Abstract

After having determined in a previous investigation the spectral energy characteristics of a high intensity quartz mercury arc of 8 mm bore for various conditions of operation, the writers here describe a similar set of experiments with an arc constricted to a tube of 2 mm internal diameter and 38 mm long, thus doing away with the outer absorbing layer of relatively cool mercury vapor. Currents of from one-third to five amperes were used, air cooling being necessary between one and two amperes, and water cooling above this point, except at high pressures, when air cooling was necessary even at low currents. Voltage gradients of from seven volts per cm to 58 volts per cm were used. The pressure in the arc, which was of special design, was measured with a mercury manometer, and varied from 29 mm to 3920 mm. The energy in each of the more important groups of lines was measured with a thermopile, and it was found that this type of arc was of very high efficiency, and of tremendous intensity and convenience for slit illumination. Curves are given showing the spectral energy variation with varying current and voltage, and it is shown that approximately the best combination of intensity, efficiency, convenience, and life is obtained at atmospheric pressure, one ampere current, and 110 volts with suitable series resistance. No decrease in efficiency with increasing voltage was observed at pressures up to five atmospheres. Where extreme intensities are desired, currents up to five amperes may be used, but the life of the lamp is shortened.

© 1925 Optical Society of America

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References

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  1. Harrison and Forbes, This Journal,  10 p. 1; 1925.
  2. Küch and Retschinsky, Ann. der Phys.,  20, p. 563; 1906.
    [Crossref]
  3. Vincent and Biggs, Jour. Sci. Inst.,  1, p. 242; 1924.
    [Crossref]
  4. Harrington, This Journal,  7, p. 689; 1923.
  5. Fabry and Buisson, Compt. Rend.,  153 p. 931911.

1925 (1)

Harrison and Forbes, This Journal,  10 p. 1; 1925.

1924 (1)

Vincent and Biggs, Jour. Sci. Inst.,  1, p. 242; 1924.
[Crossref]

1923 (1)

Harrington, This Journal,  7, p. 689; 1923.

1911 (1)

Fabry and Buisson, Compt. Rend.,  153 p. 931911.

1906 (1)

Küch and Retschinsky, Ann. der Phys.,  20, p. 563; 1906.
[Crossref]

Biggs,

Vincent and Biggs, Jour. Sci. Inst.,  1, p. 242; 1924.
[Crossref]

Buisson,

Fabry and Buisson, Compt. Rend.,  153 p. 931911.

Fabry,

Fabry and Buisson, Compt. Rend.,  153 p. 931911.

Forbes,

Harrison and Forbes, This Journal,  10 p. 1; 1925.

Harrington,

Harrington, This Journal,  7, p. 689; 1923.

Harrison,

Harrison and Forbes, This Journal,  10 p. 1; 1925.

Küch,

Küch and Retschinsky, Ann. der Phys.,  20, p. 563; 1906.
[Crossref]

Retschinsky,

Küch and Retschinsky, Ann. der Phys.,  20, p. 563; 1906.
[Crossref]

Vincent,

Vincent and Biggs, Jour. Sci. Inst.,  1, p. 242; 1924.
[Crossref]

Ann. der Phys. (1)

Küch and Retschinsky, Ann. der Phys.,  20, p. 563; 1906.
[Crossref]

Compt. Rend. (1)

Fabry and Buisson, Compt. Rend.,  153 p. 931911.

Jour. Sci. Inst. (1)

Vincent and Biggs, Jour. Sci. Inst.,  1, p. 242; 1924.
[Crossref]

This Journal (2)

Harrington, This Journal,  7, p. 689; 1923.

Harrison and Forbes, This Journal,  10 p. 1; 1925.

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Figures (5)

F. 1
F. 1

Diagram of the constricted arc arranged for pressures up to five atmospheres and currents from 0.2 to 2.0 amperes. The inserts show, at A′, the modified form of the constricted portion arranged to have water cool the hot column so that currents up to 5.0 amperes could be used, and below the enlarged ends arranged for work at atmospheric pressure.

F. 2
F. 2

Curves show the relation between voltage gradient and galvanometer deflection, at constant current, for six of the more important maxima in the light from the constricted arc.

F. 3
F. 3

Curves similar to those of Fig. 2, but with one-third the current density and twice the voltage range. Pressures are marked below the voltage scale. Galvanometer deflections above 180 cm were measured with a resistance in series with the thermopile and were then reduced to the same scale as those without resistance.

F. 4
F. 4

Curves showing the relation of galvanometer deflection to current density, for constant voltage gradient. The type of cooling used in each region is marked. Note that readings have been greatly reduced by a series resistance, and that the slit is narrower than in previous cases.

F. 5
F. 5

Chart showing the variation in intensity distribution for the various maxima observed under different conditions. The solid line is for low current and high voltage gradient, the dash-dot line for moderate current and low voltage, and the dash line for high current and moderate voltage gradient. The yellow-green maximum has been reduced to the same value in each by multiplying by a factor given in the chart. The maxima are directly connected, no minima being marked. The same slit width was used in all three cases.

Tables (1)

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Table 1