Jörg Schacht

A trigger-time-event system for the W7-X experiment

Abstract All control and data acquisition systems of the WENDELSTEIN 7-X (W7-X) fusion experiment need to be perfectly synchronised with an accuracy of ⩽10 ns. Another essential requirement is to process and record events and trigger signals in such a way that they can be used for real-time control. This paper describes the architecture of a trigger–time–event (TTE) system for the W7-X experiment and gives an overview of the characteristics of the special board of the local TTE units. The main components of the board are a local oscillator synchronised by a central timing unit, and a field programmable gate array (FPGA). The FPGA comprises an event and trigger command receiver/decoder, a local 64-bit time counter, time capture registers, delay devices, a programmable state machine, trigger generators, and a programmable switch matrix, which allows output and input signals of the devices to be interconnected. The time, fast trigger, and event information are distributed from the central timing unit to the local TTE boards via a tree-type optical network. For hardware trigger signals an electrical network may be used. The board has configurable I/O ports for trigger signals and a 64-bit time port.

Control system of WENDELSTEIN 7-X experiment

Abstract The WENDELSTEIN 7-X stellarator will be capable of running pulses of up to 30 min duration. The control system of W7-X will support all discharge scenarios compatible with this capability, i.e. short pulses with arbitrary intervals, steady state discharges, and arbitrary sequences of phases with different characteristics (“segments”) in one discharge. The use of segments substantially reduces the time required for parameter scans and permits short tests of new settings without interfering with the main programme. The hierarchical layout of the control system will reflect the structure of the experimental device. Each technical component and each diagnostic system including its data acquisition will have its own control system permitting autonomous operation for commissioning and testing. The activity of these devices will be co-ordinated by a master control during the experimental sessions. System parameters where relevant to the experiment, will be exclusively controlled by complex software objects. By synchronous changing references to these objects in all computers the whole system behaviour can be modified from one cycle to the next. This allows to switch between segments or to the end of the discharge. The switching may be determined by fixed timing, by logical conditions, or by operator action.

A "Universal Time" system for ASDEX Upgrade

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.

Synchronization of processes in a distributed real time system exemplified by the control system of the fusion experiment WENDELSTEIN 7-X

The fusion experiment Wendelstein 7-X demands synchronizing processes in many distributed technical components with an accuracy from milliseconds to nanoseconds. For this purpose a Trigger-Time-Event system (TTE system) was developed. Its main task is the synchronization of all control components and data acquisition systems. It allows time stamping, processing of trigger signals and event messages. The TTE system offers the possibility to program timing sequences and delays, logic combinations or conditions. After a description of the TTE system the task synchronization in the control system of WENDELSTEIN 7-X is discussed. A special software library (TimeLib) allows dealing with time related variables in a simple and comfortable manner. The efficiency of the synchronization system is exemplified

The WEGA Stellarator: Results and Prospects

In this article an overview is given on results from magnetic flux surface measurements, applied ECR heating scenarios for 2.45 GHz and 28 GHz, fluctuation and transport studies and plasma edge biasing experiments performed in the WEGA stellarator. Examples for the development of new diagnostics and the machine control system are given that will be used at Wendelstein 7-X stellarator, which is currently under construction in Greifswald.

Cutting edge concepts for control and data acquisition for Wendelstein 7-X

Wendelstein 7-X is intended to demonstrate steady state high performance plasma operation and to explore the physics basis of the Helias reactor concept. From there, the W7-X CoDaC concepts aim for steady state plasma stabilization at favorite operation points and largely or even fully documented plasma experiments for achieving efficiently scientific results. Several concepts are being employed that are not common to the fusion research so far. The plasma control system is based on segments consisting of control parameters and transition conditions to other segments. The data acquisition system aims at streaming all acquired data for archiving, control and monitoring purposes and tries to prevent early data reduction. This leads to data streaming rates of up to 30 GBytes/s during plasma operation of up to half an hour. The data analyses framework is intended to support largely automation with analyses chains based on service oriented architectures. A coupling to real time systems is envisaged later in the project for solving complex control problems. The envisaged model based data analyses rely on the existence of unanalyzed raw data in combination with a systematic documentation of the experimental setup, in particular for the diagnostics.

Multifunction-timing card lTTEV2 for CoDaC systems of Wendelstein 7-X

The timing system is a crucial element for the Control, Data Acquisition, and Communication (CoDaC) system of the steady-state fusion experiment Wendelstein 7-X (W7-X). Its main task is the synchronization of all clocks with sufficient accuracy. Furthermore, it is able to send, receive, and process event messages. It offers a wide range of time-related functions, e.g., time capturing, pulse generation, realization of time delays, and sending and receiving of trigger signals. The overall timing system consists of a central timing system and a considerable number of local timing systems. A revision of the existing local Trigger Time Event card version (1lTTEV1) card and Time-to-Digital Converter (TDC) card was necessary as many components used for their fabrication were no longer available. The need for a bus interface for the lTTE card with long term availability has led to the decision to use a GBit Ethernet interface. By choosing a more powerful FPGA device, it was possible to increase the time resolution by a factor of two. This contribution starts with a short introduction of the W7-X timing system. The key properties, all extended as well as new features of the lTTEV2 card to face new requirements regarding data acquisition are described. The actual state of the development is given.

Synchronization of Processes in a Distributed Real Time System Exemplified by the Control System of the Fusion Experiment WENDELSTEIN 7-X

The fusion experiment Wendelstein 7-X demands synchronizing processes in many distributed technical components with an accuracy from milliseconds to nanoseconds. For this purpose a Trigger-Time-Event system (TTE system) was developed. Its main task is the synchronization of all control components and data acquisition systems. It allows time stamping, processing of trigger signals and event messages. The TTE system offers the possibility to program timing sequences and delays, logic combinations or conditions. After a description of the TTE system the task synchronization in the control system of WENDELSTEIN 7-X is discussed. A special software library (TimeLib) allows dealing with time related variables in a simple and comfortable manner. The efficiency of the synchronization system is exemplified

A new concept for experiment program planning for the fusion experiment Wendelstein 7-X

The control and data acquisition system (CODAC system) for the fusion experiment Wendelstein 7-X is designed for miscellaneous operational scenarios: short pulses with arbitrary intervals, steady-state long pulse operation and arbitrary sequences of short phases with different characteristics in one discharge. The data structures for a description of experiment runs are very complex and comprehensive. A special editor is necessary to guide the user through the different phases of experiment program planning. A more abstract and physics-oriented description of the required machine and plasma behaviour is a suitable way to handle the complexity and to make the experiment program definition process effective and easier. This contribution introduces a concept for experiment planning based on a so called segment program boxes (SEGPROGBOX). The planned work flow of the experiment program creation will be discussed after an introduction of the SEGPROGBOX design.