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Plasma Confinement at Uniform Temperature

Description: Report discussing the properties of a plasma held in a steady state by a magnetic field. Properties such as "electric and magnetic fields, current density, particle density, and macroscopic velocity" are determined analytically by assuming uniform temperature throughout the plasma.
Date: October 24, 1956
Creator: Woods, Cornelius H.
Partner: UNT Libraries Government Documents Department

Injection of Electrons into the Astron Reactor

Description: "The injection of the E-layer electrons into the Astron reactor is described by following the electrons as they emerge from the anode of the 1-Mev electron gun through the various steps up to their injection in the reactor volume. Several problems are imposed by this injection process and their solutions are discussed briefly. The detailed mathematical theory and calculations will be presented in a separate paper now in preparation."
Date: January 27, 1958
Creator: Christofilos, Nicholas C.
Partner: UNT Libraries Government Documents Department

Duals for SU(N) SUSY Gauge Theories with an Antisymmetric Tensor: Five Easy Flavors

Description: I consider N = 1 supersymmetric SU(N{sub c}) gauge theories with matter fields consisting of one antisymmetric representation, five flavors, and enough antifundamental representations to cancel the gauge anomaly. Previous analyses are extended to the case of even N{sub c} with no superpotential. Using holomorphy I show that the theory has an interacting infrared fixed point for sufficiently large N{sub c}. These theories are interesting due to the fact that in going from five to four flavors the theory goes from a non-trivial infrared fixed point to confinement, in contradistinction to SUSY QCD, but in analogy to the behavior expected in non-SUSY QCD.
Date: December 16, 1997
Creator: Terning, John
Partner: UNT Libraries Government Documents Department

Plasma Containment Configuration

Description: Report discussing a plasma containment configuration which appears to have no escape cone. From abstract: "Arguments are given to show how the containment process works, including experimental evidence deduced from published reports on "electromagnetic levitation."
Date: October 11, 1956
Creator: Linlor, William I.
Partner: UNT Libraries Government Documents Department

Pyrotron Plasma-Heating Experiments

Description: Report discussing experiments on particle density, plasma compression, electron heating, and electron energy distribution of plasma in a pyrotron. Past experiments that led to this investigation are discussed as well.
Date: May 6, 1958
Creator: Coensgen, F. H.; Ford, F. C. & Ellis, R.E.
Partner: UNT Libraries Government Documents Department

Pyrotron High-Energy Experiments

Description: "In these studies ions of several-kilovolts energy were extracted from an ion source located inside one of the peaks of the mirror field...The extraction slot of the source is located near the field injection plane, about midway between the mirror peak and the center, and ions are injected perpendicularly to magnetic field lines. In their traversal of the distance between the mirrors, the ions are in an inhomogeneous magnetic field and have a component of velocity along curved field lines. This gives rise to a to a 'guiding center' drift in the azimuthal direction and prevents the particle trajectory from intersecting the ion source after the first reflection. The magnetic field is increased during the injection period by an amount sufficient to move the reflection surface inside the ion source region by the time the ions have precessed completely about the symmetry axis."
Date: April 11, 1958
Creator: Damm, Charles C. & Eby, F. S.
Partner: UNT Libraries Government Documents Department

Computational modeling of magentically driven liner-on-plasma fusion experiments

Description: Magnetized Target Fusion (MTF) is an approach to controlled fusion which potentially avoids the difficulties of the traditional magnetic and inertial confinement approaches. It appears possible to investigate the critical issues for MTF at low cost, relative to traditional fusion programs, utilizing pulsed power drivers much less expensive than ICF drivers, and plasma configurations much less expensive than those needed for full magnetic confinement. Computational and experimental research into MTF is proceeding at Los Alamos, VNIIEF, and other laboratories.
Date: December 31, 1996
Creator: Sheehey, P.T.; Faehl, R.J.; Kirkpatrick, R.C. & Lindemuth, I.R.
Partner: UNT Libraries Government Documents Department

Quantum confinement, carrier dynamics and interfacial processes in nanostructured direct/indirect-gap semiconductor-glass composites

Description: The behavior of semiconductor clusters precipitated in an insulated matrix was investigated. Semiconductor compositions of CdTe, Si and Ge were studies and the insulating matrix was amorphous SiO2. As a function of size, quantum confinement effects were observed in all three composite systems. However significant differences were observed between the direct-gap column 2-6 semiconductors and the indirect-gap column 4 semiconductors. As observed by others, the direct-gap 2-6 semiconductors showed a distinct saturation in the energy-gap blue shift with decreasing size. Theoretical studies using a 20-band k dot p calculation of the electronic and valence bands for a 3-dimensionally confined CdTe semiconductor showed that mixing of the conduction band states leads to a flattening of the central valley. This increases the electron mass drastically and saturates the size dependent blue shift in the bandgap. In contrast, the blue shift in the Si and Ge nanocrystals showed no sign of saturation and increased drastically with decreasing size. In fact, Si and Ge crystals were formed with blue shift values that moved the bandgap to the near UV region. We examined the absorption curves to determine whether the bandgap was direct or indirect in the quantum dots. The results are that the absorption shows an indirect gap for all but the smallest Si crystals and an indirect gap for all Ge crystals. Raman studies showed negligible size dependence due to a lack of phonon confinement in the matrix embedded clusters. Exciton saturation and recovery times were found to be very short (of the order of 400fs) and are the fastest reported for any quantum dot system. Work to examine the type of confinement obtained in a matrix that consists of a transparent conductor is under way. Studies of the photoinduced absorption change in GeSe glasses showed a significant effect of photodarkening, regardless of ...
Date: August 13, 2002
Creator: Simmons, Joseph H.
Partner: UNT Libraries Government Documents Department

The effect of current profile changes on confinement in the DIII-D tokamak

Description: Experiments in the DIII-D tokamak have demonstrated that the effect of changes in the current profile on plasma confinement varies with the discharge shape. The results are similar in many respects to those from other tokamaks. In all cases, a rapid change in the plasma current in an L-mode, circular or moderately elongated, discharge has been used to produce a transient change in the current density profile. Although the detailed results vary among tokamaks, it is generally observed that during and immediately following a negative plasma current ramp, the stored energy does not follow the L-mode scaling that predicts that confinement should be proportional to the total plasma current. The stored energy changes on the time scale of the relaxation of the current density profile rather than the shorter time scales of the energy confinement time or the change in the total current. Because of the discharge having capability of the DIII-K tokamak it has been possible to extend these current ramp experiments beyond the L-mode, moderate elongation case to highly elongated double-null divertor discharges in H-mode. In separate experiments, a rapid change in the discharge elongation has also been used to vary the current density profile. This paper shows that the dependence of the plasma confinement on the current profile changes when the discharge shape is changed. This variation with discharge shape provides evidence for a model that predicts that changes in the local magnetic shear resulting from the changes in the current profile can result in decreased local transport.
Date: May 1, 1992
Creator: Ferron, J. R.; Lao, L. L. & Taylor, T. S.
Partner: UNT Libraries Government Documents Department

Studies of global energy confinement in TFTR supershots

Description: The global energy confinement time, {tau}{sub E}, from TFTR supershot plasmas has been correlated with the hydrogen recycling and the pressure anisotropy. An expression for the global confinement was obtained that describes its value at the time of peak neutron emission for all TFTR supershots obtained in the 1990 campaign, and simultaneously describes the time evolution of {tau}{sub E} for an extensive subset of the 1990 data. The obtained expression is probably not unique and it can be written with different variables. An analysis of the energy balance for many of these supershots indicates that the primary effect of larger {tau}{sub E} is that the central particle diffusivity is lower.
Date: August 1, 1993
Creator: Strachan, J. D.
Partner: UNT Libraries Government Documents Department

The Dependence of H-mode Energy Confinement and Transport on Collisionality in NSTX

Description: Understanding the dependence of confi nement on collisionality in tokamaks is important for the design of next-step devices, which will operate at collisionalities at least one order of magnitude lower than in present generation. A wide range of collisionality has been obtained in the National Spherical Torus Experiment (NSTX) by employing two different wall conditioning techniques, one with boronization and between-shot helium glow discharge conditioning (HeGDC+B), and one using lithium evaporation (Li EVAP). Previous studies of HeGDC+B plasmas indicated a strong and favorable dependence of normalized con nement on collisionality. Discharges with lithium conditioning discussed in the present study gen- erally achieved lower collisionality, extending the accessible range of collisionality by almost an order of unity. While the confinement dependences on dimensional, engineering variables of the HeGDC+B and Li EVAP datasets differed, collisionality was found to unify the trends, with the lower collisionality lithium conditioned discharges extending the trend of increasing normalized confi nement time with decreasing collisionality when other dimension less variables were held as fi xed as possible. This increase of confi nement with decreasing collisionality was driven by a large reduction in electron transport in the outer region of the plasma. This result is consistent with gyrokinetic calculations that show microtearing and Electron Temperature Gradient modes to be more stable for the lower collisionality discharges. Ion transport, near neoclassical at high collisionality, became more anomalous at lower collisionality, possibly due to the growth of hybrid TEM/KBM modes in the outer regions of the plasma.
Date: November 27, 2012
Creator: S.M.. Kaye, S. Gerhardt, W. Guttenfelder, R. Maingi, R.E. Bell, A. Diallo, B.P. LeBlanc and M. Podesta
Partner: UNT Libraries Government Documents Department