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Strong absorption of light in a broad wavelength range and poor thermal conductance between particles of carbon nanomaterials, such as nanotubes, onions, nanodiamond, and carbon black, lead to strong thermal emission (blackbody radiation) upon laser excitation, even at a very low (milliwatts) power. The lasers commonly used during Raman spectroscopy characterization of carbon can cause sample heating to very high temperatures. While conventional thermometry is difficult in the case of nanomaterials, Raman spectral features, such as the G band of graphitic carbon and thermal emission spectra were used to estimate the temperature during light emission that led to extensive graphitization and evaporation of carbon nanomaterials, indicating local temperatures exceeding 3500 °C. [ABSTRACT FROM AUTHOR]

Highlights: [•] A localised laser dispersing of fine grained ceramic particles was investigated. [•] Dome shaped spots with significantly higher hardness values were gained. [•] Hardness and spot shape are controllable by laser parameters. [•] Hardness correlates with fraction of dispersed material. [Copyright &y& Elsevier]

Highlights: [•] An exponential growth of data amount was managed over more than twenty years of experiment operation. [•] Continuous adaptation of the diagnostic software and configuration keeps track with actual experiment demands. [•] A great number of distributed, varying diagnostics is centrally managed. [ABSTRACT FROM AUTHOR]

Compoundsrich in nitrogen are attracting significant interestnot only because of their high energy content but also because theyare potentially more environmentally benign in comparison to conventionalenergetic materials. Given this interest, it is desirable to understandtheir molecular composition and structural variations with pressureto derive their stability and determine the conditions in which theytransform physically or chemically. In this study, we examine theroom-temperature isothermal compression behavior of bis-triaminoguanidiniumazotetrazolate (TAGzT) by in situ Raman spectroscopy to pressuresnear 17 GPa. We assign the characteristic vibrational bands and reportthe effects of pressure on band intensity, line width, and frequencyshift. Two prominent peaks near 1370 and 1470 cm–1arise from the C–N and NN symmetric stretches, respectively.Overall, the intensity of these bands and others diminishes with pressure,and their spectral linewidths increase monotonically upon compression.The vibrational frequency modes blue shift linearly upon compression,indicating a generalized stiffening of the bonds as the pressure increases.These results, together with micro Raman spectroscopic analyses ofthe recovered, decompressed samples, suggest that TAGzT does not undergoany phase transitions within this pressure range. We estimate andreport the C–N and NN intermolecular bond lengths undercompression. [ABSTRACT FROM AUTHOR]

Abstract: The SIO DAQ concept used at the ASDEX Upgrade fusion experiment features data acquisition from a modular front-end (a modular crate-and-interface-cards concept for analog and digital input and output) over standardized serial lines and via a serial input/output computer interface card (the SIO card) in real-time directly into the main memory of a host computer. Deployment of a series of diagnostics using SIO led to various solutions and configurations for the different requirements. Experience has been gained and lessons learned applying the SIO concept at its technical limits. Requirements for a further development of the SIO concept have been identified, and a performance improvement by a factor of 4–8 beyond its current limits seems achievable. An effort has been started to develop a SIO version 2 (SIO II) featuring upgraded serial links and a more powerful FPGA for merging and forwarding data streams to host computer memory. (Compatibility with the existing SIO (SIO I) front-end system has to be maintained.) This paper presents results achieved and experiences gained in the deployment of SIO I, the status of SIO II development (currently in the prototype phase), and projected enhancements and updates to existing implementations. [Copyright &y& Elsevier]

Abstract: In fusion research the ability to generate and sustain high performance fusion plasmas gains more and more importance. Optimal combinations of magnetic shape, temperature and density profiles as well as the confinement time are identified as advanced regimes. Safe operation in such regimes will be crucial for the success of ITER and later fusion reactors. The operational space, on the other hand, is characterized by nonlinear dependencies between plasma parameters. Various MHD limits must be avoided in order to minimize the risk of a disruption. Sophisticated feedback control schemes help to tackle this challenge. But these in turn require detailed information on plasma state in time to allow proper reaction. Control system and diagnostic systems therefore must establish a symbiotic relationship to carry out such schemes. Today, all major fusion devices implement such a concept. An implementation of such a concept with sustained integration is presented using the example of ASDEX Upgrade. It covers data communication via a real-time network, synchronization mechanisms for data-driven algorithm execution as well as operational aspects and exception handling for failure detection and recovery. A modular distributed software framework offers standardized user algorithm interfaces, automated workflow procedures and the application of various computer and network hardware components. Designed with a special focus on reliability, robustness and flexibility, it is a sound base for exploring ITER-relevant plasma regimes and control strategies. [Copyright &y& Elsevier]

Abstract: To improve the plasma position and shape control system in ASDEX Upgrade, it is constantly expanded by the integration of data acquisition systems of important and interesting diagnostics. Usually the main responsibility of data acquisition systems is to collect data and subsequently put it into a data base archive system from where it is later analysed. The obligation now is also to simultaneously process the acquired data with an appropriate algorithm and send the pre-processed data in real-time to the plasma control system during a discharge. To achieve this requirements the used hardware must provide enough processing power and the operating system has to meet some real-time constraints. To avoid the burden of using proprietary real-time operating systems the trend is to use Open Source variants mainly based on Linux. Some of these solutions also allow us doing real-time capable communication using standard Ethernet hardware. By way of an example the implementation process of a prototype of a real-time data acquisition system based on a multi-core processor and Xenomai is demonstrated. Other possible solutions like Realtime Linux and their differences to Xenomai which we propose as the most sophisticated real-time framework for Linux are discussed in this paper. [ABSTRACT FROM AUTHOR]

Abstract: Development of a real-time (RT) data acquisition (DAQ) system for ASDEX Upgrade was started years ago. Based on a modular front-end configuration with serial input/output computer interface a small number of powerful new diagnostics were commissioned. In the course of these developments we concluded that “direct to memory” DAQ concepts hold promise for future DAQ tasks including those with a subsequent RT data processing step. A survey of the requirements of existing and future diagnostics at ASDEX Upgrade was conducted to assess the wider applicability of these DAQ techniques to the upcoming needs for new diagnostics or the refurbishment of old ones. The paper presents the results of the requirements survey and indicates in which cases the developed diagnostic concept can be applied. A series of new diagnostics implemented using these techniques is presented in detail. This covers developed front-end modules as well as whole diagnostic configurations in hardware and software. The achieved DAQ data rates, data transport latencies, and fine-tuning steps to maintain a reliable RT operation are described explicitly. An outlook is given upon the definition of a RT diagnostic standard for ASDEX Upgrade based on the developments described previously. [ABSTRACT FROM AUTHOR]

Abstract: Diagnostics at ASDEX Upgrade have available a very large number of highly developed measuring channels. The prospect of making this wealth of information usable for plasma optimisation led to the implementation of a number of diagnostics running data acquisition in real-time (RT). Ultimately, this development aims to achieve a network of intelligent diagnostics delivering analysed data for high-level plasma performance control such as profile shaping and NTM stabilisation. The new RT diagnostics consist of standard industrial 19in. servers organised in clusters and running a standard UNIX multiprocessor RT-capable operating system (RT OS). Built-to-purpose computer interface cards deliver data (e.g. via serial links) from the data acquisition (DAQ) front-ends directly into the main memory of the DAQ servers. An RT data analysis task immediately following the running direct memory access (DMA) data transfers processes the data and delivers the results to follow-up systems in the control chain. Whereas the first systems were implemented in a simple just a bunch of computers (JBOC) configuration being operated as a number of single diagnostics, newer systems are integrated into diagnostic clusters using parallel computing techniques such as message passing interface (MPI). The paper describes the hardware (ADC front-ends, serial I/O, selection criteria and performance of the involved computer busses and systems) and software (DAQ, DA, RT OS, MPI) architecture of the assembled systems. Benchmark results for DAQ and MPI bandwidth and latencies as well as for the behaviour of the RT OS will be given. [Copyright &y& Elsevier]

Abstract: At the ASDEX Upgrade tokamak experiment, a new feedback control loop is under construction with the aim of stabilizing magneto-hydrodynamic (MHD) instabilities, such as neoclassical tearing modes and sawteeth. It uses the mirrors of the electron cyclotron heating (ECH) launchers, which can be steered in real-time to guide each beam to the position needed to stabilize and suppress the mode. The control system needs highly specialized plasma state information such as island position and ECH beam deposition locations in real-time. Data from several diagnostic systems, like electron cyclotron emission (ECE), magnetic measurements and motional Stark effect must be combined in real-time to obtain the required information. These systems strongly differ in sampling characteristics and time resolutions. High sampling rates as 2MHz for ECE are often required to provide enough data for correlation or frequency analysis. On the other hand, complex analysis methods, such as equilibrium and profile reconstruction, may operate on slower rates of some milliseconds and need tight interaction with measurement systems and high computing power. In this paper, we describe a concept for distributed real-time diagnostic data handling, integration of data from several asynchronous diagnostic systems, and connection to the discharge control system for a broad spectrum of requirements. The system is structured into distributed diagnostic computer clusters, a real-time signal server to combine all information, and the discharge control system. While the focus is currently on MHD control, further real-time diagnostic related applications will be added in future. [Copyright &y& Elsevier]

Abstract: A universal time to digital converter (UTDC) and a digital I/O (DIO) card have been purpose-built for the new ASDEX Upgrade control system, the Thomson scattering diagnostic, a renovation of the magnetic measurements, and a couple of other diagnostics requiring renewed timing or real-time features. The principal features of these cards are presented and it is shown how synergy in hardware and software development was achieved. Examples of actual usage in diagnostics are given. Measurements of the real-time behaviour of cPCI-based diagnostics show low jitter of the Solaris operating system and highly reliable operation under moderate real-time conditions. Future applications of this family of cards are foreseen. [Copyright &y& Elsevier]

Abstract: ASDEX Upgrade was equipped with a distributed real-time (RT) control and diagnostic system. Application processes can be freely mapped onto controllers. They communicate through RT data exchanged via a shared memory network. Processes run self-organized with a data-driven scheme, i.e. a process executes when all required data has become available and produced data drive other processes waiting for these. The process chain starts periodically through a time-synchronous cycle master process to deterministically execute closed-loop control. Generic processes were implemented for feedback of plasma position and shape, and for performance control with fuelling and heating systems, for evaluation and monitoring of plasma quantities and Tokamak components, and generation of reference values in RT. Upon commissioning the system was speed-optimized to run a 1.6ms cycle. Methods to exchange data and time information in RT and operate distributed data-driven processes work efficiently and reliably. The ability to freely map processes to computing nodes and RT data to generic processes provides outstanding configurational flexibility for optimizing system performance or supporting in situ replay and simulation runs. In the computation of reference values in RT acting on underlying feedback controllers, demonstrated for soft-landing, we see great potential to counteract instabilities or optimize pulses. [Copyright &y& Elsevier]

ASDEX Upgrade is being equipped with a new real-time plasma control and data acquisition system and a novel time system. Major components were implemented and installed. While much work for performance optimisation and application programming remains to be done, commissioning of the new system parallel to experiment operation is being prepared. Commissioning of the new system will be done step-by-step. To facilitate testing the old and new control systems share all input signals. Switching between old and new system can be performed within 60 min: 23 fibre optics for output of actuator commands and input triggers must be connected to the active system and minor modifications done to interface the machine protection. Commissioning phases include background listening, technical discharges and full plasma operation. With the strategy chosen we minimize risk to the machine and reduce interference with ongoing experiment campaigns. [Copyright &y& Elsevier]

ASDEX upgrade investigates the integration of confinement, stability and exhaust issues into an operating scenario for ITER and a future fusion reactor. Since commissioned in 1990 the systems used to feedback control plasma position and shape as well as performance have continuously been enhanced. To overcome performance limitations and improve connectivity and steady state capability, a new plasma control system is being implemented. For the new system, adequate and reliable communication mechanisms are essential to integrate the realtime discharge control and data acquisition. We present communication methods and the process organisation of the new system and show that the new concept allows easy performance scaling. We demonstrate how existing periphery and new realtime diagnostics interface to control applications. This facilitates the realisation of novel and sophisticated control tasks combining multiple diagnostics and actuators for common physical goals. [Copyright &y& Elsevier]

ASDEX Upgrade is being equipped with new plasma controllers and advanced diagnostics. These will be integrated into a distributed system, exchanging process data and plasma state information via a real-time network. Infrastructure tasks on dedicated nodes represent a functional framework for embedding of applications. Any type of hardware or operating systems may implement these, as long as the general rules on I/O timing and signal exchange methods are observed. To avoid temporal uncertainties in the measurement process a new time system was designed. Time becomes a measurement quantity sampled with data and process values. [Copyright &y& Elsevier]

Fast data acquisition with direct transfer to memory is facilitated by the S-LINK interface protocol, developed at CERN, the European Organization for Nuclear Research. The need for customized hardware development reduces to application-specific front-end interfaces. Two applications of S-LINK data acquisition systems for microwave Doppler reflectometry and electron cyclotron emission radiometry at the ASDEX Upgrade nuclear fusion experiment are presented. [Copyright &y& Elsevier]

A two-dimensional, three-fluid code based on the two-fluid Potter code [Methods in Computational Physics (Academic, New York, 1970), Vol. 9, p. 340] was developed for simulating the plasma focus discharge. With this code it is possible to treat the neutral gas in addition to the plasma components and to model the ionization and recombination phenomena. Thus the sheet dynamics in a plasma focus can be studied and effects investigated such as the occurrence of residual gas (or plasma) density behind the current sheet in the run-down phase. This is a prerequisite to the occurrence of leak currents, which are one of the causes limiting the performance of large plasma focus devices. It is shown that fast operating foci with small dimensions behave favorably compared with the ‘‘classical’’ Mather focus [Methods of Experimental Physics (Academic, New York, 1971), Vol. 9B, p. 187] with long coaxial electrodes. [ABSTRACT FROM AUTHOR]

For the new generation of intelligent controllers for plasma diagnostics, discharge control and long-pulse experiment control a new time system supporting steady state real-time operation has been devised. A central unit counts time at nanosecond resolution, covering more than the experiment lifetime. The broadcast time information serves local units to perform application functions such as current time readout, trigger generation and sample time measurement. Time is treated as a precisely measured quantity like other physical quantities. Tagging all detected events and sampled values with measured times as [value; time]-entities facilitates real-time data analysis, steady state protocolling and time-sorted archiving. [Copyright &y& Elsevier]

Visualization of measurements together with experimental settings is a general subject in experiments analysis. The complex engineering design, 3D geometry, and manifold of diagnostics in larger fusion research experiments justify the development of special analysis and visualization programs. Novel ASDEX Upgrade (AUG) software tools bring together virtual navigation through 3D device models and advanced play-back and interpretation of video streams from plasma discharges. A third little tool allows the web-based platform independent observation of real-time diagnostic signals. While all three tools stem from spontaneous development ideas and are not considered mission critical for the operation of a fusion device, they with time and growing completeness shaped up as valuable helpers to visualize acquired data in fusion research. A short overview on the goals, the features, and the design as well as the operation of these tools is given in this paper. [ABSTRACT FROM AUTHOR]

The medium size divertor tokamak ASDEX Upgrade (major and minor radii 1.65 m and 0.5 m, respectively, magnetic-field strength 2.5 T) possesses flexible shaping and versatile heating and current drive systems. Recently the technical capabilities were extended by increasing the electron cyclotron resonance heating (ECRH) power, by installing 2 × 8 internal magnetic perturbation coils, and by improving the ion cyclotron range of frequency compatibility with the tungsten wall. With the perturbation coils, reliable suppression of large type-I edge localized modes (ELMs) could be demonstrated in a wide operational window, which opens up above a critical plasma pedestal density. The pellet fuelling efficiency was observed to increase which gives access to H-mode discharges with peaked density profiles at line densities clearly exceeding the empirical Greenwald limit. Owing to the increased ECRH power of 4 MW, H-mode discharges could be studied in regimes with dominant electron heating and low plasma rotation velocities, i.e. under conditions particularly relevant for ITER. The ion-pressure gradient and the neoclassical radial electric field emerge as key parameters for the transition. Using the total simultaneously available heating power of 23 MW, high performance discharges have been carried out where feed-back controlled radiative cooling in the core and the divertor allowed the divertor peak power loads to be maintained below 5 MW m−2. Under attached divertor conditions, a multi-device scaling expression for the power-decay length was obtained which is independent of major radius and decreases with magnetic field resulting in a decay length of 1 mm for ITER. At higher densities and under partially detached conditions, however, a broadening of the decay length is observed. In discharges with density ramps up to the density limit, the divertor plasma shows a complex behaviour with a localized high-density region in the inner divertor before the outer divertor detaches. Turbulent transport is studied in the core and the scrape-off layer (SOL). Discharges over a wide parameter range exhibit a close link between core momentum and density transport. Consistent with gyro-kinetic calculations, the density gradient at half plasma radius determines the momentum transport through residual stress and thus the central toroidal rotation. In the SOL a close comparison of probe data with a gyro-fluid code showed excellent agreement and points to the dominance of drift waves. Intermittent structures from ELMs and from turbulence are shown to have high ion temperatures even at large distances outside the separatrix. [ABSTRACT FROM AUTHOR]

Abstract: The existing VxWorks real-time system for the position and shape control in ASDEX Upgrade has been extended to calculate magnetic flux surfaces in real-time using a multi-core PCI Express system running LabVIEW RT 8.6. real-time signal processing of bolometers and manometers is performed with the on-board FPGA to calculate the measured radiated power flux and particle flux respectively from the raw data. Radiation feedback experiments use halo current measurements from the outer divertor with real-time median filter pre-processing to remove the excursions produced by ELMs. Integration of these plasma diagnostics into the control system by the exchange of XML sheets for communicating the real-time variables to be produced and consumed is in operation. Reflective memory and UDP are employed by the LabVIEW RT plasma diagnostics to communicate with the control system and other plasma diagnostics in a multi-platform real-time network. [ABSTRACT FROM AUTHOR]

We discuss the circuit design of a digital multiradian phase detector that measures the phase difference between two 10 kHz square wave TTL signals and provides the result as a binary number. The phase resolution of the circuit is 1/64 period and its dynamic range is 256 periods. This circuit has been developed for fusion plasma interferometry with submillimeter waves on the ASDEX Upgrade tokamak. The results from interferometric density measurement are discussed and compared to those obtained with the previously used phase detectors, especially with respect to the occurrence of phase jumps. It is illustrated that the new phase measurement provides a powerful tool for automatic real-time validation of the measured density, which is important for feedback algorithms that are sensitive to spurious density signals. [ABSTRACT FROM AUTHOR]

Abstract: The existing real time system for the position and shape control in ASDEX Upgrade has been extended to calculate magnetic flux surfaces in real time using a multi-core PCI Express system running LabVIEW RT. The availability of reflective memory for LabVIEW RT will allow this system to be connected to the control system and other diagnostics in a multi-platform real time network. The measured response of each magnetic probe to the individual poloidal field coil currents in the absence of plasma current is compared to the calculated value. Prior to a tokamak discharge this comparison can be used to check for failure of the magnetic probe, flux loop or integrator. [Copyright &y& Elsevier]

The article presents an addendum that lists the contributors and their affiliations from the Axially Symmetric Divertor Experiment (ASDEX) Upgrade Team for the "Review of Scientific Instruments."