Quadrupole ion entrance mask study
Theoretical and computer analyses of unstable ions in quadrupole mass spectrometer with ion source masking
Ierokomos, N.↗
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Comparative performance of double-focus and quadrupole mass spectrometers
Light-weight flight type double focus and quadruple mass spectrometer models were compared. Data cover size, weight, and power sensitivity required to achieve same resolution sensitivity at given mass number. Comparison was made using mathematical relationships. Analysis was confined to equal ion source area sensitivity variations not more than 40% over mass range.
Wilson, S. K.↗
Fluorine negative ion detachment kinetics
A study of the rate of F(-) detachment by O and H atoms via the reactions F(-) + O yields FO + e and F(-) + H yields FH+ e was undertaken using a drift tube to produce F(-) ions at various drift velocities and therefore different ion temperatures. Preliminary mobility measurements of F(-) ions in Ar were made, indicating that ion temperatures in the 300 K to 5000 K range could be achieved; however due to numerous difficulties experienced in obtaining a reliable F(-) ion source, the study could not be completed.
Burke, R. R.↗
Wind tunnel mass spectrometer design study
The sampling probe to measure the free stream gas composition in a hypersonic wind tunnel is described. Using a free expansion of the continuum flow, a series of sampling inlet-pumping stages is evaluated. Mass analysis is carried out with a quadrupole mass spectrometer employing a crossed electron beam, molecular beam ion source, and an off-axis electron multiplier. The spatial distribution of the sampled molecular flux and the pumping requirements are evaluated for varying inlet conditions of gas density and flow velocity. The signal-to-noise ratio of the molecular beam formed by this series of coaxial inlets is also determined. The signal-to-noise ratio of the unscattered flux is sufficiently high that an unambiguous determination of the beam composition and of the free stream gas properties can be made. The magnitude of the detected signal is sufficiently high that measurement of trace constituents two orders of magnitude below the primary beam signal can be made.
Hueser, J. E.↗
A survey of Kaufman thruster cathodes
A survey is presented of the various cathodes which were developed and used in the Kaufman ion thruster. The electron bombardment type ion source is briefly described. The general design, operating characteristics, and power requirements are shown for each type of cathode from the refractory metals used in 1960 to the plasma discharge hollow cathodes of today. A detailed discussion of the hollow cathode is given, including starting and cyclic operating characteristics as well as more fundamental design parameters. Tests to date show that the plasma hollow cathode is an efficient electron source with demonstrated durability over 10,000 hours.
Weigand, A. J.↗
Role of gas surface interactions in the reduction of OGO-6 neutral gas particle mass spectrometer data
The gas-surface interaction effects observed by the quadrupole mass spectrometer are described, and the technique developed to account for them in determining ambient neutral densities is summarized. The total ion current and the ion currents for ions with molecular weights 2, 4, 16, 28, and 32 are sampled for 1.125 sec once every 9.216 sec, for 258 sec out of a 368 sec cycle. An equation is given for the number density of any constituent in the ion source region, and source density data are discussed. The mass 28 background gas is considered to be CO rather than N2, and a CO model is developed. A quasi-equilibrium model of the atomic oxygen interactions is constructed, and a set of surface parameters is determined which provides a reasonable fit to the mass 16 and 32 source densities consistent with the predicted ambient atomic oxygen.
Hedin, A. E.↗
A survey of Kaufman thruster cathodes.
A survey is presented of various cathodes which have been developed and used in the Kaufman ion thruster. The electron-bombardment type ion source used in the thruster is briefly described. The general design, operating characteristics, and power requirements are shown for each type of cathode from the refractory metals used in 1960 to the plasma discharge hollow cathodes of today. A detailed discussion of the hollow cathode is given describing starting and cyclic operating characteristics as well as more fundamental design parameters. Tests to date show that the plasma hollow cathode is an efficient electron source with demonstrated durability over 10,000 hours and should offer further performance and life improvements.
Weigand, A. J.↗
Planetary exploration with electrically propelled vehicles.
The characteristics of propulsion systems required for carrying out flight missions within the solar system, as desired by planetary physicists and astronomers, are reviewed. It is shown that an encouraging answer to these requirements is available in the form of electrostatic or ion propulsion systems. The design and performance characteristics of an electrostatic thrustor employing an ion source, accelerating electrode, beam neutralizer, and power source are discussed, together with those of the Kaufmann engine (electrostatic thrustor employing bombardment type ionization). More demanding missions which will become feasible with the advent of nuclear-electric power sources (such as the incore thermionic reactor) may include close orbiters around all the planets, and asteroid and cometary missions.
Stuhlinger, E.↗
An evaluation of pyrolytic techniques with regard to the Apollo 11, 12 and 14 lunar samples analyses.
The first technique involved pyrolysis at 700 C under an inert atmosphere in a flowing He system at normal pressure. The products were collected at liquid nitrogen temperature and then allowed to pass instantaneously into a combined capillary gas chromatograph-mass spectrometer. The second technique consisted of a vacuum pyrolysis where the sample was first degassed at 150 C and then pyrolized at 500 C and 1000 C consecutively. The products were again collected at liquid nitrogen temperature and then they were directly introduced to the ion source of the mass spectrometer through a modified gas inlet system. The experiments have shown the importance of taking into account the factors that influence pyrolytic degradation and/or the synthesis of products. Pyrolysis of Apollo 14 lunar fines and scrapings from an astronaut's glove gave different products by mass spectroscopy and showed different looking flaky materials upon scanning electron microscopy.
Nagy, B.↗
Study of neutral composition of lower thermosphere at Fort Churchill.
On Feb. 4 and 6, 1969, and May 11, 1970, Aerobee rockets carrying neutral mass spectrometers were flown at Fort Churchill, Canada during conditions of low geomagnetic activity. As in earlier flights at White Sands, New Mexico, each rocket carried both 'open' and 'closed' ion source instruments. Vertical profiles of N2, O2, O, Ar, and He were measured. Results obtained were essentially the same as those observed at White Sands except that for the winter flights helium appeared to be in diffusive equilibrium.
Nier, A. O.↗
A field-ionization neutral-particle mass spectrometer
Description of laboratory model of a neutral-particle mass spectrometer that could make localized direct measurements of the neutral densities at 1 AU. Using a magnet that has a circular pole face 2.54 cm in diameter and a gap flux density of 8.0 kG, the following sensitivities were obtained for the various species: 10 to the 10th power counts per second per Torr for H2, 3 times 10 to the eighth power counts per second per Torr for He, and 2 times 10 to the 9th power counts per second per Torr for N2. Overall sensitivity may be increased through the use of electrostatic focusing elements between the ion source and the magnetic analyzer.
Curtis, C. C.↗
The repulsive 1 Sigma g/+/ He2 potential obtained from total cross sections
An improved apparatus for obtaining short-range molecular potentials is described. The setup is a refined version of that used by Jordan-Amdur and by Leonas. The ion source is provided with a mass analyzing magnet, the capacitance manometer in the scattering cell is calibrated with a McCleod gauge, and the detection unit substitutes a Channeltron multiplier for the thermopile. The measured ground-state He-He potential for radii between 0.49 and 1.56 A is approximately V(r) = 215 x exp(-3.95r) eV, which is 25% higher than the earlier experiments. The result is supported by molecular orbital and statistical model calculations.
Foreman, P. B.↗
Content of lithium, beryllium, boron, and titanium, and the isotopic composition of lithium, boron, and magnesium in Luna 16 regolith sample
The abundance of the following elements in the L 16-19 No. 118 regolith sample, zone V was determined by isotopic dilution using a mass spectrometer equipped with a scattering ion source: Li -- 9.8, Be -- 1.2, Be -- 2.6, and Ti -- 1.92 percent. For comparison, these same elements were measured in samples of surface material returned by Apollo 11, Apollo 12, and Apollo 14, and in the terrestrial reference standard diabase W-1. The content of Li, Be, and B in the Luna 16 sample is nearly the same as in the Apollo 11 surface material. The surface material returned by Apollo 12 and Apollo 14 contains two to four times more of these elements. However, the abundance ratios of Li, Be, and B are remarkably similar in the surface materials from the four different lunar regions. With respect to basaltic achondrites and especially with respect to chondrites, the lunar basalts are enriched in Li, Be, and B up to 100 times.
Eugster, O.↗
Practical aspects of plasma processes in thermionic energy converters
Over a decade of cesium vapor thermionic converter research has yielded sufficient understanding of the basic plasma processes to permit application of this understanding to improvement of converter performance. A performance index is defined which relates such converter improvements directly to increases in system performance. A prime practical objective of current research is to reduce or eliminate the arc potential drop presently required to sustain the plasma in the ignited cesium diode. This will substantially increase the energy conversion efficiency, and will permit operation at substantially lower emitter temperatures without requiring lower collector (heat rejection) temperature. Present work is concentrating on evaluating and reducing to practice the several methods employing auxiliary ion sources to eliminate the arc drop which were demonstrated over a decade ago: i.e., various ignited and unignited triode concepts, and the pulse-enhanced diode and triode. These methods are reviewed in light of present understanding and recent experimental data.
Rasor, N. S.↗
Investigation of hydrogen and helium pumping by sputter ion pumps for Jupiter and outer planets mass spectrometer
The phenomena of ion pumping is reviewed with emphasis on the pumping mechanism for hydrogen and helium. The experimental tests measure the performance of a small, flight proven ion pump which has a nominal four liter/second pumping speed for air. The speed of this pump for hydrogen and helium, and for hydrogen/helium mixes, is presented with particular detail regarding the time dependence. Pump test results are related to anticipated performance of the mass spectrometer by the pumping speeds for the gases to the partial pressure in the ion source. From this analysis, the pump specifications are quantified in terms of mission goals and in terms of observed pumping speeds for the various gases, load levels, and time periods.
Scott, B. W.↗
Advanced thermionic energy conversion: Joint highlights
A theoretical model was used to study the effects of structured electrodes on converter I-V characteristics and results are given. An auxiliary-ion-source triode operated as a plasmatron was used for studying the enhancement distribution and magnetic effects, and results are reported. Design features of the high current-zero power (ZEPO) converter tests are given.
Source record↗
The plasmatron: Advanced mode thermionic energy conversion
A theory of the plasmatron was developed. Also, a wide range of measurements were obtained with two versatile, research devices. To gain insight into plasmatron performance, the experimental results are compared with calculations based on the theoretical model of plasmatron operation. Results are presented which show that the plasma arc drop of the conventional arc (ignited) mode converter can be suppressed by use of an auxiliary ion source. The improved performance, however, is presently limited to low current densities because of voltage losses due to plasma resistance. This resistance loss could be suppressed by an increase in the plasma electron temperature or a decrease in spacing. Plasmatron performance characteristics for both argon and cesium are reported. The argon plasmatron has superior performance. Results are also presented for magnetic cutoff effects and for current distributing effects. These are shown to be important factors for the design of practical devices.
Hansen, L. K.↗
The plasmatron as an advanced performance thermionic converter
A study concerned with the improvement of thermionic converter performance has shown that the plasma arc drop of the conventional arc (ignited) mode converter can be suppressed by use of an auxiliary ion source as in a plasmatron converter. However, this improved performance is now limited to low current densities and narrow interelectrode spacings because of voltage losses due to plasma resistance. An examination of plasmatron performance characteristics for both argon and cesium plasma has shown that the argon plasmatron is superior.
Hansen, L. K.↗