Abstract

A study of the total radiation in the visible region from vacuum spark discharges between electrodes of aluminum, magnesium, copper, and carbon has been made. With a capacitance of 21.6 µf charged to potentials up to 20 kv and inductance variable from 2.4 to 45 µh, peak currents up to 65 000 amperes were obtained. Oscilloscope traces of the output voltage from a photocell show that for the underdamped discharge the light output closely follows the current oscillations, dropping to zero between current cycles. The maximum light intensity in a single spark train varies as the third to the seventh power of the peak discharge current, or with the 3/2 to the 7/2 power of the discharge energy, depending on the electrode material and the inductance. For a given electrode material, the exponent increases as the inductance is decreased, while at constant current the maximum light intensity decreases slightly as the inductance is decreased. With aluminum electrodes ranging from 12 to 116inch in diameter, the maximum light intensity varies inversely with the electrode cross-sectional area. Estimates of current densities as high as 100 000 amperes per cm2 in a 10 000-ampere aluminum spark were made from measurements of the anode spots on the electrodes. Bursts of luminous vapor from the anode, apparently not a part of the current-carrying column, appear to constitute the principal source of light in the critically damped aluminum spark.

© 1953 Optical Society of America

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References

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  1. B. Edlén, Nova Acta Reg. Soc. Sci. Ups., IV,  9, No. 6 (1934).
  2. Kebler, McCormick, and Sawyer, Phys. Rev. 87, 212 (1952).
  3. P. Gerald Kruger, Rev. Sci. Instr. 4, 128 (1933).
    [Crossref]

1952 (1)

Kebler, McCormick, and Sawyer, Phys. Rev. 87, 212 (1952).

1934 (1)

B. Edlén, Nova Acta Reg. Soc. Sci. Ups., IV,  9, No. 6 (1934).

1933 (1)

P. Gerald Kruger, Rev. Sci. Instr. 4, 128 (1933).
[Crossref]

Edlén, B.

B. Edlén, Nova Acta Reg. Soc. Sci. Ups., IV,  9, No. 6 (1934).

Gerald Kruger, P.

P. Gerald Kruger, Rev. Sci. Instr. 4, 128 (1933).
[Crossref]

Kebler,

Kebler, McCormick, and Sawyer, Phys. Rev. 87, 212 (1952).

McCormick,

Kebler, McCormick, and Sawyer, Phys. Rev. 87, 212 (1952).

Sawyer,

Kebler, McCormick, and Sawyer, Phys. Rev. 87, 212 (1952).

Nova Acta Reg. Soc. Sci. Ups., IV (1)

B. Edlén, Nova Acta Reg. Soc. Sci. Ups., IV,  9, No. 6 (1934).

Phys. Rev. (1)

Kebler, McCormick, and Sawyer, Phys. Rev. 87, 212 (1952).

Rev. Sci. Instr. (1)

P. Gerald Kruger, Rev. Sci. Instr. 4, 128 (1933).
[Crossref]

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Figures (8)

F. 1
F. 1

Photographs of typical traces observed on the oscilloscope.

F. 2
F. 2

Variation of the maximum light intensity (plotted vertically in arbitrary units) with energy stored in the condenser, for 1 4 - inch aluminum electrodes at four different inductance values.

F. 3
F. 3

Representative data for the four elements copper, magnesium, aluminum, and carbon. For the upper four curves the inductance is 2.4 µh, and for the lower four, 45 µh.

F. 4
F. 4

Variation of the maximum light intensity with peak discharge current for 1 4 - inch aluminum electrodes at four different inductance values.

F. 5
F. 5

Variation of the maximum light intensity with reciprocal electrode cross-sectional area, for aluminum electrodes at five values of voltage and one value of inductance.

F. 6
F. 6

Photograph of a 1 2 - inch diameter aluminum electrode (left) showing the anode spot resulting from the critically damped spark shown at right.

F. 7
F. 7

Photographs of critically damped sparks between 1 4 - inch diameter electrodes.

F. 8
F. 8

Photographs of critically damped sparks between 1 8 - inch diameter aluminum electrodes.