Non-linear temperature oscillations in the plasma centre on Tore Supra and their interplay with MHD

Regular oscillations of the central electron temperature have been observed by means of ECE and SXR diagnostics during non-inductively driven discharges on Tore Supra. These oscillations are sustained by LHCD, do not have a helical structure and, therefore, cannot be ascribed as MHD phenomena. The most probable explanation of this oscillating regime (O-regime) is the assumption that the plasma current density (and, thus, the q-profile) and the electron temperature evolve as a non-linearly coupled predator-pray system. The integrated modelling code CRONOS has been used to demonstrate that the coupled heat transport and resistive diffusion equations admit solutions for the electron temperature and the current density which have a cyclic behaviour. Recent experimental results in which the O-regime co-exists with MHD modes will be presented. Because both phenomena are linked to details of the q-profile, some interplay between MHD and oscillations may occur. The localisation of magnetic islands allows to obtain an accurate picture of the q-profile in the plasma core. In some case, MHD-driven reconnection helps in maintaining a weakly inverted q-profile that is found to be, in the CRONOS simulations, a necessary condition to trigger the oscillations.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

Present status and future plans for Tore Supra

Tore Supra is a limiter tokamak with circular plasma cross-section. The superconducting toroidal magnet is a unique feature which allows very long pulse discharges. Tore Supra has ion cyclotron resonance heating and an electron cyclotron system is being installed. Noninductive currents are driven by lower hybrid and by the bootstrap effect. Highlights of previous results include long pulses lasting up to 2 minutes with 280 MJ coupled into the plasma and fully non-inductive discharges lasting up to 75 seconds. Tore Supra is presently in the middle of a major shutdown for the installation of a new toroidal pumped limiter. This will be actively cooled with capability for steady state operation at total power levels around 20 MW. Future plans include upgrades to the ion cyclotron heating and lower hybrid current drive systems and a new pellet injector

Edge localized mode control with an edge resonant magnetic perturbation

A low amplitude (δbr∕BT=1 part in 5000) edge resonantmagnetic field perturbation with toroidalmode number n=3 and poloidal mode numbers between 8 and 15 has been used to suppress most large type I edge localized modes(ELMs) without degrading core plasma confinement. ELMs have been suppressed for periods of up to 8.6 energy confinement times when the edge safety factor q95 is between 3.5 and 4. The large ELMs are replaced by packets of events (possibly type II ELMs) with small amplitude, narrow radial extent, and a higher level of magnetic field and density fluctuations, creating a duty cycle with long “active” intervals of high transport and short “quiet” intervals of low transport. The increased transport associated with these events is less impulsive and slows the recovery of the pedestal profiles to the values reached just before the large ELMs without the n=3 perturbation. Changing the toroidal phase of the perturbation by 60° with respect to the best ELM suppression case reduces the ELM amplitude and frequency by factors of 2–3 in the divertor, produces a more stochastic response in the H-mode pedestal profiles, and displays similar increases in small scale events, although significant numbers of large ELMs survive. In contrast to the best ELM suppression case where the type I ELMs are also suppressed on the outboard midplane, the midplane recycling increases until individual ELMs are no longer discernable. The ELM response depends on the toroidal phase of the applied perturbation because intrinsic error fields make the target plasma nonaxisymmetric, and suggests that at least some of the variation in ELM behavior in a single device or among different devices is due to differences in the intrinsic error fields in these devices. These results indicate that ELMs can be suppressed by small edge resonantmagnetic field perturbations. Extrapolation to next-step burning plasma devices will require extending the regime of operation to lower collisionality and understanding the physical mechanism responsible for the ELM suppression.This work was funded by the U.S. Department of Energy under Grant Nos. DE-FC02-04ER54698, DE-FG02- 04ER54758, DE-FG03-01ER54615, W-7405-ENG-48, DEFG03-96ER54373, DE-FG02-89ER53297, DE-AC05- 00OR22725, and DE-AC04-94AL85000

Listeria spp. and L. monocytogenes in raw goat`s milk

Objetivo. Detectar Listeria spp. y Listeria monocytogenes en leches crudas de cabras, provenientes del corregimiento de la Garita, Norte de Santander. Materiales y métodos. Se tomaron 90 muestras de leche cruda de cabra, mediante muestreo estratificado, en un período de 4 meses; durante el muestreo se tomó la temperatura de las leches. Para el aislamiento de L. monocytogenes se utilizó la técnica sugerida por el INVIMA y se confirmó la especie por PCR. Resultados. Se encontraron ocho productores de leches de cabra en esta zona, ninguno refrigera, ni pasteuriza la leche. Se encontró una ocurrencia de 3% de L. monocytogenes y 15% de otras especies. Se demostró que la leches obtenidas en esta zona contienen este patógeno que puede llegar a causar Listeriosis en los grupos de riesgo como niños menores de 5 años, mujeres en etapa de gestación, adultos mayores y pacientes inmunocomprometidos. Conclusiones. Se demostró la circulación de este patógeno en la leche de cabra y al ser un producto que se consume directamente por las personas pone en riesgo su salud

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)