Recent results of iodine and water diagnostics in supersonic COIL

Abstract

Water vapor measurements at DLRs supersonic chemical oxygen iodine laser (COIL) have been carried out applying a tunable diode laser system. During a typical hot flow of 8 s, the water molar flow rate increases from 35 mmol/s to 85 mmol/s. Simultaneous measurements in the subsonic and supersonic region showed that about 10 percent of water in front of the expansion nozzle is lost. Standard mathematical expressions for water vapor pressure have been used to estimate the water partial pressure over basic hydrogen peroxide from the gas temperature measured by thermocouples at the exit of the singlet oxygen generator. A second tunable laser diode system was used to measure the iodine small signal gain for different iodine flow rates. Gain values were found at 1.2 percent/cm. From the recorded iodine atom absorption profiles the temperatures were calculated to be 190-220 K. The high starting temperatures are in accordance with the water measurements and a temperature increase due to water condensation.