Showing papers on "Buffer gas published in 1986"

The High-Pressure Sodium Lamp

Abstract: Introduction - General Considerations Concerning Power Balance and Spectrum - Spectrum and Related Discharge Properties - Power Balance and Related Discharge Properties - Influence of a Buffer Gas on Discharge Properties - Ignition and Stabilisation - High-Frequency and Pulse Operation - Discharge-Tube Material and Ceramic-to-Metal Seal - Electrodes - Lamp Design - References

Gas‐phase hydrolysis of SOF2 and SOF4

Abstract: The rates for gas‐phase hydrolysis of SOF2 (thionylfluoride) and SOF4 (thionyl tetrafluoride) have been measured at a temperature of 298 K. The second order rate constant for SOF2 hydrolysis in SF6 buffer gas was found to have the value (1.2±0.3)×10−23 cm3/s which agrees with previous estimates of Sauers et al., but is three orders of magnitude lower than the value obtained by Ruegsegger et al. at 340 K. The rate constant for SOF4 hydrolysis has not previously been measured and its value in both SF6 and N2 buffer gases was found here to be (1.0±0.3)×10−21 cm3/s.

Photolithographic mask repair system

Abstract: A method and device are provided to accomplish laser driven pyrolytic, photolytic and photoactivativation process requiring controlled atmosphere without the use of gas tight cells. A method and device are provided to correct clear faults on a photo-lithographic mask by metallic deposition on the mask at standard temperature and pressure. The deposition is formed by the pyrolytic decomposition of an organometallic gas mixture which may include chromium and molybdenum hexacarbonyls, and a buffer gas. The decomposition is done utilizing a laser beam. The device may be incorporated into a system which has other members used to correct opaque faults in the same mask.

Electrodeless high pressure sodium iodide arc lamp

Abstract: High pressure xenon is used as a buffer gas in an elec- rodeless sodium iodide arc lamp. Very high efficacies are achieved by using an arc tube with rounded edges and by surrounding a portion of the arc tube with quartz wool. The arc tube may also contain small amounts of mercury iodide.

Influence of molecular gases on the output characteristics of a copper vapor laser

Abstract: The effect of molecular gas impurities in the Ne buffer gas on the output characteristics of a copper-vapor laser has been investigated. Molecules with hydrogen atoms are found to increase the laser output power and improve the intensity distribution over the cross section of the beam. Hydrogen improves the average output power by as much as 50% and the efficiency by 60%. A maximum average power of 27 W is obtained using the plasma tube with a 32 mm×70 cm active volume.

Kinetics of the OH + CO reaction under atmospheric conditions

Abstract: A pulsed laser photolysis-pulsed laser-induced fluorescence technique is used to directly measure the temperature, pressure, and H2O concentration dependence on k1 in air. K1 is found to increase linearly with increasing pressure at pressures of not greater than 1 atm, and the pressure dependence of k1 at 299 K is the same in N2 buffer gas as in O2 buffer gas. The rate constant in the low-pressure limit and the slope of the k1 versus pressure dependence are shown to be the same at 262 K as at 299 K. The present results significantly reduce the current atmospheric model uncertainties in the temperature dependence under atmospheric conditions, in the third body efficiency of O2, and in the effect of water vapor on k1.

Superpurifier for argon gas and process for purifying argon gas

Abstract: The present invention relates to a superpurifier for argon gas and to a process for superpurifying an argon gas According to the invention, the superpurifier comprises means for contacting an impurity-containing argon gas with a getter material which is an alloy of zirconium, vanadium and iron The getter material of the superpurifier selectively sorbs impurities from an impurity-containing argon gas thereby producing a purified argon gas The present invention also relates to a method of purifying an impurity-containing argon gas using this superpurifier The present invention provides means for obtaining an argon gas of higher purity than can be obtained by prior purifying processes and apparatus

Low solar background, high sensitivity active atomic resonance filter for underwater laser communications

Abstract: An optical atomic resonance filter using two pump lasers, a buffer gas and magnesium as an atomic vapor converts underwater signals in the Fraunhofer wavelengths in the green portion of the spectrum to UV light which is readily detectable by conventional photomultiplier tubes.

Three-photon resonantly enhanced multiphoton ionization and third-harmonic generation with unfocused laser beams.

Abstract: Several extensions are made in theoretical studies of multiphoton ionization associated with third-harmonic fields that are generated near three-photon resonances in gaseous media. The treatment includes the strong coherent cancellation effect which occurs between three-photon pumping of a resonant level and pumping by the third-harmonic field that is generated in the same medium. The incomplete spoiling of the cancellation effect with counterpropagating beams is quantitatively described. Also, treatment of the multiphoton-ionization problem involving phase-matched, third-harmonic fields is generalized to include quantitative effects of index changes due to a buffer gas, absorption due to dimers, and collisional dephasing of coherent excitations. Finally, we show how measurements of linewidths, phase-matching positions, and pressure dependences of ionization yields associated with third-harmonic generation and subsequent absorption can be used to determine oscillator strengths of a resonant level, absorption coefficients for a resonant species and a buffer-gas species, and the refractive index of the buffer gas at the third-harmonic frequency.

Electron attachment rate constants of SO2 and CS2 in Ar, N2, and CH4 at varied E/N

Abstract: The electron attachment rate constants of SO2 and CS2 in the buffer gases of Ar, N2, and CH4 (150 to 530 Torr) at various E/N (1–16 Td) were measured by a parallel‐plate drift‐tube electron‐swarm technique. The electrons were produced by irradiating the cathode with KrF laser photons. For the SO2–Ar mixture, the electron attachment rate constant of SO2 increases with increasing E/N and is independent of Ar pressure. For SO2 in N2 and CH4, the electron attachment rates decrease with increasing E/N and increase with increasing buffer gas pressure. For CS2 in N2 and CH4, the electron attachment rates increase with increasing CS2 and buffer gas pressures and decrease with increasing E/N. The electron attachment to SO2 and CS2 in the buffer gases of N2 and CH4 is a three‐body process. The collisional‐stabilized rates of ‘‘temporary’’ negative compound ions SO−*2 and CS−*2 by various gases are investigated.

Feeder of oxygen gas containing steam

Abstract: A feeder of oxygen gas containing steam comprising a combustion chamber, an oxygen gas induction tube for inducing oxygen gas to the combustion chamber, a hydrogen gas chamber separated from the combustion chamber by a hydrogen osmotic film between it and the combustion chamber, a hydrogen gas induction chamber which induces the hydrogen gas to the hydrogen gas chamber, an exhaust tube communicated with the hydrogen gas chamber and a heater.

Formation dynamics of excited components in discharge XeCl laser plasma from the data of dye laser absorption probing

Abstract: The absorption spectra in the 335-610 nm spectral range and the time dependences of the concentrations of Xe*, He*, Ne*, Ar*, Xe+*, Cl-, and XeCl* were measured by the pulse dye laser absorption (gain) probing of the active medium of a XeCl discharge laser for different buffer gas mixtures. The formation dynamics of excited atoms, ions, and excimer molecules is discussed. It is shown that at the initial stage of discharge the dominant process in the formation of XeCl* molecules is the "harpooning" reaction, whereas at the following stages the ion-ion recombination gains predominance. The rate constants of the ionic XeCl* formation reaction are determined for He, Ne, and Ar buffer gases.

On collision-induced amplified emission of alkali atoms

Abstract: The recently discovered amplified emission of alkali atoms resonantly excited to theP3/2 state by intense laser beam is analyzed theoretically. This effect is caused essentially by collisions with buffer gas atoms building up a population inversion of theP1/2 state with respect to theS1/2 ground state. Our theoretical calculations based on dressed-atom density matrix analysis agree with most experimental results.

Performance evaluation of lead vapor heat-pipe as a stimulated Raman converter for XeCl lasers

Abstract: High power (6.6 W at 43 pps) stimulated Raman scattering at 459 nm was obtained by down shifting the radiation of a XeCl excimer laser in a lead vapor heat-pipe. Experiments were conducted with different buffer gas species. Photon conversion efficiency as high as 66 percent and energy slope efficiency of 53 percent obtained with Xe as the buffer gas at 1300°C. The apparatus was in daily use for a period of six months without maintenance.

Method for starting fuel cell power systems

Abstract: A method for starting fuel cell power systems comprises heating a fuel cell stack to a predetermined operating temperature with a circulating heat-exchanger fluid, while feeding a pressurized inert gas into a pressure vessel and process gas chambers of the fuel cell stack to increase pressures in the process gas chambers and pressure vessel to a predetermined pressure, detecting a temperature of the stack and a pressure of the inert gas in the process gas chambers, and controlling a vapor pressure in the inert gas fed to said chambers in proportion to the detected temperature and pressure in the process gas chambers so that a volume of an electrolyte is approximately kept constant.

Line-tunable cw ortho- and para-NH 3 lasers operating at wavelengths of 11 to 14 μm

Abstract: A cw CO2 laser operating on the 9R(30) line was used to pump either the sR(5,0) or the sR(5,1) transition of NH3. Collisions with a buffer gas (either N2 or Ar) thermalized the NH3 rotational population, and gain occurred throughout the ν2 band. As there is no collisional coupling of ortho-NH3 (K = 3n) to para (K = 3n ± 1) states, it was necessary to pump the two species separately. Output powers as high as 5.5 W and conversion efficiencies of 33% were measured. A total of sixty-five (ortho and para) transitions were observed to lase at wavelengths ranging from 10.3 to 13.8 μm. The operation of the laser is in good agreement with the predictions of a simple model.

Stimulated processes in a mixture of rubidium vapor and buffer gas under two-photon excitation

Abstract: The article gives the results of a study of the effect of He buffer gas on nonlinear processes during two-photon excitation of rubidium vapor In addition to four-photon parametric luminescence and a stimulated four-photon parametric process, lines of two-photon decay and stimulated electronic Raman scattering, not previously observed in rubidium vapor, have been obtained The dependences of these processes on the pressure of the buffer gas and on the frequency of the exciting radiation are investigated and discussed

Influence of Ne on the energy characteristics of high-pressure lasers with electron-beam-pumped mixtures of He with Ar, Kr, and Xe

Abstract: Three-component mixtures are recommended for increasing the output energy characteristics of high-pressure lasers pumped by an electron beam and emitting as a result of infrared transitions in ArI, KrI, and XeI. It is shown experimentally that dilution of helium (used as the buffer gas) with neon in the ratio [Ne]/([Ne+[He])=0.35–0.45 makes it possible to increase the output energy by a factor of 2–3. An analysis of the experimental results is given.

Characterization of an atom beam produced with the help of a hollow-cathode discharge

Abstract: A hollow‐cathode type discharge is used as a refractory element vapor generator for the formation of an atomic beam. The development of the technique brings us to discuss its possibilities in spectroscopic studies of refractory elements. We focus primarily on the production of a uranium atomic beam and its characterization by laser‐induced fluorescence spectroscopy. We determine, among other things, the beam divergence and the most probable velocity along its axis for specific current and pressure conditions in the discharge. We also discuss beam behavior with respect to buffer gas pressure and electric current in the discharge.

IR MPD of CDF3 in Two-frequency IR Fields

Abstract: The effectiveness of various sets of laser frequencies was analyzed for two-frequency MPD of CDF3 molecule at the different pressures of buffer gas. It was shown that MPD yield increased compared to either single-frequency or two adjacent frequencies irradiation.

Transversely excited atmospheric‐pressure copper‐vapor laser

Abstract: We report the results of the measurements of the performance parameters of the transversely excited atmospheric‐pressure (TEA) copper‐vapor laser (CVL). A specific laser energy density of 36 μJ/cm3 was achieved in an excited volume of 0.6×1×20 cm3. This corresponds to a specific power density of 3.6 kW/cm3 for a 10‐ns pulse. Because of the high buffer gas pressure that can be used in the TEA‐CVL, containment of the copper vapor in the heated zone can be maintained for an extended period, making a sealed system possible.

Selective ir laser chemistry of CDF3 in natural fluoroform

Abstract: Selective decomposition of CDF3 at natural abundance level (≈150ppm) in fluoroform has been achieved by infra-red multiple-photon excitation at moderate substrate pressure using 100 ns FWHM CO2 laser pulses. Effects of energy fluence, number of laser pulses, buffer gas pressure and substrate pressure on decomposition yield and bulk selectivity are reported and discussed.

Laser initiation of an electrical discharge channel in cesium contained gas

Abstract: A high power laser light tuned to the resonance line (455.5 nm) of the cesium atom induced photoionization in argon buffer gas and initiated a channel discharge of 60 cm length. The time lag from the laser injection to the channel breakdown was observed and compared with numerical result based on a simple model of the discharge channel. It was confirmed that good agreement was obtained between both time lags. A simple model well described the fundamental characteristic of the channel breakdown.

Ternary gas mixture for diffuse discharge switch

Abstract: A new diffuse discharge gas switch wherein a mixture of gases is used to take advantage of desirable properties of the respective gases. There is a conducting gas, an insulating gas, and a third gas that has low ionization energy resulting in a net increase in the number of electrons available to produce a current.

Quenching of resonant laser-driven ionisation at high buffer gas pressures

Abstract: The modification of ion production efficiency via resonant laser-driven ionisation in the presence of high buffer gas atmospheres has been experimentally investigated in a barium vapour The populations of several energy levels of neutral and singly ionised Ba were measured as a function of both helium and argon pressures by the time-resolved hook technique The behaviours of He and Ar are quite distinct The percentage of ionisation decreased monotonically from nearly 100% to less than 10% as the helium pressure was increased from 001 to 1 atm, while no quenching was observed in 1 atm of Ar These observations are consistent with a quenching mechanism based in part on cooling of the 'hot' electrons through momentum-changing elastic collisions with the He atoms

Short‐length large‐bore metal vapor cell

Abstract: Stainless‐steel cells with a small cooled length (window to hot zone) to tube diameter ratio designed for use at electron storage rings have been constructed and tested using barium metal. Under optimum conditions of barium sample size and helium buffer gas pressure the cell and oven system can be operated for at least 8 h with constant (within experimental errors) line‐of‐sight number densities, Nl, of ∼1016 cm−2. When Nl values begin to fall toward the end of their initially constant period or the light path becomes blocked by barium condensed at the edge of the hot zone, the original cell conditions can be regenerated within 15 min. These regeneration procedures provide essentially unlimited (though segmented) operation of the system with constant Nl values.