GaInSn, a eutectic alloy, has been successfully used in the Magneto-Thermofluid Research Laboratory at the University of California-Los Angeles and at the Princeton Plasma Physics Laboratory for the past six years. This paper describes the handling and safety of GaInSn based on the experience gained in these institutions, augmented by observations from other researchers in the liquid metal experimental community. GaInSn is an alloy with benign properties and shows considerable potential in liquid metal experimental research and cooling applications.

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GaInSn usage in the research laboratory

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.

MARTe: A Multiplatform Real-Time Framework

This review of the potential of robust plasma facing components (PFCs) with liquid surfaces for applications in future D/T fusion device summarizes the critical issues for liquid surfaces and research being done worldwide in confinement facilities, and supporting R&D in plasma surface interactions. In the paper are a set of questions and related criteria by which we will judge the progress and readiness of liquid surface PFCs. Part-II (separate paper) will cover R&D on the technology-oriented aspects of liquid surfaces including the liquid surfaces as integrated first walls in tritium breeding blankets, tritium retention and recovery, and safety.

Liquid surfaces for fusion plasma facing components—A critical review. Part I: Physics and PSI

Although the use of solid materials as targets of divertor plasmas in magnetic fusion research is accepted as the standard solution for the very challenging issue of power and particle handling in a fusion reactor, a generalized feeling that the present options chosen for ITER will not represent the best choice for a reactor is growing up. The problems found for tungsten, the present selection for the divertor target of ITER, in laboratory tests and in hot plasma fusion devices suggest so. Even in the absence of the strong neutron irradiation expected in a reactor, issues like surface melting, droplet ejection, surface cracking, dust generation, etc., call for alternative solutions in a long pulse, high efficient fusion energy-producing continuous machine. Fortunately enough, decades of research on plasma facing materials based on liquid metals (LMs) have produced a wealth of appealing ideas that could find practical application in the route to the realization of a commercial fusion power plant. The options presently available, although in a different degree of maturity, range from full coverage of the inner wall of the device with liquid metals, so that power and particle exhaust together with neutron shielding could be provided, to more conservative combinations of liquid metal films and conventional solid targets basically representing a sort of high performance, evaporative coating for the alleviation of the surface degradation issues found so far. In this work, an updated review of worldwide activities on LM research is presented, together with some open issues still remaining and some proposals based on simple physical considerations leading to the optimization of the most conservative alternatives.

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Present status of liquid metal research for a fusion reactor

Fusion energy conversion in magnetically confined plasma reactors

Interaction of a liquid gallium jet with the tokamak ISTTOK edge plasma

e-lab is a remote laboratory which provides the control of real physics experiments over the internet. The robustness of the laboratory framework has allowed the implementation of new experiments outside the main physical laboratory, for instance in high schools and science centres. To reduce costs and the number of maintenance interventions, a new and simple hardware platform to access and control the remote experiment, including video encoding and streaming was developed over the Raspberry Pi computer. Such hardware platform and network implementations are presented in this paper as a case study of a new hydrostatic e-lab experiment. The solution has been bench-marked against previous hardware configurations and proved to be adequate for the given purpose.

Distributed e-lab setup based on the Raspberry Pi: The hydrostatic experiment case study

The achievement of long duration, alternating current discharges on the tokamak IST‐TOK requires a real‐time plasma position control system. The plasma position determination based on magnetic probes system has been found to be inadequate during the current inversion due to the reduced plasma current. A tomography diagnostic has been therefore installed to supply the required feedback to the control system. Several tomographic methods are available for soft X‐ray or bolo‐metric tomography, among which the Cormack and Neural networks methods stand out due to their inherent speed of up to 1000 reconstructions per second, with currently available technology. This paper discusses the application of these algorithms on fusion devices while comparing performance and reliability of the results. It has been found that although the Cormack based inversion proved to be faster, the neural networks reconstruction has fewer artifacts and is more accurate.

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Fast tomographic methods for the tokamak ISTTOK

Liquid gallium jet–plasma interaction studies in ISTTOK tokamak

e-lab is a remote laboratory infrastructure that provides access to several distinct experiments that may be performed independently. A new experiment to be introduced in this remote laboratory is our first geographically distributed experiment: the World Pendulum. It consists in multiple identical pendulum apparatuses connected to e-lab and scattered throughout different locations across several countries. The World Pendulum is intended at exploring a unique feature allowed by remote experimentation - experimental repetition in different locations. This demonstration aims at presenting the e-lab interface and its main features as well as exploring the new World Wide distributed Pendulum experiment.

T. Pereira

Papers

Interaction of a liquid gallium jet with the tokamak ISTTOK edge plasma

Distributed e-lab setup based on the Raspberry Pi: The hydrostatic experiment case study

Fast tomographic methods for the tokamak ISTTOK

Liquid gallium jet–plasma interaction studies in ISTTOK tokamak

World wide remote distributed experiment on e-lab