سیستم زمان واقعی توزیع شده برای کنترل رویداد محور و اکتساب داده های پویا در یک آزمایش پلاسمای همجوشی

A distributed real-time trigger and timing system, designed in a tree-type topology and implemented in VME and CAMAC versions, has been developed for a magnetic confinement fusion experiment. It provides sub-microsecond time latencies for the transport of small data objects allowing event-driven discharge control with failure counteraction, dynamic pre-trigger sampling and event recording as well as accurate simultaneous triggers and synchronism on all nodes with acceptable optimality and predictability of timeliness. This paper describes the technical characteristics of the hardware components (central unit composed by one or more reflector crates, event and synchronism reflector cards, event and pulse node module, fan-out and fan-in modules) as well as software for both tests and integration on a global data acquisition system. The results of laboratory operation for several configurations and the overall performance of the system are presented and analysed.

The new generation of magnetic confinement fusion experiments aims at long-pulse or even steady state operation [1], [2], [3] and [4]. Control and data acquisition will be merged in a distributed real-time system permitting the implementation of dynamic experiment scheduling, event-driven discharge control with failure counteraction and dynamic data acquisition [5] and [6]. Such control and data acquisition system consists on multiple nodes sharing plasma state variables, that are propagated through the interconnections of a low time latency network, which provides support for management and transmission of prioritised signals, alarms, events and other objects as well as trigger scheduling and synchronism distribution. Actual network links are oriented for bulk transfer of data having time latencies of no less than tens of ms and provide no-deterministic propagation of triggers and synchronism. These restrictions limit real-time operation since results may not be attained with acceptable optimality and predictability of timeliness. Even multimedia-oriented links, with its reserved bandwidth for time-critical tasks, cannot fully satisfy the required performance. A distributed trigger and timing system (TTS) has been developed in order to fill this gap by providing sub-microsecond time latencies for the transport of small objects as well as providing accurate simultaneous triggers and synchronism on all nodes in a large experiment campus where previous timing systems architectures are unsuitable. The architecture and hardware components of this system are described elsewhere [7] and [8]. This paper is organised as follows: Section 2 includes a short description of the system; Section 3 presents the technical characteristics of the VME hardware components; Section 4 contains the test results; in Section 5 the software implementation is described and in Section 6 the conclusions are presented.

The VME versions of a distributed real-time trigger and timing system have been developed. Tests have showed that optimal time latencies in the microsecond scale have been attained as well as a predictable propagation of triggers and synchronism, thereby allowing real-time operation of the system. The adaptation of the hardware and software to the CAMAC standard is under development. Several enhancements can be done for current and future designs in order to reduce event propagation time, implement absolute time representation and to improve real-time programming of the system. These goals can be achieved using more powerful programmable logic devices. This system will be implemented on the MAST tokamak, presently under construction at Culham Laboratory.