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The optimized superconducting stellarator device Wendelstein 7-X (with major radius , minor radius , and plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This paper reports on the results from the first high-performance plasma operation. Glow discharge conditioning and ECRH conditioning discharges in helium turned out to be important for density and edge radiation control. Plasma densities of with central electron temperatures were routinely achieved with hydrogen gas fueling, frequently terminated by a radiative collapse. In a first stage, plasma densities up to were reached with hydrogen pellet injection and helium gas fueling. Here, the ions are indirectly heated, and at a central density of a temperature of with was transiently accomplished, which corresponds to with a peak diamagnetic energy of and volume-averaged normalized plasma pressure . The routine access to high plasma densities was opened with boronization of the first wall. After boronization, the oxygen impurity content was reduced by a factor of 10, the carbon impurity content by a factor of 5. The reduced (edge) plasma radiation level gives routinely access to higher densities without radiation collapse, e.g. well above line integrated density and central temperatures at moderate ECRH power. Both X2 and O2 mode ECRH schemes were successfully applied. Core turbulence was measured with a phase contrast imaging diagnostic and suppression of turbulence during pellet injection was observed.

The superconducting stellarator Wendelstein 7-X has successfully concluded its third operation phase in October 2018. The machine will see substantial changes during the next two years when an actively cooled divertor will be installed, as well as many new diagnostic systems. The W7-X Control, Data Acquisition and Communication (CoDaC) group is responsible for the integration of all new diagnostics into the W7-X control ecosystem (around ten systems) as well as carrying out significant upgrades to the I&C and data acquisition of another 15 systems. This article will present an overview of the integration challenges for Operation Phase 2 (OP2) both from a technical perspective as well as highlight the strategy employed by the W7-X CoDaC group to meet those challenges within the time and resource budget. The cornerstone for this strategy is standardization as far as possible to minimize individual integration effort. Siemens PLCs already handle general slow control throughout the project. However, up until now, the integration work is still predominantly done fully in-house. In order to handle the large scope of work within the time budget, CoDaC will have to be in a position to outsource a significant part of the work. In addition, efforts are underway to make validation and commissioning of the central systems as efficient as possible using modeling and simulation environments as well as industry-standard requirements’ management.

Contextual metadata becomes an important factor for the work with research data, which is created in large amounts at fusion experiments. In its first operational phases, the stellarator experiment Wendelstein 7-X (W7-X) produces about 500 TB of experimental data in only a few weeks of scientific campaign. A new central logbook software was implemented for the processing of contextual metadata at W7-X. The bulk data of W7-X experiments can be enriched with additional information, such as comments and tags for categorizing. Since its introduction, many enhancements have been implemented based on user feedback. This was possible due to a flexible software architecture. By using the logbook REST API, users can integrate logbook requests into their own software and programmatically add new content. The logbook quickly became a crucial tool for W7-X operation and is now considered a central hub for all experiment-related information. This paper describes the implementation of the W7-X logbook and the experience with the integration of metadata via REST API.

In the past two campaigns of Wendelstein 7-X (W7-X) stellarator the overview video diagnostics played a key role in the daily experiments. The current software implementations went through numerous improvements and changes according to the continuously changing requirements. However, while the control software could handle all the needs, the changes reached a point where the redesign and re-implementation became necessary to ensure high reliability. In the next campaign of W7-X real-time data streaming will be implemented to W7-X’s Archive, which can be practically a limitless real-time data backup. Other improvements involve high-level interaction with the trigger-time-event (TTE) network, intense graphical user interface (GUI) improvements such as the grouping of cameras, visual display of measurement settings (e.g. exposure and readout timing). This new software package is arranged into two standalone pieces, similarly as in the previous version. One of the main upgrades is that the software will be able to send so-called event descriptions over the network during the measurement to a central event display, where events from several diagnostics will be visualized. This feature can provide essential information for machine operators, as they can visually monitor dangerous events inside the machine in real-time. This paper will present the detailed experiences, new requirements and detailed design, implementation and testing of this new software package.

The stellarator Wendelstein 7-X (W7-X) is a fusion device designed for steady state operation. It is a complex technical system. To cope with the complexity a modular, component-based control and data acquisition system has been developed. During operation phases of W7-X components steadily evolve. For instance, measurement devices for diagnostics are improved, technical processes are optimized, experienced limits of the machine have to be taken into account or simple “bug fixing” is done. This requires continuous further development of the components while operating them at W7-X – a typical use case for DevOps practices. DevOps is a software engineering practice. The term is a compound of development and operations. It aims at shorter development cycles, while the quality of the changed system must stay at a high level. This is achieved by using a highly automated tool chain.

Wendelstein 7-X (W7-X) completed its second operation phase in December 2017. A large number of diagnostics were operated in nearly 1000 experiment programs (XP) by an international research team. For the documentation of W7-X XPs, a new electronic logbook software has been developed. The software has been designed for the needs of W7-X researchers and engineers: a web-based logbook application for the entire team. For an effective documentation, large parts of the logbook content comes from automatically generated logs, complemented by the team members via web browser or REST API. The W7-X control software generates log entries for an XP during program execution. This includes automatic extraction of configuration information from the planned program, which is later represented as searchable tags within the logbook. In addition, users can add supplementary tags and rich-text comments to all logs. The logbook allows full-text search and range queries for numeric values: both with millisecond response times. A dedicated web page for each XP log contains overview plots from measurement data, generated on the fly from archived data. Separate component logs are created in the same way for diagnostics and machine sub-systems for different use cases, e.g., XPs, standalone tests, or calibrations. The logbook hosts separate pages for device operation and the W7-X components, providing status information and additional features. In this way it effectively supports the operation of W7-X.

W endelstein 7-X is, as a stellerator, in principle capable of very long operation. The Control and Data-acquisition ( codac ) systems around w7x have, therefore, been designed for continuous operation. One aspect of this design is the recording of the absolute time of every measurement. Whereby for every relevant event, such as every sample-clock tick of every adc , the time is recorded as a 64 bit integer value. On the one hand, this approach has several advantages. On the other hand, it generates much more data to process and archive. In extreme cases it can lead to a multiplication of the data amounts. Compression of these time-stamps data can be expected to save storage and network resources. However, even though most of these time-stamps have a high degree of predictability, the normal, de-facto standard, compression approaches ( zip , flac , etc.) perform rather poorly on this type of data. Thus, inspired by well-known audio compression approaches, we developed a specialised loss-less compression algorithm, aimed at fairly constantly incrementing 64 bit long-integers. Experiments on data collected in the past demonstrate very large compression factors, whilst retaining all details in the timing data.

Wendelstein 7-X was built for the research on steady state operation of stellarators. This sets high requirements on the control and data acquisition (CoDaC) system, with the archive database as one of its main components. W7-X Archive database is the storage of all operational and scientific data. It stores raw data as well as processed data and provides a single database for a wide range of components and data types. The Archive WEB API provides a unified access to the archive database by using web service technologies. The API is based on the REST architecture style, using HTTP as the application protocol: the data is represented as a unified signal resource, which can be addressed via a URL. The users can read data in standard formats, like JSON or PNG. In the same way, the WEB API can be used to import new data to ArchiveDB. This paper describes the concepts of the WEB API and the experiences during the first operational phase of W7-X.

The Wendelstein 7-X steady state plasma control and data acquisition system has been successfully commissioned and well established to investigate the plasma startup and run the first complex physics programs during the initial operation phase of W7-X. The main components of W7-X and a set of operational diagnostics have been integrated into the CoDaC system. The various different requests from the experimenters could be satisfied using the well established set of tools and interfaces − demonstrating their qualification for continuous operation. This paper summarizes the workflow from the users’ point of view while presenting the main tools and interfaces for W7-X Segment Control.

Wendelstein 7-X (W7-X) is a superconducting stellarator having undergone the first experimental campaign after its construction. It is capable of steady state magnetic field operation. After an upgrade to cope with permanent heat loads of several Megawatts, W7-X will be able to run steady state discharges, too. The W7-X control system demonstrated to support all types of experiments compatible with steady state magnetic field operation, i.e. short plasma discharges and sequences of discharges with arbitrary time intervals. The contribution describes the basic concepts of the W7-X control system. Application examples are presented and discussed. Further planned extensions to the control systems are presented.