Time-resolved temperature and number density measurements in a repetitively pulsed nanosecond-duration discharge

This paper presents a fast detection technique using diode laser absorption spectroscopy as an optical diagnostic tool to measure time-resolved temperature and number density in a repetitively pulsed nanosecond-duration discharge. Argon atoms in the 1s3 metastable state were optically probed by current scanning a vertical cavity surface emitting laser diode over the 1s3→2p4 transition at 794 nm. Temperature and number density measurements are presented at pulse energies from 20 μJ to 300 μJ, at a constant pressure of 2.67 kPa and 10 kHz repetition frequency. A time resolution of 2 ns was achieved for the measurements during and after the discharge pulse. We demonstrate the method used to make nanosecond resolution measurements, the precision of this technique and the effect of pulse energy on the translational temperature and number density of the metastable atoms. Our measurements show that, for small input pulse energies, the peak temperature of the argon atoms in the 1s₃ state can exceed ambient room temperature by up to an order of magnitude.