Results 1 - 10 of 2031
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[en] The rapid progress in fast imaging gives new opportunities for fusion research. The data obtained by fast cameras play an important and ever-increasing role in analysis and understanding of plasma phenomena. The fast cameras produce a huge amount of data which creates considerable problems for acquisition, analysis, and storage. We use a number of fast cameras on the Mega-Amp Spherical Tokamak (MAST). They cover several spectral ranges: broadband visible, infra-red and narrow band filtered for spectroscopic studies. These cameras are controlled by programs developed in-house. The programs provide full camera configuration and image acquisition in the MAST shot cycle. Despite the great variety of image sources, all images should be stored in a single format. This simplifies development of data handling tools and hence the data analysis. A universal file format has been developed for MAST images which supports storage in both raw and compressed forms, using either lossless or lossy compression. A number of access and conversion routines have been developed for all languages used on MAST. Two movie-style display tools have been developed-Windows native and Qt based for Linux. The camera control programs run as autonomous data acquisition units with full camera configuration set and stored locally. This allows easy porting of the code to other data acquisition systems. The software developed for MAST fast cameras has been adapted for several other tokamaks where it is in regular use
[en] The limited memory and data rate of CAMAC data acquisition systems is unable to accommodate proposed increases in the MAST plasma duration of up to an order of magnitude. Therefore, some recent pilot exercises have evaluated new technology to replace CAMAC. One of the pilot systems explored the use of modern CompactPCI 'intelligent' data acquisition devices. These can operate stand-alone, using an onboard Linux operating system and Ethernet connection without the need for a host computer. The approach to data capture and management was simplified to minimise development time. A simple Linux shell script running on each device was found sufficient to automate the whole acquisition cycle, and this was successfully commissioned in one day. This approach avoided the need for compiled programs but prevented use of the in-house standard shot file archiving library. Instead, each channel's data was written to a separate file as a simple array of samples. This work around was found to offer advantages in terms of flexibility, simplicity and scalability. The experience of handling much higher volumes of acquired data than was practicable with CAMAC has also raised important issues about the scalability of existing data management and analysis systems when each data item contains many mega-samples. The experience and lessons learned will help guide the future direction of data acquisition strategy on MAST
[en] The MAST (Mega-Amp Spherical Tokamak) data acquisition system is being radically upgraded. New hardware with completely different control interface and logic has been installed on all system levels from front-end devices to plant control. MAST plant control has been moved from VMS to a Windows-based OPC system. Old CAMAC and VME units are being replaced by cPCI and PXI units. A number of CAMAC crates have been upgraded with new Ethernet controllers supporting useful front-end devices. The upgrade is being performed without disturbing operations; the data acquisition units are being replaced gradually. Such an upgrade is possible due to the structure of the MAST data acquisition system which is build as a set of autonomous units, each one controlled by a computer. Modern computers are capable of controlling several units, and this has been the major opportunity and challenge because it radically changes the unit control logic. As a result practically all system components had to be redesigned. The new unit software is a step in system evolution towards greater flexibility and universality. Each unit can now manage multiple data files, possibly with different formats, and many units can be hosted on the same computer. This feature is provided by a message proxy server. Each unit is controlled independently and transparently, exactly like a stand-alone unit. A message interface has been modified for consistent handling of new functions. The unit software supports event-triggered and real-time data acquisition at the system level. New software has been developed for a number of new hardware devices, and the device modules for all usable old devices have been rewritten to operate with the new control interface. The new software allows units to be upgraded even during operations. The system structure and logic provide easy extension. The system as a whole or system design elements could also be used on other fusion facilities.
[en] The NSTX (National Spherical Torus Experiment) facility located at Princeton Plasma Physics Laboratory is the newest national fusion science experimental facility for the restructured US Fusion Energy Science Program. The NSTX project was approved in FY 97 as the first proof-of-principle national fusion facility dedicated to the spherical torus research. On Feb. 15, 1999, the first plasma was achieved 10 weeks ahead of schedule. The project was completed on budget and with an outstanding safety record. This paper gives an overview of the NSTX facility construction and the initial plasma operations
[en] The spherical tokamak (ST) is the low aspect ratio limit of the conventional tokamak and appears to offer attractive physics properties in a simpler device. The START (Small Tight Aspect Ratio Tokamak) experiment provided the world's first demonstration of the properties of hot plasmas in an ST configuration and was operational at Culham from January 1991 to March 1998, obtaining plasma currents of up to 300 kA and pulse durations of ∼ 50 ms. Its successor, MAST, is nearing completion and is a purpose built, high vacuum machine designed to have a tenfold increase in plasma volume with plasma currents of up to 2 MA. Current drive and heating will be by a combination of induction-compression as on START, a high performance central solenoid, with 1.5 MW ECRH and 5 MW of NBI. The promising results from START are reviewed, and the many challenges posed for the next generation of purpose built STs (such as MAST) are described. (author)
[en] A new diagnostic for the National Spherical Torus Experiment (NSTX) is described whose function is to measure ion rotation and temperature at the plasma edge. The diagnostic is sensitive to C III, C IV, and He II intrinsic emission, covering a radial region of 15 cm at the extreme edge of the outboard midplane. Thirteen chords are distributed between toroidal and poloidal views, allowing the toroidal and poloidal rotation and temperature of the plasma edge to be simultaneously measured with 10 ms resolution. Combined with the local pressure gradient and the EFIT code reconstructed magnetic field profile, the edge flow gives a measure of the local radial electric field
[en] The MDSplus data acquisition system has been used successfully since the 1999 startup of NSTX [National Spherical Torus Experiment] for control, data acquisition, and analysis for diagnostic subsystems. For each plasma ''shot'' on NSTX about 75 MBs of data is acquired and loaded into MDSplus hierarchical data structures in 2-3 minutes. Physicists adapted to the MDSplus software tools with no real difficulty. Some locally developed tools are described. The support from the developers at MIT [Massachusetts Institute of Technology] was timely and insightful. The use of MDSplus has resulted in a significant cost savings for NSTX
[en] MAST PCS, a port of General Atomics' generic Plasma Control System, is a large software system comprising many source files in C and IDL. Application parameters can affect multiple source files in complex ways, making code development and maintenance difficult. The MAST PCS configuration system aims to make the task of the application developer easier, through the use of XML-based configuration files and a configuration tool which processes them. It is presented here as an example of a useful technique with wide application
[en] Distributing control mechanisms across modern commercial off the shelf (COTS) GNU/Linux systems often introduces difficult to mitigate non-deterministic behavior. Existing methods to address this problem involve non-real-time technologies such as Remote Direct Memory Access (RDMA) over Infiniband or custom Ethernet solutions, such as RDMA over Converged Ethernet (RoCE) or userspace Ethernet drivers, that trade determinism for ease of use or lower cost. The National Spherical Torus Experiment Upgrade (NSTX-U) is pursuing a new design that allows direct communication between heterogeneous systems with scalable, microsecond latency with 1 μs of jitter on that latency, outside of the constant transmission delay at the physical layer. The future design of the NSTX-U Real-time Communication System will utilize direct PCIe-to-PCIe communication with kernel support tuned for low overhead, allowing two (or more, through a switch) real-time (RT) systems to communicate and share resources as one larger entity. This greatly increases the processing capability of the primary Plasma Control System (PCS), turning previously insurmountable computational challenges into a more manageable divide and conquer parallel task.
[en] The paper presents the application of modern computational methods for tokamak plasma control system analysis. Several different approaches for feedback controller synthesis are described. General positions of the modern robust analysis theory are briefly formulated. The technique of robust features comparative analysis for feedback controllers is presented. The application of these computational methods is illustrated by the example of the MAST tokamak plasma vertical feedback control system