Showing papers on "Buffer gas published in 1996"

Structural Information from Ion Mobility Measurements: Effects of the Long-Range Potential

Abstract: In a number of recent studies, information about the structure of large polyatomic ions has been deduced from gas phase ion mobility measurements by comparing mobilities measured in helium to those estimated for assumed geometries using a hard sphere projection approximation. To examine the validity of this approach, we have compared mobilities calculated using the hard sphere projection approximation for a range of fullerenes (C20−C240) to those determined from trajectory calculations with a more realistic He−fullerene potential. The He−fullerene potential we have employed, a sum of two-body 6-12 interactions plus a sum of ion-induced dipole interactions, was calibrated using the measured mobility of C60+ in helium over an 80−380 K temperature range. For the systems studied, the long-range interactions between the ion and buffer gas have a small, less than 10%, effect on the calculated mobility at room temperature. However, the effects are not insignificant, and in many cases it will be necessary to cons...

Efficient excimer ultraviolet sources from a dielectric barrier discharge in rare‐gas/halogen mixtures

Abstract: The generation of excimer radiation in mixtures of the rare‐gases Kr or Xe together with chlorine gas has been investigated by a dielectric barrier discharge. The characteristics of the emission spectra of the excimers formed, centered around 222 and 308 nm, were obtained for different gas mixtures and total gas pressures using an ultraviolet (UV) monochromator. The influence of the gas mixture, chlorine gas concentration, total gas pressure, and buffer gas dependence of the UV intensity has been investigated using chemical actinometry. Conversion efficiencies (from input electrical to output optical energy) as high as 15% can be achieved under optimal conditions. This low‐cost and high‐power excimer lamp system can provide an interesting alternative to conventional UV lamps for industrial large‐scale UV processes.

Confinement narrowing and absorber speed dependent broadening effects on co lines in the fundamental band perturbed by xe, ar, ne, he and n2

Abstract: Lines of the CO fundamental band are studied at low concentration in He, Ne, Ar, Xe or N2 as buffer gas from 10 to 600 torr. The coefficient β0 associated with the Dicke narrowing effect is determined for each of the five mixtures. To obtain the proper value of this coefficient, when the pressure increases, the absorber speed dependence of the pressure broadening γ0 must be taken into account. Pressure shifts are also measured, and a faint asymmetry is observed for the COXe mixture. The line scanning is done with a TDL tightly controlled by a Michelson interferometer. A precision better than one-thousandth for absorbed intensity and a wavenumber precision of a few 10−5 is reached. These precisions were found necessary for the needed parameter measurements.

Evolution of ion internal energy during collisional excitation in the Paul ion trap: A stochastic approach

Abstract: A first‐order model is developed for collisional activation as effected via resonance excitation and helium buffer gas in the Paul ion trap. For an ion population at steady‐state under specified experimental conditions, the kinetic theory of ion transport in gases is first used to calculate an effective temperature shown to be identical to the internal temperature for molecular ions in an atomic gas. The evolution of the ion internal energy is then followed by a random walk simulation designed to be representative of the actual collisional energy transfer process, except ion losses due to dissociation and reactive processes during collisional activation are excluded. During the simulation, inelastic ion‐neutral collisions increase the average ion internal energy via small energy changes (both positive and negative) until a steady‐state condition is reached in which excitation and deexcitation processes are balanced. Histogramming the simulated data reveals a Boltzmann‐type internal energy distribution whose average internal energy is the same as that calculated for a true Boltzmann distribution at the same internal temperature.

Beams of short lived nuclei produced by selective laser ionization in a gas cell

Abstract: An on-line laser ion source has been developed for the production of elemental and isobaric pure beams of radioactive ions. It is based on selective resonant laser ionization of nuclear reaction products thermalized and neutralized in a noble gas at high pressure. The ion source has been tested in a wide range of recoil energies going from 1.3 MeV to ∼ 90 MeV. Efficient schemes of two step laser ionization through autoionizing states have been found for nickel, cobalt and rhodium. Residence times of the reaction products in a gas cell have been measured for helium and argon as buffer gas. Elementally pure beams of 54,55Ni and 54Co, produced in a light-ion induced fusion-evaporation reaction, and of 113Rh, produced in proton-induced fission of 238U, were obtained. An efficiency of the ion source of 6.6% for fusion reactions and of 0.22% for fission reactions has been obtained. A selectivity of the ion source of 300 for fusion and 50 for fission reactions has been achieved.

X-ray generator

Abstract: PROBLEM TO BE SOLVED: To provide an X-ray generator using buffer gas for inhibiting scattering particles from a plasma X-ray source, capable of reducing, adhering and deposition of the scattering particles in convenient, relative to an X-ray extracting direction and capable of being used constantly for a long time as a result, even if plasma generation is long at a short time intervals SOLUTION: An X-ray generator is constituted to irradiate a target member 401 in a pressure-reduced vacuum container 443 with an exciting energy beam 411, form a plasma 402, and extract and X-ray from the plasma 402 so that buffer gas is used to inhibit scattering particles to be radiated from the target member 401 and/or the plasma 402 In this case, the X-ray generator is provided with a scattering particle-inhibiting member 422 adjacent to or in the vicinity of a solid angle area 412, equivalent to a range in which the X-ray is to be extracted and a scattering particle dispersion inhibiting member 433, having a movable part 432 that can pass through the solid angle area 412 COPYRIGHT: (C)1997,JPO

Hydrogen and oxygen gas generating system

Abstract: A hydrogen/oxygen gas generating system includes a deionized water container and a cell for water electrolysis having anode and cathode compartments, the cell being submerged in deionized water in the container. Oxygen gas generated in the anode compartment is channeled to an oxygen gas separating chamber defined in the container at its top whereas hydrogen gas generated in the cathode compartment is channeled to a gas/liquid separator. The pressures of these gases are detected, and in accordance with the detected gas pressures, a first gas piping line for delivering oxygen gas outward from the oxygen gas separating chamber and a second gas piping line for delivering hydrogen gas outward from the separator are controlled such that the differential pressure between the gases may fall in a limited range. Water level in the oxygen gas separating chamber and water level in the gas/liquid separator are detected, and the detected levels are utilized to control the pressures and the supply of deionized water into the container. The system can generate hydrogen and oxygen gases of high purity under high pressure in a safe manner without a need for gas compressors.

High intensity electrodeless low pressure light source driven by a transformer core arrangement

Abstract: An electric lamp assembly includes an electrodeless lamp having a closed-loop, tubular envelope enclosing mercury vapor and a buffer gas at a pressure less than about 0.5 torr, a transformer core disposed around the lamp envelope, an input winding disposed on the transformer core and a radio frequency power source coupled to the input winding. The radio frequency source supplies sufficient radio frequency energy to the mercury vapor and the buffer gas to produce in the lamp envelope a discharge having a discharge current equal to or greater than about 2 amperes. The electrodeless lamp preferably includes a phosphor on an inside surface of the lamp envelope for emitting radiation in a predetermined wavelength range in response to ultraviolet radiation emitted by the discharge.

Pulsed gas introduction for increasing peptide CID efficiency in a MALDI/quadrupole ion trap mass spectrometer

Abstract: A pulsed valve was used for studying the effects of introducing heavy gases at different stages of operation of a quadrupole ion trap and for increasing the efficiency of collision-induced dissociation (CID) of peptide ions at low values of the Mathieu parameter q z . When amounts of heavy gases comparable to that of the helium buffer gas were introduced during the ion trapping, ion isolation, and mass spectral recording stages, the effects on performance were generally small or negative. However, injection of heavy gases during CID provided considerable improvement in fragmentation efficiency that depended upon the particular gas used, its mass and pressure, and the amplitude of the excitation voltage. Efficient peptide fragmentation could be demonstrated for values of q z as low as 0.05, which permitted trapping of low-mass product ions and (in many cases) full recovery of the amino acid sequence. In this report, examples are provided of monoisotopic tandem mass spectra of peptide ions with masses up to 1570 Da.

Rotationally inelastic scattering in CH4+He, Ne, and Ar: State‐to‐state cross sections via direct infrared laser absorption in crossed supersonic jets

Abstract: Absolute integral state‐to‐state cross sections are reported for rotationally inelastic scattering in crossed jets of CH4 with the rare gases He, Ne, Ar, at center of mass collision energies of 460±90, 350±70, and 300±60 cm−1, respectively. CH4 seeded in Ar buffer gas is cooled in a pulsed supersonic expansion into the three lowest rotational levels allowed by nuclear spin statistics corresponding to A(J=0), F(J=1), and E(J=2) symmetry. Rotational excitation occurs in single collisions with rare gas atoms from a second pulsed supersonic jet. The column integrated densities of CH4 in both initial and final scattering states are subsequently probed in the jet intersection region via direct absorption of light from a narrow bandwidth (0.0001 cm−1), single mode color center laser. Total inelastic cross sections for collisional loss out of the J=0, 1, and 2 methane states are determined in absolute units from the linear decrease of infrared absorption signals as a function of collider gas concentration. Tuning...

Multiparticle Simulation of Ion Injection into the Quadrupole Ion Trap Under the Influence of Helium Buffer Gas Using Short Injection Times and DC Pulse Potentials

Abstract: The motion of an ensemble of ions during their gated injection into the three-dimensional radio-frequency quadrupole ion trap was simulated considering helium buffer gas collisions, injection at certain RF phase angles and using DC impulsive fields to optimize the trapping efficiency. Simulations using a simple model of ion–neutral collisions show that buffer gas alone, even at 1–10 mTorr pressure, is not able to remove sufficient kinetic energy from the injected ions through ion–neutral collisions to prevent their loss and does not solve the problem of low efficiency of ion retention in the trap, even under qz-optimization. Accumulation of ions over long periods is not very effective, in such cases trapping efficiencies are less than 5%. It is shown that under RF phase angles between 110° and 220° the injected ions can be trapped, although only temporarily, with very high efficiencies. The simulations lead to the conclusion that all of the desired injected ions covering a wide mass/charge range can be trapped for indefinite times when short injection pulses are used together with dipolar DC pulses applied during injection. The additional damping achieved through these dipolar DC impulsive fields and the resulting cooling of the ion cloud is shown to give efficient trapping.

Thermodynamic and transport properties of argon/carbon and helium/carbon mixtures in fullerene synthesis

Abstract: The equilibrium composition and thermodynamic and transport properties of argon; carbon and helium/carbon mixtures are calculated in the temperature range 300–20,000 K. The curves for the composition of mixtures of 50%, carbon in argon or helium are shown fir a pressure of 1.33 × 104 Pa. The calculations for the heat capacity at constant pressure (Cp) and transport coefficients are validated with other studies, for the cases or pure argon and pure helium at a pressure of 105 Pa. The properties of mixtures with various proportions of carbon in argon and helium are calculated. Results are presented at pressures of 105 and 1.33 × 104 Pa, typical of reactors for the synthesis of fullerenes and nanotubes. It is observed that the properties of carbon and mixtures of carbon with a buffer gas (argon or helium) are very different from those of the buffer gas, thus the need to consider this effect in simulations. In general, the mixtures follow trends intermediate to those of the pure gases from which they are composed except for the thermal conductivity which shows a deviation from this tendency in the region between 11,500 and 19,000 K for argon/carbon mixtures and between 8,000 and 12,000 K for helium/carbon mixtures. Also, the electrical conductivity of mixtures of low carbon concentration is very close to that ofpure carbon. A datafile containing the transport properties of mixtures for pressures between 104 and 105 Pa is available free of charge from the authors.

Gas recovery unit

Abstract: Provided is a gas recovery unit which is more efficient in its recovery and less expensive to run. The gas recovery unit comprises a CVD device, an exhaust gas recovery part and an exhaust gas purification part. The exhaust gas recovery part is constructed so as to have an inert gas reservoir part capable of accommodating liquid nitrogen, to have an exhaust gas supply part for supplying an exhaust gas to said inert gas reservoir part so that it can be brought in gasliquid contact with the liquid nitrogen, and to have a recovered and liquefied gas discharge part for discharging the recovered and liquefied gas which has been liquefied in the inert gas reservoir part. The exhaust gas purification part is constructed so as to have a recovered and liquefied gas reception part, an evaporator and a condenser for carrying out a heat exchange between said liquid nitrogen and the recovered and liquefied gas which has been evaporated, and cleaning gas recovery parts, and to have a cooling inert gas discharge part, wherein the cooling inert gas discharge part is connected to the inert gas supply path.

Stimulated processes in sodium vapour in the presence of molecular buffer gas systems

Abstract: The influence of hydrocarbon compounds such as methane, ethane and ethylene on collision-induced amplified emission in sodium vapour has been investigated. The intensity dependence of the stimulated resonant emission and stimulated Raman effects on the buffer gas and sodium vapour pressures and the intensity of the excitation radiation has been obtained. The dependence of the stimulated resonant emission bandwidth on the buffer gas pressure has also been measured. It is shown that saturated hydrocarbon molecules can be used as an efficient buffer gas for the generation of stimulated emission in other alkali atoms such as rubidium and caesium.

Method and apparatus for improved low pressure collimated magnetron sputter deposition of metal films

Abstract: A method and apparatus are provided which increase the collimation of sputter deposited films by increasing the mean free path (MFP) of sputtered atoms so as to reduce redirecting collisions with the buffer gas. This is accomplished by reducing buffer gas pressure while employing mechanisms to maintain or increase plasma electron density so as to sustain the plasma in the absence of normally required gas pressure. A first mechanism used to permit reduced gas pressure is to provide gas flow directly to the immediate region of the plasma discharge rather than to another remote area of the sputter deposition chamber. A second mechanism used to permit reduced gas pressure is to provide an electron emitting source near the plasma discharge to increase the plasma electron density without requiring further ionization of buffer gas atoms. These two mechanisms can be used either alone or together, as desired, in view of the circumstances presented.

Method for injection of externally produced ions into a quadrupole ion trap

Abstract: A method of ion collection over a wide mass-to-charge range from continuous ion source into a quadrupole ion trap filled with a buffer gas directing an ion beam, from an external ion source to a radio frequency ion trap through a gating device for a predetermined period of accumulation time to allow the beam to enter the trap, trapping ions over a range of masses by applying a radio frequency voltage to the trap and changing an amplitude of the radio frequency voltage adiabatically to achieve a uniform trapping efficiency for ions over a predetermined mass range. The predetermined period of accumulation time may be divided into a plurality of segments, and the amplitude of the radio-frequency voltage is changing adiabatically within each segment.

Gas leak detection method for polymer electrolyte membrane (PEM) fuel cell

Abstract: The detection method detects a gas leak between the anode and cathode gas spaces of the fuel cell, by providing the anode and cathode gas spaces with different hydrogen partial pressures and measuring the time characteristic of the cell voltage. Pref. the gas space provided with the higher hydrogen partial pressure is provided with a higher gas pressure. The anode gas space can be supplied with hydrogen while the cathode gas space is supplied with an inert gas e.g. nitrogen.

High intensity electrodeless low pressure light source

Abstract: An electric lamp assembly includes an electrodeless lamp having a closed-loop, tubular envelope enclosing mercury vapor and a buffer gas at a pressure less than about 0,5 torr, a transformer core disposed around the lamp envelope, an input winding disposed on the transformer core and a radio frequency power source coupled to the input winding. The radio frequency source applies sufficient radio frequency energy to the mercury vapor and the buffer gas to produce in the lamp envelope a discharge having a discharge current equal to or greater than about 2 amperes. The electrodeless lamp preferably includes a phosphor on an inside surface of the lamp envelope for emitting radiation in a predetermined wavelength range in response to ultraviolet radiation emitted by the discharge.

Optimization of H/sub 2/-Ne buffer gas mixtures for copper vapor lasers

Abstract: We present results of a detailed study comparing the effects of H/sub 2/ buffer gas additive on the output power and the spatio-temporal evolution of laser output produced by copper vapor lasers of varying aperture-size. We show that while the optimum H/sub 2/ concentration is relatively insensitive to the laser diameter, it is influenced by the type of resonator employed and the total neon buffer gas pressure.

Gas separation method

Abstract: A method of separating a gas, especially carbon dioxide, from a gas mixture of the gas and nitrogen at a low temperature of -20° C. to 50° C. using a gas separation membrane permeable to the gas, including the step of cooling the gas mixture using at least one cooling medium selected from the group consisting of liquefied petroleum gas and liquefied natural gas. The liquefied petroleum gas comprises at least one selected from the group consisting of propane gas and butane gas in an amount of more than 50 vol. %. The gas separation membrane has a CO2 permeation rate of 1×10-4 to 5×10-2 N cm3 /(cm2 cm Hg sec) at 25° C. and a CO2 /N2 separation factor of 10 to 200 at 25° C.

Krypton gas mixture for insulating windows

Abstract: A mixture of noble gases having desirable insulative properties for use as a window fill gas is derived from an air separation process without substantial further separation or concentration of the noble gases in the mixtures. The mixture of noble gases is processed to form the fill gas using relatively economical catalytic oxidation processes and drying techniques to provide a suitable fill gas. The processed noble gas or fill gas may contain from about 89 to 95% krypton, 5 to 8% xenon and 0.5 to 2% contaminants including oxygen, nitrogen, hydrocarbons and other constituents typically found in air separation processing.

A radiometric investigation of low‐pressure rf sulfur discharges

Abstract: This investigation focuses on low‐pressure S2 molecular rf discharges for use as diffuse radiators. Cylindrical fused silica S2–Ar and S2–Ne lamps have been tested at 13.56 MHz and the absolute radiative efficiencies have been measured. The radiation is emitted primarily between 2800 and 3500 A. The UV radiative efficiencies were studied as a function of input power, buffer gas pressure, discharge radius, and applied external cooling. The maximum observed efficiency for a low power density, diffuse rf discharge is 7%. The measured UV efficiencies of the 13.56 MHz discharges are somewhat lower than those of low‐pressure S2–Ar dc discharges. A reentrant lamp design has been tested as well and no improvements in efficiency were observed.