A Spectroscopic Temperature Measurement of Converging Detonations by the Emission Spectral Matching Method

Abstract

Experimental studies on converging detonations have been performed aiming at application to high-power pulse lasers and production of hightemperature plasmas. Viewing that the duration time of the detonation is relatively short (< 10 μs) at the converging point, spectroscopic measurements have often been used as diagnostic techniques. In the present study, the emission of CN violet bands from a converging point was analyzed using a microdensitometer. In order to determine the temperature at the converging point of a detonation, a method of matching the entire emission spectra was utilized. The anticipated emission spectra of the observed band can be theoretically calculated with a combination of the gasdynamic quantities, assuming Boltzmann distributions for rotational, vibrational and electronic energy levels. After several trial-and-error processes, the best fit was obtained for T = 11 000 K, N = 7.5 x 1016/cc and the Lorentian broadening half-width Wl = 0.003 nm : The detonation was produced using equi-molar oxyacetylene mixtures at P1 = 60 Torr (8.0 x 103 Pa) and T1 = room temperature in an 80-cm-dia. double-disc-type detonation chamber. It was found, as a result, that unavoidable doppler broadening inherent to high temperature experiments and a wide slit function could be handled with no essential difficulty and a correct rotational/vibrational temperature could be obtained.