Showing papers on "Buffer gas published in 1978"

Detection of atomic hydrogen and deuterium by resonant three‐photon ionization

Abstract: Resonantly enhanced three‐photon ionization spectroscopy is employed for the detection of ground‐state atomic hydrogen and deuterium. Concentrations as low as 4×109 atoms/cm3 in the presence of 1017 atoms/cm3 of buffer gas are detected with an implicit time resolution of less than 10 nsec. A useful dynamic range of at least 4×104 is demonstrated and saturation of the ionization in a 2×10−4‐cm3 focal volume is observed. The presence of H can easily be distinguished from that of D and the three‐dimensional spatial distribution of H or D can be determined.

Ionic recombination of Kr+ and Kr+2 with F− in dense buffer rare gases

Abstract: Rates, α, for the recombination of Kr+ and Kr+2 with F− in various buffer rare gases (He, Ne, Ar, Kr, Xe) at 300 K are calculated for a wide range of gas pressures For pressures 1–5 atm, the population of KrF* via recombination is greatest for Ne and Ar as third bodies, yielding α∼3×10−6 cm3 sec−1, while for pressures ≳10 atm, He is to be preferred as a buffer gas

The role of buffer gases in optoacoustic spectroscopy

Abstract: The dependence of an acoustically resonant optoacoustic signal on the molecular weight and thermodynamic and transport properpties of the buffer gas is reported. Our results show that careful selection of such gases can significantly increase the sensitivity and flexibility of optoacoustic spectroscopy. We also demonstrate that such thermodynamic quantities as γ (≡Cp/Cv) and sound velocity can now be measured readily and accurately. Other potential applications are suggested.

Apparatus for the coloration of laser‐quality alkali halide crystals

Abstract: A heat‐pipe apparatus allowing for the additive coloration of laser‐quality alkali halide crystals is described. It has the following features: (1) Prepolished crystals emerge ready for direct installation in the laser; (2) F‐center densities are directly proportional to the buffer gas pressure; (3) An air lock allows the same charge of alkali metal to be used many times over.

Multiwatt optically pumped ammonia laser operation in the 12–13 μm

Abstract: Design and operating caracteristics of high pulse repetition rate NH3 laser producing up to 20 W of average output power are described. The NH3 laser, operating in the 12–13 μm region was optically pumped with a high pulse repetition rate TEA CO2 laser. Dependences of the NH3 laser output on the pump energy, ammonia and buffer gas pressures and pulse repetition rate have been studied. The conversion efficiency of up to 16% has been received.

Stimulated emission mechanism of a copper vapor laser

Abstract: An investigation is made of the elementary processes and characteristics of a pulsed nanosecond discharge plasma in a copper vapor–buffer gas mixture and of their correlation with the laser energy parameters. It is shown that the saturation of the stimulated emission power with rising pressure must be associated with a drop in the effective electron temperature. The complex dependence of the stimulated emission energy on the buffer gas (neon) pressure is identified and explained. It is established that at high operating pressures the pulse repetition frequency is governed by the electron cooling rate and by the plasma recombination in the afterpulse interval. At low pressures and for small laser tube apertures the pulse frequency is governed by the quenching of the metastable states by the walls. The excitation conditions are optimized and an efficiency of 2.1 % is achieved.

Measuring the velocity of individual atoms in real time

Abstract: It is proposed that the thermal velocity of a single atom could be measured in real time using a laser time-of-flight velocimeter (LTV) operating on the principle of laser resonance fluorescence. Theoretical data are presented for several atomic species that have resonances within the range of available dye-laser systems. It is shown that measurements in the subsonic region are certainly feasible. The atoms could be either in vacuum or in a buffer gas, e.g., at atmospheric pressure. Measurements in the transonic and supersonic region also appear possible. One potential application is the measurement of flow speeds in wind tunnels, perhaps as high as Mach 45.

Effect of gaseous additives on the response of the helium ionization detector

Abstract: Changes in the response of the helium ionization detector which occur when varying amounts of gases are added to the helium carrier gas at different applied voltages have been investigated. The addition of hydrogen, argon, oxygen, or nitrogen to the helium carrier gas causes an increase in the detector response when the voltage applied to the detector is more than 350 V, and a decrease in the detector response when the applied voltage is less than 350 V. It was also found that the detector responds positively and linearly to neon when high concentrations of gaseous additives were added to the helium.

A continuously pulsed copper halide laser with a cable-capacitor Blumlein discharge circuit

Abstract: Experimental characteristics of a continuously pulsed copper halide laser with a cable-capacitor Blumlein discharge circuit are reported. Quartz laser tubes 1 m in length and 1.5 and 2.5 cm in diameter were employed to study the effects of the electrical circuit, lasant, and buffer gas on laser performance. Measured properties of the Blumlein circuit are compared with an analytic solution for an idealized circuit. Both CuCl and CuBr with neon and helium buffer gas were studied. A maximum average power of 12.5 W was obtained with a 1.5 nF capacitor charged to 8 kV and discharged at 31 kHz with CuCl and neon buffer gas at 0.7 kPa in a 2.5-cm-diam tube. A maximum efficiency of 0.72 percent was obtained at 9 W average power. Measurements of the radial distribution of the power in the laser beam and the variation of laser power at 510.6 and 578.2 nm with halide vapor density are also reported. Double and continuously pulsed laser characteristics are compared, and the role of copper metastable level atoms in limiting the laser pulse energy density is discussed.

Buffer gas effect on ground and metastable populations in a pulsed CuBr laser

Abstract: We have measured the time dependence of the concentration of copper atoms in the ground and metastable states in a pulsed CuBr laser by monitoring the absorption of the atomic copper lines 244.2 and 510.6 nm. In agreement with previous measurements in a CuCl laser, we found the populations to grow after the dissociation pulse, peaking many tens of microseconds later. Temperature and buffer gas species and pressure have a considerable influence on the details of the temporal evolution. The results are interpreted in terms of a schematic mechanism involving parallel dissociation processes. Qualitative agreement with the experimental results is quite good, but no attempt was made to elucidate the physical processes which actually occur during and after the dissociation pulse. In the course of the experiment the radiative transition probability of the 244.2 nm line was measured and found to be 0.26 \times 10^{-7} s-1.

Electrically excited mercury halide laser

Abstract: An improved electric-discharge-excited mercury halide dissociation laser operable on the (B-X) transitions in HgCl, HgBr and HgI at 558, 502 and 443 nm respectively. The laser discharge cell is elongated and made from temperature-resistant silicon-glass laminate or any other suitable material and includes separate ceramic crucibles for containing mercuric dihalide crystals. A pair of electrodes, each having external terminals, extend along the linear axis of the cell in parallel relationship with the linear axis and each other. Ultraviolet discharge means is also provided for preionizing a buffer gas of helium to which nitrogen has been added. The improvement comprises the addition of about 10% nitrogen to the buffer gas of helium which is admitted to the laser cell prior to excitation. The addition of nitrogen may act to selectively remove the terminal levels of the mercury halide laser transitions, thereby permitting more efficient extraction of the optical energy from the laser media. Thus improvements in both efficiency and output energy are obtained. The laser cavity is completed by a fully and a partially reflective surface for the wavelength of operation. The gases are preionized and excited by pulsed electrical energy from separate sources.

Long‐duration high‐efficiency operation of a continuously pulsed copper laser utilizing copper bromide as a lasant

Abstract: A copper laser utilizing copper bromide as a lasant and neon as the buffer gas has been operated at an average laser power of between 16 and 19.5 W for a period of 68 h. Lasing was attained at a pulsing rate of 16.7 kHz in a quartz discharge tube 2.5 cm in diameter with an electrode separation of 200 cm. The laser energy/pulse and peak power/pulse corresponding to an average power of 19.5 W are 1.2 mJ and 30 kW, respectively. The ratio of laser power at 510.6 and 578.2 nm varied from 3.9 to 1.1 corresponding to a total average laser power of 4 and 18 W, respectively. The highest wall plug and capacitor efficiency measured during 68 h of operation was 0.7 and 1.1%, respectively.

Metal dihalide photodissociation cyclic laser

Abstract: A pulsed laser produces emitted laser energy by photodissociation of metal dihalide and cyclic recombination. A metal dihalide selected from sub-group II-B of the periodic table of elements is contained within an elongated sealed enclosure. Ultraviolet photons supplied from another laser employed as an excitation pump causes dissociation of the metal dihalide for achieving the ultimate laser action. An inert buffer gas is included within the enclosure for aiding photon energy transfer uniformity and to provide vibrational relaxation of the lasing medium in its electronic states. Two reflective surfaces, one of which is only partially reflective, are aligned with the principal axis of the laser assembly for producing an optical resonator for the emitted laser energy.

Pulsed electron impact dissociation cyclic laser

Abstract: A pulsed laser produces emitted laser energy by electron impact dissociation of metal dihalide and cyclic recombination. A metal dihalide selected from sub group II-B of the periodic table of elements is contained within an elongate sealed enclosure. Two elongate electrodes having external terminals are supported in parallel relationship within the enclosure, forming a gap parallel to the principal axis of the enclosure. A source of pulsed electric power is connected to the terminals of the two electrodes, producing repetitive transverse electric discharges across the gap. An inert buffer gas is included within the enclosure for aiding electric discharge uniformity, and to provide vibrational relaxation of the lasing medium in its electronic states. The buffer gas is ionized by a third electrode within the enclosure connected to a source of pulses which immediately precede the pulses applied to the first and second electrode so that the lasing medium is preionized immediately prior to the principal electric discharge. Two reflective surfaces, one of which is only partially reflective, are aligned with the principal axis of the laser assembly for producing an optical resonator for the emitted laser energy.

High pressure sodium lamp

Abstract: PURPOSE:To obtain a high-pressure sodium lamp, which has a whitish luminous color akin to that of an incandescent lamp and an output of below 100W, by restricting the inner diameter, the wall load, the molar sodium proportion and the color temperature of an emission tube, which is made of a light-transmitting ceramic member and both ends of which are provided with electrodes. CONSTITUTION:An emission tube 1 is constituted by charging electrode structures 3 and 4 at both ends of a pipe 2, which is made of a light-transmitting insulating matter having both excellent heat resistance and high corrosion resistance. It includes tungsten electrodes 7 and 8 which are attached to ends of exhast-pipes 5 and 6 made of niobium and is charged with a given amount of sodium used as a luminous metal, a given amount of mercury used as a buffer gas, and xenon gas having a given pressure and is used as a starting gas. The inner diameter (D) of the pipe 2 is restricted to the range of within 5.5mm.-8.0mm., and the load of the all of the emission tube 1 is restricted to the range of within 8 W/cm -22 W/15 2. The molar proportion of sodium to the charged amalgam should be in the range of 50mol%-70mol%. The tube 1 is lit so that its color temperature becomes in the range of 1,900K-2,300K.

Long-life sealed copper vapor laser

Abstract: It is shown practically that a sealed copper vapor laser can operate for more than 2000 h and that the increase in laser service life caused by increasing the buffer gas pressure is associated with some reduction in laser efficiency. The possibility is discussed of increasing the laser efficiency and also of reducing the time taken for the laser to heat up to the working temperature.

Pulsed cyclic laser based on dissociative excitation

Abstract: A pulsed laser produces emitted laser energy by dissociative excitation ofetal dihalide and cyclic recombination. A metal dihalide selected from subgroup II-B of the periodic table of elements is contained within an elongate sealed enclosure. Two elongate electrodes having external terminals are supported in parallel relationship within the enclosure, forming a gap parallel to the principal axis of the enclosure. A source of pulsed electric power is connected to the terminals of the two electrodes, producing repetitive transverse electric discharges across the gap. An inert buffer gas is included within the enclosure for aiding electric discharge uniformity, and to provide vibrational relaxation of the lasing medium in its electronic states. The buffer gas is ionized by a third electrode within the enclosure connected to a source of pulses which immediately precede the pulses applied to the first and second electrode so that the lasing medium is preionized immediately prior to the principal electric discharge. Two reflective surfaces, one of which is only partially reflective, are aligned with the principal axis of the laser assembly for producing an optical resonator for the emitted laser energy.

Chemical kinetics and gasdynamics of a Q-switched iodine laser with an optically thick active medium

Abstract: A calculation technique is proposed and numerical calculations are made of the spatial distributions of the energy stored in an iodine laser with an optically thick active medium pumped by a planar blackbody radiation source in the 180–700 nm spectral range. In describing the evolution of the laser active medium, simultaneous allowance is made for: relaxation and chemical processes (using recent data on their rate constants), heat liberation and its influence on the rates of elementary processes, absorption band profiles, and motion of the gas, which is mainly caused by nonuniform heating of the medium. Calculations are made of the laser output energy as a function of the degree of dilution with the buffer gas and the single-pulse switching time, and of the efficiency. The spatial distributions of the population inversion, gas temperature, density, velocity and pressure, pumping rate, and microparticle concentration are determined for different times.

Infrared spectroscopic lamps and gas detectors incorporating such lamps

Abstract: A novel enhanced infrared spectral light source employing gas discharge, to be designated hereafter as EISLS, and a detection system using such an EISLS lamp for gas detection of a given molecular gas, the lamp adapted to produce spectral radiation at selected, sharply defined, spontaneous emission frequencies in the infrared corresponding to an absorbing molecular rotation-vibration transition band of the given gas. According to one feature, a gas mixture within the chamber provides an excitable buffer gas and a quantity of the given gas, the buffer gas having a state excitable by the excitation means and matched to the given gas in the manner that energy from the buffer gas state can transfer via collisions to the given gas and excite the upper levels of the absorbing transition band, whereby resultant radiative decay of the upper levels to the lower levels of the absorbing transition band produces the desired selected spontaneous emissions from the given gas, enhanced by the buffer gas. The given gas may be placed in the chamber or may be produced by interactions of other gases and the electrical discharge within the chamber. According to another feature, in such an EISLS spectroscopic lamp which produces spontaneous emissions corresponding to an absorbing band and other undesired spontaneous emissions as a result of excitation of other levels, the parameters being selected to make the desired emissions have a decay time long relative to the decay time of the undesired emissions, means are provided to interrupt the excitation means periodically and to delay the utilization of emission from the lamp a time following the instant of each interruption to the period when the other levels and associated emissions are decayed and the given gas continues to emit at the desired transition. According to another feature an EISLS spectroscopic lamp which produces sharply defined spontaneous emissions corresponding to an absorbing band of a given gas is arranged to direct its emission along a detection path in which the given gas may appear, and is combined with means to provide a modulated magnetic field either in the detection path to cause modulation of the absorbing transitions of paramagnetic gas to be detected or in paramagnetic emitting gas in the lamp to cause frequency modulation of the emitted spectral radiation, and an electronic detection means is provided, responsive to the resultant modulated intensity reaching the detector, to enhance the detection sensitivity.

Investigation of the fluorescence of molecular iodine in the 340 nm band

Abstract: Results are presented of observations of the fluorescence of iodine vapor, subjected to cw optical pumping, as a function of the temperature and pressure of the SF6, N2, Ar, Xe, He, and Kr buffer gases. It is shown that an increase of the fluorescence in the 340 nm band with rising buffer gas pressure is accompanied by a decrease in the iodine fluorescence in the 250–330 nm band. The efficiency of the action of the buffer gas depends on its molecular weight and on the wavelength of the exciting light. The intensity depends on the buffer gas used. An estimate is made of the rate of quenching of the fluorescence by iodine molecules in the ground state kqτ =(3.0±0.30)×10−18 cm3. For Xe, kqτ = (1.2±0.6)×10−18 cm3. It is shown that the fluorescence quantum efficiency η does not depend on the mixture temperature up to 425 °C. The value of η for optical pumping (λ = 190 nm) of a mixture of iodine vapor and 5 atm SF6 is η = 0.04±0.02 and for a mixture with 1.5 atm Ar, is η = 0.05±0.02.

Investigation of the properties of an optothermal detector

Abstract: An optothermal detector with a pyroelectric sensitive element is described. Estimates are given of the limits of applicability of this device and its performance compared with the spectrophone. The dependences of the absorption coefficient of formaldehyde CH2O on its pressure and that of the buffer gas, determined experimentally at the P12–11 (17) CO line wavelength, are discussed. It is shown that the device can be used at low pressures of the investigated gas.

Technique for measurement of inert gases in liquids by gas chromatography.

Abstract: A method for quantitative analysis of inert gases in liquids by gas chromatography is described. The technique comprises an equilibration system for partial extraction of dissolved gases from liquids and a gas chromatograph equipped with helium ionization detector. The method is particularly devised for determination of solubility coefficients of gases in liquid materials, e. g. water, aqueous solutions, blood, tissue homogenates, and for simultaneous measurement of several inert gases dissolved in liquids. Coefficients of variation for serial analyses of individual samples were ≦ 3%. The method is applicable to studies of blood-tissue transfer of respiratory and inert gases.

Explosion-proof inert gas producing method in tanker

Abstract: PURPOSE: To reduce the capacity and the fuel consumption quantity in an inert gas generator, by means of mixing by cooling and washing the inert gas of alow oxygen concentration and the waste gas of a diesel engine of a high oxygne concentration. CONSTITUTION: The waste gas is introduced to a scrubber 5 which cools, washes, and desulfurizes the waste gas, from an exhaust pipe 2 of a diesel engine 1 via a stop valve 4 of the high temp. gas by means of passing through a duct 3, and after being dewatered and removed dust by a demister 6, is sent to a buffering tank 15. The waste gas is sent to an inert gas supplying tube 18 by menas of mixing the waste gas with an inert gas of a low oxgen concentration produced by a combustion type inert gas generator 12. And an oxygen concentration detector 19 and a pressure detector 20 are aranged in the inert gas supplying tube 18, and the exact quality and exact quantity of an inert gas are sent by means of controlling a main supplying valve 16, an atmosphere discharge valve 17, an opening degree regulating valve 9, and a regulating valve 11. COPYRIGHT: (C)1980,JPO&Japio

Coaxial copper-vapor laser with a buffer gas at above atmospheric pressure

Abstract: A laser with a radial transverse discharge was found to operate effectively at above-atmospheric buffer gas pressures. A specific energy output of 25 mJ/cm3 was obtained at the melting point of copper (1500?C) for a neon pressure of 1.5 atm and a pump current density of 100 A/cm.