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

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.