 1 ( σ ¯ 1 σ ) G ( σ ) d σ , U ( σ ¯ 2 ) = 0 S 2 ( σ ¯ 2 σ ) G ( σ ) d σ , U ( σ ¯ N ) = 0 S N ( σ ¯ N σ ) G ( σ ) d σ .
U ( σ ¯ k ) = 0 H ( σ ) S ( σ σ ¯ k ) d σ .
U ( σ ¯ k ) = 0 G ( σ ¯ ) U ( σ σ ¯ k ) d σ .
Γ D = ( Γ U 2 Γ S 2 ) ½ ,
T D = 1.69 × 10 8 M ( Γ D / σ ) 2 ,
γ = 0.48 ( σ ¯ N σ ¯ 1 = 8.34 cm 1 ) ,

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