Tokamak

Development of real-time applications is usually associated with nonportable code targeted at specific real-time operating systems. The boundary between hardware drivers, system services, and user code is commonly not well defined, making the development in the target host significantly difficult. The Multithreaded Application Real-Time executor (MARTe) is a framework built over a multiplatform library that allows the execution of the same code in different operating systems. The framework provides the high-level interfaces with hardware, external configuration programs, and user interfaces, assuring at the same time hard real-time performances. End-users of the framework are required to define and implement algorithms inside a well-defined block of software, named Generic Application Module (GAM), that is executed by the real-time scheduler. Each GAM is reconfigurable with a set of predefined configuration meta-parameters and interchanges information using a set of data pipes that are provided as inputs and required as output. Using these connections, different GAMs can be chained either in series or parallel. GAMs can be developed and debugged in a non-real-time system and, only once the robustness of the code and correctness of the algorithm are verified, deployed to the real-time system. The software also supplies a large set of utilities that greatly ease the interaction and debugging of a running system. Among the most useful are a highly efficient real-time logger, HTTP introspection of real-time objects, and HTTP remote configuration. MARTe is currently being used to successfully drive the plasma vertical stabilization controller on the largest magnetic confinement fusion device in the world, with a control loop cycle of 50 ?s and a jitter under 1 ?s. In this particular project, MARTe is used with the Real-Time Application Interface (RTAI)/Linux operating system exploiting the new ?86 multicore processors technology.

This paper describes some of the control problems faced by the engineers working at the Joint European Torus (JET), focusing mostly on the control of plasma shape, position, and current. It details the control methodology used on JET, which can serve as guide for the design of sophisticated multivariable, yet user friendly, controllers for the next generation of fusion experiments.

G. A. Wurden
Los Alamos National Laboratory
Workshop: MFE Roadmapping in the ITER Era
Princeton, NJ
Sept. 9, 2011
LA-UR-11-11465

ITER (and someday DEMO) will operate subject to multiple physics and engineering constraints, and to be successful they must satisfy many constraints simultaneously. One of the most serious issues a large tokamak will face is controlling 100’s of MJ of plasma energy that can be quickly released in the event of a disruption, whether due to burning plasma issues, or more everyday tokamak physics. The number of full energy disruptions that an armor system in a large  tokamak can survive is very small, due to the opposing engineering constraints of rapid heat removal in steady-state, versus designing survivability to transient events.  Multimegaampere beams of runaway electrons (created by the avalanche effect after a disruption) hitting thin armor tiles will prevent achieving the desired science or energy missions, if not eliminated. A coordinated global effort to avoid,  control, and mitigate tokamak disruptions must be developed with the highest priority. The timing for this effort must be now, before ITER begins operation, as a key element of prudent risk management in a global MFE program. Supported by DOE Contract DE-AC52-06-NA25396

A new model-based plasma current and shape controller has been set up and tested on the JET Tokamak with the existing active circuits and control. The installation has been carried out without causing any interference to the plasma operation and without requiring a long commissioning time. Eventually, the new controller was used on really extremely shaped internal transport barrier experiments at high poloidal beta and in the presence of quite large variations of the plasma current density profile (variation range Δβpol up to 1.5 and Δli up to 0.5). The extreme shape controller (XSC) controller architecture and philosophy also offer new interesting opportunities, e.g., the separatrix sweeping on the divertor plates without significantly affecting the overall plasma shape, and the possibility of improving the overall tokamak performance via combined control of plasma shape, current and profile. The adopted methodology constitutes also an important test bed for feedback control strategies of ITER relevance.

The need to achieve increasingly better performance in present and future tokamak devices has made plasma control increasingly important in tokamak engineering. When high performance and robustness are required, it is essential to adopt a model-based approach to design a control system. We introduce the basics of plasma current, position, and shape control in tokamaks. As an example, the plasma magnetic control systems of the JET tokamak is presented, together with an approach proposed for plasma axisymmetric magnetic control at the ITER tokamak.

The Multithreaded Application Real-Time executor (MARTe) is a data driven framework environment for the development and deployment of real-time control algorithms. The main ideas which led to the present version of the framework were to standardize the development of real-time control systems, while providing a set of strictly bounded standard interfaces to the outside world and also accommodating a collection of facilities which promote the speed and ease of development, commissioning and deployment of such systems. At the core of every MARTe based application, is a set of independent inter-communicating software blocks, named Generic Application Modules (GAM), orchestrated by a real-time scheduler. The platform independence of its core library provides MARTe the necessary robustness and flexibility for conveniently testing applications in different environments including non-real-time operating systems. MARTe is already being used in several machines, each with its own peculiarities regarding hardware interfacing, supervisory control configuration, operating system and target control application. This paper presents and compares the most recent results of systems using MARTe: the JET Vertical Stabilization system, which uses the Real Time Application Interface (RTAI) operating system on Intel multi-core processors; the COMPASS plasma control system, driven by Linux RT also on Intel multi-core processors; ISTTOK real-time tomography equilibrium reconstruction which shares the same support configuration of COMPASS; JET error field correction coils based on VME, PowerPC and VxWorks; FTU LH reflected power system running on VME, Intel with RTAI.

The need to improve the performance of modern tokamak operations has led to a further development of the plasma shape and position control systems. In particular, extremely elongated plasmas, with high vertical-instability growth rate, are envisaged to reach the required performance for ignition. This request for better performance from the experimentalists' side has motivated the development of the new vertical-stabilization (VS) system at the JET tokamak, which has been proposed within the Plasma Control Upgrade project. The main aim of the project is to enhance the capabilities of the plasma vertical position control system in order to operate with very highly elongated plasmas in the presence of large perturbations. This paper focuses on the new software architecture of the VS system, which relies on a highly configurable real-time framework. Due to its flexibility, the new VS system executes different control algorithms, and it schedules the one which maximizes the performance in each plasma phase.

The Multithreaded Application Real-Time executor (MARTe) is a data driven framework environment for the development and deployment of real-time control algorithms. The main ideas which led to the present version of the framework were to standardize the development of real-time control systems, while providing a set of strictly bounded standard interfaces to the outside world and also accommodating a collection of facilities which promote the speed and ease of development, commissioning and deployment of such systems. At the core of every MARTe based application, is a set of independent inter-communicating software blocks, named Generic Application Modules (GAM), orchestrated by a real-time scheduler. The platform independence of its core library provides MARTe the necessary robustness and flexibility for conveniently testing applications in different environments including non-real-time operating systems. MARTe is already being used in several machines, each with its own peculiarities regarding hardware interfacing, supervisory control configuration, operating system and target control application. This paper presents and compares the most recent results of systems using MARTe: the JET Vertical Stabilization system, which uses the Real Time Application Interface (RTAI) operating system on Intel multi-core processors; the COMPASS plasma control system, driven by Linux RT also on Intel multi-core processors; ISTTOK real-time tomography equilibrium reconstruction which shares the same support configuration of COMPASS; JET error field correction coils based on VME, PowerPC and VxWorks; FTU LH reflected power system running on VME, Intel with RTAI.

As part of the ITER design review, a reassessment of the specifications underlying the design of the vertical stabilization system (VS) was performed. Recent results from experiments, aimed at the evaluation of the feasibility of the ITER reference scenarios, have raised several concerns regarding mostly the ramp-up and ramp-down phases of the pulse. The main issue is the value of the internal inductance li which may reach values outside the range 0.7–1, considered as reference for the ITER control system design. Similar ...

The PCU-Project [1] launched for the enhancement of the vertical stabilisation system at JET required the design of a new real-time control system with the challenging specifications of  and a cycle time of 50 s. The RTAI based architecture running on an x86 multi-core processor technology demonstrated to be the best platform for meeting the high requirements. Moreover, on this architecture thanks to the smart allocation of the interrupts it was possible to demonstrate simultaneous data streaming at 50 MBs on Ethernet while handling a real-time 100 kHz interrupt source with a maximum jitter of just 3 s.

Because of the memory limitation imposed by 32 bit version Linux running in kernel mode, the RTAI-based new controller allows a maximum practical data storage of 800 MB per pulse. While this amount of data can be accepted for JET normal operation it posed some limitations in the debugging and commissioning of the system. In order to increase the capability of the data acquisition of the system we have designed a mechanism that allows continuous full bandwidth (56 MB/s) data streaming from the real-time task (running in kernel mode) to either a data collector (running in user mode) or an external data acquisition server. The exploited architecture involves a peer to peer mechanisms where the sender running in RTAI kernel mode broadcasts large chunks of data using UDP packets, implemented using the ‘fcomm’ RTAI extension [2], to a receiver that will store the data. The paper will present the results of the initial RTAI operating system tests, the design of the streaming architecture and the first experimental results.

... A. Malaquias, I. Nedzelsky, B. Gonçalves, CAF Varandas, JAC Cabral, A. Melnikov, L. Eliseev ... three-dimensional trajectory nature of the ions requires a curved blanket opening allowing collection ... An indication of the feasibility of these measurements can be given by comparison ...

This paper describes the new JET enhancement project “Plasma Control Upgrade”(PCU). Initially aimed at an overhaul of JET plasma control capabilities it was eventually focused on improving the vertical stabilisation (VS) system ability to recover from large ELM (edge localised mode) perturbations. The paper describes the results of the first two years where the activity was aimed principally at researching a solution that could be implemented within the timing and budget constraints. A very important task was that of improving the ...

Neutronic studies of European demonstration fusion power plant (DEMO) have been so far based on plasma physics low confinement mode (L-mode). Future tokamaks, nevertheless, may likely use alternative confinement modes such as high or advanced confinement modes (H&A-mode). Based on analytical formulae used in plasma physics, H&A-modes D-T neutron sources formulae are proposed in this paper. For that purpose, a tokamak random neutron source generator, TRANSGEN, has been built generating bidimensional (radial and poloidal) neutron source maps to be used as input for neutronics Monte-Carlo codes (TRIPOLI-4 and MCNP5). The impact of such a source on the neutronic behavior of the European DEMO-2007 Helium-cooled lithium–lead reactor concept has been assessed and compared with previous results obtained using a L-mode neutron source. An A-mode neutron source map from TRANSGEN has been used with the code TRIPOLI-4. Assuming the same fusion power, results show that main reactor global neutronic parameters, e.g. tritium breeding ratio and neutron multiplication factor, evolved slightly when compared to present uncertainties margin. However, local parameters, such as the neutron wall loading (NWL), change significantly compared to L-mode shape: from −22% to +11% for NWL.

As part of the ITER design review, a reassessment of the specifications underlying the design of the vertical stabilization system (VS) was performed.

Recent results from experiments, aimed at the evaluation of the feasibility of the ITER reference scenarios, have raised several concerns regarding mostly the ramp-up and ramp-down phases of the pulse. The main issue is the value of the internal inductance li which may reach values outside the range 0.7–1, considered as reference for the ITER control system design. Similar concerns apply to the low current L-mode plasmas, needed to the exploitation of the machine towards the development of the 15 MA pulse. The performance of the reference vertical stabilization system, under the revised conditions may be marginal, in particular if the effect of plasma generated noise on the velocity measurement is considered.

A reliable and robust VS is mandatory to guarantee the operation of ITER at the reference elongation and plasma current values. To avoid de-scoping of the machine mission, several solutions have been proposed to improve the VS performances, ranging from an upgrade of the maximum voltage available to the present external coils system, to the introduction of in-vessel passive and/or active conductors.

The paper presents an overview of the modelling and experimental effort aimed at the assessment of the baseline ITER VS and analyses the proposed solutions to improve the system performance.

In this paper, we revisit the dynamic allocation scheme for input redundant plants proposed in Zaccarian (2009). within a set-point regulation setting and propose generalizations that apply to cases where the plant under consideration is not input redundant but the control specifications allow us to modify the set-point regulation within certain bounds. In this case, the input allocator is extended to the nonredundant case by allowing it to improve the input allocation selection at the price of some output regulation error. We also establish here desirable convergence properties of the allocator, which were only addressed for the linear case in Zaccarian (2009). In particular, we design the allocator dynamics as the gradient of a cost function and establish its convergence to the minimum of the cost function under some mild conditions. The allocation scheme is applied to the JET tokamak shape controller by illustrating its capabilities to enforce coil currents selections that tend to move away from the saturation limits within the allowable degrees of freedom.

Some analytical kinetic solutions are obtained for the primary and plasma electrons in multi-cusp ion source. The characteristics based on these solutions are discussed, such as frictional coefficient, collision frequency, electron current,electron diffusion,electron density, and electrical conductivity. A code based on one of these solutions is developed to discuss the plasma electrons diffusion; the simulation results are qualitatively consistent with our current experiences.

DOI:10.13140/RG.2.2.21463.14249


Em atenção aqueles que duvidam de aceleração de decaimento e exigem referências cientificas destas possibilidades, reunimos alguns estudos que demonstram [1][2][3][4][5][6][7] o que nos leva a calcular o que ocorreu em termos de emissão de nêutrons por efeito piezzoelétrico quando a crosta da terra se partiu violentamente formando milhares de topografias semelhantes ao rio de janeiro (RJ) , topografias presentes ao longo de toda na plataforma da América do Sul e África, as quais revelalam pelas gigantescas formação magmáticas se tratar de uma LPI (large provincius ignea) [8] [9][10][11][12] ; (agradecimento a dois professores de geologia neste ponto , o primeiro é o Dr Nahor Souza, ex- professor da USP, quem me mostrou que a fenda meso-oceânica na verdade é uma gigantesca LPI, e a outro, que provavelmente prefira agora que não seja identificado , devido a polêmica envolvida, que foi quem me explicou confirmando o Dr Nahor Souza , aspectos violentíssimos da separação inicial da África da América revelados pelas formações gigantescas ígneas, entre elas , o conhecidíssimos pão de açucar, pedra da gávea , corcovado e muitos outros; lembrando que o RJ é apenas uma elevação (não explicada ainda) da topografia da plataforma ; o decaimento acelerado e emissões de nêuntros e prótons também está observado em relação a queda de asteroides[13](falta mais referências que quando tiver tempo coloco) e que quando ajuntamos os efeitos aceleradores de elétrons na velocidade de atingir o núcleo , percebemos que reações nucleares em cadeia não somente foi possível, “envelhecendo” rochas, como de fato aconteceu também criando diversos novos elementos, inclusive e sobretudo os instáveis, conforme citações principalmente relacionadas a crosta acima. Lembrando novamente que o padrão gigantesco fóssil necessitaria de uma terra de atmosfera e radioatividade diferente e que o c14 é radioativo e tem naturalmente suas consequências na diminuição da longevidade , tamanho e aumento de doenças em todas as populações.


VOLKOVISH, A., GOVORUM, A., GULYAEV, A., ZHUKOV, S., KUZNETSOV, V., RUKHADZE, A., … & URUTSKOEV, L. (2005). Experimental observation of the distortion of the uranium isotopic relationship and violation of the thorium-234 secular equilibrium upon electric explosion. In Annales de la Fondation Louis de Broglie (Vol. 30, No. 1, pp. 63-70). Fondation Louis de Broglie. https://fondationlouisdebroglie.org/AFLB-301/aflb301m182.htm https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.620.2867&rep=rep1&type=pdf

↑ Cardone, Fabio; Mignani, Roberto; Petrucci, Andrea (11 de maio de 2009). «Piezonuclear decay of thorium». Physics Letters A (em inglês) (22): 1956–1958. ISSN 0375-9601. doi:10.1016/j.physleta.2009.03.067. Consultado em 5 de abril de 2022
↑ VOLKOVISH, A., GOVORUM, A., GULYAEV, A., ZHUKOV, S., KUZNETSOV, V., RUKHADZE, A., … & URUTSKOEV, L. (2005). «Experimental observation of the distortion of the uranium isotopic relationship and violation of the thorium-234 secular equilibrium upon electric explosion Ann. Fond. Louis de Broglie vol 30 no 1 (2005)». fondationlouisdebroglie.org. Consultado em 5 de abril de 2022  Verifique data em: |arquivodata= (ajuda) !CS1 manut: Nomes múltiplos: lista de autores (link)
↑ Cardone, F.; Carpinteri, A.; Lacidogna, G. (2 de novembro de 2009). «Piezonuclear neutrons from fracturing of inert solids». Physics Letters A (em inglês) (45): 4158–4163. ISSN 0375-9601. doi:10.1016/j.physleta.2009.09.026. Consultado em 5 de abril de 2022
↑ Carpinteri, A.; Cardone, F.; Lacidogna, G. (1 de outubro de 2010). «Energy Emissions from Failure Phenomena: Mechanical, Electromagnetic, Nuclear». Experimental Mechanics (em inglês) (8): 1235–1243. ISSN 1741-2765. doi:10.1007/s11340-009-9325-7. Consultado em 5 de abril de 2022
↑ Carpinteri, A.; Cardone, F.; Lacidogna, G. (agosto de 2009). «Piezonuclear Neutrons From Brittle Fracture: Early Results of Mechanical Compression Tests». Strain (4): 332–339. ISSN 0039-2103. doi:10.1111/j.1475-1305.2008.00615.x. Consultado em 5 de abril de 2022
↑ «ShieldSquare Captcha» (em inglês). doi:10.1088/0954-3899/40/1/015006/meta. Consultado em 5 de abril de 2022
↑ Carpinteri, A.; Cardone, F.; Lacidogna, G. (agosto de 2009). «Piezonuclear Neutrons From Brittle Fracture: Early Results of Mechanical Compression Tests». Strain (4): 332–339. ISSN 0039-2103. doi:10.1111/j.1475-1305.2008.00615.x. Consultado em 5 de abril de 2022
↑ Carpinteri, A.; Manuello, A. (18 de agosto de 2010). «Geomechanical and Geochemical Evidence of Piezonuclear Fission Reactions in the Earth’s Crust». Strain: 267–281. ISSN 0039-2103. doi:10.1111/j.1475-1305.2010.00766.x. Consultado em 5 de abril de 2022
↑ CARPINTERI, A.; LACIDOGNA, G.; BORLA, O.; MANUELLO, A.; NICCOLINI, G. (1 de fevereiro de 2012). «Electromagnetic and neutron emissions from brittle rocks failure: Experimental evidence and geological implications». Sadhana (em inglês) (1): 59–78. ISSN 0973-7677. doi:10.1007/s12046-012-0066-4. Consultado em 5 de abril de 2022
↑ Widom, A.; Swain, J.; Srivastava, Y. N. (1 de maio de 2015). «Photo-disintegration of the iron nucleus in fractured magnetite rocks with magnetostriction». Meccanica (em inglês) (5): 1205–1216. ISSN 1572-9648. doi:10.1007/s11012-014-0007-x. Consultado em 5 de abril de 2022
↑ Carpinteri, Alberto; Manuello, A. (1 de janeiro de 2012). «An indirect evidence of piezonuclear fission reactions: Geomechanical and geochemical evolution in the Earth’s crust». Physical Mesomechanics (em inglês) (1): 37–46. ISSN 1990-5424. doi:10.1134/S1029959912010043. Consultado em 5 de abril de 2022
↑ Carpinteri, A.; Lacidogna, G.; Manuello, A.; Borla, O. (30 de julho de 2012). «Piezonuclear neutrons from earthquakes as a hypothesis for the image formation and the radiocarbon dating of the Turin Shroud». Scientific Research and Essays (29): 2603–2612. ISSN 1992-2248. doi:10.5897/SRE12.379. Consultado em 5 de abril de 2022
↑ Uzonyi, I.; Szöőr, Gy.; Vekemans, B.; Vincze, L.; Rózsa, P.; Szabó, Gy.; Somogyi, A.; Adams, F.; Kiss, Á. Z. (8 de outubro de 2004). «Application of combined micro-proton-induced X-ray emission and micro-synchrotron radiation X-ray fluorescence techniques for the characterization of impact materials around Barringer Meteor Crater». Spectrochimica Acta Part B: Atomic Spectroscopy. 17th International Congress on X-Ray Optics and Microanalysis (em inglês) (10): 1717–1723. ISSN 0584-8547. doi:10.1016/j.sab.2004.05.030. Consultado em 5 de abril de 2022


RESUMO – Dando sequência a nossa publicação em 2017 na “Academia Journal Scientific Research” sob o título ” Morfologia Repetida nos Fósseis Registrados em Camadas Geológicas Globais Indica Sepultamento de Populações Globais, acrescentamos aqui a observação do fato de que quintilhões e inumeráveis pedras rachadas, pontiagudas, angulares, encontradas em todo planeta terra, com pouco desgaste de tempo, ou com pouco tempo de sedimentação acima das mesmas (você desenterra e já as encontra) , revelam um imenso acidente recente na terra. Isso sem contar as inumeráveis cachoeiras e encostas recebendo grandes impactos de águas com grande energia, que não se desgastaram tanto. Você pode ver pedras lisas ao lado da parte que recebe agua forte ; ora, você se lembra do ditado não é? “água mole em pedra dura tanto bate até que fura ” (esta expressão os índios chamam de itararé); e por quê não furou nem desgastou um pouquinho a mais? Logicamente que é devido ao acidente global ser recente .

Os aspectos catastrofistas desta quantidade imensa de rochas não desgastadas pelo tempo, implicam em efeitos piezoelétricos, plasma, som , que são aceleradores de elétrons capazes de perturbar o núcleo arrancando nêutrons e prótons (como ocorre em TOKAMAKS em menor escala) , e consequentemente no fato de ter criado proporção de elementos químicos que passaram a ser instáveis, e também, ter criado rochas com aparência de bilhões de anos, feitas em poucos milésimos de segundos.

Também alertamos que o conjunto de evidências evolutivas, genéticas, paleontológicas, geológicas, astronômicas, dos estudos em física de plasma e colisão de íons pesados, demonstram claramente que temos uma outra cronologia e historia do universo, da terra e das espécies . Neste trabalho apresentamos evidências de que impactos de asteroides possam ter participado deste evento recente , na forma de chuva de asteroides, pois possuem poder de gerar  aceleração de partículas perturbadoras do núcleo atômico para não somente acelerar decaimento radioativo “envelhecendo rochas” como também criar elementos instáveis a partir de estáveis, explicando pequenas proporções deles na terra e milhares de meteoros que nos rodeiam. Esta quebra de paradigma datacional , tão esperada na academia que passa tanta vergonha e descrédito ao ver fósseis contendo tecidos orgânicos serem datados em milhões de anos, nos abre espaço para conjugar acontecimentos consequentes ocorridos imediatamente um depois do outro (temporalidade), que estavam separados por uma espécie de absolutismo datacional na geologia e paleontologia convencional  atual, que restringiam o saber científico livre, e impediam sobretudo de harmonizar arqueologias (274 fontes incluindo bíblica) , aspectos genéticos (entropia e meia vida curta do DNA), evolutivos-paleontológicos (falta de mudança morfológica fóssil e repetição de formas de vida em 71% nas amostragens fósseis o que expressa sepultamento em larga escala de todas as espécies da terra em um tempo único e não separado  ) .

In this paper, dynamic neural networks are proposed to predict the plasma disruptions in a nuclear fusion device. Disruptions are critical events where the plasma, which is magnetically confined in a vacuum vessel, becomes unstable, cools down and the confinement is suddenly destroyed. These events may damage to the vessel, so they have to be foreseen well in advance in order to take mitigating action. Dynamic neural networks act as filters, which predict one step ahead the value of diagnostic signals acquired during a plasma pulse. The prediction error of the neural network depends on the regularity of signals. For this reason, an increasing prediction error reveals that the plasma operative conditions are changing, hence a disruption could be imminent. In this work, different diagnostic approaches, network adapting parameters, and diagnosis thresholds have been tested in order to determine the best performance in terms of prediction capability.

The nonlinear thermal balance equation for classical plasma in a toroidal geometry is analytically and numerically investigated including ICRH power. The determination of the equilibrium temperature and the analysis of the stability of the solution are performed by solving the energy balance equation that includes the transport relations obtained by the classical kinetic theory. An estimation of the confinement time is also provided. We show that the ICRH heating in the IGNITOR experiment, among other applications, is expected to be used to trigger the thermonuclear instability. Here a scenario is considered where IGNITOR is led to operate in a slightly sub-critical regime by adding a small fraction of ^3He to the nominal 50%-50% Deuterium-Tritium mixture. The difference between power lost and alpha heating is compensated by additional ICRH heating, which should be able to increase the global plasma temperature via collisions between ^3He minority and the background D-T ions.

The aim of this work is to provide an understanding of detachment at TCV with emphasis on analysis of the Balmer line emission. A new Divertor Spectroscopy System has been developed for this purpose. Further development of Balmer line analysis techniques has allowed detailed information to be extracted on free-free and three-body recombination. During density ramps, the plasma at the target detaches as inferred from a drop in density at, and ion current to, the target. At the same time the Balmer 6 → 2 and 7 → 2 line emission near the target is dominated by recombination, indicating that the ionization region has also detached from the target to be replaced by a recombining region with densities more than a factor 2 higher than at the target. As the core density increases further, the density and recombination rate are rising all along the outer leg to the x-point while remaining highest at the target. Even at the highest core densities accessed (Greenwald fraction 0.7) the peaks in...

For the manipulator which is used to execute maintenance tasks in the Tokamak reactor, solving the problem of collision-free path planning is the premise. This paper introduced the Single-RRT and Bi-RRT algorithms then used BiRRT algorithm to make the path planning for the motion of a redundant manipulator in the vacuum chamber, finally made a Matlab simulation analysis. The result shows that RRT algorithm can effectively achieve the purpose of collision-free path planning, and using Bi-RRT can reduce the number of searches and invalid search points compared with Single-RRT. The better path can be obtained and used in the actual control by means of multiple searches and replacements

This paper describes the installation of the new JET Shape Controller System [M. Garribba, R. Litunovsky, P. Noll, S. Puppin, The new control scheme for the JET plasma position and current control system, in: Proceedings of the 15th SOFE Conference, Massachusetts, 1993, pp. 33–36; F. Sartori, A. Cenedese, Plasma position and current control management at JET, in: Proceedings of the 42nd IEEE Conference on Decision and Control, Maui, 2003] especially focusing on the addition of the Extreme Shape Controller [G. Ambrosino, et al., A new shape controller for extremely shaped plasmas in JET, Fusion Eng. Des. 66–68 (2003) 797–802]. The activity was performed by the JET Operator in co-operation with the ENEA-CREATE design team, and involved both changes in the hardware and system software of JET and tuning of the proposed Extreme Shape Controller (XSC) design to satisfy the practical requirements of tokamak operation. The application of 10 years experience of controller implementation and commissioning combined with a modern and efficient modelling and design methodology has allowed an unprecedented fast and easy commissioning of the new system.

A project dedicated to the enhancement of the JET vertical stabilization system was launched in 2006, including an upgrade of the Power Supply of the Radial Field Amplifier, of hardware and software of the vertical stabilization control system. The main aim was to double the JET capability in stabilising high current plasmas when subject to perturbations, in particular large Edge Localised Modes. We present here the results of first plasma operation with the new Enhanced Radial Field Amplifier and its data acquisition and control system, focussing on the benefits of an approach based on phased commissioning, modelling and offline algorithm validation.

JETRT is a software framework particularly suited for implementation of both real-time control and data acquisition systems. It is especially designed to work in a complex experimental environment such as the JET nuclear fusion facility. This new architecture maximizes the software reusability. The project-specific algorithm is compiled into a separate software component, in order to achieve a separation from the plant interface code. JETRT provides a set of tools to perform most of the validation phase on a Windows running desktop PC. Thanks to these design choices, both the development costs and the commissioning time have been reduced and even non-specialist programmers can easily contribute to the deployment of a new real-time system.

The effects of nitrogen gas seeding in the edge and scrape-off layer (SOL) regions of a tokamak plasma are studied through 2D fluid simulations using the BOUT++ code. Proper account is taken of the presence of multiple charged states of nitrogen ions due to ionization, recombination, and dissociation processes, and a self-consistent study of the interaction of these ions with the turbulent plasma in the edge and SOL regions is carried out. The self-consistent model includes the effects of polarization drifts of the main plasma and impurity ions for determining the plasma vorticity. Nitrogen seeding is found to modify the turbulence as well as to influence the profiles of the equilibrium plasma density and the electron temperature. The densities of N 3 + to N 5 + ions are found to be relatively higher than the other charged states. This is understood and further validated by a 0D simulation. The radial profiles of these impurity ions are mapped, and their radiation energy losses are estimated. The radial profile of the radiation losses is maximum near to the edge-to-SOL transition region and becomes broader in the edge region than the SOL region.

ABSTRACT The realization of commercialized fusion power will involve the development of new materials that can withstand the uniquely harsh nuclear fusion environment. Of particular interest are those materials that are closest to the plasma. The combination of thermal loading, neutron damage, material sputtering and redeposition provide uniquely hostile conditions under which no material testing has yet occurred. An experimental Fusion Nuclear Science Facility (FNSF) is required that will create the environment that simultaneously achieves high energy neutrons and high ion nuence necessary in order to bridge the gaps from ITER to the realization of a fusion nuclear power plant. One concept for achieving this is a high duty cycle spherical tokamak (ST) (I). The centerpost is a critical component of the spherical tokamak design, as it controls the size of the entire reactor. The centerpost will experience significant thermal loading and thermal gradients from Ohmic heating, nuclear heating, and water cooling. Nuclear heating will also produce embrittlement and swelling in the centerpost. In addition to thermal loads, the centerpost must be designed to carry mechanical loads produced from the various magnetic fields (TF, PF, plasma currents), both steady-state and transient. The centerpost temperature must remain low enough to permit water cooling, and stresses must remain low enough so that the centerpost remains structurally sound. This study will focus on the stress analysis of a centerpost optimized to reduce the thermal gradients in the cross-section.

Steady State Superconducting Tokamak (SST-1) is a medium size Tokamak (major radius = 1.1 m, minor radius = 0.2 m) and is operational at the Institute for Plasma Research (IPR), India. In the last few experimental campaigns SST-1 has successfully achieved plasma current in order of 60-70kA and plasma duration in excess of ~ 500 ms at a central magnetic field of 1.5T. An attempt has made to study the behavior of the magneto-hydrodynamic (MHD) activity during different phases of plasma pulse which leads to major/minor disruptions, its present modes (poloidal/toroidal mode number i.e. m = 2, n = 1) impact on plasma confinement and signature of lock mode and its frequency in the SST-1 plasma using experimental data from Mirnov signals. Observed MHD phenomenon has also been correlated with other diagnostics (i.e. ECE, Density, Soft X-Ray etc.) and heating system (ECRH) for the recent campaigns of SST-1.

The thermonuclear fusion is realised by a main technique of magnetic confinement of the plasma fusion. This reaction has for object if the production of energy. After many researches, the scientists have found that the most promoter configuration is the Tokamak machine which permits this reaction of fusion in similar conditions to the one of reactions in the sun.