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Sigman, D. R.

Publications and source records attributed to Sigman, D. R..

13 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Parametric study of ion heating in a burnout device (HIP-1)

Results of further studies on the Lewis Research Center hot-ion plasma source (HIP-1) are reported. Changes have been made in both the electrode geometry and materials to produce higher ion temperatures. Ion temperature increased significantly with increased vacuum pumping speed. The best ion temperatures achieved, so far, for H(+), D(+), and He(+) plasmas are estimated to be equal to, or greater than 0.6, equal to, or greater than 0.9, and equal to, greater than 2.0 keV, respectively. Electrode pairs produced high ion temperatures whether on the magnetic axis or off it by 5.5 cm. Multiple sources, one on-axis and one off-axis, were run simultaneously from a single power supply by using independent gas feed rates. A momentum analyzer has been added to the charge-exchange neutral particle analyzer to identify particles according to mass, as well as energy. Under any given plasma condition, the higher mass ions have higher average energies but not by as much as the ratio of their respective masses.

Sigman, D. R.↗
NASA NTRS1973

Steady-state hot-ion plasma produced by crossed electric and magnetic fields

Results of initial diagnostics on the Lewis Research Center hot-ion-plasma source (HIP-1) are reported. The mirror-contained plasma was heated by applying a radial electric field similar to that used in the ORNL burnout experiments. An electrostatic neutral particle analyzer was used to make a parametric study of ion energy distributions in both hydrogen and euterium plasmas. Ion temperatures as high as 2 keV were measured in plasmas with electron densities greater than 10 to 12th power/cu cm. The performance of the device was found to be extremely sensitive to a magnetic field. There are indications that ion heating was reduced when the size of the Larmor orbit was larger than the region of a strong radial electric field.

Sigman, D. R.↗
NASA NTRS1972

A comparison of coupling efficiencies for a Stix coil and an m equals 1 coil

This theoretical and experimental study compares the ion-cyclotron wave generating characteristics of a Stix coil (which generates waves with azimuthal mode number m = 0) with those of a coil which produces primarily m = + or -1 ion-cyclotron modes. The theoretical work of J.E. Hipp, which predicted very good coupling for the m = 1 coil, was extended to determine the scaling laws for plasma column radius and coil wavelength. Experimentally, an m = 1 coil and an m = 0 coil were used to generate ion-cyclotron waves on a beam generated plasma column with electron density = 10 to the 12th power/cu cm. Coupling resonances with peak efficiencies of approximately 40 to 50 percent were measured for both coils in low power (approximately 10k W) experiments. For equal power transfer to the plasma, the m = 0 coil voltage was more than a factor of two greater than that for the m = 1 coil.

Sigman, D. R.↗
NASA NTRS1972

Temporal survey of electron number density and electron temperature in the exhaust of a megawatt MPD-arc thruster.

Temporal and radial profiles are obtained 30 cm downstream from the anode for two peak arc currents (11.2 kA and 20 kA) and for various auxiliary magnetic fields (0, 1.0 T, and 2.0 T) using the Thomson scattering technique. Average density and temperature are relatively constant for over 100 microseconds with significant fluctuations. Radial profiles obtained are relatively flat for 4 cm from the axis. Compared to earlier 20 cm data, the exhaust density has decreased significantly, the average temperature has not changed, and the density ?hole' with an auxiliary magnetic field has enlarged.

Michels, C. J.↗
NASA NTRS1971

Temporal survey of electron number density and electron temperature in the exhaust of a megawatt MPD-Arc thruster

Temporal and radial profiles are obtained 30 cm downstream from the anode for two peak arc currents (11.2 kA and 20 kA) and for various auxiliary magnetic fields (0, 1.0 T, and 2.0T) using the Thomson scattering technique. Average density and temperature are relatively constant for over 100 microseconds with significant fluctuations. Radial profiles obtained are relatively flat for 4 cm from the axis. Compared to earlier 20 cm data, the exhaust density has decreased significantly, the average temperature (4.6 eV) has not changed, and the density hole with an auxiliary magnetic field has enlarged.

Michels, C. J.↗