Scaling of spontaneous rotation with temperature and plasma current in tokamaks

Using theoretical arguments, a simple scaling law for the size of the intrinsic rotation observed in tokamaks in the absence of momentum injection is found: the velocity generated in the core of a tokamak must be proportional to the ion temperature difference in the core divided by the plasma current, independent of the size of the device. The constant of proportionality is of the order of $10\,\mathrm{km \cdot s^{-1} \cdot MA \cdot keV^{-1}}$. When the intrinsic rotation profile is hollow, i.e. it is counter-current in the core of the tokamak and co-current in the edge, the scaling law presented in this Letter fits the data remarkably well for several tokamaks of vastly different size and heated by different mechanisms.Comment: 5 pages, 3 figure

Interplay between intrinsic plasma rotation and magnetic island evolution in disruptive discharges

The behavior of the intrinsic toroidal rotation of the plasma column during the growth and eventualsaturation of m/n = 2/1 magnetic islands, triggered by programmed density rise, has been carefully investigatedin disruptive discharges in TCABR. The results show that, as the island starts to grow and rotate at aspeed larger than that of the plasma column, the angular frequency of the intrinsic toroidal rotation increasesand that of the island decreases, following the expectation of synchronization. As the island saturates at alarge size, just before a major disruption, the angular speed of the intrinsic rotation decreases quite rapidly,even though the island keeps still rotating at a reduced speed. This decrease of the toroidal rotation is quitereproducible and can be considered as an indicative of disruption

Characterization of toroidal intrinsic rotation with MHD activity in theTCABR tokamak

Plasma rotation has an important play in stabilization of MHD modes and reducing turbulenttransport of particles and energy. Because in fusion reactors it is expected the torque provided byexternal sources will be small, the intrinsic (or spontaneous) rotation is of great interest[1, 2, 3].Furthermore, the origin and physics of plasma rotation is also an important issue by itself.The behavior of the intrinsic toroidal rotation during the growth and saturation of m/n =2/1 magnetic islands, triggered by programmed density ramp up, has been investigated in Lmodeohmic discharges in the TCABR tokamak. In those discharges R = 0.61 m, a = 0.18 m,Ip 80 kA, Bt = 1.07 T, q(a) 3.5 and the toroidal spontaneous rotation of the plasma coreis in the counter-current direction. The results show that the plasma is accelerated as the islandstarts to grow, while the island frequency slows down. And, as the island saturates, the toroidalrotation decreases quite rapidly (faster than the island), and the discharge is followed by a majordisruption. In some discharges, where the density decreases after the island saturation (and thus,avoiding the plasma disruption), the MHD instability becomes smaller until it vanishes, and thetoroidal rotation slows down to its original value before the gas injection

Measurements of the natural plasma flow during the precursor of TCABR density limit disruptions

Magnetic islands are known to degrade confinement of energy and particles in tokamak plasmas.They are also present in the precursor of density limit disruptions being observed untilthe onset of the energy quench of the disruption. The subject of the effect of plasma flow ontearing mode stability has been studied both theoretically [1] and experimentally [2]. Howeverthe experimental work has focused on plasmas with Neutral Beam Injection (NBI), which addshigh momentum to both the plasma and the island, deviating them from their natural velocities.It is important to know the plasma/island rotation behavior without NBI, not just to know theirnatural values but because future large tokamaks, like ITER, are expected to have low plasmarotation due to both large plasma inertia and low applied torque. In this work we will showexperimental values of the ion velocity and the magnetic island velocity measured in TCABRohmic plasmas, without NBI, and during the precursor of a density limit disruption. In this wayit was possible to compare the natural plasma velocity with the island velocity. The ion velocitywas inferred from Doppler spectroscopy of the impurity lines of CVI. Details of this diagnosticsystem and an error analysis of the measured signal can be found in [3]. With the present set up,the toroidal velocity can be measured with time resolution equivalent to 600 Hz and precisionsomewhat better than 5 km/s

Comparative electron temperature measurements of Thomson scattering and electron cyclotron emission diagnostics in TCABR plasmas

We present the first simultaneous measurements of the Thomson scattering and electron cyclotron emission radiometer diagnostics performed at TCABR tokamak with Alfven wave heating. The Thomson scattering diagnostic is an upgraded version of the one previously installed at the ISTTOK tokamak, while the electron cyclotron emission radiometer employs a heterodyne sweeping radiometer. For purely Ohmic discharges, the electron temperature measurements from both diagnostics are in good agreement. Additional Alfven wave heating does not affect the capability of the Thomson scattering diagnostic to measure the instantaneous electron temperature, whereas measurements from the electron cyclotron emission radiometer become underestimates of the actual temperature values. (C) 2010 American Institute of Physics. [doi:10.1063/1.3494379]811

Elaboração de doces utilizando batata-doce biofortificada cv. Beauregard.

A batata-doce cv. Beauregard é biofortificada e apresenta maiores teores de carotenoides (pró vitamina A). Dessa forma, foram elaboradas duas formulações de doces utilizando a batata-doce cv. Beauregard. Conclui-se que a elaboração de doces com batata-doce biofortificada é uma alternativa viável para a inserção de doces mais saudáveis na alimentação suprindo desta forma a carência de vitaminas e minerais

Elaboration of food products with biofortified sweet potatoes: characterization and sensory acceptability.

Beauregard sweet potato is an orange color crop rich in β-carotene, a precursor of vitamin A. β-carotene improve immunity and decrease of incidence of degenerative diseases. The objective of this work was to introduce sweet potato in the diet through of some food products, such as bread, cake and sweets. The effect of processing on the chemical composition, as well as the quantification of phenols and total carotenoids, antioxidant activity, and sensory acceptability were evaluated. Cakes and coconut sweets presented higher levels of carotenoids. Higher phenolic and antioxidant activity were verified in cocoa sweets. All foods had good acceptability: 86% for bread, 83.3% for cake and 84,4%, and 86% for coconut and cocoa sweets, respectively. Servings of 95g of roasted sweet potato, 330g of bread, 182g of cake, 187g of coconut sweet and 391g end of cocoa sweet, would provide the recommended daily intake of vitamin A for children 10 years and older. It was concluded that the elaboration of foods containing sweet potato is a viable alternative to inserting biofortified foods into the human diet

BRS Pampa: cultivar de arroz irrigado de alta produtividade e excelência na qualidade de grãos.

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