Abstract

The ultraviolet characteristics of a 0.5-kw d.c. arc through high pressure xenon were investigated. The lamp has a quartz envelope and contains pure xenon under a pressure of roughly 20 atmospheres when operating; its general characteristics have been described by Schulz. The absolute spectral radiance between 2000A and 5000A was measured photographically by comparison with the positive crater of a spectroscopically pure carbon arc. An ultraviolet radiance contour map of the arc stream was obtained by analysis of direct photographs. It was found that the lamp radiates a smooth ultraviolet continuum, which extends to the air cut-off and is interrupted by only a few weak lines. The radiance of the central spot exceeds that of the carbon crater by a factor of 23 at 2500A, 12 at 3000A, and 6 at 3500A. Comparison with other ultraviolet-continuum sources shows the xenon arc to be unusually intense.

© 1950 Optical Society of America

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References

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  1. P. Schulz, Zeits. f. Naturforschung 2a, 583 (1947); Ann. d. Physik 1, 95 (1947); Ann. d. Physik 1, 107 (1947).
  2. H. G. MacPherson, J. Opt. Soc. Am. 30, 189 (1940).
    [Crossref]
  3. A. S. Allen and R. G. Franklin, J. Opt. Soc. Am. 29, 453 (1939).
    [Crossref]
  4. C. H. Matz and D. P. Merrill, J. Opt. Soc. Am. 39, 635A (1949).

1949 (1)

C. H. Matz and D. P. Merrill, J. Opt. Soc. Am. 39, 635A (1949).

1947 (1)

P. Schulz, Zeits. f. Naturforschung 2a, 583 (1947); Ann. d. Physik 1, 95 (1947); Ann. d. Physik 1, 107 (1947).

1940 (1)

1939 (1)

Allen, A. S.

Franklin, R. G.

MacPherson, H. G.

Matz, C. H.

C. H. Matz and D. P. Merrill, J. Opt. Soc. Am. 39, 635A (1949).

Merrill, D. P.

C. H. Matz and D. P. Merrill, J. Opt. Soc. Am. 39, 635A (1949).

Schulz, P.

P. Schulz, Zeits. f. Naturforschung 2a, 583 (1947); Ann. d. Physik 1, 95 (1947); Ann. d. Physik 1, 107 (1947).

J. Opt. Soc. Am. (3)

Zeits. f. Naturforschung (1)

P. Schulz, Zeits. f. Naturforschung 2a, 583 (1947); Ann. d. Physik 1, 95 (1947); Ann. d. Physik 1, 107 (1947).

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Figures (11)

Fig. 1
Fig. 1

High pressure xenon arc lamps. The ultraviolet characteristics of only the large lamp are described in this paper.

Fig. 2
Fig. 2

The electrodes and the arc stream of the 500 watt xenon lamp.

Fig. 3
Fig. 3

Densitometer traces of the xenon arc spectrum. The upper portion shows that the spectrum is a smooth continuum in the ultraviolet; the breaks are due to densitometer range changes introduced to spread the record and are additive in density. The lower portion includes the visible region and is limited by loss of sensitivity of the photographic film; in this region weak lines are superimposed on the continuum.

Fig. 4
Fig. 4

Spectral radiant intensity of the xenon arc continuum and of the carbon arc crater used as reference standard of radiant intensity. The broken lines indicate the range over which the reference data were extrapolated.

Fig. 5
Fig. 5

Ultraviolet map of the xenon arc showing isoradiance contours at 3300A. The contours are drawn for percentages of the maximum measured radiance. The electrodes and arc stream are drawn to scale.

Fig. 6
Fig. 6

The percentage contribution to the total radiant output from the portions of the arc stream contained within the isoradiance contours shown in Fig. 5. The shaded areas indicate the contributions from the areas between isoradiance contours for 10 percent intervals.

Fig. 7
Fig. 7

The percentage contribution to the total radiant output as a function of the area of arc stream included within the isoradiance contours. The total area of the arc stream covers above 20 mm2 but 80 percent of the total radiation originates in the inner 10 mm2.

Fig. 8
Fig. 8

The spectral radiance of the xenon arc stream. Each curve refers to an average taken over the total area within a particular isoradiance contour. The carbon arc crater used as reference standard of radiance is shown and the broken lines indicate the range over which the carbon arc data were extrapolated.

Fig. 9
Fig. 9

The spectral radiance for the most intense portion of the xenon arc stream is fitted in the ultraviolet by the distribution curve for a black body at 6600°K of emissivity 0.058. At wave-lengths below 2200A the xenon intensity is reduced due to absorption by the quartz envelope. The carbon arc reference standard is also shown.

Fig. 10
Fig. 10

Ratio of the spectral radiance of the most intense part of the xenon arc to the spectral radiance of the positive crater of the carbon arc. The sudden drop below 2400A is probably largely due to absorption by the quartz envelope. The broken section indicates where the carbon arc is actually relatively more intense than the curve indicates, due to band spectra emitted by the gas column.

Fig. 11
Fig. 11

Comparison of ultraviolet sources. The xenon arc radiates a much more intense continuum than available hydrogen arcs; the radiance of the xenon continuum compares favorably with that of the pseudo-continuum of the H-6 mercury arc.

Tables (1)

Tables Icon

Table I Characteristics of xenon arcs.