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Tomassian, A. D.

Publications and source records attributed to Tomassian, A. D..

5 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Development of a miniaturized, light-weight magnetic sector for a field-portable mass spectrograph

A miniaturized, lightweight magnetic sector for a focal plane mass spectrograph (Mattauch-Herzog design) has been designed and fabricated by using a new high-energy-product magnet material (Nd-B-Fe alloy) and a high permeability magnet yoke material (V-Co-Fe alloy). The magnetic sector weighs less than 10 kg, has a focal plane of 5.1 cm in length, and covers a nominal mass range of 40-240 amu. Such a magnetic sector, in conjunction with an array detector and a short microbore capillary column, is well suited for the development of a field-portable gas chromatograph-mass spectrometer instrument of high performance.

Sinha, M. P.↗
NASA NTRS1983

Development of a miniature scanning electron microscope for in-flight analysis of comet dust

A description is presented of an instrument which was developed with the original goal of being flown on the International Comet Mission, scheduled for a 1985 launch. The Scanning Electron Microscope and Particle Analyzer (SEMPA) electron miniprobe is a miniaturized electrostatically focused electron microscope and energy dispersive X-ray analyzer for in-flight analysis of comet dust particles. It was designed to be flown on board a comet rendezvous spacecraft. Other potential applications are related to asteroid rendezvous and planetary lander missions. According to the development objectives, SEMPA miniprobe is to have the capability for imaging and elemental analysis of particles in the size range of 0.25 microns and larger.

Conley, J. M.↗
NASA NTRS1972

Inner-zone energetic-electron repopulation by radial diffusion.

Quantitative study of the intrusion of natural electrons into the inner radiation zone during and after the geomagnetic storm of Sept. 2, 1966. It is shown that the transport is consistent with a radial-diffusion mechanism in which the first two invariants are conserved. Except for the three-day period of the storm main phase when data were missing, the radial-diffusion coefficient is found to have a value which could be produced by a variation of a large-scale electric field across the magnetosphere having an amplitude of 0.28 mV/m and a period of 1600 sec. Electric fields having approximately these characteristics have been inferred from previous observations of the motion of whistler ducts within the plasmapause. If fields of this amplitude and period exist throughout the magnetosphere, the radial diffusion of all geomagnetically trapped particles except the high-energy inner-zone protons is strongly influenced by electric-field variations. A comprehensive review of previously reported radial-diffusion coefficients shows reasonable agreement for L less than about 3.0, but serious discrepancies among reported values exist for determinations made in the outer zone. These discrepancies cannot be explained by the simple theory of radial diffusion due to variation of large-scale electric or magnetic fields.

Tomassian, A. D.↗