Search NASA⌕ Search

SEARCH · Search NASA

Results for “field ionization”

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.

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

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Interpretation of the electric fields measured in an ionospheric critical ionization velocity experiment

The quasi-dc electric fields measured in the CRIT I ionospheric release experiment are studied. In the experiment, two identical barium shaped charges were fired toward a main payload, and three-dimensional measurements of the electric field inside the streams were made. The relevance of proposed mechanisms for electron heating in the critical ionization velocity (CIV) mechanism is addressed. It is concluded that both the 'homogeneous' and the 'ionizing front' models probably are valid, but in different parts of the streams. It is also possible that electrons are directly accelerated by a magnetic field-aligned component of the electric field. The coupling between the ambient ionosphere and the ionized barium stream is more complicated that is usually assumed in CIV theories, with strong magnetic-field-aligned electric fields and probably current limitation as important processes.

Brenning, N.↗
NASA NTRS2008

Effect of Nitrogen Gas on the Lifetime of Carbon Nanotube Field Emitters for Electron-Impact Ionization Mass Spectrometry

The lifetime of a patterned carbon nanotube film is evaluated for use as the cold cathode field emission ionization source of a miniaturized mass spectrometer. Emitted current is measured as a function of time for varying partial pressures of nitrogen gas to explore the robustness and lifetime of carbon nanotube cathodes near the expected operational voltages (70-100 eV) for efficient ionization in mass spectrometry. As expected, cathode lifetime scales inversely with partial pressure of nitrogen. Results are presented within the context of previous carbon nanotube investigations, and implications for planetary science mass spectrometry applications are discussed.

Getty, Stephanie A.↗
NASA NTRS1970

Quadrupole ionization gage measures ultrahigh vacuum

Quadrupole system, energized with a 200 MHz electric field, restrains ionizing electrons within the center of the ionization gage. Oscillatory trajectory of the electrons increases the probability of ionizing the gas molecules, lowers background X-ray level, and increases the signal-to-noise ratio.

Schwarz, H. J.↗
NASA NTRS1977

Narrow radio recombination lines from ionization fronts

Model weak D-type ionization fronts are used to show that narrow H I radio recombination lines, such as those observed in the directions of several galactic H II regions, may be formed in the outermost layers of an ionization front bounding an H II region. Four model ionization fronts are computed with different values of magnetic-field strength, ionizing photon energy, and initial conditions. The recombination line strengths given by the models are compared with observed line strengths for the H II region NGC 2024, and the observed line profiles are found to be about twice as broad as the model profiles. Some likely explanations for the discrepancy are considered, particularly a variation in front velocity over the observing beam width (Stark broadening is ruled out).

Hill, J. K.↗