Remote participation tools at TEXTOR

Remote Participation is a widely used term with different meanings. In the fusion community it has gained an increasing interest with the shut down of small experiments and participation of associations in larger experiments. Also at TEXTOR Remote Participation becomes more and more important with an increasing number of collaborations.At TEXTOR we differentiate between active and passive remote experiment participation. In addition potential users of TEXTOR like to be involved in the experiment preparation phase where the experiment schedule and the availability of diagnostic systems is discussed as well. After an experiment joint groups of users like to share the results and communicate with each other.The final step in publishing the results is also made more transparent for the users in a twofold process. Using a web based pinboard to spread the publication within the user community allows an extensive and early discussion of the results. (C) 2010 Elsevier B.V. All rights reserved

Optimised plasma stabilisation at TEXTOR with an advanced real-time digital control scheme

The tokamak TEXTOR at the Research Centre in Julich is in operation since more than 25 years. The various control systems at the start, in 1982, were based on analogue techniques, a standard at the time, and were later partly replaced by specially developed digital systems. These systems proved their robustness over the years. As a replacement for the old system, off-the-shelf products were used to ensure continuity, reliability and to reduce the development cost. To provide advanced control scenarios, the new system allows the implementation of more sophisticated algorithms for magnetic and kinetic control. The LabVIEW Real-Time (RT) modules and real-time hardware from National Instruments satisfy these requirements to a large extent. The new system has already been successfully commissioned at TEXTOR and is used to calculate in real-time the plasma density profile (10 ms), the Shafranov shift (10 ms), the plasma vertical and horizontal position (20 mu s) and to control the plasma shape (1 ms). TEXTOR has circular plasmas and has an iron core. Its central part is operated in saturation. During the saturation phase, stray fields change the plasma shape from nearly circular to slightly triangular. By using a shape-control coil set, we can control and adjust the plasma form. The new real-time system is presented as well as the implemented control applications. (C) 2009 Elsevier B.V. All rights reserved

Dust investigations in TEXTOR: Impact of dust on plasma–wall interactions and on plasma performance

Dust will have severe impact on ITER performance since the accumulation of tritium in dust represents a safety issue, a possible reaction of dust with air and steam imposes an explosion hazard and the penetration of dust in core plasmas may degrade plasma performance by increasing radiative losses. Investigations were performed in TEXTOR where known amounts of pre-characterized carbon, diamond and tungsten dust were mobilized into plasmas using special dust holders. Mobilization of dust changed a balance between plasma–surface interactions processes, significantly increasing net deposition. Immediately after launch dust was dominating both core and edge plasma parameters. Remarkably, in about 100 ms after the launch, the effect of dust on edge and core plasma parameters was vanished: no increase of carbon and tungsten concentrations in the core plasmas was detected suggesting a prompt transport of dust to the nearby plasma-facing components without further residence in the plasma