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Gerdin, G. A.

Publications and source records attributed to Gerdin, G. A..

10 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Characteristics of the NASA Lewis Bumpy Torus plasma generated with positive applied potentials

Experimental observations have been made during steady-state operation of the NASA Lewis Bumpy Torus experiment at input powers up to 150 kW in deuterium and helium gas, and with positive potentials applied to the midplane electrodes. This steady-state ion heating method utilizes a modified Penning discharge operated in a bumpy torus confinement geometry such that the plasma is acted upon by a combination of strong electric and magnetic fields. Experimental investigation of a deuterium plasma revealed electron temperatures from 14 to 140 eV and ion kinetic temperatures from 160 to 1785 eV. At least two distinct modes of operation exist, each of which is associated with a characteristic range of background pressure and electron temperature. Experimental data show that the average ion residence time in the plasma is virtually independent of the magnetic field strength.

Roth, J. R.↗
NASA NTRS1976

Characteristics of the NASA Lewis bumpy torus plasma generated with high positive or negative applied potentials

The toroidal ring of plasma contained in the NASA Lewis bumpy-torus superconducting magnet facility may be biased to positive or negative potentials approaching 50 kilovolts by applying direct-current voltages of the respective polarity to 12 or fewer of the midplane electrode rings. The electric fields which are responsible for heating the ions by E/B drift then point radially outward or inward. The low-frequency fluctuations below the ion cyclotron frequency appeared to be dominated by rotating spokes.

Roth, J. R.↗
NASA NTRS1976

Characteristics of the NASA Lewis bumpy-torus plasma generated with positive applied potentials

Experimental observations were made during steady-state operation of a bumpy-torus plasma at input powers up to 150 kW in deuterium and helium gas and with positive potentials applied to the midplane electrodes. In this steady-state ion heating method a modified Penning discharge is operated such that the plasma is acted upon by a combination of strong electric and magnetic fields. Experimental investigation of a deuterium plasma revealed electron temperatures from 14 to 140 eV and ion kinetic temperatures from 160 to 1785 eV. At least two distinct modes of operation exist. Experimental data shows that the average ion residence time in the plasma is virtually independent of the magnetic field strength. Data was taken when all 12 anode rings were at high voltage, and in other symmetric configurations in which the toroidal plasma was generated by applying positive potentials to six anode rings, three anode rings, and a single anode ring.

Roth, J. R.↗
NASA NTRS1974

Spoke wavenumbers and mode transitions in NASA-Lewis bumpy torus

Waveforms of fluctuations of plasma potential, resulting from rotating electron and ion charge concentrations, have been observed in the Lewis bumpy torus. Since these fluctuations are thought to be spoke rotations in the direction of the E x B drift, measuring the direction of spoke rotation should determine the direction of the electric fields over much of the plasma surface. Since inward pointing electric fields should enhance confinement of the hot ions in this device, knowledge of the direction of the spoke rotation could give valuable information on the mechanism of plasma confinement and radial transport. A Langmuir probe was inserted into the plasma to measure the floating potential of the plasma; hence the direction of the electric field could be checked another way.

Gerdin, G. A.↗
NASA NTRS1974

Radio frequency studies in the NASA Lewis Bumpy Torus

The fluctuations in potential of the plasma in the NASA Lewis Bumpy Torus are observed using capacitive probes over frequencies from 1 kHz to 25 MHz and a wide range of operating conditions. The spectra are found to differ greatly above and below a background gas pressure of .000034 torr deuterium. Above this pressure, the spectrum is dominated by the ion spoke frequency and a spectral index may be defined. Below this pressure, the spectrum below 200 kHz is lower in amplitude by a factor of ten and no spectral index can be defined. At these lower pressures, fluctuations appearing to be ion spokes are observed, but have a dependence of frequency on operating conditions which is previously unreported.

Gerdin, G. A.↗
NASA NTRS1974

Radio frequency studies in the NASA Lewis Bumay Torus

The fluctuations in potential of the plasma in the NASA Lewis Bumpy Torus were observed using capacitive probes over frequencies from 1 kHz to 25 MHz and a wide range of operating conditions. The spectra were found to differ greatly above and below a background gas pressure of 3.0.000034 torr deuterium. Above this pressure the spectrum was dominated by the ion spoke frequency and a spectral index was defined. Below this pressure the spectrum below 200 kHz was lower in lower in amplitude by a factor of ten and no spectral index could be defined. At these lower pressures, fluctuations that appeared to be ion spokes were observed, but had a dependence of frequency on operating conditions which was previously unreported.

Gerdin, G. A.↗
NASA NTRS1974

Spoke wavenumbers and mode transitions in the NASA Lewis bumpy torus

Waveforms of fluctuations of plasma potential, resulting from rotating electron and ion charge concentrations, were observed in a bumpy torus. Since these fluctuations were thought to be spoke rotations in the direction of the ExB drift, measuring the direction of spoke rotation should determine the direction of the electric fields over much of the plasma surface. A Langmuir probe was inserted into the plasma to measure the floating potential of the plasma, hence the direction of the electric field could be checked another way.

Gerdin, G. A.↗
NASA NTRS1973

Initial results from the NASA Lewis Bumpy Torus experiment

Initial results are given for low power operation of the NASA Lewis Bumpy Torus experiment in which a steady-state ion heating method based on a modified Penning discharge is applied to a bumpy torus confinement geometry. The magnet facility consists of 12 superconducting coils capable of 3.0 T each and equally spaced in a toroidal array 1.52 m in major diameter. A 18 cm i.d. anode ring is located at each of the 12 midplanes and is maintained at high positive potentials by a dc power supply. Initial observations indicate electron temperatures from 10 to 150 eV, and ion kinetic temperatures from 200 eV to 1200 eV. Two modes of operation with different radial density profiles can be achieved, depending on the background pressure applied.

Roth, J. R.↗
NASA NTRS1973

Initial results from the NASA Lewis Bumpy Torus experiment

Initial results were obtained from low power operation of the NASA Lewis Bumpy Torus experiment, in which a steady-state ion heating method based on the modified Penning discharge is applied in a bumpy torus confinement geometry. The magnet facility consists of 12 superconducting coils, each 19 cm i.d. and capable of 3.0 T, equally spaced in a toroidal array 1.52 m in major diameter. A 18 cm i.d. anode ring is located at each of the 12 midplanes and is maintained at high positive potentials by a dc power supply. Initial observations indicate electron temperatures from 10 to 150 eV, and ion kinetic temperatures from 200 eV to 1200 eV. Two modes of operation were observed, which depend on background pressure, and have different radial density profiles. Steady state neutron production was observed. The ion heating process in the bumpy torus appears to parallel closely the mechanism observed when the modified Penning discharge was operated in a simple magnetic mirror field.

Roth, J. R.↗