Achievement of 30 conversion from O_2 to O_2(a~1△) at 50 torr using an integrally cooled, controlled avalanche ionized electric O_2(a~1△) generator

摘要

The electric oxygen iodine laser (EOIL) offers a vastly more practical, implementable, and safer alternative to its predecessor, the chemical oxygen iodine laser (COIL), particularly for airborne or other mobile military applications. Despite its promise and after 25 years effort, numerous laboratories around the world have not succeeded in providing the known basic physical requirements needed to electrically convert O_2 into O_2(a~1△) with the fractional yields and efficiencies needed to make a practical laser. Hence, as of this date, the world record power generated from an EOIL device is only 5 watts. In this paper, a 30% conversion from O_2 into O_2(a~1△) operating at substantial oxygen mass flow rates (0.090 moles O_2/sec at 50 torr) and 40% electrical efficiency is reported. The O_2(a~1△) flow stream being produced carries 2400 watts. Gain measurements are currently in progress, to be followed shortly by power extraction. Current conditions imply that initial power extraction could push beyond 1 KW. Efforts to date have failed to generate substantial laser power because critical criteria have not been met. In order to achieve good O_2(a~1△) fractional yield, it is normally mandatory to impart on the order of 100 KJ/mole O_2 while efficiently removing the waste heat energy from the generator so that less than a few hundred degrees Kelvin rise occurs due to gas heating. The generator must be excited by an electric field on the order of 10 Td. This is far below glow potential; hence, a fully externally sustained plasma generation technique is required. Ionization is supplied by means of applying short (tens of nanosecond) pulses to the O_2(a~1△) generator at 50,000 PPS, which are on the order of ten times breakdown potential. This enables a quasi-steady adjustable DC current to flow through the generator, being conducted by application of a DC, 10 to 14 Td pump E-field. This field is also independently tunable. The result is that up to 180 KJ/mole O_2 gets imparted to the gas by means of the ～6 KW sub-breakdown pump field, while another 2700 watts is applied to the controlled avalanche field. The generator consists of 24 each, 1 cm diameter tubes that are submerged in rapidly circulating cold fluorinert. Heat is efficiently removed so that that the gas temperature, initially 273°K, raises only by 125°K, as evidenced by spectrographic analysis of the fine structure of O_2(a~1△) at lower pressure. Since all necessary conditions have been met, a 30% conversion rate of O_2 to O_2(a~1△) has been achieved. Fortuitously, neither O atom production nor O_2(b~1∑) production is visible in the spectra of the higher pressure, best yield runs. Essentially all other spectral lines are dwarfed in comparison the O_2(a~1△) line. Energy normally partitioned to O_2(b~1∑) and apparently O atoms now feeds into O_2(a~1△) directly, enabling electrical efficiency to exceed 40%.