Integrated operation of diagnostic and control systems

Treutterer, W.; Behler, K.; Buhler, A.; Cole, R.; Giannone, L.; Kagarmanov, A.; Lüddecke, K.; Neu, G.; Raupp, G.; Reich, M.; Zasche, D.; Zehetbauer, T.

doi:10.1016/j.fusengdes.2010.12.074

Cited by 12 publications

(8 citation statements)

References 15 publications

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“…This way, the DCN measurement with its lower noise level can still be used in the plasma ramp-up phase. Although safe plasma operation was possible this way, integrated operation of diagnostics and control schemes [20] had to be applied for experiments with combined gas and pellet fuelling, e.g. feedback controlled action responding to the neutral gas pressure n 0 rather than to n e .…”

Section: Experimental Set-up and Status Of Coil And Pellet Systemmentioning

confidence: 99%

High-density H-mode operation by pellet injection and ELM mitigation with the new active in-vessel saddle coils in ASDEX Upgrade

et al. 2012

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Recent experiments at ASDEX Upgrade demonstrate the compatibility of ELM mitigation by magnetic perturbations with efficient particle fuelling by inboard pellet injection. ELM mitigation persists in a high density, high collisionality regime even with the strongest applied pellet perturbations. Pellets injected into mitigation phases trigger no type-I ELM like events unlike when launched into unmitigated type-I ELMy plasmas. Furthermore, the absence of ELMs results in improved fuelling efficiency and persistent density build up. Pellet injection is helpful to access the ELM-mitigation regime by raising the edge density beyond the required threshold level, mostly eliminating the need for strong gas puff. Finally, strong pellet fuelling can be applied to access high densities beyond the density limit encountered with pure gas puffing. Core densities of up to 1.6 times the Greenwald density have been reached while maintaining ELM mitigation. No upper density limit for the ELM-mitigated regime has been encountered so far; limitations were set solely by technical restrictions of the pellet launcher. Reliable and reproducible operation at line averaged densities from 0.75 up to 1.5 times the Greenwald density is demonstrated using pellets. However, in this density range there is no indication of the positive confinement dependence on density implied by the ITERH98P(y,2) scaling.Final version, 6.1.2012 2 IntroductionThe power load deposited by type-I ELMs onto the first wall and divertor presents a severe danger for ITER. Currently, there are several options for ELM mitigation: Operating with plasma scenarios which develop no or only benign ELMs, ELM pace-making to enhance the ELM frequency by at least a factor of 15 -30 in order to reduce individual ELM losses by this same factor, or ELM mitigation or ELM suppression with non-axisymmetric magnetic perturbations. Pace-making tries to reduce the type-I ELM size by triggering the instability through an external perturbation, e.g. pellet injection with a rate higher than the natural ELM frequency. Avoidance of type-I ELMs is preferred over ELM pace-making if it can be achieved without significant deleterious impact on the plasma performance. Nonaxisymmetric magnetic perturbations have been investigated in DIII-D where full suppression or at least significant mitigation of ELMs has been achieved over a wide operational range [1]. This successful first demonstration prompted further experiments at JET [2,3], NSTX [4] and MAST [5] with different perturbation field configurations. In theses experiments, quite different results with respect to ELM mitigation were obtained, and so far full ELM suppression has not been reproduced in any of them. Recently, the ASDEX Upgrade tokamak has been enhanced with a set of in-vessel coils [6] in order to study ELM amelioration, shed light on the physics involved, and to improve the extrapolation base for ITER. In a first stage of this enhancement, n=2 magnetic perturbations are found to allow suppressing type-I ELMs and replace th...

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Section: Experimental Set-up and Status Of Coil And Pellet Systemmentioning

confidence: 99%

High-density H-mode operation by pellet injection and ELM mitigation with the new active in-vessel saddle coils in ASDEX Upgrade

et al. 2012

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“…For example, a free-boundary equilibrium reconstruction of the Tokamak à Configuration Variable (TCV) in Lausanne, Switzerland, is evaluated in a fraction of a millisecond 13 , which satisfies the real-time control needs. Information on the plasma equilibrium is usually the key part of complex real-time control systems, such as that of the Axially Symmetric Divertor Experiment-Upgrade (ASDEX Upgrade) tokamak 14 in Garching, Germany, which includes real-time control of the microwave launcher for plasma heating and stabilization 15 . Fixed-boundary equilibrium codes, on the other hand, assume a given shape of the last closed flux surface and solve the Grad-Shafranov equation within this surface.…”

Section: Nature Physics Doi: 101038/nphys3744mentioning

confidence: 99%

Computational challenges in magnetic-confinement fusion physics

et al. 2016

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Magnetic-fusion plasmas are complex self-organized systems with an extremely wide range of spatial and temporal scales, from the electron-orbit scales (⇠10 11 s, ⇠10 5 m) to the di usion time of electrical current through the plasma (⇠10 2 s) and the distance along the magnetic field between two solid surfaces in the region that determines the plasma-wall interactions (⇠100 m). The description of the individual phenomena and of the nonlinear coupling between them involves a hierarchy of models, which, when applied to realistic configurations, require the most advanced numerical techniques and algorithms and the use of state-of-the-art high-performance computers. The common thread of such models resides in the fact that the plasma components are at the same time sources of electromagnetic fields, via the charge and current densities that they generate, and subject to the action of electromagnetic fields. This leads to a wide variety of plasma modes of oscillations that resonate with the particle or fluid motion and makes the plasma dynamics much richer than that of conventional, neutral fluids.T he most straightforward way for describing plasmas would be the microscopic particle approach: solving the equations of motion for the many individual particles that form the plasma in externally imposed electromagnetic fields and in the fields that the particles themselves generate. However, this is computationally impossible to apply to realistic magnetic-fusion plasmas, which typically contain 10 22 -10 23 particles. (For a review of the basic concepts of magnetically confined fusion plasmas, see ref. 1.)A statistical treatment leads to the kinetic model, based on the Vlasov equation (equation (1)), essentially Liouville's theorem applied to the specific plasma environment, with interactions that are dominated by electromagnetic fields and a separation between particle collisions -that is, interactions at microscopic scales-and long-range fields. The Vlasov equation describes the evolution of f s (x,v,t), the single-particle phase-space distribution function of the species labelled 's' (electrons or ions), under the e ect of the longrange electric and magnetic fields E and B, which evolve according to Maxwell's equations with plasma charge and current densities as sources:Here, x, v, q s and m s stand for the position, velocity, charge and the mass of a particle of species 's' , respectively. In the Vlasov model, collisions are neglected, an approximation that is generally justified for fusion plasmas because small-scale e ects based on Coulomb interactions become very weak at high temperatures. In fact, Coulomb collisions' cross-sections for the exchange of momentum and energy, and related quantities such as the electrical resistivity ⌘, scale with T 3/2 . In ITER core plasmas (see ref. 1), for example, T ⇡ 10 keV (⇡10 8 K) and the electron-electron ('ee'), electron-ion ('ei') and ion-ion ('ii') collisional exchanges of momentum and energy ('E') occur over relatively long characteristic times:2)-justifying the collisi...

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“…For control and monitoring in DCS raw sensor signals are processed to reconstruct main physics quantities such as plasma separatrix geometry [6], magnetic flux coordinates [7], electron and neutral density and density profiles [8], radiated power, power fluxes, effective heating power components, stored energy, plasma confinement parameters [9,10], MHD and locked mode amplitudes and locations [11,12] and disruption precursors [13,14]. To distribute and parallelise the working load, part of these quantities are not computed by DCS but directly by real-time enabled digital diagnostic systems [15].…”

Section: Measurements and Plasma Reconstructionmentioning

confidence: 99%

ASDEX Upgrade Discharge Control System—A real-time plasma control framework

Treutterer

Cole²,

Lüddecke³

et al. 2014

Fusion Engineering and Design

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ASDEX Upgrade is a fusion experiment with a size and complexity to allow extrapolation of technical and physical conditions and requirements to devices like ITER and even beyond. In addressing advanced physics topics it makes extensive use of sophisticated real-time control methods. It comprises real-time diagnostic integration, dynamically adaptable multivariable feedback schemes, actuator management including load distribution schemes and a powerful monitoring and pulse supervision concept based on segment scheduling and exception handling. The Discharge Control System (DCS) supplies all this functionality on base of a modular software framework architecture designed for real-time operation. It provides system-wide services like workflow management, logging and archiving, self-monitoring and inter-process communication on Linux, VxWorks and Solaris operating systems. By default DCS supports distributed computing, and a communication layer allows multi-directional signal transfer and data-driven process synchronisation over shared memory as well as over a number of real-time networks. The entire system is built following the same common design concept combining a rich set of re-usable generic but highly customisable components with a configurationdriven component deployment method.We will give an overview on the architectural concepts as well as on the outstanding capabilities of DCS in the domains of inter-process communication, generic feedback control and pulse supervision. In each of these domains, DCS has contributed important ideas and methods to the on-going design of the ITER plasma control system. We will identify and describe these essential features and illustrate them with examples from ASDEX Upgrade operation.

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Integrated operation of diagnostic and control systems

Cited by 12 publications

References 15 publications

High-density H-mode operation by pellet injection and ELM mitigation with the new active in-vessel saddle coils in ASDEX Upgrade

High-density H-mode operation by pellet injection and ELM mitigation with the new active in-vessel saddle coils in ASDEX Upgrade

Computational challenges in magnetic-confinement fusion physics

ASDEX Upgrade Discharge Control System—A real-time plasma control framework

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