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The ITER Heating Neutral Beam injectors will be implemented in three steps: development of the ion source prototype, development of the full injector prototype, and, finally, construction of up to three ITER injectors. The first two steps will be carried out in the ITER neutral beam test facility under construction in Italy. The ion source prototype, referred to as SPIDER, which is currently in the development phase, is a complex experiment involving more than 20 plant units and operating with beam-on pulses lasting up to 1 h. As for control and data acquisition it requires fast and slow control (cycle time around 0.1 ms and 10 ms, respectively), synchronization (10 ns resolution), and data acquisition for about 1000 channels (analogue and images) with sampling frequencies up to tens of MS/s, data throughput up to 200 MB/s, and data storage volume of up to tens of TB/year. The paper describes the architecture of the SPIDER control and data acquisition system, discussing the SPIDER requirements and the ITER CODAC interfaces and specifications for plant system instrumentation and control.

The real-time control system of RFX-mod, in operation since 2005, has been successful and has allowed several important achievements in the RFX physics research program. As a consequence of this fact, new control algorithms are under investigation, which are more demanding in terms of both enhanced computing power and reduced system latency, currently around 1.5 ms. For this reason, a major upgrade of the system is being considered, and a new architecture has been proposed, taking advantage of the rapid evolution of computer technology in the last years. The central component of the new architecture is a Linux-based multicore server, where individual cores replace the VME computers. The server is connected to the I/O via PCI-e based bus extenders, and every PCI-e connection is managed by a separate core. The system is supervised by MARTe, a software framework for real-time applications written in C++ and developed at JET and currently used for the JET vertical stabilization and in other fusion devices.

We adopt a model of a real-time distributed network where the synchronization is done by an external timing network that triggers the acquisitions. A Switched Ethernet is used to send the synchronously sampled data from nodes to nodes to perform the distributed control algorithm. In order to guarantee low latencies and jitter, the traffic on the Switched Ethernet must be carefully analyzed to be able to correctly model closed-loop systems and potentially identify events that might lead to large delays or even packet losses. In this paper we discuss the most relevant results from a testbed control network with synchronous data acquisition nodes. A switched Gigabit Ethernet is adopted and each node uses RTnet running in a RTAI/Linux Operating System. To resolve the problem of timing uncertainties at the data link layer, we propose a new custom solution based on a TDMA discipline.

The Ion Source experiment, called SPIDER, is the first experiment to be realized in the ITER Neutral Beam Test Facility under construction at Consorzio RFX, Padova, Italy. Its data acquisition system will provide the collection of around one thousand signals at a sampling rate ranging from a few S/s to 10 MS/s and of diagnostics and inspection images produced at a frame frequency from 10 to 150 frame per second, for beam durations of up to one hour. As the final product of the Test Facility will be the ITER Heating Neutral Beam Injector, we decided to follow the ITER CODAC guidelines. Therefore, the EPICS system provided in the CODAC Core System has been assessed and adopted in plant control. In addition to EPICS, the MDSplus system will be adopted for the overall data management. MDSplus can handle a rich set of data types and offers support for both local and remote data access in a variety of languages, a feature not fully supported by EPICS. All experiment data in SPIDER will be maintained in a single MDSplus database containing both experiment configuration and acquired data. The seamless integration of EPICS and MDSplus in a single system requires the development of some new tools, namely: A Channel Archiver which provides storage into MDSplus pulse files of data produced by EPICS Input Output Controllers (IOC) and exported as Process Variables via Channel Access; A set of IOC records providing direct access from IOC into MDSPlus files; A Channel Access Server to export MDSplus data as EPICS Process Variables, making them directly accessible by IOCs. We expect that the integration of the two frameworks will result in a system that combines the best features from each one, i.e., the management of distributed Process Variables and the IOC concept for EPICS, the sophisticated data management and remote access for MDSplus.

The PCU-Project [1] launched for the enhancement of the vertical stabilisation system at JET required the design of a new real-time control system with the challenging specifications of 2 Gops and a cycle time of 50 μ s. The RTAI based architecture running on an x86 multi-core processor technology demonstrated to be the best platform for meeting the high requirements. Moreover, on this architecture thanks to the smart allocation of the interrupts it was possible to demonstrate simultaneous data streaming at 50 MBs on Ethernet while handling a real-time 100 kHz interrupt source with a maximum jitter of just 3 μ s. Because of the memory limitation imposed by 32 bit version Linux running in kernel mode, the RTAI-based new controller allows a maximum practical data storage of 800 MB per pulse. While this amount of data can be accepted for JET normal operation it posed some limitations in the debugging and commissioning of the system. In order to increase the capability of the data acquisition of the system we have designed a mechanism that allows continuous full bandwidth ( 56 MB/s) data streaming from the real-time task (running in kernel mode) to either a data collector (running in user mode) or an external data acquisition server. The exploited architecture involves a peer to peer mechanisms where the sender running in RTAI kernel mode broadcasts large chunks of data using UDP packets, implemented using the ‘fcomm’ RTAI extension [2] , to a receiver that will store the data. The paper will present the results of the initial RTAI operating system tests, the design of the streaming architecture and the first experimental results.

The Plasma Control Upgrade (PCU) enhancement project was setup with the aim of effectively increasing the JET operating space by both improving the Vertical Stabilization System Controller and by procuring a more powerful Radial Field Amplifier. The hardware and software technological advancements that have been used allowed to implement a 200 channel, 20 kHz control system with less than 2 μ s jitter and over 2 G o p s of processing capability. The software design, driven by an object oriented analysis, enabled a good compromise between real-time performances and reliability–maintainability objectives. The first operational experience of the system will be presented.

A new framework for the development and execution of real-time codes is currently being developed and commissioned at JET. The foundations of the system are Linux, the Real Time Application Interface (RTAI) and a wise exploitation of the new i386 multi-core processors technology. The driving motivation was the need to find a real-time operating system for the i386 platform able to satisfy JET Vertical Stabilisation Enhancement project requirements: 50 μs cycle time. Even if the initial choice was the VxWorks operating system, it was decided to explore an open source alternative, mostly because of the costs involved in the commercial product. The work started with the definition of a precise set of requirements and milestones to achieve: Linux distribution and kernel versions to be used for the real-time operating system; complete characterization of the Linux/RTAI real-time capabilities; exploitation of the multi-core technology; implementation of all the required and missing features; commissioning of the system. Latency and jitter measurements were compared for Linux and RTAI in both user and kernel-space. The best results were attained using the RTAI kernel solution where the time to reschedule a real-time task after an external interrupt is of 2.35 ± 0.35 μs. In order to run the real-time codes in the kernel-space, a solution to provide user-space functionalities to the kernel modules had to be designed. This novel work provided the most common functions from the standard C library and transparent interaction with files and sockets to the kernel real-time modules. Kernel C++ support was also tested, further developed and integrated in the framework. The work has produced very convincing results so far: complete isolation of the processors assigned to real-time from the Linux non real-time activities, high level of stability over several days of benchmarking operations and values well below 3 μs for task rescheduling after external interrupt. From being the alternative option, RTAI has been finally chosen as the platform for the project. A first stable version of the framework has been integrated on the JET system and is already being commissioned. It will be soon be used on the Vertical Stabilisation Enhancement for the Plasma Control Upgrade (PCU) project at JET.

SPIDER, the ITER-size ion-source test bed in the ITER Neutral Beam Test Facility, is a fusion device requiring a complex central system to provide control and data acquisition, referred to as CODAS. The CODAS software architecture will rely on EPICS and MDSplus, two open-source, collaborative software frameworks, targeted at control and data acquisition, respectively. EPICS has been selected as ITER CODAC middleware and, as the final deliverable of the Neutral Beam Test Facility is the procurement of the ITER Heating Neutral Beam Injector, we decided to adopt this ITER technology. MDSplus is a software package for data management, supporting advanced concepts, such as platform and underlying hardware independence, self description data, and data driven model. The combined use of EPICS and MDSplus is not new in fusion, but their level of integration will be new in SPIDER, achieved by a more refined data access layer. The paper presents the integration software to use effectively EPICS and MDSplus, including the definition of appropriate EPICS records to interact with MDSplus. The MDSplus and EPICS archive concepts are also compared on the basis of performance tests and data streaming is investigated by ad-hoc measurements.

The Multithreaded Application Real-Time executor (MARTe) is a data driven framework environment for the development and deployment of real-time control algorithms. The main ideas which led to the present version of the framework were to standardise the development of real-time control systems, while providing a set of strictly bounded standard interfaces to the outside world and also accommodating a collection of facilities which promote the speed and ease of development, commissioning and deployment of such systems. At the core of every MARTe based application, is a set of independent inter-communicating software blocks, named Generic Application Modules (GAM), orchestrated by a real-time scheduler. The platform independence of its core library provides MARTe the necessary robustness and flexibility for conveniently testing applications in different environments including non-real-time operating systems. MARTe is already being used in several machines, each with its own peculiarities regarding hardware interfacing, supervisory control configuration, operating system and target control application. This paper presents and compares the most recent results of systems using MARTe: the JET Vertical Stabilisation system, which uses the Real Time Application Interface (RTAI) operating system on Intel multi-core processors; the COMPASS plasma control system, driven by Linux RT also on Intel multi-core processors; ISTTOK real-time tomography equilibrium reconstruction which shares the same support configuration of COMPASS; JET error field correction coils based on VME, PowerPC and VxWorks; FTU LH reflected power system running on VME, Intel with RTAI.

EPICS is used worldwide mostly for controlling accelerators and large experimental physics facilities. Although EPICS is well fit for the design and development of automation systems, which are typically VME or PLC-based systems, and for soft real-time systems, it may present several drawbacks when used to develop hard real-time systems/applications especially when general purpose operating systems as plain Linux are chosen. This is in particular true in fusion research devices typically employing several hard real-time systems, such as the magnetic control systems, that may require strict determinism, and high performance in terms of jitter and latency. Serious deterioration of important plasma parameters may happen otherwise, possibly leading to an abrupt termination of the plasma discharge. The MARTe framework has been recently developed to fulfill the demanding requirements for such real-time systems that are alike to run on general purpose operating systems, possibly integrated with the low-latency real-time preemption patches. MARTe has been adopted to develop a number of real-time systems in different Tokamaks. In this paper, we first summarize differences and similarities between EPICS IOC and MARTe. Then we report on a set of performance measurements executed on an x86 64 bit multicore machine running Linux with an IO control algorithm implemented in an EPICS IOC and in MARTe.

The paper addresses two important aspects: event-driven data acquisition and accurate timing reconstruction. Event-driven data acquisition allows reducing the requirements in data storage and transfer bandwidth retaining at the same time all the necessary information for a proper reconstruction of acquired signals. In many cases, in fact, the required bandwidth in data acquisition is not constant, being higher only in correspondence of particular events during the discharge. Event detection is performed in real time and the system has to guarantee a higher sampling speed in a time window centered on the event occurrence. Possible technological solutions are discussed and a new “soft trigger” approach is suggested, which allows using the same hardware for both low and high sampling speed acquisition, as well as using the general network for event transmission in place of dedicated links. Accurate timing reconstruction of acquired signals is necessary, regardless of the duration of the discharge. Care is then required in the implementation of timing systems in order to ensure both time stability and reliability over the whole plasma discharge, and possibly over the whole experiment lifetime. The typical architecture for such systems is based on a GPS clock generator that is connected to all data acquisition devices via a dedicated fiber-optics link carrying the synchronization clock. The paper introduces a different approach in timing reconstruction using IEEE 1588, a recent standard for accurate time synchronization, and discusses its potentialities and limits in data acquisition systems.

The paper discusses the requirements and presents an architectural overview of a new general-purpose framework for real-time control, currently under development at the RFX laboratory. This represents the third generation of control framework developed at RFX. It takes into account the experience gained in the development of the previous frameworks and exploits the evolution of computer technology, in particular, the evolution of Linux towards real-time functionality and the availability of multicore CPUs in most general-purpose computing boards. The framework will supervise data flow among the participating components, which may produce data, consume data, or apply some sort of computation. Some system components have been already developed, while the architecture of others is still being refined. In particular, we are going to integrate the infrastructure layer of the new framework with a real-time framework recently in use at JET. The aim of this collaboration is a general purpose real-time system which can be used on both experiments.

The Multithreaded Application Real-Time executor (MARTe) software provides an environment for the hard real-time execution of codes while leveraging a standardized algorithm development process. The Experimental Physics and Industrial Control System (EPICS) software allows the deployment and remote monitoring of networked control systems. Channel Access (CA) is the protocol that enables the communication between EPICS distributed components. It allows to set and monitor process variables across the network belonging to different systems. The COntrol and Data Acquisition and Communication (CODAC) system for the ITER Tokamak will be EPICS based and will be used to monitor and live configure the plant controllers. The reconfiguration capability in a hard real-time system requires strict latencies from the request to the actuation and it is a key element in the design of the distributed control algorithm. Presently, MARTe and its objects are configured using a well-defined structured language. After each configuration, all objects are destroyed and the system rebuilt, following the strong hard real-time rule that a real-time system in online mode must behave in a strictly deterministic fashion. This paper presents the design and considerations to use MARTe as a plant controller and enable it to be EPICS monitorable and configurable without disturbing the execution at any time, in particular during a plasma discharge. The solutions designed for this will be presented and discussed.

Real-time control applications will benefit in the near future from the enhanced performance provided by multi-core processor architectures. Nevertheless real-time communication will continue to be critical in distributed plasma control systems where the plant under control typically is distributed over a wide area. At RFX-mod real-time communication is crucial for hard real-time plasma control, due to the distributed architecture of the system, which consists of several VMEbus stations. The system runs under VxWorks and uses Gigabit Ethernet for sub-millisecond real-time communication. To optimize communication in the system, a set of detailed measurements has been carried out on the target platforms (Motorola MVME5100 and MVME5500) using either the VxWorks User Datagram Protocol (UDP) stack or raw communication based on the data link layer. Measurements have been carried out also under Linux, using its UDP stack or, in alternative, RTnet, an open source hard real-time network protocol stack. RTnet runs under Xenomai or RTAI, two popular real-time extensions based on the Linux kernel. The paper reports on the measurements carried out and compares the results, showing that the performance obtained by using open source code is suitable for sub-millisecond real-time communication in plasma control.

We report on a set of performance measurements executed on VMEbus MVME5500 boards equipped with MPC7455 PowerPC processor, running four different operating systems: Wind River VxWorks, Linux, RTAI, and Xenomai. Some components of RTAI and Xenomai have been ported to the target architecture. Interrupt latency, rescheduling and inter-process communication times are compared in the framework of a sample real-time application. Performance measurements on Gigabit Ethernet network communication have also been carried out on the target boards. To this purpose, we have considered the Linux IP stack and RTnet, an open-source hard real-time network protocol stack for Xenomai and RTAI, which was ported to the considered architecture. Performance measurements show that the tested open-source software is suitable for hard real-time applications.

Development of real-time applications is usually associated with nonportable code targeted at specific real-time operating systems. The boundary between hardware drivers, system services, and user code is commonly not well defined, making the development in the target host significantly difficult. The Multithreaded Application Real-Time executor (MARTe) is a framework built over a multiplatform library that allows the execution of the same code in different operating systems. The framework provides the high-level interfaces with hardware, external configuration programs, and user interfaces, assuring at the same time hard real-time performances. End-users of the framework are required to define and implement algorithms inside a well-defined block of software, named Generic Application Module (GAM), that is executed by the real-time scheduler. Each GAM is reconfigurable with a set of predefined configuration meta-parameters and interchanges information using a set of data pipes that are provided as inputs and required as output. Using these connections, different GAMs can be chained either in series or parallel. GAMs can be developed and debugged in a non-real-time system and, only once the robustness of the code and correctness of the algorithm are verified, deployed to the real-time system. The software also supplies a large set of utilities that greatly ease the interaction and debugging of a running system. Among the most useful are a highly efficient real-time logger, HTTP introspection of real-time objects, and HTTP remote configuration. MARTe is currently being used to successfully drive the plasma vertical stabilization controller on the largest magnetic confinement fusion device in the world, with a control loop cycle of 50 ?s and a jitter under 1 ?s. In this particular project, MARTe is used with the Real-Time Application Interface (RTAI)/Linux operating system exploiting the new ?86 multicore processors technology.