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Accurate equilibrium reconstruction and detailed stability analysis of a strongly shaped, double-null, βT=11% discharge shows that the plasma core is in the second stable regime to ideal ballooning modes. The equilibrium reconstruction using all the available data (coil currents, poloidal magnetic loops, motional Stark effect data, the kinetic pressure profile, the magnetic axis location, and the location of the two q=1 surfaces) shows a region of negative magnetic shear near the magnetic axis, an outer positive shear region, and a low shear region connecting the two. The inner negative shear region allows a large positive shear region near the boundary, even at low q (q95=2.6), permitting a large outer region pressure gradient to be first regime stable. The inner region is in the second stable regime, consistent with the observed axial beta [βT(0)=44%]. In the low shear region p′ vanishes, consistent with Mercier stability. This is one way to extend the ballooning limit in shaped plasmas while maintaining stability against external kinks. The n=1 analysis shows that the plasma is unstable to an ideal internal mode, consistent with the experimental observations of a saturated internal m/n=l/l mode. The core plasma pressure, not being limited by ballooning stability, appears to be reaching a local equilibrium limit at the magnetic axis. © 1992 American Institute of Physics.

Recent results from the DIII-D tokamak have provided significant contributions to the understanding of many of the elements of tokamak physics and the application of this understanding to the design of next generation devices including ITER and CIT. The limitations of magnetohydrodynamic stability on the values of plasma beta (the ratio of kinetic pressure to the containing pressure of the magnetic field) that can be attained has been experimentally demonstrated and found to be described by existing theory. Values of beta (10.7%) well in excess of those required for proposed devices (ITER and CIT) have been demonstrated. Regimes of confinement (H-mode) have been established that scale favorably to proposed next generation devices, and experiments demonstrating the dependence of the energy confinement on plasma size have been completed. Understanding of confinement is rapidly developing especially in the areas of bulk transport and the role of turbulence in the plasma edge. Key experimental results in areas of plasma transport and edge plasma phenomena are in agreement with theories based on short wavelength turbulence. Control of the divertor heat loads and impurity influx has been demonstrated, and new progress has been made in the understanding of plasma edge phenomena. Experiments with ion Bernstein wave heating have not found regimes in which these waves can produce effective central ion heating. Electron cyclotron current drive experiments have demonstrated 70 kA of driven current in 400 kA discharges.

The authors' data indicate that the L-mode to H-mode transition in the DIII-D tokamak is associated with the sudden reduction in anomalous, fluctuation-connected transport across the outer midplane of the plasma. In addition to the reduction in edge density and magnetic fluctuations observed at the transition, the edge radial electric field becomes more negative after the transition. They have determined the scaling of the H-mode power threshold with various plasma parameters; the roughly linear increase with plasma density and toroidal field are particularly significant. Control of the ELM frequency and duration by adjusting neutral beam input power has allowed us to produce H-mode plasmas with constant impurity levels and durations up to 5 s. Energy confinement time in ohmic H-mode plasmas and in deuterium H-mode plasmas with deuterium beam injection can exceed saturated ohmic confinement times by at least a factor of two. Energy confinement times above 0.3 s have been achieved in these beam-heated plasmas with plasma currents in the range of 2.0 to 2.5 MA. Local transport studies have shown that electron and ion thermal diffusivities and angular momentum diffusivity are comparable in magnitude and all decrease with increasing plasma current.

The passive cooling, including the transient start-up process, of a leadless chip carrier package mounted on a vertical substrate in a liquid filled cubic enclosure is investigated numerically. A relatively detailed thermal model of the electronic package is included. The governing three-dimensional unsteady equations for natural convection within the fluid and for the coupled heat conduction in the package are solved numerically using a finite difference method. The transient heat up of the system can be characterized by four stages: 1) initial heat up of the chip with some conduction through the package and the surrounding fluid; 2) increased conduction characterized by symmetric thermal spreading through the substrate, accompanied by the development of the natural convection flow field; 3) increased convection effects, as the buoyant driving force reaches its peak level, leading to asymmetric spreading through the substrate and a strong plume above the package; 4) gradual approach to steady state as the fluid in the enclosure is slowly heated, with reduced buoyant driving force and hence decreasing velocities. Steady-state conditions are characterized by thin boundary layers along the hot and cold surfaces, well stratified temperature in the core, a strong plume above the package, and oval shaped isotherms along the substrate surface. With FC-75 as the coolant, a large fraction of the heat generated in the chip is conducted to the substrate and then transferred to the fluid, due to the high thermal conductivity of the substrate relative to that of the fluid. Even when the upper lid of the package is removed, exposing the chip directly to the fluid, the chip temperature drops only by 5 percent, indicating the importance of substrate conduction. Use of a chip that has twice the cross-sectional area as the base case results in a 25 percent drop in chip temperature, with little effect on the remainder of the flow. When water is used as the coolant instead of FC-75, the nondimensional temperature of the chip increases, due to the lower Rayleigh number and lower ratio of substrate-to-fluid thermal conductivity. In dimensional units, however, the actual chip temperature is 25 [degrees] C cooler., The passive cooling of a leadless chip carrier package in a liquid-filled enclosure is analyzed. The finite difference method is used to solve the three-dimensional equations of the natural convection in the enclosure and the coupled conduction in the package and substrate. Using FC-75 as the coolant conducts a large amount of heat from the chip to the substrate which is then transferred to the fluid. Water used as the coolant increases the nondimensional temperature of the chip.

The National Antimicrobial Resistance Monitoring System for Enteric Bacteria retail food surveillance programme screens retail meat samples for the presence of Salmonella spp. to track antimicrobial resistance in food. In this study, a laboratory developed real‐time PCR assay that detects Salmonella spp. was evaluated as a screening method to replace the discountinued 3M TECRA kit. The 3M TECRA kit was a commercially available, visual immunoassay used to screen food samples for the presence of Salmonella spp. This kit was discontinued in September 2016 by the manufacturer and an alternative screening method was needed to replace the discontinued TECRA kit. Salmonella spp. is detected by the real‐time PCR assay earlier in the screening process than by the TECRA kit. Salmonella spp. can also be reliably isolated from the enrichment broth earlier in the protocol. Additionally, cost analysis shows that the real‐time PCR assay saves $2·50 per sample. New York State Department of Health currently uses this real‐time PCR assay as a screening method for the presence of Salmonella spp. in retail meat samples. The assay allows for continued monitoring of antimicrobial resistance in Salmonella spp., while providing a cost savings and a decrease in turnaround time. Significance and Impact of the Study: The National Antimicrobial Resistance Monitoring System for Enteric Bacteria (NARMS) tracks antimicrobial susceptibility of enteric bacteria in people, food and animals (https://www.fda.gov/animalveterinary/safetyhealth/antimicrobialresistance/nationalantimicrobialresistancemonitoringsystem/). The New York State Department of Health (NYSDOH) became a NARMS retail food surveillance (RFS) site in 2003. The NARMS‐RFS programme screens retail meat samples from grocery stores in the United States for the presence of Salmonella spp. and other enteric pathogens to monitor the prevalence of antimicrobial resistance among these pathogens. The NYSDOH developed a rapid and cost‐effective real‐PCR assay to screen for Salmonella spp. in retail meat products. [ABSTRACT FROM AUTHOR]

Investigates the role of ExB flow shear on confinement enhancement in DIII-D high internal inductance discharges. Discharges with stronger ExB flow shear at similar internal inductance; Importance of the ExB flow shear.

Presents detailed analysis of recent high beta discharges in the DIII-D tokamak, which demonstrates that the resistive vacuum vessel can provide stabilization of low n magnetohydrodynamic modes. Importance of plasma rotation to stabilization; Effects of the slowing of the plasma rotation.

Discusses the measurement of the scaling of cross-field heat transport with relative gyroradius in low and high mode tokamak plasmas using the technique of dimensionally similar discharges. Relative gyroradius scalings of the electron and ion thermal diffusivities; Effective diffusivity and global confinement time scalings.

Reports on experiments that explore the long-time evolution of noninductive, high beta plasmas in the DIII-D tokamak and identify a quiescent, high performance regime. Disappearance of magnetohydrodynamic activity with an increase in stored energy; Experimental conditions.