Out-of-plane displacements and stresses in a torus.
Circumferential displacement and shearing stresses in out-of-plane elasticity problem for solid torus
ELASTICITY↗
SEARCH · Search NASA
Results for “Torus”
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.
Length of winding on a torus in two ideal models
Length of winding on torus in two ideal models
Niedra, J. M.↗
Explicit expressions for triangular torus element stiffness matrix.
Explicit expressions for stiffness matrix of triangular torus elements associated with linear displacement fields and generalized Hookian material
Utku, S.↗
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.↗
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.↗
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.↗
Time-dependent outgassing and impurities in the NASA Lewis Bumpy Torus
To investigate the importance to fusion devices of desorption of gas from walls or cryosurfaces under long time operation, preliminary mass spectrometric investigations were carried out on the NASA Lewis Bumpy Torus with a 0.1-2A discharge in D2 at a pressure of 4.0 to 6.6 x 0.00001 torr. During the initial tens of minutes of discharge operation large quantities of a component with mass number 28, believed to be nitrogen, were released. The decrease with time of the nitrogen density after its initial maximum, indicated a diffusion controlled outgassing from cryodeposits or wall material. When cold surfaces were allowed to warm up, large quantities of gas were released. The integrated amount of N2 was typically the same as that released during a discharge, while the amount of H2O was orders of magnitude larger.
Persson, H.↗
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.↗
Pioneer 10 ultraviolet photometer observations of the Jovian hydrogen torus - The angular distribution
The Pioneer 10 ultraviolet photometer observations of the Jovian hydrogen torus are analyzed to obtain the angular distribution. The cloud is asymmetric about Io, where the atoms presumably originate, with the greater density occurring in the trailing portion. A simple model which assumes Jeans escape from the atmosphere of Io is developed and compared to the observations. The results suggest that the exospheric temperature is high (approximately 3000 K) and that the ionization lifetime of the cloud atoms is approximately 100,000 sec.
Carlson, R. W.↗
Eclipses by an elliptical torus
A general procedure for computing the effects of eclipses by a torus, including both the outer horizon and the inner or hole horizon, was developed. The procedure can be used for any of the simple figures of revolution encountered in binary-star models. That is, the thickness can be made negligible to produce a thin ring, the hole radius can be set to zero to yield a thin disk, the radius to the center of the elliptical meridian section can be brought to zero to give an ellipsoid of revolution, or the equatorial axis of the elliptical meridian section can be made to equal zero to produce a section of a right circular cylinder.
Wilson, R. E.↗
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.↗
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.↗
Preliminary scaling laws for plasma current, ion kinetic temperature, and plasma number density in the NASA Lewis bumpy torus plasma
Parametric variation of independent variables which may affect the characteristics of bumpy torus plasma have identified those which have a significant effect on the plasma current, ion kinetic temperature, and plasma number density, and those which do not. Empirical power law correlations of the plasma current, and the ion kinetic temperature and number density were obtained as functions of potential applied to the midplane electrode rings, the background neutral gas pressure, and the magnetic field strength. Additional parameters studied included the type of gas, the polarity of the midplane electrode rings, the mode of plasma operation, and the method of measuring the plasma number density. No significant departures from the scaling laws appear to occur at the highest ion kinetic temperatures or number densities obtained to date.
Roth, J. R.↗
Preliminary scaling laws for plasma current, ion kinetic temperature, and plasma number density in the NASA Lewis Bumpy Torus plasma
Parametric variation of independent variables which may affect the characteristics of the NASA Lewis Bumpy Torus plasma have identified those which have a significant effect on the plasma current, ion kinetic temperature, and plasma number density, and those which do not. Empirical power-law correlations of the plasma current, and the ion kinetic temperature and number density were obtained as functions of the potential applied to the midplane electrode rings, the background neutral gas pressure, and the magnetic field strength. Additional parameters studied include the type of gas, the polarity of the midplane electrode rings (and hence the direction of the radial electric field), the mode of plasma operation, and the method of measuring the plasma number density. No significant departures from the scaling laws appear to occur at the highest ion kinetic temperatures or number densities obtained to date.
Roth, J. R.↗
Investigation of possible lower hybrid emission from the NASA Lewis bumpy torus plasma
Radio frequency emission has been detected near the power hybrid frequency of a bumpy torus plasma by using a responsive detection system that consists of a spectrum analyzer and a 50 ohm miniature coaxial antenna concentrically located in a re-entrant quartz tube. The frequency shift of a broad emission peak was monitored as a function of background pressure, electrode voltage, and the strength of the dc magnetic field. Simultaneous measurements of the average plasma density were made with a polarization diplexing microwave interferometer. The information derived from the experiment is discussed with particular reference to the following: (1) whether the emissions are dominated by atomic or molecular species of deuterium; (2) the strength of the dc magnetic field in the emitting region; (3) the geometric location of the emitting region of the plasma; (4) comparison of the lower hybrid plasma density with the average plasma density; and (5) relation of ion spoke geometry to lower hybrid emission.
Mallavarpu, R.↗
Investigation of possible lower hybrid emission from the NASA Lewis Bumpy Torus plasma
Radio frequency emission detected near the lower hybrid frequency of the NASA Lewis Bumpy Torus plasma is studied, using a simple detection system that consists of a spectrum analyzer and a 50-ohm miniature co-axial antenna concentrically located in a re-entrant quartz tube. The frequency shift of a broad emission peak is monitored as a function of the background pressure, electrode voltage, and the strength of the dc magnetic field. Simultaneous measurements of the average plasma density are made with a polarization diplexing microwave interferometer. Information from the experiment is discussed with particular reference to the role of atomic or molecular species of deuterium in the emissions, the strength of the dc magnetic field in the emitting region, the geometric location of the emitting region of the plasma, the lower hybrid plasma density as compared with the average plasma density, and the relation of the ion spoke geometry to the lower hybrid emission.
Mallavarpu, R.↗
Fluctuation spectra in the NASA Lewis bumpy-torus plasma
The electrostatic potential fluctuation spectrum in the NASA Lewis bumpy-torus plasma was studied with capacitive probes in the low pressure (high impedance) mode and in the high pressure (low impedance) mode. Under different operating conditions, the plasma exhibited electrostatic potential fluctuations (1) at a set of discrete frequencies, (2) at a continuum of frequencies, and (3) as incoherent high-frequency turbulence. The frequencies and azimuthal wave numbers were determined from digitally implemented autopower and cross-power spectra. The azimuthal dispersion characteristics of the unstable waves were examined by varying the electrode voltage, the polarity of the voltage, and the neutral background density at a constant magnetic field strength.
Singh, C. M.↗
Effects of applied dc radial electric fields on particle transport in a bumpy torus plasma
The influence of applied dc radial electric fields on particle transport in a bumpy torus plasma is studied. The plasma, magnetic field, and ion heating mechanism are operated in steady state. Ion kinetic temperature is more than a factor of ten higher than electron temperature. The electric fields raise the ions to energies on the order of kilovolts and then point radially inward or outward. Plasma number density profiles are flat or triangular across the plasma diameter. It is suggested that the radial transport processes are nondiffusional and dominated by strong radial electric fields. These characteristics are caused by the absence of a second derivative in the density profile and the flat electron temperature profiles. If the electric field acting on the minor radius of the toroidal plasma points inward, plasma number density and confinement time are increased.
Roth, J. R.↗