Showing papers on "Buffer gas published in 1990"

Broadly tunable vacuum-ultraviolet radiation source employing resonant enhanced sum–difference frequency mixing in krypton

Abstract: Vacuum-ultraviolet (VUV) generation by resonant third-order sum–difference frequency conversion (wVUV = 2wR − wT) in krypton has been investigated. The frequency wR (λR = 212.55 nm) was resonant with the Kr two-photon transition 4p–5p[1/2, 0]. By tuning wT in the range λT = 220–860 nm it was possible to generate wVUV in the wavelength range λVUV = 200–120 nm. The conversion efficiency was enhanced in the range 121–123 nm by phase matching with a normally dispersive buffer gas (Ar); under the best phase-matched conditions employed, VUV output powers at the Lyman-α wavelength of the order of 1 kW were inferred from the estimated VUV pulse energy. This source was used to measure high-lying members of the Mg principal series near 162 nm. High resolution and excellent sensitivity of detection, when a thermionic diode detector was used, have been demonstrated.

Chemical reactivity of iron atoms near room temperature

Abstract: The reactivity of ground state iron atoms with respect to atom transfer and adduct formation reactions with a variety of simple molecules in Ar buffer gas near room temperature has been investigated. Iron atoms are produced by visible multiphoton dissociation of iron pentacarbonyl or ferrocene, and their removal by added gases under pseudo‐first‐order conditions is monitored by resonance fluorescence excitation at variable time delay following the photolysis pulse. Upper limits for second‐order rate constants for reaction of ground state iron atoms with O2, CO, H2O, (CH3)2O, C2H2, C2H4, N2O, C2H4O, and CF3Cl at room temperature and 100 Torr total pressure are estimated to be in the range (2–10)× 10−15 cm3 molecule−1 s−1, which corresponds to reaction probabilities of less than ≂10−5 per hard sphere collision. Pseudo‐second‐order rate constants in the range (2–60)× 10−14 cm3 molecule−1 s−1 are found for 1:1 adduct formation reactions of ground state iron atoms with C6H6, 1,3‐butadiene, NH3, and NO. The for...

Apparatus for controlling the composition of a laser gas or gas mixture

Abstract: Apparatus for controlling the composition of a laser gas or gas mixture includes a cryogenic gas-processor (2) connectible to a gas laser (1) selectively to receive gas or a gas mixture therefrom, remove impurities from the gas or gas mixture and selectively return the purified gas or gas mixture to the laser (1). A high temperature gas-purifier (3) is provided in gas flow connection with the processor (2) and with the laser (1) selectively to receive gas or a gas mixture therefrom, remove halogen and/or impurities from the gas or gas mixture and selectively return the dehalogenated or purified gas or gas mixture to the laser (1). Gas analysis means (4) is provided for receiving gas or gas mixture from the laser (1) to analyze it and produce output signals indicative of the actual composition of the laser gas or gas mixture. The output signals are passed to control means (6) operative to compare the actual composition values with desired composition values and operate the processor (2) and/or purifier (3) and/or a clean gas or gas mixture source (5) selectively connectible to the laser (1) to control the laser gas or gas mixture composition.

High efficacy electrodeless high intensity discharge lamp

Abstract: Improved efficacy and color rendition are achieved in a high intensity discharge, solenoidal electric field (HID-SEF) lamp by using in the arc tube (10) a novel combination of fill ingredients, including lanthanum halide, sodium halide, cerium halides and xenon or krypton as a buffer gas. The preferred lamp structure is that of a short cylinder having rounded edges in order to achieve isothermal lamp operation and further efficacy improvement.

Effective ion temperatures in a quadrupole ion trap

Abstract: The reaction of O 2 .+ with methane is used as a «chemical thermometer» to obtain information concerning effective ion temperatures in a Paul-type quadrupole ion trap using He buffer gas. The rate constant as well as the product distribution indicates an effective temperature of 600-700 K for O 2 .+ ions trapped for long times; i.e., a similar rate constant and a similar product distribution is obtained at 600-700 K for O 2 .+ ions with a Maxwell-Boltzmann energy distribution. Other results suggest that this temperature may also adequately describe the behavior of some polyatomic ions in the ion trap

Stimulated collision induced processes in sodium vapor in the presence of helium

Abstract: Stimulated resonant emission and stimulated Raman effects in sodium vapor in the presence of helium are investigated experimentally. The intensity dependence of these effects on the buffer gas and sodium vapor pressures, and on the intensity and detuning of the exciting radiation are obtained in experiment. Our experimental results agree with the most recent theoretical calculations.

Observation of CH3Zn as a stable product in the KrF laser photodissociation of (CH3)2Zn

Abstract: Single‐photon dissociation of (CH3)2Zn has been examined at 248 nm in the gas phase. The relative yields of CH3Zn and Zn as a function of buffer gas pressure were determined by laser‐induced fluorescence. With He as the buffer gas, the yield of CH3Zn increases from ∼20% at very low pressure to ∼65% at 500 Torr. The yield of Zn atoms correspondingly drops over the same pressure range. This behavior is due to the increasing probability for collisional stabilization of the primary photoproduct, vibrationally hot CH3Zn, as the buffer gas pressure increases, thereby quenching its subsequent thermal dissociation to CH3 and Zn. Information on the nascent vibrational energy distribution of the CH3Zn photoproduct is obtained by examining the probability of CH3Zn stabilization vs buffer gas pressure.

Linear ion trap for second-order Doppler shift reduction in frequency standard applications

Abstract: The authors have designed and are presently testing a novel linear ion trap that permits storage of a large number of ions with reduced susceptibility to the second-order Doppler effect caused by the RF confining fields. This new trap should store about 20 times the number of ions as a conventional RF trap with no corresponding increase in second-order Doppler shift from the confining field. In addition, the sensitivity of this shift to trapping parameters, i.e., RF voltage, RF frequency, and trap size, is greatly reduced. The authors have succeeded in trapping mercury ions and xenon ions in the presence of helium buffer gas. Trap times as long as 2* 10/sup 3/ s have been measured. >

Time-resolved measurements of excited state densities in a copper vapor laser

Abstract: Time-resolved measurements of copper and neon buffer gas excited-state densities in a copper vapor laser (CVL) during the excitation pulse and early afterglow are reported for both optimum and nonoptimum power-input conditions. The optimum condition results demonstrate that the termination of the laser pulse in the CVL is due not only to filling of the lower laser level, but also to a reduction in the upper laser-level pumping related to the collapse of power input to the plasma during the excitation pulse. Time-resolved measurements of excited-state densities over a wide range of input-power conditions clearly illustrate that the increase in copper density with power input reduces the peak electron temperature in the plasma during the excitation pulse. This reduction in peak electron temperature is important in limiting the scaling of CVL output power with input-power-copper density. >

Apparatus for removing carbon dioxide gas and moisture from methane-rich gas mixture

Abstract: This invention relates to the improvement of the so-called PSA method, and more particularly to an apparatus for removing inert gases such as C0 2 gas, moisture and the like, and recovering active gases such as H 2 , CH 4 and the like as useful fuel gases for city gas with the utmost effciency, which are commonly produced during the intermediate process of city gas production on SNG basis in using the PSA method. The present inventive system comprises four adsorption column units (A)(B)(C)(D), each of which is used in sequence cyclically under the rotation including an adsorption process, a super-adsorption process with a rinsing step, a desorption process with a series of depressurization steps by suction, and a pressurization process by means of a carbon type adsorbent filled within the columns. The recovered gases obtained in the desorbed gases are recycled into a crude gas feeding pipe line (a), as these still contain a combustible component such as H 2 , CH 4 and the like which require further refinement repeatedly without any gas pressure fluctuation because of the employment of a water-sealed gas holder (12) positioned between a desorbed gas pipe line (g) and a recovered gas pipe line (f).

Substance vaporizing apparatus

Abstract: A substance vaporizing apparatus which uses a vapor (5) of a substance (4) generated by heating the substance in a gas-filled tube (2) as an exciting medium or an ionizing medium. The apparatus employs an improved container for containing the substance within the gas-filled tube (2). The improved container suppresses the rate of emission of the vapor of the substance into a discharge space (3) defined by the gas-filled tube (2) to hold the vapor density of the substance (4) at an optimum low value for laser oscillation relative to the buffer gas density in the discharge space (3). Thus, the mean free path of the atoms of the substance (4), namely the average distance traveled by the atoms between elastic collisions with the electrons, ions and neutral atoms of the buffer gas, is increased to increase the number of atoms of the substance (4) excited to a higher energy level, which, consequently, increases laser power and enhances laser beam or ion beam accelerating energy. The employment of segmental discharge electrodes (43,44) each consisting of a plurality of partial electrodes (43a,43b,43c,44a,44b,44c) diametrically distributed in the discharge space (3) of the gas-filled tube (2) enables heating the buffer gas in a substantially uniform diametrical temperature distribution, which enables to increase the length and diameter of the laser medium. The employment of two pulse generating circuits (200,300) promotes the relaxation of the atoms of the substance (4) from a lower energy level to the ground energy level to enable the next application of a pulse voltage to establish a complete population inversion, which enables the substance vaporizing apparatus to operate at a high efficiency at a high discharge frequency.

Anharmonic oscillation of ions trapped in a rf trap with light buffer gas

Abstract: The effect of a light buffer gas on the anharmonic oscillation of ions trapped in a rf trap is studied. The rf resonance absorption signals showed a change of the signal height and the hysteresis with the sweep direction of the dc voltage or the probing frequency due to the anharmonicity of the pseudopotential well of a rf trap. It was found that the signals changed drastically or even disappeared depending on the pressure of buffer gas, although almost the same number of ions were trapped. These effects indicate that the sensitivity of detection of the trapped ions can be improved by appropriately choosing the pressure of the buffer gas and the sweep direction. The trapped ions could be detected until 76 h 20 min and the storage time of 1.3×105 s was determined when these parameters were optimized.

2.5 kHz high repetition rate XeCl excimer laser

Abstract: An XeCl excimer laser was operated at the high repetition rate of 2.5 kHz, which can circulate the laser gas uniformly and efficiently. The characteristics of the gas flow rate and the average laser power versus the repetition rate were investigated in both He and Ne buffer gas mixtures. In He buffer gas, the average laser power saturates at 1.3 kHz and, thereafter, drops abruptly. On the other hand, stable operation at the highest repetition rate, 2.5 kHz, has been attained in Ne buffer at a gas flow rate of 54 m/s with an average laser power of 87 W.

Improvement of the KrF(B→X) excimer lamp with 248 and 193 nm dual wavelength emission using an Ar buffer

Abstract: A quasi‐continuous KrF(248 nm:B→X)fluorescence of over 8 ms pulse duration with a 100 Hz operation frequency was observed in a microwave‐discharge‐pumped KrF lamp with an Ar buffer gas in place of the He/Ne buffer. With an average microwave power deposition of 517.1 W, the maximum average KrF fluorescence power was 58.2 W obtained at a KrF intrinsic efficiency of 11.2% with the lamp gas mixture of F2/Kr/Ar=4/2/94(%) at 50 Torr and simultaneously an average ArF(193 nm:B→X) fluorescence power of 17.4 W with over 8 ms pulse duration at a 100 Hz operation frequency was also obtained. Based on the total fluorescence power of ArF and KrF, the intrinsic efficiency becomes as high as 14.6%. The maximum KrF intrinsic efficiency was 13.8% obtained with a lamp gas mixture of F2/Kr/Ar=2/2/96(%) at 50 Torr. The maximum average KrF fluorescence power and KrF intrinsic efficiency with the Ar buffer has exceeded the maximum average KrF fluorescence of 53 W and the corresponding KrF intrinsic efficiency of 8.3% achieved previously with the lamp gas mixture of F2/Kr/He/Ne=2/1/48.5/48.5(%) at 50 Torr. Dual wavelength emission should be useful for those that need both the 248 and 193 nm wavelengths.

Rapid gas quenching process

Abstract: Increased cooling rate of an article heated to an elevated temperature is achieved by flowing an inert gas mixture of helium and another inert gas over the article under conditions of turbulent flow.

Metallic vapor laser apparatus

Abstract: A metallic vapor laser apparatus includes a cylindrical discharge tube (31) having an internal space (2), a heat-insulating material (6) encompassing the periphery of the discharge tube (31), and two electrodes (3a) and (3b) having a cylindrical portion coaxial with the discharge tube (31) and disposed at both ends of the discharge tube (31). The internal space (2) are filled with a gas containing the vapor of copper as a laser medium for effecting laser oscillation by the excitation of the filler gas and the discharge. A gas inlet (40) from introducing a buffer gas (G) into the inside is formed at one of the outside position of the two electrodes (3a) and (3b) in the axial direction and gas exhaust ports (33a) for exhausting the buffer gas (G) to the outside are formed in the proximity of both ends of the heat-insulating material (6) so that flow paths in which the buffer gas flows from the side of the internal space (2) to the side of the heat-insulating material are formed between the discharge tube (31) and the electrodes (3a) and (3b).

Experimental study of the laser diode pumped rubidium maser

Abstract: The continuous operation of an /sup 87/Rb maser, using a laser diode as the optical pumping source, is reported. The maser uses a TE/sub 021/ cavity surrounding a cell containing the atoms and 10 torr of N/sub 2/ as a buffer gas. The optical pumping is accomplished by using a commercial laser diode frequency-locked with the use of an external rubidium cell. The power and frequency of the RF output signal of the maser as a function of the laser frequency detuning are presented. >

Efficient XeF(C to A) laser excited by a coaxial electron beam at intermediate pumping rates

Abstract: Experiments carried out with an electron-beam apparatus that produced pump pulses with an intermediate pulse length of about 174 ns (FWHM) and a power-deposition rate on the order of 1 MW/cm/sup 3/ are described. The authors present initial measurements with gas mixtures in which part of the Ar is replaced by Ne as a buffer gas. The lower stopping power of Ne can be compensated for by using a higher gas pressure because the system presented can be pressurized to a total gas pressure of 10 bar. It was found in earlier experiments with other excimers (ArF,KrF) that the variation of the buffer gas may have important effects on the optimum pressure regime total output energy, and kinetics. Useful information can be gained for discharge-excited systems, although the ionic channel dominates the electron-beam excitation kinetics. >

Light-induced drift of Na in molecular buffer gases

Abstract: Conventional light-induced drift is based on purely elastic velocity-changing collisions. The authors discuss qualitatively the potentialities of light-induced drift originating from inelastic velocity-changing collisions, which may occur in a molecular buffer gas. In such collisions a large fraction of the electronic excitation energy of the absorbing particle may be transformed into kinetic energy thus affecting light-induced drift. The authors report experiments on light-induced drift of Na in various molecular buffer gases and compare these with their predictions.

Hydrogenated Amorphous Silicon by Infrared Multiphoton Absorption with a Pulsed CO2‐Laser

Abstract: The following work gives a discussion on hydrogenated amorphous silicon (a-Si:H) film preparation by laser induced chemical vapor deposition (LICVD) using a pulsed CO2-laser in a parallel configuration. Deposition rate and initiation of polymerization were studied as a function of total pressure, gas flow, gas mixture (buffer gas, silane and/or disilane), substrate temperature, and radiation flux. The results lead to a reaction model where higher silane homologues play an important role for the film production. The film properties strongly depend on the substrate temperature Ts. The activation energy Ea of the dark conductivity decreases from 1.1 eV to 0.7 eV for films prepared at Ts = 230°C to 450°C. In the same temperature range, the dark conductivity σd increases from ∼10−14 to ∼10−10 (Ω cm)−1, whereas the photo conductivity σph shows a maximum of ∼10−6 (Ω cm)−1 at Ts = 320-330°C. These values, especially their temperature behaviour, are compared with the results of other CO2-LICVD works and further production methods. It is shown that the film formation depends on the gas phase chemistry as well as on the substrate temperature.

Process and apparatus for gas treatment of a product

Abstract: Process for the gas treatment of a product in a confined treatment zone by a flow of an inert gas, such as nitrogen, wherein a gas flow which originates from a gas treatment containing a high proportion of nitrogen, becomes loaded with impurities such as: oxygen, and/or carbon dioxide, and/or water, and wherein the flow of gas which originates from the treatment undergoes at least substantially in part, a removal of the impurities in a separator of the adsorption or permeation type before being recycled as treatment gas, with addition of a compensating gas flow predominantly containing nitrogen. Application for example to the deoxygenation of liquids, in particular nutritious liquids, to the providing of inert conditions in ovens or storage enclosures for products such as electronic pieces, or in chambers used for preserving nutritious products in an atmosphere which is substantially free from oxygen.

Helium pumping by argon frosting on a 4.5 K surface

Abstract: Pumping of helium gas by means of argon frosting on a bare copper surface cooled to ∼4.5 K has been investigated in one of the neutral beamlines of the DIII‐D tokamak. The beamline is designed to handle high power hydrogen and deuterium beams and corresponding high gas feed rates. By prefrosting the cryo panels with argon in an actual beamline, multisecond helium gas pulses have been handled at a background gas pressure low enough for formation and transport of helium beams. Appreciable pumping of helium gas was observed even at an argon‐to‐helium ratio as low as 20.

Collisional broadening of Ba I line (553.5 nm) by He or Ar

Abstract: The Doppler-free line shape of the 6s21S0 − 6s16p11P1 transition at 553.5 nm in natural Ba in the presence of an argon or helium buffer gas has been measured at 744 K for gas pressures from 0.2 to 100 Torr. Using the measured data for pressures above 5 Torr, the broadening rate coefficients for the half width at half maximum (HWHM) are determined to be (4.9±0.5)⊗10−9 and (5.0±0.5)⊗10−9 s−1 cm−3 for helium and argon respectively.

Electrolytic treatment of water to be treated

Abstract: PURPOSE: To reduce the gaseous hydrogen concn. at the time of treating water using a fixed-bed three-dimensional electrode-electrolytic cell while liberating gas by introducing an inert gas into a discharge pipe for water to be treated and a storage tank. CONSTITUTION: Gaseous hydrogen and oxygen are generated on a fixed bed 5 in the electrolysis of water, and the gaseous mixture consisting of both gases and having a hydrogen concn. within the explosion limits and the water to be treated are introduced into a storage tank 15 through a discharge pipe 9 for the water to be treated. A specified amt. of an inert gas such as air is introduced from an inert gas inlet 11 and an inert gas inlet pipe 17, the hydrogen content of the gaseous mixture in the pipe 9 and storage tank 15 is reduced to <4vol.% which is beyond the explosion limits, and the danger of explosion due to gaseous hydrogen is averted. Although the gas pressure in the storage tank is increased by the introduction of an inert gas, the excess gas is leaked out from the joint between the tank 15 and a lid 16, and the pressure in the tank 15 is kept almost constant. COPYRIGHT: (C)1992,JPO&Japio

Improved short-pulse pumping of stimulated Raman scattering in lead vapor

Abstract: Improved efficiency for short pulse stimulated Raman scattering (SRS) in Pb vapor is obtained using accumulation of gain between a closely spaced pulse pair. The peak power conversion efficiency of the delayed pulse is increased to 40%, in contrast to 15% for a single pulse. Numerical modeling gives good agreement with observation, and suggests that this enhancement is caused by the continued presence of coherent excitation produced by the first pulse. The dependence of the enhancement in delayed-pulse efficiency on Xe buffer gas pressure in the Pb-vapor cell is attributed to changes in the transient response time T/sub 2/ of the Pb medium with Xe pressure. >