Abstract

Spectral radiances R_λ and luminances B in the center axis of high density 8–20-nsec spark channels as produced by Nanolite sources were systematically studied by comparison with the emission from a calibrated dc-carbon arc. The maximum value of R_λ was 53 W cm⁻² Å⁻¹ sr⁻¹ in 1 atm of air at 4850 Å with a breakdown voltage of 2.5 kV when the Nanolite (C = 2.9 nF, L = 2 nH) was charged slowly. This value increased to over 70 W cm⁻² Å⁻¹ sr⁻¹ when the source was pulse charged. Saturation values of R_λ were 38 W cm⁻² Å⁻¹ sr⁻¹ in 3 atm of argon and 60 W cm⁻² Å⁻¹ sr⁻¹ in 32 atm of helium (slow charged). All values were reproducible to within 10%, the absolute error being estimated to be smaller than ±20%. Equivalent maximum blackbody temperatures of the channel surface in air were 62,000 K (pulse charged) and 38,000 K in argon and 54,000 K in helium (slowly charged). Maximum spectral radiant intensity in 1 atm of air was 0.18 W Å⁻¹ sr⁻¹ at 4850 Å (pulse charged).

© 1974 Optical Society of America

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