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A Sensitive Radiation Monitor for a Large Laboratory Area

Description: An instrument has been built to survey releases of radioactivity within the 22-acre enclosure of the Savannah River Laboratory. The device consists of a 2-in.diameter x 2-in. sodium iodide scintillation crystal with associated detector counting and recording circuits which provide a permanent record of radioactivity movements within the Laboratory area. The monitor detects signals of 6.9 mu r/hr from a 0.48-curie cobalt-60 source located 265 ft away. (auth)
Date: November 1, 1963
Creator: Cathey, L. & Moyer, R. A.
Partner: UNT Libraries Government Documents Department
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Toward more accurate loss tangent measurements in reentrant cavities

Description: Karpova has described an absolute method for measurement of dielectric properties of a solid in a coaxial reentrant cavity. His cavity resonance equation yields very accurate results for dielectric constants. However, he presented only approximate expressions for the loss tangent. This report presents more exact expressions for that quantity and summarizes some experimental results.
Date: May 1, 1980
Creator: Moyer, R. D.
Partner: UNT Libraries Government Documents Department
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MODELING OF COUPLED EDGE STOCHASTIC AND CORE RESONANT MAGNETIC FIELD EFFECTS IN DIVERTED TOKAMAKS

Description: Attaining the highest performance in poloidally diverted tokamaks requires resonant magnetic perturbation coils to avoid core instabilities (locked, resistive wall and neoclassical tearing modes). These coils also perturb the pedestal and edge region, causing varying degrees of stochasticity with remnant islands. The effects of the DIII-D locked mode control coil on the edge and core of Ohmic plasmas are modeled with the field line integration code TRIP3D and compared with experimental measurem… more
Date: June 1, 2002
Creator: Evans, T. E. & Moyer, R. A.
Partner: UNT Libraries Government Documents Department
open access

Enhanced Scrape-Off Layer Plasma in DIII-D Double-Null Discharges

Description: In this paper, the authors examine a denser and broader scrape-off layer (SOL) plasma, first seen in VH mode, in the DIII-D tokamak. The enhanced SOL appears in many types of double-null (DN) discharges and is not a property of VH-mode only. The DN enhanced SOL density and temperature profiles exhibit a 5--6 cm broad profile outside the separatrix. For DN and single-null (SN) boundary geometry with similar core plasma conditions, the enhanced SOL is only observed in high triangularity discharge… more
Date: July 1, 1994
Creator: Watkins, J. G.; Jong, R. A. & Moyer, R. A.
Partner: UNT Libraries Government Documents Department
open access

Target Plate Conditions During Stochastic Boundary Operation on DIII-D

Description: A major concern for large tokamaks like ITER is the presence of edge localized modes (ELMs) that repeatedly send large bursts of particles and heat into the divertor plates. Operation with resonant magnetic perturbations (RMP) at the boundary of DIII=D has suppressed ELMs for values of q95 {approx} 3.7. At the target plate, the conditions during ELM suppressed operation for both high and low collisionality are observed by a set of radially distributed Langmuir probes. At high collisionality (n*… more
Date: May 15, 2006
Creator: Watkins, J; Evans, T; Moyer, R; Lasnier, C & Rudakov, D
Partner: UNT Libraries Government Documents Department
open access

Experimental and Numerical Studies of Separatrix Splitting and Magnetic Footprints in DIII-D

Description: A numerical field line integration code is used to study the structure of divertor footprints produced by small non-axisymmetric magnetic perturbation in the DIII-D tokamak. The numerical modeling results are compared to experimental infrared camera data which show a splitting of the divertor target plate heat flux into several distinct peaks when an n=3 magnetic perturbation from the DIII-D I-coil is applied. The heat flux splitting consistently appears when the n=3 perturbation is applied and… more
Date: May 15, 2006
Creator: Evans, T; Joseph, I; Moyer, R; Fenstermacher, M; Lasnier, C & Yan, L
Partner: UNT Libraries Government Documents Department
open access

A radial transmission line material measurement apparatus

Description: A radial transmission line material measurement sample apparatus (sample holder, offset short standards, measurement software, and instrumentation) is described which has been proposed, analyzed, designed, constructed, and tested. The purpose of the apparatus is to obtain accurate surface impedance measurements of lossy, possibly anisotropic, samples at low and intermediate frequencies (vhf and low uhf). The samples typically take the form of sections of the material coatings on conducting obje… more
Date: May 1, 1993
Creator: Warne, L. K.; Moyer, R. D.; Koontz, T. E. & Morris, M. E.
Partner: UNT Libraries Government Documents Department
open access

DIII-D Edge Plasma, Disruptions, and Radiative Processes. Final Report

Description: The scientific goal of the UCSD-DIII-D Collaboration during this period was to understand the coupling of the core plasma to the plasma-facing components through the plasma boundary (edge and scrape-off layer). To achieve this goal, UCSD scientists studied the transport of particles, momentum, energy, and radiation from the plasma core to the plasma-facing components under normal (e.g., L-mode, H-mode, and ELMs), and off-normal (e.g., disruptions) operating conditions.
Date: January 1, 2001
Creator: Boedo, J. A.; Luckhardt, S.C. & Moyer, R. A.
Partner: UNT Libraries Government Documents Department
open access

Study of the phase transition dynamics of the L to H transition

Description: A highly radiating zone (MARFE) just above the divertor X-point has been used to access the marginal transition regime P{sub sep} {approx} P{sub thres} to study the existence of a critical point for the L to H transition. Phase transition models predict that at the critical point, the transition duration increases and the plasma parameters vary continuously between L-mode and H-mode. In these experiments, the L to H transition duration increased 50--100 times over fast transitions. However, the… more
Date: September 1, 1997
Creator: Moyer, R. A.; Rhodes, T. L. & Rettig, C. L.
Partner: UNT Libraries Government Documents Department
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Plasma pressure and flows during divertor detachment

Description: MHD theory applied to tokamak plasma scrape-off layer (SOL) equilibria requires Pfirsch-Schlueter current, which, because the magnetic lines are open, normally closes through electrically conducting divertor or limiter components. During detached divertor operation the Pfirsch-Schlueter current path to the divertor target is sometimes blocked, in which case theory predicts that the plasma develops a poloidal pressure gradient around the upstream SOL and a corresponding parallel flow, in order t… more
Date: August 1, 1998
Creator: Schaffer, M. J.; Brooks, N. H.; Boedo, J. A.; Isler, R. C. & Moyer, R. A.
Partner: UNT Libraries Government Documents Department
open access

Reactor operation environmental information document

Description: This volume is a reactor operation environmental information document for the Savannah River Plant. Topics include meteorology, surface hydrology, transport, environmental impacts, and radiation effects. 48 figs., 56 tabs. (KD)
Date: December 1, 1989
Creator: Bauer, L.R.; Hayes, D.W.; Hunter, C.H.; Marter, W.L. & Moyer, R.A.
Partner: UNT Libraries Government Documents Department
open access

Scrape-Off Layer Features of the QH-Mode

Description: The quiescent high confinement (QH-mode) and quiescent double barrier (QDB) modes in DIII-D have long-duration H-mode confinement without ELMs, possibly an alternative operating mode in future tokamaks for avoiding damage by ELMS. Instead of ELMs, there is an edge harmonic oscillation (EHO), which is a continuous electromagnetic mode with associated density fluctuations. The edge pedestal is similar to ELMing H-mode, but at very low density to daw. We see C{sup +6} ion temperatures of 3-7 keV i… more
Date: May 23, 2002
Creator: Lasnier, C. J.; Burrell, K. H.; deGrassie, J. S.; Leonard, A. W.; Moyer, R. A.; Porter, G. D. et al.
Partner: UNT Libraries Government Documents Department
open access

Calculation of the Thermal Footprint of Resonant Magnetic Perturbations in DIII-D

Description: The effect of resonant magnetic perturbations on heat transport in DIII-D H-mode plasmas has been calculated by combining the TRIP3D field-line tracing code with the E3D two-fluid transport code. Simulations show that the divertor heat flux distribution becomes non-axisymmetric because heat flux is efficiently guided to the divertor along the three-dimensional invariant manifolds of the magnetic field. Calculations demonstrate that heat flux is spread over a wider area of the divertor target, t… more
Date: September 14, 2007
Creator: Joseph, I; Evans, T; Moyer, R; Fenstermacher, M; Groth, M; Kasilov, S et al.
Partner: UNT Libraries Government Documents Department
open access

Comparison of Edge Plasma Perturbation During ELM Control Using One vs Two Toroidal Rows of RMP Coils in ITER Similar Shaped Plasmas on DIII-D

Description: Large Type-I edge localized modes (ELMs) were suppressed by n = 3 resonant magnetic perturbations (RMPs) from a set of internal coils (I-coil) in plasmas with an ITER similar shape at the ITER pedestal collisionality, {nu}*{sub e} {approx} 0.1 and low edge safety factor (q{sub 95} {approx} 3.6), with either a single toroidal row of the internal RMP coils or two poloidally separated rows of coils. ELM suppression with a single row of internal coils was achieved at approximately the same q{sub 95… more
Date: May 21, 2008
Creator: Fenstermacher, M. E.; Evans, T. E.; Osborne, T. H.; Schaffer, M. J.; deGrassie, J. S.; Gohil, P. et al.
Partner: UNT Libraries Government Documents Department
open access

Reciprocating and fixed probe measurements of n{sub e} and T{sub e} in the DIII-D divertor

Description: This paper describes divertor density and temperature measurements using both a new reciprocating Langmuir probe (XPT-RCP) which plunges vertically above the divertor floor up to the X-point height and swept, single, Langmuir probes fixed horizontally across the divertor floor. These types of measurements are important for testing models of the SOL and divertor which then are used to design plasma facing components in reactor size tokamaks. This paper presents an overview of the new divertor pr… more
Date: November 1, 1996
Creator: Watkins, J. G.; Moyer, R. A.; Cuthbertson, J. W.; Buchenauer, D. A.; Carlstrom, T. N.; Hill, D. N. et al.
Partner: UNT Libraries Government Documents Department
open access

Stochastic Transport Modeling of Resonant Magnetic Perturbations in DIII-D

Description: Three-dimensional two-fluid simulations of heat transport due to resonant magnetic perturbations of tokamaks have been computed by coupling the TRIP3D field line tracing code to the E3D edge transport code. The predicted electron temperature contours follow the new separatrix represented by the perturbed invariant manifold structure of the X-point in qualitative agreement with X-point TV observations. However, preliminary modeling predicts that the resulting stochastic heat transport is greater… more
Date: June 1, 2006
Creator: Joseph, I.; Moyer, R. A.; Evans, T. E.; Schaffer, M. J.; Runov, A. M.; Schneider, R. et al.
Partner: UNT Libraries Government Documents Department
open access

Experimental Characterization of Coherent, Radially-Sheared Zonal Flows in the Diii-D Tokamak

Description: A271 EXPERIMENTAL CHARACTERIZATION OF COHERENT, RADIALLY-SHEARED ZONAL FLOWS IN THE DIII-D TOKAMAK. Application of time-delay-estimation techniques to two-dimensional measurements of density fluctuations, obtained with beam emission spectroscopy in DIII-D plasmas, has provided temporally and spatially resolved measurements of the turbulence flow-field. Features that are characteristic of self-generated zonal flows are observed in the radial region near 0.85 {<=} r/a {<=} 1.0. These featur… more
Date: November 1, 2002
Creator: Mckee, G. R.; Fonck, R. J.; Jakubowski, M.; Burrell, K. H.; Hallatschek, K.; Moyer, R. A. et al.
Partner: UNT Libraries Government Documents Department
open access

An evaluation of kinetic effects in the DIII-D divertor

Description: Under certain conditions, high temperature electrons diffusing across the separatrix near the midplane can propagate to the divertor without collision and produce a high energy tail in the electron distribution function near the separatrix. The authors evaluate a kinetic criterion along the field using measurements from divertor Thomson scattering and compare temperature measurements from target plate Langmuir probes to estimate the magnitude of the high energy tail. A Fokker-Planck kinetic mod… more
Date: August 1, 1998
Creator: Watkins, J. G.; Batishchev, O.; Boedo, J. A.; Lehmer, R.; Moyer, R. A.; Hill, D. N. et al.
Partner: UNT Libraries Government Documents Department
open access

ELM-Induced Plasma Transport in the DIII-D SOL

Description: High temporal and spatial resolution measurements in the boundary of the DIII-D tokamak show that edge localized modes (ELMs) are composed of fast bursts of hot, dense plasma that travel radially starting at the separatrix at {approx}450 m/s and rotate in the scrape off layer (SOL), convecting particles and energy to the SOL and walls. The temperature and density in the ELM plasma initially correspond to those at the top of the density pedestal but decay with radius in the SOL. The temperature … more
Date: December 1, 2004
Creator: Boedo, J.; Rudakov, D.; Hollmann, E.; Moyer, R.; McKee, G.; Burrell, K. et al.
Partner: UNT Libraries Government Documents Department
open access

SCRAPE-OFF LAYER FEATURES OF THE QH-MODE

Description: The quiescent high confinement (QH-mode) and quiescent double barrier (QDB) modes in DIII-D have long-duration H-mode confinement without ELMs, possibly an alternative operating mode in future tokamaks for avoiding damage by ELMs . Instead of ELMs, there is an edge harmonic oscillation (EHO), which is a continuous electromagnetic mode with associated density fluctuations. The edge pedestal is similar to ELMing H-mode, but at very low density to date. We see C{sup +6} ion temperatures of 3-7 keV… more
Date: August 1, 2002
Creator: Lasnier, C. J.; Burrell, K. H.; Degrassie, J. S.; Leonard, A. W.; Moyer, R. A.; Porter, G. D. et al.
Partner: UNT Libraries Government Documents Department
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