The Concentrated-Arc Lamp as a Source of Modulated Radiation

The concentrated arc is a new type of lamp whose radiation emitting source is a thin film of molten zirconium and a cloud of excited and ionized zirconium vapor and argon gas which forms on and very close to the end of the specially prepared negative electrode. By modulating the lamp current, the radiation may be modulated at audio frequencies. — The continuous radiation from the molten zirconium can be only partly modulated, the per cent modulation decreasing with increase in modulating frequency and in spectral wavelength. The line radiation from the cathode-glow region close to the electrode modulates almost completely at all audio frequencies. It is particularly strong in the near-ultraviolet and infrared. — By using suitable modulator circuits, which are adapted to the rather unusual impedance characteristics of these lamps, and by using optical filters to select the spectral region used, the light output may be made to follow the lamp current modulation with good fidelity.

Print ISSN

0097-5834

Published

1947-04

Content type

Original Research

DOI

10.5594/J12706