42 research outputs found
Letter from Terry L. Medley to Henry Spira
We agree that there is an urgent need to focus on the causes and means of preventing food-borne illness from pathogens. Several agencies throughout the Department of Agriculture, including the Animal and Plant Health Inspection Service, the Extension Services, and the Food Safety and Inspection Service, are taking a new look at conditions on the farm to determine whether they could be factors in the spread of pathogenic contamination of food animals. Secretary Espy also is interested in reexamining issues that may relate to food safety
Interpretative and predictive modelling of Joint European Torus collisionality scans
Transport modelling of Joint European Torus (JET) dimensionless collisionality scaling experiments in various operational scenarios is presented. Interpretative simulations at a fixed radial position are combined with predictive JETTO simulations of temperatures and densities, using the TGLF transport model. The model includes electromagnetic effects and collisions as well as □(→┬E ) X □(→┬B ) shear in Miller geometry. Focus is on particle transport and the role of the neutral beam injection (NBI) particle source for the density peaking. The experimental 3-point collisionality scans include L-mode, and H-mode (D and H and higher beta D plasma) plasmas in a total of 12 discharges. Experimental results presented in (Tala et al 2017 44th EPS Conf.) indicate that for the H-mode scans, the NBI particle source plays an important role for the density peaking, whereas for the L-mode scan, the influence of the particle source is small. In general, both the interpretative and predictive transport simulations support the experimental conclusions on the role of the NBI particle source for the 12 JET discharges
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Alpha particle diagnostics using impurity pellet injection
We have proposed using impurity injection to measure the energy distribution of the fast confined alpha particles in a reacting plasma. The ablation cloud surrounding the injected pellet is thick enough that an equilibrium fraction F{sub o}{sup {infinity}}(E) of the incident alphas should be neutralized as they pass through the cloud. By observing neutrals created in the large spatial region of the cloud which is expected to be dominated by the helium-like ionization state, e.g., Li{sup +} ions, we can determine the incident alpha distribution dn{sub He}2+/dE from the measured energy distribution of neutral helium atoms. Initial experiments were performed on TEXT in which we compared pellet penetration with our impurity pellet ablation model, and measured the spatial distribution of various ionization states in carbon pellet clouds. Experiments have recently begun on TFTR with the goal of measuring the alpha particle energy distribution during D-T operation in 1993--94. A series of preliminary experiments are planned to test the diagnostic concept. The first experiments will observe neutrals from beam-injected deuterium ions and the high energy {sup 3}He tail produced during ICH minority heating on TFTR interacting with the cloud. We will also monitor by line radiation the charge state distributions in lithium, boron, and carbon clouds
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Alpha particle diagnostics using impurity pellet injection
We have proposed using impurity injection to measure the energy distribution of the fast confined alpha particles in a reacting plasma. The ablation cloud surrounding the injected pellet is thick enough that an equilibrium fraction F{sub o}{sup {infinity}}(E) of the incident alphas should be neutralized as they pass through the cloud. By observing neutrals created in the large spatial region of the cloud which is expected to be dominated by the helium-like ionization state, e.g., Li{sup +} ions, we can determine the incident alpha distribution dn{sub He}2+/dE from the measured energy distribution of neutral helium atoms. Initial experiments were performed on TEXT in which we compared pellet penetration with our impurity pellet ablation model, and measured the spatial distribution of various ionization states in carbon pellet clouds. Experiments have recently begun on TFTR with the goal of measuring the alpha particle energy distribution during D-T operation in 1993--94. A series of preliminary experiments are planned to test the diagnostic concept. The first experiments will observe neutrals from beam-injected deuterium ions and the high energy {sup 3}He tail produced during ICH minority heating on TFTR interacting with the cloud. We will also monitor by line radiation the charge state distributions in lithium, boron, and carbon clouds
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Achieving high fusion reactivity in high poloidal beta discharges in TFTR
High poloidal beta discharges have been produced in TFTR that achieved high fusion reactivities at low plasma currents. By rapidly decreasing the plasma current just prior to high-power neutral beam injection, relatively peaked current profiles were created having high l{sub i} > 2, high Troyon-normalized beta, {beta}N > 3, and high poloidal beta. {beta}{sub p} {ge} 0.7 R/a. The global energy confinement time after the current ramp was comparable to supershots, and the combination of improved MHD stability and good confinement produced a new high {epsilon}{beta}{sub p} high Q{sub DD} operating mode for TFTR. Without steady-state current profile control, as the pulse lengths of high {beta}p discharges were extended, l{sub i} decreased, and the improved stability produced immediately after by the current ramp deteriorated. In four second, high {epsilon}{beta}{sub p} discharges, the current profile broadened under the influence of bootstrap and beam-drive currents. When the calculated voltage throughout the plasma nearly vanished, MHD instabilities were observed with {beta}{sub N} as low as 1.4. Ideal MHD stability calculations showed this lower beta limit to be consistent with theoretical expectations
OVERVIEW OF RECENT TFTR RESULTS
Robin Kundis Craig, left, and Stegner Lecturer Mary Evelyn Tucker, center