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ABSTRACT: A real-time plasma position control system is mandatory to achieve long duration (up to 250 ms), Alternating Current (AC) discharges on the ISTTOK tokamak. Such a system has been used for some time supported only on magnetic field diagnostic data. However, this system is clearly challenged when the plasma current is low, rendering it inoperative during the plasma current reversal. A tomography diagnostic with 3 pinhole cameras and 8 silicon photodiode channels per camera was installed and customized to supply alternative plasma position to be used for plasma position control. As no filtering is applied most of the radiation detected is in the visible/near-UV range. The data acquisition and control system is based on a 2MSPS, 32 channel acquisition ATCA module and the data processing is performed on a GPU that is connected to another ATCA module via the PCI-Express port for fast data access. Control commands are relayed to the plasma positioning PF power supplies via optical serial ports. In this work, an overview of some of the tomographic reconstruction algorithms most commonly used for tokamak plasmas is done and an assessment is made on the best candidate for the proposed real-time implementation. The tomography acquisition and plasma control systems operating at ISTTOK are also described. This system aims at achieving the following goals: (i) execute a tomographic reconstruction; (ii) determine the average emissivity position from it; (iii) calculate the shift from the axis and (iv) supply the vertical field power supply with the desired current value, all in less than 100 μs. The horizontal magnetic field power supply unit, essential for vertical plasma positioning, is foreseen to be integrated in the system and will have no impact in the processing time.
IEEE Transactions on Nuclear Science 09/2011; · 1.45 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: A real-time plasma position control system is mandatory to achieve long duration (up to 250ms), Alternating Current (AC) discharges on the ISTTOK tokamak. Such a system has been used for some time supported only on magnetic field diagnostic data. However, this system is clearly challenged when the plasma current is low, rendering it inoperative during the plasma current reversal. A tomography diagnostic with 3 pinhole cameras and 8 silicon photodiode channels per camera was installed and customized to supply alternative plasma position to be used for plasma position control. As no filtering is applied most of the radiation detected is in the visible/near-UV range. The data acquisition and control system is based on a 2MSPS, 32 channel acquisition ATCA module and the data processing is performed on a GPU that is connected to another ATCA module via the PCI-Express port for fast data access. Control commands are relayed to the plasma positioning PF power supplies via optical serial ports. In this work, an overview of some of the tomographic reconstruction algorithms most commonly used for tokamak plasmas is done and an assessment is made on the best candidate for the proposed real-time implementation. The tomography acquisition and plasma control systems operating at ISTTOK are also described. This system aims at achieving the following goals: (i) execute a tomographic reconstruction; (ii) determine the average emissivity position from it; (iii) calculate the shift from the axis and (iv) supply the vertical field power supply with the desired current value, all in less than 100μs. The horizontal magnetic field power supply unit, essential for vertical plasma positioning, is foreseen to be integrated in the system and will have no impact in the processing time.
Real Time Conference (RT), 2010 17th IEEE-NPSS; 06/2010
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Fusion Engineering and Design 01/2010; In Press, Corrected Proof:-. · 1.49 Impact Factor
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ABSTRACT: With the implementation of alternating discharges (ac) at the ISTTOK tokamak, the typical duration of the discharges increased from 35 to 250 ms. This time increase created the need for a real-time electron density measurement in order to control the plasma fueling. The diagnostic chosen for the real-time calculation was the microwave interferometer. The ISTTOK microwave interferometer is a heterodyne system with quadrature detection and a probing frequency of 100 GHz (lambda(0)=3 mm). In this paper, a low-cost approach for real-time diagnostic using a digital signal programmable intelligent computer embedded system is presented, which allows the measurement of the phase with a 1% fringe accuracy in less than 6 micros. The system increases its accuracy by digitally correcting the offsets of the input signals and making use of a judicious lookup table optimized to improve the nonlinear behavior of the transfer curve. The electron density is determined at a rate of 82 kHz (limited by the analog to digital converter), and the data are transmitted for each millisecond although this last parameter could be much lower (around 12 micros--each value calculated is transmitted). In the future, this same system is expected to control plasma actuators, such as the piezoelectric valve of the hydrogen injection system responsible for the plasma fueling.
The Review of scientific instruments 11/2008; 79(10):10E711. · 1.52 Impact Factor
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ABSTRACT: Plasma positioning on the ISTTOK tokamak has usually been done, resorting to magnetic pickup coils. However, during alternating current (ac)-type discharges with plasma current reversal, this method has been found to be inadequate. The recently installed tomography diagnostic can be an alternative for determining the plasma position. The presented image shows tomographic reconstructions of the ISTTOK plasma during ac discharges, showing the position of maximum and average emissivity positions.
IEEE Transactions on Plasma Science 09/2008; · 1.17 Impact Factor
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C. Silva,
H. Fernandes,
C. A. F. Varandas,
D. Alves,
P. Balan,
B. B. Carvalho,
I. Carvalho,
P. Carvalho,
P. A. Carvalho,
R. Coelho, [......],
A. Klyukin,
I. Nedzelskij,
A. Neto, T. Pereira,
E. Platacis,
V. Plyusnin,
R. Schrittwieser,
A. Sharakovski,
I. Tale,
D. Valcárcel
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ABSTRACT: This paper reviews the recent work developed on ISTTOK. A wide variety of diagnostic tools, instrumentation and systems have been developed demonstrating that small tokamaks can play an important role in the fusion community. Furthermore, a physics programme has been carried out with particular emphasis on the control and characterization of the edge fluctuations. Recently, the ISTTOK programme has also dedicated particular attention to the development of plasma facing components being both liquid metal limiters and nanostructured materials.
AIP Conference Proceedings. 04/2008; 996(1):3-13.
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Fusion Engineering and Design 01/2008; 83(2-3):458 - 461. · 1.49 Impact Factor
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D.F. Valcárcel,
A. Neto,
J. Sousa,
B.B. Carvalho,
H. Fernandes,
J.C. Fortunato,
A.S. Gouveia,
A.J.N. Batista,
A.G. Fernandes,
M. Correia, T. Pereira,
I.S. Carvalho,
A.S. Duarte,
C.A.F. Varandas,
M. Hron,
F. Janky,
J. Písačka
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ABSTRACT: The Compass tokamak is currently being installed in Prague, Czech Republic. Its control and data acquisition system is being redesigned and built from scratch and it will be based on novel digital technologies. The proposed hardware for the controller is based on the PICMG 3.0 Advanced Telecommunications Computing Architecture ™ (ATCA) standard. The platform contains one ATCA controller with a Gigabit Ethernet interface, up to 12 ATCA Digitizer-Generator-Processor (DGP) cards and trigger and clock inputs, all on a 12U shelf. The multi-core ×86-based General Purpose Processor (GPP) controller will be connected to the DGP cards by Peripheral Component Interconnect Express ™ (PCIe) point-to-point links through the ATCA backplane. Multiple-input multiple-output (MIMO) signal processing will be shared by the DGP cards using the built-in Field Programmable Gate Arrays (FPGAs) and the controller’s × 86 general processor. Eleven Aurora ™ 2.5 Gbit/s links allow to further parallelize the execution of code among several FPGAs. In order to guarantee real-time execution of the control codes a framework based on Linux and the Real-Time Application Interface (RTAI) will be used. This will explore the features provided by the new multi-core technologies. Synchronization between the subsystems will be guaranteed by a real-time event network. The interface to the system will be provided by the FireSignal control and data acquisition system. This will allow the operators and diagnostic coordinators to configure the hardware, prepare the discharges, pre-program events of interest and follow results from the discharge. FireSignal will also orchestrate the data flow coming from the different diagnostics into the database and to registered data clients.
Fusion Engineering and Design.
