Nikolai P. Vagin

Repetitively pulsed chemical oxygen-iodine laser with a discharge generation of atomic iodine

Pulsed chemical oxygen-iodine laser with a discharge generation of atomic iodin is described. Having the output energy like that with photolysis iodine atoms generation such a laser exhibits higher plug-in efficiency. The efficiency value of 91% is reported. Pulse power of 100 kW was obtained which exceeds two orders of magnitude that for cw laser with the same chlorine flowrate. Repetitively pulsed operation is reported.

The methods of singlet oxygen detection for DOIL program

The problem of development of a singlet delta oxygen O2(1Δg) (SDO) generators alternative to chemical one needs application of the accurate methods of measuring the SDO concentration. A chemical SDO generator providing efficient operation of a chemical oxygen-iodine laser (COIL) is proposed to be used as a reference source for absolute calibration of the system measuring the SDO concentration. The principle of the COIL operation results in the threshold and output COIL parameters make it possible to evaluate the SDO yield with a satisfactory accuracy. A convenient sparger chemical SDO generator was applied as a reference source for absolute calibration of detectors of dimole (λ=634nm) and b→X (λ=762 nm) radiations. The values of b-state concentration formed in a longitudinal electric discharge were evaluated. The intracavity laser spectroscopy (ICLS) was absolutely calibrated for measuring the SDO concentration. ICLS method has a very high sensitivity and makes it possible to monitor the absorption corresponding to the O2(1Δg)→O2(1Σg+) (λ = 1.91 μm) transition. The cross-sections of lines of the Q - branch of the vibrational 0-0 band of the a1Δg → b1Σg+ transition of molecular oxygen were measured. The method developed was applied to measure the concentration of singlet oxygen produced in the microwave discharge. He - Ne laser (λ = 633 nm) was used for absolute calibration of a system monitoring the dimole radiation. The rate constant of the process responsible for dimole emission was measured. The value obtained kd=7.34•10-23 cm3/s is in agreement with literature.

Pulsed COIL with volume generation of iodine atoms in electric discharge

The method of volume generation of iodine atoms to obtain the pulsed mode of COIL is the most effective by the ratio of pulsed power to cw one at the same flowrate of chemicals. The electric discharge is a very convenient tool to produce iodine atoms in an active medium. The electrical efficiency close to 100% was obtained when longitudinal glow discharge was used. The investigation of both influence of the discharge gap length on the performance of pulsed COIL initiated with longitudinal discharge and transverse discharge initiated pulsed COIL based on the Jet Singlet Oxygen Generator were performed. The lasing of Jet SOG based pulsed COIL has been obtained for the first time. The operation pressure of 17 Torr at oxygen partial pressure of 7 Torr in the laser cavity has been obtained The temperature parameters of active medium being under electric discharge initiation were analyzed. The active medium temperature growth was shown to be responsible for decrease of specific output energy in discharge initiated COIL unlike that for photolytic initiation.

Singlet delta oxygen production in e-beam sustained discharge: theory and experiment

Singlet delta oxygen (SDO) production in a pulsed e-beam sustained discharge (EBSD) ignited in molecular oxygen with carbon monoxide stabilizing this discharge is theoretically and experimentally studied. Temporal behavior of SDO concentration and yield in the EBSD afterglow is analyzed. Experimentally measured SDO yield for oxygen mixture O2:Ar:CO=1:1:0.05 at total gas pressure 30 Torr comes up to 7% at specific input energy (SIE) of ~3.0 kJ/(1 atm(O2+CO)), whereas its theoretical value riches ~ 17.5%. The efficiency of SDO production is theoretically analyzed as function of the SIE.

Theoretical studies on kinetics of singlet oxygen in nonthermal plasma

An idea to replace singlet delta oxygen (SDO) generator working with wet chemistry by electric discharge generator has got much attention last years. Different kinds of discharge were examined for this purpose, but without a great success. The existing theoretical models are not validated by well-characterized experimental data. To describe complicated kinetics in gas discharge with oxygen one needs to know in detail processes involving numerous electronic excited oxygen molecules and atoms. To gain new knowledge about these processes experimental studies were made on electric discharge properties in gas mixture flow with independent control of inlet SDO concentration. The theoretical model extended to include minor additives like oxygen atoms, water molecules, ozone was developed. Comparison with careful experimental measurements of electric characteristics along with gas composition allows us to verify the model and make theoretical predictions more reliable. Results of numerical simulations using this model for an electron-beam sustained discharge are reported and compared with the experimental data.

Experimental investigation of chemical oxygen-iodine laser

Results of an experimental investigation of a chemical oxygen-iodine laser (COIL) are presented. We determine the factors influencing the efficiency of a chemical singlet-oxygen generator (SOG) of the bubbler type operating on the chlorination of an alkaline solution of oxygen peroxide. We describe SOG constructions. A cw COIL with output power up to 400 W is developed on the basis of the investigated SOG. The feasibility of a modular construction of high-power COIL is demonstrated. A power-output level of 1 kW was achieved with a two-section laser. The feasibility is analyzed of COIL operation in a pulsed regime by pulsed bulk accrual of iodine atoms. We show that in this regime the laser can be operated without a low-temperature trap. An advantage of such a regime is also the possibility of controlling, in a wide range, the lasing pulse duration. A strong influence of molecular chlorine on the energy content of the active medium is observed when alkyliodides are used as iodine donors. The possibilities of using a pulsed COIL for controlled thermonuclear fusion are discussed.

Electron-beam sustained discharge in oxygen gas mixtures: singlet delta oxygen production for oxygen-iodine laser

Electric properties and spectroscopy of an e-beam sustained discharge (EBSD) in oxygen and oxygen gas mixtures at gas pressure up to 100 Torr were experimentally studied. The pulsed discharge in pure oxygen and its mixtures with noble gases was shown to be very unstable and characterized by low input energy. When adding small amount of carbon monoxide or hydrogen, the electric stability of the discharge increases, specific input energy (SIE) per molecular component being more than order of magnitude higher and coming up to 6.5 kJ/(l atm) for gas mixture O2:Ar:CO = 1:1:0.1. The results of experiments on spectroscopy of the singlet delta oxygen O2(a1Δg)(SDO) and O2(b1Σg+) states in the EBSD are presented. The calibration of the optical scheme for measuring the SDO absolute concentration and yield using the detection of luminescence of the SDO going from a chemical SDO generator was done. The preliminary measurement of the SDO yield demonstrated that it was ~3% for the SIE of ~1 kJ/(l atm), which is close to the results of theoretical calculations for such a SIE. Theoretical calculations demonstrated that for the SIE of 6.5 kJ/(l atm) the SDO yield may reach ~20% exceeding its threshold value needed for oxygen-iodine laser operation at room temperature, although a part of the energy loaded into the EBSD goes into the vibrational energy of the molecular admixture, (which was experimentally demonstrated by launching a CO laser operating on an oxygen-rich mixture O2:Ar:CO = 1:1:0.1 and measuring its small-signal gain).

Singlet delta oxygen production in a slab discharge in oxygen

Singlet delta oxygen O2a1&Dgr;g (SDO) production in a slab discharges ignited in oxygen gas mixtures was experimentally studied. An influence of gas mixture content and input electric power on SDO yield was analyzed. In self-sustained RF slab discharge SDO yield of 10±5 % was measured by comparison luminescence intensity of SDO going from a chemical generator and SDO generated in electric discharge. SDO yield of 7.2 % was measured by intracavity laser spectroscopy method. It was demonstrated that the choice of electrodes material is very important. Experiments on SDO production in slab non-self-sustained discharge with external ionization by repeating high-voltage pulses were carried out. SDO concentration was measured by the method of intracavity laser spectroscopy. The measured concentration of SDO was about 1.5×1016 cm-3, with SDO yield of ~10.6 %. A development of electric discharge oxygen-iodine laser with SDO production in long electrodes slab discharge is discussed.

Electric properties, spectroscopy, and singlet delta oxygen yield of electron-beam sustained discharge in oxygen gas mixtures

Electric properties and spectroscopy of an e-beam sustained discharge (EBSD) in oxygen and oxygen gas mixtures at gas pressures up to 100 Torr was experimentally studied in large excitation volume (~18 liter). The discharge in pure oxygen and its mixtures with noble gases was shown to be very unstable and characterized by low input energy. When adding small amount of carbon monoxide or hydrogen, the electric stability of the discharge increases, specific input energy per molecular component being higher more than order of magnitude and coming up to 6.5 kJ/(l atm). Theoretical calculations demonstrated that for the experimental conditions the singlet delta oxygen yield may reach ~20% exceeding its threshold value needed for oxygen-iodine laser operation at room temperature. The results of experiments on spectroscopy of the singlet delta and singlet sigma oxygen states in the EBSD are presented.

Features of kinetic processes in the active medium of a pulsed chemical oxygen-iodine laser

ConclusionIt can be concluded from our experiments and calculations that the product CF3O2 of the interaction between the CF3 radical and the O2 molecule quenches the oxygen O2(1Δ) more strongly. At low chlorine admixture density in the singlet-oxygen stream this output energy of the oxygen-iodine laser with CF3I as the atomic iodine donor is lower compared with CH3I. The rate constant of quenching singlet oxygen by CF3O2 molecules is (3–5)·10−11 cm3·sec−1. It would be possible to decrease the influence of CF3O2 by adding to the initial O2*−O2−CF3I−Ar active mixture some other substance causing the CF3 radicals to enter in a chemical reaction with a shorter characteristic time than that for CF3O2 formation. Of course, neither the initial substance nor the reaction products should quench O2* noticeably. This role can be possibly assumed by the NO molecule.The influence of the chlorine additive on the output energy of a laser with CH3I and CF3I differs greatly. The choice of the chlorine donor must therefore be determined by the amount of this additive. CH3I is preferable if the chlorine is fully utilized in the singlet-oxygen laser, and CF3I in the opposite case.