scholarly journals Plasma-wall self-organization in magnetic fusion

2021 ◽  
Author(s):  
Dominique Franck Escande ◽  
Fabio Sattin ◽  
Paolo Zanca
Keyword(s):  
Basins Of Attraction ◽  
Input Power ◽  
Self Organization ◽  
Magnetic Fusion ◽  
Density Limit ◽  
Radiated Power ◽  
Start Up ◽  
Physical Sputtering ◽  
Total Input ◽  
Divertor Plates

Abstract This paper introduces the concept of plasma-wall self-organization (PWSO) in magnetic fusion. The basic idea is the existence of a time delay in the feedback loop relating radiation and impurity production on divertor plates. Both a zero and a onedimensional description of PWSO are provided. They lead to an iterative equation whose equilibrium fixed point is unstable above some threshold. This threshold corresponds to a radiative density limit, which can be reached for a ratio of total radiated power to total input power as low as 1/2. When detachment develops and physical sputtering dominates, this limit is progressively pushed to very high values if the radiation of non-plate impurities stays low. Therefore, PWSO comes with two basins for this organization: the usual one with a density limit, and a new one with density freedom, in particular for machines using high-Z materials. Two basins of attraction of PWSO are shown to exist for the tokamak during start-up, with a high density one leading to this freedom. This basin might be reached by a proper tailoring of ECRH assisted ohmic start-up in present middle-size tokamaks, mimicking present stellarator start-up. In view of the impressive tokamak DEMO wall load challenge, it is worth considering and checking this possibility, which comes with that of more margins for ITER and of smaller reactors.

First neutral-beam heating experiments in JET

1987 ◽  
Vol 322 (1563) ◽  
pp. 109-123 ◽  
Keyword(s):  
Power Input ◽  
Input Power ◽  
Confinement Time ◽  
Plasma Parameters ◽  
Energy Confinement ◽  
Energy Confinement Time ◽  
Radiated Power ◽  
Total Input ◽  
Wide Range ◽  
Beam Heating

Hydrogen beams at particle energies of up to 65 keV, total beam powers of up to 5.5 MW , and beam-pulse durations of up to 7 s have been injected into deuterium plasmas. Experiments were performed over a wide range of plasma parameters with limiter plasmas and inner-wall plasmas. The operational regime was extended by 70% over the current ohmic density limit. In medium density experiments, ion temperatures of ca . 6.5 keV were reached with electron temperatures of 4.8 keV. The expected degradation of energy confinement with additional heating was observed. At 4 MA plasma current and 8 MW total input power, the global energy confinement time is ca. 0.4 s. The metallic impurity concentration and Zeff drop with the rise of plasm a density during beam pulses. The rise of radiated power closely follows that of the density. In most cases, the highest value of the radiated power stays below 50 % of the power input, with very low radiation from the centre of the plasma.

IDENTIFICATIONS OF HASLER'S CLASSES OF LINEAR RESISTIVE CIRCUIT STRUCTURES

2004 ◽  
Vol 13 (05) ◽  
pp. 957-980
Author(s):  
J. CEL
Keyword(s):  
Sufficient Conditions ◽  
Input Power ◽  
Maximal Entropy ◽  
Cactus Graph ◽  
Resistance Function ◽  
Total Input ◽  
Feedback Structure ◽  
Ill Posed ◽  
System Of Parameters ◽  
Necessary And Sufficient

Formulae on first and second derivatives of various functions associated with a linear nullator–norator–resistance network such as total input power, driving-point and transfer resistances with respect to parameters are established. As a consequence, the concavity of the driving-point resistance with respect to the system of parameters is obtained which generalizes a scalar result of Schneider. An example is given showing that the driving-point resistance R of a nonreciprocal one-port is not monotone or convex or concave with respect to the system of resistances which shows that the Cohn–Vratsanos and the Shannon–Hagelbarger theorems which characterize R of reciprocal one-port cannot be extended in this way. Next, a simplified variant of the Shannon–Hagelbarger theorem is used to derive separate necessary and sufficient conditions characterizing always well-posed, sometimes ill-posed and always ill-posed classes of linear resistive circuit structures introduced and characterized by Hasler, both new in formulation and proof. This reveals that the form of the second partial derivative of the resistance function is responsible for various kinds of the structural solvability of linear circuits. Alternative "if and only if" criteria for these classes are established. They involve replacements of reciprocal circuit elements by combinations of contractions and removals leading to pairs of complementary directed nullator and directed norator trees with appropriately defined signs, and resemble therefore earlier famous Willson–Nielsen feedback structure and Chua–Nishi cactus graph criteria for circuits containing traditional controlled sources. Finally, the qualitative parts of the Cohn–Vratsanos and the Shannon–Hagelbarger theorems are shown to be simple consequences of much more general principles governing all aspects of life, such as maximal entropy and energy conservation laws.

Review and present status of the TEXTOR radiative improved (RI) mode

1998 ◽  
Vol 59 (4) ◽  
pp. 587-610 ◽  
Author(s):  
P. E. VANDENPLAS ◽  
A. M. MESSIAEN ◽  
J. P. H. E. ONGENA ◽  
U. SAMM ◽  
B. UNTERBERG
Keyword(s):  
Density Profile ◽  
High Power ◽  
Present Status ◽  
Particle Transport ◽  
Density Limit ◽  
Radiated Power ◽  
Edge Radiation ◽  
Intermediate Size ◽  
Power Fraction ◽  
Better Than

From 1990, the boronized TEXTOR tokamak was characterized by an improved confinement (coined the ‘I mode’) at high power that was substantially better than the L mode, but densities had to be limited to n[bar]e0/nGR[lsim ]0.5–0.6, where nGR is the Greenwald density limit. With the injection of Ne, Si or Ar in order to increase the edge radiation and provided that γ=Prad/Ptot[greater, similar]0.5, PNBI-co/Ptot[greater, similar]0.25 and n[bar]e0/nGR[greater, similar]0.75, a further improved confinement called the radiative improved mode (RI mode) was discovered in 1993 on TEXTOR, a tokamak of intermediate size, and confirmed on TEXTOR-94. The radiated power fraction γ can reach 0.9, and the radiation is nearly isotropically distributed over the torus wall. The RI mode is characterized by its ability to obtain simultaneously and stationarily high densities and high confinement. It is linked to a substantial lowering of edge ne, Te and Ti, a reduction in particle transport and a peaking of the density profile. The RI-mode confinement scales on TEXTOR as τE= (n[bar]e0/nGR)τITERH93-P and values up to n[bar]e0/nGR≈1.2 are obtained. There is no detrimental concentration of the seeded impurity at the centre of the plasma. Results of three different interpretative and modelling approaches are in agreement with the improved confinement features; the preliminary indications are that ITG turbulence is strongly reduced. The Z mode observed on ISX-B has a clear resemblance to the RI mode. The very favourable features of the RI mode justify efforts in trying to establish it on larger machines to verify if the present scaling then holds.

scholarly journals Design of a Four-Branch Optical Power Splitter Based on Gallium-Nitride Using Rectangular Waveguide Coupling for Telecommunication Links

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Retno W. Purnamaningsih ◽  
Nji R. Poespawati ◽  
Elhadj Dogheche
Keyword(s):  
Gallium Nitride ◽  
Power Distribution ◽  
Optical Power ◽  
Power Input ◽  
Input Power ◽  
Propagation Length ◽  
Power Splitter ◽  
Excess Loss ◽  
Total Input ◽  
Rectangular Waveguides

This paper reports design of a simple four-branch optical power splitter using five parallel rectangular waveguides coupling in a gallium-nitride (GaN) semiconductor/sapphire for telecommunication links. The optimisation was conducted using the 3D FD-BPM method for long wavelength optical communication. The result shows that, at propagation length of 925 μm, the optical power input was successfully split into four uniform output beams, each with 24% of total input power. It is also shown that the relative output power distribution is almost stable through the C-band range. At the operating wavelength of 1.55 μm, the proposed power splitter has an excess loss lower than 0.2 dB. This study demonstrates the opportunity to develop optical interconnections from UV-Visible to near IR wavelengths.

scholarly journals A Hybrid Microenergy Storage System for Power Supply of Forest Wireless Sensor Nodes

Electronics ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 1409 ◽  
Author(s):  
Huamei Wang ◽  
Wenbin Li ◽  
Daochun Xu ◽  
Jiangming Kan
Keyword(s):  
Power Supply ◽  
Storage System ◽  
Input Power ◽  
Sensor Nodes ◽  
Wireless Sensor ◽  
Wireless Sensor Nodes ◽  
Ultra Low Power ◽  
Hybrid Energy ◽  
Total Input ◽  
Self Powered

Wireless sensor nodes (WSNs) are widely used in the field of environmental detection; however, they face serious power supply problems caused by the complexity of the environmental layout. In this study, a new ultra-low-power hybrid energy harvesting (HEH) system for two types of microenergy collection (photovoltaic (PV) and soil-temperature-difference thermoelectric (TE)) was designed to provide stable power to WSNs. The power supply capabilities of two microenergy sources were assessed by analyzing the electrical characteristics and performing continuous energy data collection. The HEH system consisted of two separated power converters and an electronic multiplexer circuit to avoid impedance mismatch and improve efficiency. The feasibility of the self-powered HEH system was verified by consumption analysis of the HEH system, the WSNs, and the data analysis of the collected microenergy. Taking the summation of PV and TEG input power of 1.26 mW (PPV:PTEG was about 3:1) as an example, the power loss of the HEH system accounted for 33.8% of the total input power. Furthermore, the ratio decreased as the value of the input power increased.

Chip on Board Packaging and Thermal Solutions for a 100 W Large Monolithic LED

2009 ◽  
Vol 6 (2) ◽  
pp. 143-148
Author(s):  
Jay G. Liu ◽  
Daxi Xiong ◽  
Paul Panaccione
Keyword(s):  
Power Systems ◽  
Thermal Resistance ◽  
Input Power ◽  
High Current ◽  
Large Area ◽  
Die Attach ◽  
Total Input ◽  
Thermal Solution ◽  
Current Operation ◽  
Heat Spreading

Thermal challenges are now widely recognized as one of the key barriers to LED's fast penetration to broader market. This paper demonstrates an effective packaging and thermal solution for a commercial realization of a large area monolithic LED of 12 mm2, with high current operation and total input power as high as 100 W. A direct chip on board (COB) die attach method was used to eliminate one level of interface such as existed in an SMD LED on an insulated metal substrate. High thermal conductivity LED submount and copper core board were designed for effective heat spreading without a dielectric in the thermal path. The thermal resistance of the 12 mm2 LED from junction to heat sink, including core board and associated TIM1 and TIM2, is as low as 0.7°C/W. A thermal model was developed using FEA to describe the temperature and thermal resistance at each interface, and is shown to be in agreement with measured data. The LED chipsets described here have been used to power systems such as rear projection TVs and front projectors.

scholarly journals Zigzag Solitons and Spontaneous Symmetry Breaking in Discrete Rabi Lattices with Long-Range Hopping

Symmetry ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 277
Author(s):  
Haitao Xu ◽  
Zhelang Pan ◽  
Zhihuan Luo ◽  
Yan Liu ◽  
Suiyan Tan ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Long Range ◽  
Input Power ◽  
Discrete Soliton ◽  
Coupled Effect ◽  
Total Input ◽  
New Type ◽  
Discrete Solitons ◽  
Symmetric Soliton

A new type of discrete soliton, which we call zigzag solitons, is founded in two-component discrete Rabi lattices with long-range hopping. The spontaneous symmetry breaking (SSB) of zigzag solitons is also studied. Through numerical simulation, we found that by enhancing the intensity of the long-range linearly-coupled effect or increasing the total input power, the SSB process from the symmetric soliton to the asymmetric soliton will switch from the supercritical to subcritical type. These results can help us better understand both the discrete solitons and the Rabi coupled effect.

scholarly journals Experimental Determination of the Performances during the Cold Start-Up of an Air Compressor Unit for Electric and Electrified Heavy-Duty Vehicles

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3664
Author(s):  
Gianluca Valenti ◽  
Stefano Murgia ◽  
Ida Costanzo ◽  
Matteo Scarnera ◽  
Francesco Battistella
Keyword(s):  
Volume Flow Rate ◽  
Cold Start ◽  
Input Power ◽  
Compressed Air ◽  
Compressor Unit ◽  
Heavy Duty ◽  
Air Compressor ◽  
Start Up ◽  
Heavy Duty Vehicle ◽  
Heavy Duty Vehicles

Compressed air is crucial on an electric or electrified heavy-duty vehicle. The objective of this work was to experimentally determine the performance parameters of the first prototype of an electric-driven sliding-vane air compressor, specifically designed for electric and electrified heavy-duty vehicles, during the transient conditions of cold start-ups. The transient was analyzed for different thermostatic temperatures: 0 °C, −10 °C, −20 °C, and −30 °C. The air compressor unit was placed in a climatic chamber and connected to the electric grid, the water-cooling loop, and the compressed air measuring and controlling rig. The required start-up time was greater the lower the thermostatic temperature, ranging from 30 min at 0 °C to 221 min at −30 °C and depending largely on the volume of the lubricant oil filled initially. The volume flow rate of the compressed air was lower than nominal at the beginning, but it showed a step increase well beyond nominal when the oil reached 50 °C and then decreased gently towards nominal, while the input power kept steady at nominal after a short initial peak. These facts must be considered when estimating the time and the energy required by the air compressor unit to fill up the compressed air tanks of the vehicles.

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