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The results of experimental and numerical-theoreticalsupersonic COIL study carried out at RFNC-VNIIEF in 1998 are performed. The novel data concern our research into the twisted-flow SOG (TA SOG) performance. The experimental investigations of gas-dynamic and energy performance, chemical efficiency, and optical quality are reported and discussed for the supersonic COIL with the parallel-flow system of gaseous iodine and singlet oxygen mixing. Application of TA-SOG together with the parallel-flow mixing system was shown to allow high values of COIL operation. The peculiarities of numerical-theoretical model developed at RFNC-VNIIEF are discussed. INTRODUCTIONIndustrial applications of the Oxygen -Iodine Laser (COIL) have been under active consideration in the last 5-7 years [1][2][3][4]. The interest in development of industrial COIL is stipulated by a number of its advantageous peculiarities such as: first, high emission power at good beam quality; second, possibility for powerful emission of COIL to reach remote workplaces via virtually loss-less fiber-silica beam delivery, which opens new technological areas of application. Due to the purely chemical pumping method, an independent powerful industrial laser facility wouldn't have too high demand in electric energy. Together with other unique features, all the above properties give COIL a definite priority over other industrial lasers, especially in such applications as dismantling of outserved nuclear plants or accident response operations [3][4][5]. COIL development for industrial purposes faces a set of difficulties, the most serious of them being as follows: i) keeping of the working vacuum inside the laser cavity; ii) safety and ecological problems related to the presence of chlorine, iodine, and corrosive solutions; iii) effective procedures of hydrogen peroxide alkali solution (BlIP) preparation and re-circulation. These and other problems refer to the tasks that will be solved in the course of industrial COIL development in VNIIEF. The principal problem at which the developers are currently focusing their efforts is pressure recovery at the exit COIL duct. The highest singlet oxygen pressure that may ensure high laser efficiency is supposed to be determined experimentally. Increasing the singlet oxygen pressure one can obtain higher output power with the same size of a facility; and increase in

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The present paper is concerned with automatic optimization of tunable C02 laser emission power that has been realized by changing the in-resonator polarization direction.We have begun with the investigation into the experimental reflection efficiency of the grating in use for first and zero diffraction orders as a function of the incident polarization plane orientation relative to the grating line length obtained from the first-order Littrow system. The dependencies measured were then used to determined the angle y(J) between the grating line length and the polarization vector such that the zero-order reflection factor was equal to its optimal value that is a function ofthe active medium gain for the J-th line, active length, and useless loss inside the laser cavity. After this, the monitoring and control software of the laser has been enhanced with the y(J)-values found out in accordance with the above procedure for each laser line associated with its intrinsic gain. Hence, the laser tuning in J-th line is accompanied with automatic orientation ofthe Brewster window at the angle y(J).Due to the given optimization we were able to acquire for each particular line the highest power at the maximum line amount in the output spectrum.

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