After a long device enhancement phase, scientific operation resumed in 2022. The main new device components are the water cooling of all plasma facing components and the new water-cooled high heat flux divertor units. Water cooling allowed for the first long-pulse operation campaign. A maximum discharge length of 8 min was achieved with a total heating energy of 1.3 GJ. Safe divertor operation was demonstrated in attached and detached mode. Stable detachment is readily achieved in some magnetic configurations but requires impurity seeding in configurations with small magnetic pitch angle within the edge islands. Progress was made in the characterization of transport mechanisms across edge magnetic islands: Measurement of the potential distribution and flow pattern reveals that the islands are associated with a strong poloidal drift, which leads to rapid convection of energy and particles from the last closed flux surface into the scrape-off layer. Using the upgraded plasma heating systems, advanced heating scenarios were developed, which provide improved energy confinement comparable to the scenario, in which the record triple product for stellarators was achieved in the previous operation campaign. However, a magnetic configuration-dependent critical heating power limit of the electron cyclotron resonance heating was observed. Exceeding the respective power limit leads to a degradation of the confinement.

The mission of WEST (tungsten-W Environment in Steady-state Tokamak) is to explore long pulse operation in a full tungsten (W) environment for preparing next-step fusion devices (ITER and DEMO) with a focus on testing the ITER actively cooled W divertor in tokamak conditions. Following the successful completion of phase 1 (2016-2021), phase 2 started in December 2022 with the lower divertor made entirely of actively cooled ITER-grade tungsten mono-blocks. A boronization prior the first plasma attempt allowed for a smooth startup with the new divertor. Despite the reduced operating window due to tungsten, rapid progress has been made in long pulse operation, resulting in discharges with a pulse length of 100 s and an injected energy of around 300 MJ per discharge. Plasma startup studies were carried out with equatorial boron nitride limiters to compare them with tungsten limiters, while Ion Cyclotron Resonance Heating assisted startup was attempted. High fluence operation in attached regime, which was the main thrust of the first campaigns, already showed the progressive build up of deposits and appearance of dust, impacting the plasma operation as the plasma fluence increased. In total, the cumulated injected energy during the first campaigns reached 43 GJ and the cumulated plasma time exceeded 5 h. Demonstration of controlled X-Point Radiator regime is also reported, opening a promising route for investigating plasma exhaust and plasma-wall interaction issues in more detached regime. This paper summarises the lessons learned from the manufacturing and the first operation of the ITER-grade divertor, describing the progress achieved in optimising operation in a full W environment with a focus on long pulse operation and plasma wall interaction.

The Wendelstein 7-X stellarator (W7-X) started operation in December 2015 and has performed three experimental campaigns up to November 2018. Since then the device has been completed to the planned configuration (most importantly with predominantly actively cooled first wall, including the High Heat Flux divertor and a divertor cryo pump) to be able to perform stationary plasma programs. After this completion pFhase, at the end of 2021, the commissioning has been performed and scientific operation has started in the fall of 2022.

WEST is an MA class superconducting, actively cooled, full tungsten (W) tokamak, designed to operate in long pulses up to 1000 s. In support of ITER operation and DEMO conceptual activities, key missions of WEST are: (i) qualification of high heat flux plasma-facing components in integrating both technological and physics aspects in relevant heat and particle exhaust conditions, particularly for the tungsten monoblocks foreseen in ITER divertor; (ii) integrated steady-state operation at high confinement, with a focus on power exhaust issues. During the phase 1 of operation (2017-2020), a set of actively cooled ITER-grade plasma facing unit prototypes was integrated into the inertially cooled W coated startup lower divertor. Up to 8.8 MW of RF power has been coupled to the plasma and divertor heat flux of up to 6 MW m(-2) were reached. Long pulse operation was started, using the upper actively cooled divertor, with a discharge of about 1 min achieved. This paper gives an overview of the results achieved in phase 1. Perspectives for phase 2, operating with the full capability of the device with the complete ITER-grade actively cooled lower divertor, are also described.

We present recent highlights from the most recent operation phases of Wendelstein 7-X, the most advanced stellarator in the world. Stable detachment with good particle exhaust, low impurity content, and energy confinement times exceeding 100 ms, have been maintained for tens of seconds. Pellet fueling allows for plasma phases with reduced ion-temperature-gradient turbulence, and during such phases, the overall confinement is so good (energy confinement times often exceeding 200 ms) that the attained density and temperature profiles would not have been possible in less optimized devices, since they would have had neoclassical transport losses exceeding the heating applied in W7-X. This provides proof that the reduction of neoclassical transport through magnetic field optimization is successful. W7-X plasmas generally show good impurity screening and high plasma purity, but there is evidence of longer impurity confinement times during turbulence-suppressed phases.

The Wendelstein 7-X project is aimed at demonstrating that an optimised stellarator is an attractive candidate for a fusion reactor. This requires the achievement of a number of technical and physics goals. Several of these goals have already been achieved in the first three experimental campaigns. We shall exemplify this by a number of results. One important goal is the demonstration of quasi-steady-state operation at high plasma density and temperature for half an hour, which encompasses the physical and technical requirements of stable operation with density and impurity control, cw heating, water-cooled targets, particle exhaust, and an appropriate control and data acquisition system for long-pulse operation. In the previous experimental campaigns, with uncooled targets, stationary discharges for up to 25 s with 5 MW heating power and up to 100 s with 2 MW heating power were achieved. For the next operational phase, to start in 2022, water-cooled targets are being installed, water cooling will be provided for all first-wall components, and a number of further upgrades to plasma heating, vacuum and fuelling systems as well as diagnostics will become available. With this equipment, the further goals of the project will be tackled, including the stepwise extension of discharge intervals to the multi-minute range. The experimental results so far have confirmed the neoclassical theory underlying several of the optimisation goals. At the same time, they showed that an optimisation is also required with respect to anomalous transport. In the future operational phases we aim at building a solid theoretical, experimental and technical foundation for the design of a next-step stellarator device.

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 & x0026;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 & x2019; 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.

Complex experiments such as the stellarator Wendelstein 7-X demand efficient experimental planning, operation, and data evaluation. To assist the process organization at W7-X, a metadata framework has been implemented. It annotates a physics program with tags describing its intention, main parameters, boundary conditions, and evaluation results. The approach enables relevant metadata to be collected exactly where information is available and to forward it from experimental planning and execution to the related entry in the central W7-X Logbook. In consequence, these metadata offer possibilities for classifying, searching, filtering, and so on, both in the database of the prepared programs and in the logbook of the executed programs. Wherever possible, metadata are generated automatically. Starting from the parameters of the program, the framework allows typical physics or technical quantities or any programmatically extractable information describing the programs intention to be extracted already while editing. During discharge preparation, metadata are retrieved from the related session planning documents and from the actual session environment. Supplementary tags can be added manually from an extendible tag catalog to categorize experimental programs or to provide metadata for not fully integrated diagnostics. All metadata are logged together with status and progress information during execution and are available within the program's log-where the metadata can be finally completed, for example, to manually qualify the success of the program or by adding programmatically produced metadata using the logbook's programming interface.

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.

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.

WENDELSTEIN 7-X is, as a stellerator, in principle capable of very long operation. The Control and Data-acquisition (comae) 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.

The Wendelstein 7-X stellarator experiment by its nature has the need for continuous live data monitoring. New technical and security related requirements make a redesign of the monitoring architecture, originating in the first years of the century, necessary. Besides that, new developments in technologies, user interfaces and generally IT supported work flows, generate new expectations at the system user level, including live remote participation. To answer these upcoming demands, the CoDaC team at Wendelstein 7-X has designed a new architecture for monitoring data management, distribution and observation. As a very flexible user interface, a client web application was developed, utilizing modern technologies like WebSockets and WebGL for high performance live data visualization. A touch friendly interface design offers both broad support for new access tools (like tablets, smart phones, smart TV sets) and a very flexible and intuitive work flow. This paper describes the new MonA-LISA monitoring architecture and gives a short overview over the options provided by the web based monitoring client.

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.

In 2015, the optimized stellarator Wendelstein 7-X stellarator (W7-X) started with operation. The main objective of W7-X is the demonstration of the integrated reactor potential of the optimized stellarator line. An important element of this mission is the achievement of high heating power and high confinement in the steady-state operation. The approach to this mission is the following three steps. First, plasmas were produced in a limiter configuration [operation phase (OP 1.1)], then a test divertor unit is being installed (temporary divertor unit) for the next campaign, OP 1.2, before the full steady-state capability will be achieved implementing active cooling of all in-vessel components and a steady-state high heat-flux divertor. In December 2015, the first helium plasma was generated using electron cyclotron resonance heating (ECRH), in February 2016, the working gas was switched to hydrogen. The first OP (OP 1.1) was successfully finished in March 2016. At the end of OP 1.1, the discharge duration was close to 6 s, the limit for the integrated heating power was increased to 4 MJ and electron temperatures of ~10 keV were achieved. Due to the low densities in the range of 1019 cm−3 and the pure electron heating by ECRH, the ion temperatures reached only 2 keV. At present, W7-X is undergoing the next completion phase, including the installation of the test divertor unit, the installation of the carbon tiles on the inner plasma vessel wall, an upgrade of existing diagnostics, and the installation of new diagnostics. This paper discusses the first operational phase, lessons learned and implemented, and the status before the start of the second OP (OP 1.2).

After completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning the device, first plasma operation started at the end of 2015. Integral commissioning of plasma start-up and operation using electron cyclotron resonance heating (ECRH) and an extensive set of plasma diagnostics have been completed, allowing initial physics studies during the first operational campaign. Both in helium and hydrogen, plasma breakdown was easily achieved. Gaining experience with plasma vessel conditioning, discharge lengths could be extended gradually. Eventually, discharges lasted up to 6 s, reaching an injected energy of 4 MJ, which is twice the limit originally agreed for the limiter configuration employed during the first operational campaign. At power levels of 4 MW central electron densities reached 3 x 10(19) m(-3), central electron temperatures reached values of 7 keV and ion temperatures reached just above 2 keV. Important physics studies during this first operational phase include a first assessment of power balance and energy confinement, ECRH power deposition experiments, 2nd harmonic O-mode ECRH using multi-pass absorption, and current drive experiments using electron cyclotron current drive. As in many plasma discharges the electron temperature exceeds the ion temperature significantly, these plasmas are governed by core electron root confinement showing a strong positive electric field in the plasma centre.