Abstract

The performance of a plane, unblazed grating (600 lines/mm) as a predisperser has been investigated. Placed 7 cm in front of the primary slit of a 2-m grazing incidence vacuum spectrograph, the foregrating allowed passage of uv (100 to 500 Å) into the spectrograph in 50 to 150 Å bands. The spurious background observed when radiation passed directly through the primary slit was found to be absent from the predispersed spectra, which have been observed by both photographic and photoelectric methods. These spectra, free from scattered background and second-order images, exhibited measurable line displacement, up to 0.3 mm from the line image positions of the direct spectra. Such displacement, occuring naturally with the plane foregrating and shown to be in agreement with theoretical predictions, are sometimes found as a result of source misalignment with grazing incidence instruments. Use was made of the foregrating for isolation of true continuum radiation for the Vodar vacuum sliding spark and linear pinch sources.

© 1966 Optical Society of America

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References

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    [Crossref]
  17. Josef Gschwendtner designed and built this source.
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  20. J. C. Miller, J. Opt. Soc. Am. 54, 353 (1964).
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  21. T. Namioka, J. Opt. Soc. Am. 49, 450 (1959).

1965 (1)

G. L. Weissler, ICO Conference, September 1964, Tokyo and Kyoto, Japan. J. Appl. Phys. Suppl. 4, 486 (1965).

1964 (3)

E. Alexander, U. Feldman, and B. S. Fraenkel, J. Quant. Spectry. Radiative Transfer 4, 501 (1964).
[Crossref]

H. Schindler, Z. Naturforsch. 19a, 697 (1964).

J. C. Miller, J. Opt. Soc. Am. 54, 353 (1964).
[Crossref]

1963 (2)

1962 (1)

1961 (1)

C. R. Detwiler, J. D. Purcell, and R. Tousey, Mem. Soc. Roy. Sci. Liège 4, 253 (1961).

1960 (2)

J. D. Purcell and R. Tousey, J. Geophys. Res. 65, 370 (1960); Mem. Soc. Roy. Sci. Liège 4, 283 (1961).
[Crossref]

G. Balloffet, Ann. Phys. (France) 5, 1256 (1960).

1959 (1)

T. Namioka, J. Opt. Soc. Am. 49, 450 (1959).

1957 (2)

1955 (2)

1954 (1)

P. A. Brix and G. Herzberg, Can. J. Phys. 32, 110 (1954).
[Crossref]

1950 (1)

B. Vodar and N. Astoin, Nature 166, 1029 (1950).
[Crossref]

1947 (1)

1931 (1)

Alexander, E.

E. Alexander, U. Feldman, and B. S. Fraenkel, J. Quant. Spectry. Radiative Transfer 4, 501 (1964).
[Crossref]

Astoin, N.

B. Vodar and N. Astoin, Nature 166, 1029 (1950).
[Crossref]

Balloffet, G.

G. Balloffet, Ann. Phys. (France) 5, 1256 (1960).

Bedo, D. E.

Brix, P. A.

P. A. Brix and G. Herzberg, Can. J. Phys. 32, 110 (1954).
[Crossref]

Davis, S. P.

Detwiler, C. R.

C. R. Detwiler, J. D. Purcell, and R. Tousey, Mem. Soc. Roy. Sci. Liège 4, 253 (1961).

Douglas, A. E.

Eldén, B.

Feldman, U.

E. Alexander, U. Feldman, and B. S. Fraenkel, J. Quant. Spectry. Radiative Transfer 4, 501 (1964).
[Crossref]

Fraenkel, B. S.

E. Alexander, U. Feldman, and B. S. Fraenkel, J. Quant. Spectry. Radiative Transfer 4, 501 (1964).
[Crossref]

Herzberg, G.

A. E. Douglas and G. Herzberg, J. Opt. Soc. Am. 47, 625 (1957).
[Crossref]

P. A. Brix and G. Herzberg, Can. J. Phys. 32, 110 (1954).
[Crossref]

Jarrell, R. F.

Mack, J. E.

Marquet, L. C.

Miller, J. C.

Murty, M. V. R. K.

Namioka, T.

T. Namioka, J. Opt. Soc. Am. 49, 450 (1959).

Pierce, A. K.

Purcell, J. D.

C. R. Detwiler, J. D. Purcell, and R. Tousey, Mem. Soc. Roy. Sci. Liège 4, 253 (1961).

J. D. Purcell and R. Tousey, J. Geophys. Res. 65, 370 (1960); Mem. Soc. Roy. Sci. Liège 4, 283 (1961).
[Crossref]

Reader, J.

Sawyer, R. A.

R. A. Sawyer, Experimental Spectroscopy (Prentice-Hall, Inc., New York, 1951), p. 153.

Schindler, H.

H. Schindler, Z. Naturforsch. 19a, 697 (1964).

Sprague, G.

Stehn, J. R.

Tomboulian, D. H.

Tousey, R.

C. R. Detwiler, J. D. Purcell, and R. Tousey, Mem. Soc. Roy. Sci. Liège 4, 253 (1961).

J. D. Purcell and R. Tousey, J. Geophys. Res. 65, 370 (1960); Mem. Soc. Roy. Sci. Liège 4, 283 (1961).
[Crossref]

Vodar, B.

B. Vodar and N. Astoin, Nature 166, 1029 (1950).
[Crossref]

Weissler, G. L.

G. L. Weissler, ICO Conference, September 1964, Tokyo and Kyoto, Japan. J. Appl. Phys. Suppl. 4, 486 (1965).

Wood, R. W.

Ann. Phys. (France) (1)

G. Balloffet, Ann. Phys. (France) 5, 1256 (1960).

Appl. Opt. (1)

Can. J. Phys. (1)

P. A. Brix and G. Herzberg, Can. J. Phys. 32, 110 (1954).
[Crossref]

ICO Conference, September 1964, Tokyo and Kyoto, Japan (1)

G. L. Weissler, ICO Conference, September 1964, Tokyo and Kyoto, Japan. J. Appl. Phys. Suppl. 4, 486 (1965).

J. Geophys. Res. (1)

J. D. Purcell and R. Tousey, J. Geophys. Res. 65, 370 (1960); Mem. Soc. Roy. Sci. Liège 4, 283 (1961).
[Crossref]

J. Opt. Soc. Am. (10)

J. Quant. Spectry. Radiative Transfer (1)

E. Alexander, U. Feldman, and B. S. Fraenkel, J. Quant. Spectry. Radiative Transfer 4, 501 (1964).
[Crossref]

Mem. Soc. Roy. Sci. Liège (1)

C. R. Detwiler, J. D. Purcell, and R. Tousey, Mem. Soc. Roy. Sci. Liège 4, 253 (1961).

Nature (1)

B. Vodar and N. Astoin, Nature 166, 1029 (1950).
[Crossref]

Z. Naturforsch. (1)

H. Schindler, Z. Naturforsch. 19a, 697 (1964).

Other (2)

Josef Gschwendtner designed and built this source.

R. A. Sawyer, Experimental Spectroscopy (Prentice-Hall, Inc., New York, 1951), p. 153.

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Figures (15)

Fig. 1
Fig. 1

Optical arrangement of a 2-m vacuum spectrograph with a predisperser grating. Radiation from one source is incident directly on the primary slit (P) and from the other is dispersed by the foregrating (G′). The position of the main grating (G) and photographic plate (R) is shown. The inset shows the rotation of G′, for selection of the passband Δλ, and the lateral motion for removing G′ from the optic axis.

Fig. 2
Fig. 2

Sagittal (rs) focal curve and tangential [rt(α)] focal curve of a plane grating for several angles of incidence (α).

Fig. 3
Fig. 3

Schematic representation of virtual-source image points, sagittal (Ss) and tangential (St), in relation to the primary slit of the spectrograph. The distance OP = r0 (distance from grating center to primary slit); OSs = r (distance from grating center to real source); OSt = rt, a function of angle of incidence α.

Fig. 4
Fig. 4

(a) Arrangement of primary slit, plane grating, real source (S) and virtual focal curve (F). Indicated are positions of virtual source images of several wavelengths. The passband of the primary slit may be defined as that range of wavelengths between λ2 and λ4. (b) Intensity patterns produced by on- and off-axis virtual source images illustrating passband intensity distribution.

Fig. 5
Fig. 5

Image displacement (A to B) in a concave-grating spectrograph resulting from an off-axis virtual source (S′).

Fig. 6
Fig. 6

Plane view of vacuum uv instrument illustrating monochromator operation with attached experimental chamber.

Fig. 7
Fig. 7

Ceramic capillary-spark source. The spark passes from the water-cooled high-voltage electrode (B) through the capillary drilled into a boron-nitride cylinder (C) to an electrode (D), which is also water cooled. The ground-return current flows from (D) via the water-cooled cylindrical enclosure (F) back to the discharge capacitor (not shown) by way of a high-voltage cable (G). Gas and water inlet lines are insulated from the external shield by lucite spacers. The source as a whole is electrically separated from the monochromator or spectrograph by the lucite cylindrical spacers (E).

Fig. 8
Fig. 8

Microdensitometer traces of spectra obtained with (a) capillary spark, (b) two-electrode sliding vacuum spark, (c) three-electrode vacuum spark (Vodar source), and (d) linear-pinch source. The clear plate or residual plate-fog level f is indicated by a dashed line.

Fig. 9
Fig. 9

Microdensitometer recording showing both direct and predispersed capillary-spark spectra. (a) shows the direct spectrum with a strong background of stray light and superimposed lines, 10-sec exposure time; (b) the predispersed radiation with grating angle = 8 3 4 °, 6 min; (c) 8°, 1 min; (d) 7 1 4 °, 1 min; (e) 6 1 2 °, 1 min.

Fig. 10
Fig. 10

Three-electrode vacuum-spark spectrum. (a) shows microdensitometer recording of direct spectrum with the continuum and superimposed lines, (b) the predispersed radiation with grating angle = 8 1 4 °, (c) 8°.

Fig. 11
Fig. 11

Photomultipler recording showing on the upper trace the direct and on the lower one the predispersed ( = 8°) capillary-spark spectrum. At the point 0 the shutter was opened allowing the source radiation to enter the spectrograph. Time progresses from right to left.

Fig. 12
Fig. 12

Observed intensity distributions of zero order (CI), first-order inside, and first-order outside, for the plane-predisperser grating. A distribution is obtained by fixing the detector at a given wavelength and rotating the foregrating through the angles .

Fig. 13
Fig. 13

Ratio of outside to inside first-order intensities. The solid line represents the estimated variation of this ratio. Open circles represent experimental observations.

Fig. 14
Fig. 14

Parameters used to define image displacement resulting from use of plane-grating predisperser.

Fig. 15
Fig. 15

Spectral-line displacement (Δx) as calculated from Eq. (8) (solid and dashed lines) and observed (plotted points) for two foregrating angles.

Equations (11)

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r t = - ( cos β / cos α ) 2 r
r s = - r ,
N λ = σ ( sin α + sin β ) ,
I ( diffracted ) / I ( incident ) [ cos β / ( r + r 0 ) 2 + cos β / ( r cos 2 β / cos 2 α + r 0 ) 2 ] cos α / r 2 .
R P N = D N 2 | n 2 cos α - ( n 2 - sin 2 β ) 1 2 n 2 cos β + ( n 2 - sin 2 β ) 1 2 | 2 ( cos β cos α )
R S N = D N 2 | cos α - ( n 2 - sin 2 β ) 1 2 cos β + ( n 2 - sin 2 β ) 1 2 | 2 ( cos β cos α ) .
n 2 = 1 - ζ λ 2 ,
Δ β ¯ = ( A 0 / 2 R 3 cos α ¯ cos 2 β ¯ 0 ) w ¯ 3 ,
Δ x ¯ = [ ( sin 2 α ¯ / cos α ¯ + sin 2 β ¯ 0 / cos β ¯ 0 ) / 2 R 2 cos β ¯ 0 ] w ¯ 3 .
w ¯ = R [ tan ( β - ) - r 0 / r t cos ( β - ) + tan α ¯ ] - 1 .
β - = π / 2 implies Δ x ¯ = 0 , β - < π / 2 implies Δ x ¯ < 0 ( shift toward short λ ) , β - > π / 2 implies Δ x ¯ > 0 ( shift toward long λ ) .