SEARCH · Engineering Papers

Results for “GAS DISCHARGE”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28

All sources NASA NTRS DOE OSTI

NASA NTRS1999

Microliter-sized ionization device and method

A microliter-sized metastable ionization device with a cavity, a sample gas inlet, a corona gas inlet and a gas outlet. A first electrode has a hollow and disposed in the cavity and is in fluid communication with the sample gas inlet. A second electrode is in fluid communication with the corona gas inlet and is disposed around the first electrode adjacent the hollow end thereof. A gap forming means forms a corona gap between the first and second electrodes. A first power supply is connected to the first electrode and the second power supply is connected to the second electrode for generating a corona discharge across the corona gap. A collector has a hollow end portion disposed in the cavity which is in fluid communications with the gas outlet for the outgassing and detection of ionized gases. The first electrode can be a tubular member aligned concentrically with a cylindrical second electrode. The gap forming means can be in annular disc projecting radially inwardly from the cylindrical second electrode. The collector can have a tubular opening aligned coaxially with the first electrode and has an end face spaced a short distance from an end face of the first electrode forming a small active volume therebetween for the generation and detection of small quantities of trace analytes.

Cohen, Martin J.↗

NASA NTRS1987

Isotopic fractionation of Kr and Xe implanted in solids at very low energies

Results on the implantation of Kr and Xe in W under closed system conditions at very low energies (50-500 eV) are reported. Investigation of the fraction of gas trapped as a function of time reveals the existence of competing trapping and release mechanisms, and analysis of recovered trapped gas and residual gas phases shows that both elemental and isotropic fractionation result from these mechanisms. It is determined that the mass dependence for the overall implantation process is at or near m exp 1, with heavier isotopes enriched in the implanted gas. This mass dependence is inferred to result from implantation and a combination of diffusive and gas sputtering release mechanisms. These results reaffirm the conclusion of Bernatowicz and Fahey (1986) that previously observed isotopic fractionation of Kr and Xe in carbonaceous material synthesized in electrical discharges owes its origin to low-energy ion implantation, and also suggest that this process may be relevant to incorporation of noble gases in early solar system materials. The implication of these results for noble gas mass spectrometry are discussed.

Bernatowicz, Thomas J.↗

NASA NTRS1966

Neon isotopes cancel errors in gas laser

Neon isotopes cancel frequency pushing errors arising from unequal gain in the two contracirculating beams of a helium-neon filled discharge tube used in a ring laser.

Macek, W. M.↗

NASA NTRS2005

Influence of the Gas Pressure on Single-wall Carbon Nanotubes Formation

Experiments and modeling have been performed to predict the effect of gas pressure on species distribution and nanotube growth rate under specific conditions of synthesis of singlewall carbon nanotubes (SWCNTs) by arc discharge. Numerical results were compared with experiments in order to find a consistent correlation between the nanotube growth and the pressure. We used argon and helium as buffer gases with a total pressure varied between 0.1 and 1 bar. We experimentally observed that both the anode erosion rate and the Brunauer-Emmett-Teller (BET) surface area of the as produced nanotube soot material are very sensitive to the total gas pressure in the reactor

Hinkov, I.↗

NASA NTRS2000

Process for Ignition of Gaseous Electrical Discharge Between Electrodes of a Hollow Cathode Assembly

The design and manufacturing processes for Hollow Cathode Assemblies (HCA's) that operate over a broad range of emission currents up to 30 Amperes, at low potentials, with lifetimes in excess of 17,500 hours. The processes include contamination control procedures which cover hollow cathode component cleaning procedures, gas feed system designs and specifications, and hollow cathode activation and operating procedures to thereby produce cathode assemblies that have demonstrated stable and repeatable operating conditions, for both the discharge current and voltage. The HCA of this invention provides lifetimes of greater than 10,000 hours, and expected lifetimes of greater than 17,500 hours, whereas the present state-of-the-art is less than 500 hours at emission currents in excess of 1 Ampere. Stable operation is provided over a large range of operating emission currents, up to a 6:1 ratio, and this HCA can emit electron currents of up to 30 Amperes in magnitude to an external anode that simulates the current drawn to a space plasma, at voltages of less than 20 Volts.

Patterson, Michael J.↗

NASA NTRS1991

Atmospheric pressure flow reactor: Gas phase chemical kinetics under tropospheric conditions without wall effects

A flow reactor for simulating the interaction in the troposphere is set forth. A first reactant mixed with a carrier gas is delivered from a pump and flows through a duct having louvers therein. The louvers straighten out the flow, reduce turbulence and provide laminar flow discharge from the duct. A second reactant delivered from a source through a pump is input into the flowing stream, the second reactant being diffused through a plurality of small diffusion tubes to avoid disturbing the laminar flow. The commingled first and second reactants in the carrier gas are then directed along an elongated duct where the walls are spaced away from the flow of reactants to avoid wall interference, disturbance or turbulence arising from the walls. A probe connected with a measuring device can be inserted through various sampling ports in the second duct to complete measurements of the first and second reactants and the product of their reaction at selected XYZ locations relative to the flowing system.

Koontz, Steven L.↗

NASA NTRS1976

15 cm multipole gas ion thruster

A 15-cm multipole thruster was operated on argon and xenon. The multipole approach used has been shown capable of low discharge losses and flat ion beam profiles with a minimum of redesign. This approach employs low magnetic field strengths and flat or cylindrical sheet-metal parts, hence is suited to rapid optimization and scaling. Only refractory metal cathodes were used in this investigation.

Isaacson, G. C.↗

NASA NTRS1975

Flow lasers

The present work reviews the fluid-mechanical aspects of high-power continuous-wave (CW) lasers. The flow characteristics of these devices appear as classical fluid-mechanical phenomena recast in a complicated interactive environment. The fundamentals of high-power lasers are reviewed, followed by a discussion of the N2-CO2 gas dynamic laser. Next, the HF/DF supersonic diffusion laser is described, and finally the CO electrical-discharge laser is discussed.

Christiansen, W. H.↗

NASA NTRS1979

Quantitative energy extraction measurements in a photoionization-stabilized self-sustained XeF laser

Detailed time-correlated gain, fluorescence, and laser energy measurements were used to obtain quantitative data on energy extraction efficiencies for a photoionization-stabilized self-sustained XeF laser. A current pulse of 25 ns full width at half-maximum produced an 80-cu-cm XeF plasma in NF3:Xe:He gas mixtures with a maximum output energy of 80 mJ. The results show that the maximum small-signal gain and the maximum specific output energy is proportional to the NF3 content of the gas mixture. This suggests that there is an optimum fractional utilization of the NF3 molecules in the discharge. Under high-gain conditions, 30-40% of the energy stored in XeF(asterisk) can be extracted in a gain-switched pulse. The output energy represents less than 1% of the input energy.

Lee, C. M.↗

NASA NTRS1986

Approximations useful for the prediction of electrostatic discharges for simple electrode geometries

The report provides approximations for estimating the capacitance and the ratio of electric field strength to potential for a certain class of electrode geometries. The geometry consists of an electrode near a grounded plane, with the electrode being a surface of revolution about the perpendicular to the plane. Some examples which show the accuracy of the capacitance estimate and the accuracy of the estimate of electric field over potential can be found in the appendix. When it is possible to estimate the potential of the electrode, knowing the ratio of electric field to potential will help to determine if an electrostatic discharge is likely to occur. Knowing the capacitance will help to determine the strength of the discharge (the energy released by it) if it does occur. A brief discussion of discharge mechanisms is given. The medium between the electrode and the grounded plane may be a neutral gas, a vacuum, or an unchanged homogeneous isotropic dielectric.

Edmonds, L.↗

NASA NTRS1988

Approximations useful for the prediction of electrostatic discharges for simple electrode geometries

Edmonds, Larry D.↗

NASA NTRS1989

Effect of reactor loading on atomic oxygen concentration as measured by NO chemiluminescence

It has previously been observed that the etch rate of polyethylene samples in the afterglow of an RF discharge in oxygen increases with reactor loading. This enhancement of the etch rate is attributed to reactive gas phase products of the polymer etching. In the present work, emission spectroscopy is employed to examine the species present in the gas phase during etching of polyethylene. In particular, the concentration of atomic oxygen downstream from the polyethylene samples is studied as a function of the reactor loading. It is found that the concentration of atomic oxygen increases as the reactor loading is increased. The increase of etch rate with increased reactor loading is attributed to the increase of atomic oxygen concentration in the vicinity of the sample.

Lerner, N. R.↗

NASA NTRS1994

Non-isolated 30 kW class arcjet PCU

A 30 kW class arcjet Power Conditioning Unit, PCU, was built and tested during this Phase 2 SBIR contract. The PCU is an improved version of two previously developed PCU's. All of these units are 3-phase, 20 kHz buck regulators with current mode feed back to modulate the duty cycle to control the arcjet current at any selected operating point. The steady state control can assure arcjet stability despite the negative dynamic resistance of the arc discharge. The system also has a circuit to produce a high voltage start pulse to breakdown the gas and initiate the arc. The start pulse is formed by temporarily switching a short current path across the output terminals with a special solid state switching array. The switches then open rapidly, and the energy stored in the output inductors of the buck regulator produces a pulse of approximately 2500 V for approximately 500 nsec. The system was tested and modified until the transition to steady operation occurred after start up with a very small surge current overshoot. The system also can withstand a direct short circuit across the output without damage. The automatic feed back control simply reduces the duty cycle to hold the current at the set point. When the short is removed the full power output is immediately restored. This latest version arcjet PCU is conduction cooled to remove waste heat by conduction to the base plate. This unit is closer to flight a type of design than the previous functional bread boards. Waste heat is small because the PCU has a very high efficiency, 296 percent. The PCU was extensively tested with resistor loads to simulate operation with an arcjet. The unit was tested with ammonia arcjets at the Jet Propulsion Laboratory. Approximately 400 hours of testing were completed, with several starts. Many hours were also demonstrated with resistive loads. Some testing with hydrogen arcjets was also carried out at NASA LeRC. This system concept is now the design base for the ATTD program.

Wong, See-Pok↗

NASA NTRS1974

A spark gap switching system for gasdynamic facilities

A spark gap switching system has been developed to coordinate the discharge of a 300 kJ capacitor bank with the high speed flow of helium in a shock tube driver. The trigger system includes a flow transducer, a pulse forming circuit, a high voltage spark generator, and four heavy duty spark gaps that can carry total peak currents greater than 1.5 million A. A glow gauge flow transducer sensitive to small gas density changes was used whose input power and signal output can withstand high voltage fluctuations. This switching system is of use with gasdynamic discharge devices requiring a minimum number of switches.

Leibowitz, L. P.↗

NASA NTRS2014

Properties of the Flight Model Gas Electron Multiplier for the GEMS Mission

We present the gain properties of the gas electron multiplier (GEM) foil in pure dimethyl ether (DME) at 190 Torr. The GEM is one of the micro pattern gas detectors and it is adopted as a key part of the X-ray polarimeter for the GEMS mission. The X-ray polarimeter is a time projection chamber operating in pure DME gas at 190 Torr. We describe experimental results of (1) the maximum gain the GEM can achieve without any discharges, (2) the linearity of the energy scale for the GEM operation, and (3) the two-dimensional gain variation of the active area. First, our experiment with 6.4 keV X-ray irradiation of the whole GEM area demonstrates that the maximum effective gain is 2 x 10(exp 4) with the applied voltage of 580 V. Second, the measured energy scale is linear among three energies of 4.5, 6.4, and 8.0 keV. Third, the two-dimensional gain mapping test derives the standard deviation of the gain variability of 7% across the active area.

gas electron multiplier (GEM)↗

NASA NTRS1978

Experimental Studies of the Formation/Deposition of Sodium Sulfate in/from Combustion Gases

Processes related to the hot corrosion of gas turbine components were examined in two separate investigations. Monochromatic laser light was used to probe condensation onset and condensate film growth (via interference of reflected light) on electrically heated ribbons immersed in seeded, flat flame combustion product gases. Boron trichloride is used as the seed gas in these preliminary experiments conducted to obtain precise measurements of the dew point/deposition rates. Because of the importance of gaseous Na(g) as a precursor to NaSO4 formation, the kinetics and mechanisms of the heterogeneous reaction H(g) + NaCl(s) yields Na(g) + HCl(g) was studied using atomic absorption spectroscopy combined with microwave discharge-vacuum flow reactor techniques at moderate temperatures. Preliminary results indicate the H-atom attack of solid NaCl vaporization is negligible; hence the corresponding gas phase (homogeneous) reaction no role in the observed Na(g) production.

Rosner, D. E.↗

NASA NTRS1986

Temperature dependence of the NO3 absorption spectrum

The absorption spectrum of the gas-phase NO3 radical has been studied between 220 and 700 nm by using both flash photolysis and discharge flow reactors for the production of NO3. In the flash photolysis method, cross sections at the peak of the (0,0) band at 661.9 nm were measured relative to the cross section of ClONO2 at several different wavelengths. From the best current measurements of the ClONO2 spectrum, the NO3 cross section at 661.9 nm was determined to be (2.28 + or 0.34) x 10 to the -17th sq cm/molecule at 298 K. Measurements at 230 K indicated that the cross section increases by a factor of 1.18 at the peak of the (0,0) band. The discharge flow method was used both to obtain absolute cross sections at 661.9 nm and to obtain relative absorption spectra between 300 and 700 nm at 298 and 230 K. A value of (1.83 + or - 0.27) x 10 to the -17th sq cm/molecule was obtained for sigma NO3 at 661.9 nm at 298 K. Upper limits to the NO3 cross sections were also measured between 220 and 260 nm with the discharge flow method.

Sander, Stanley P.↗

NASA NTRS1986

A Penning discharge source for extreme ultraviolet calibration

A Penning discharge lamp for use in the calibration of instruments and components for the extreme ultraviolet has been developed. This source is sufficiently light and compact to make it suitable for mounting on the movable slit assembly of a grazing incidence Rowland circle monochromator. Because this is a continuous discharge source, it is suitable for use with photon counting detectors. Line radiation is provided both by the gas and by atoms sputtered off the interchangeable metal cathodes. Usable lines are produced by species as highly ionized as Ne IV and Al V. The wavelength coverage provided is such that a good density of emission lines is available down to wavelengths as short as 100A. This source fills the gap between 100 and 300A, which is inadequately covered by the other available compact continuous radiation sources.

Finley, David S.↗