[en] Highlights: • The Magnum-PSI facility is available for plasma-material interaction studies. • Magnum-PSI is capable to reach relevant plasma parameters for the ITER divertor. • Particle fluxes over 10²⁵ m⁻²s⁻¹ and heat fluxes of up to 50 MW m⁻² are obtained. • Particle fluences of up to 10³⁰ particles m⁻² have been achieved. • Linear regression and artificial neural network analysis have been applied. -- Abstract: The Magnum-PSI facility is unique in its ability to produce and even exceed the heat and particle fluxes expected in the divertor of a fusion reactor, combined with good access to the plasma-material interaction region for diagnostics and relatively easy sample manipulation. In addition, it is possible to study the effects of transient heat loads on a plasma-facing surface, similar to those expected during so called Edge Localized Modes. By virtue of a newly installed superconducting magnet, Magnum-PSI can now maintain these conditions for hours on end for truly long term tests of candidate plasma facing materials. The electron density and temperature in the plasma beam center as a function of different magnetic fields up to 1.6 T, gas flow and source current are determined: particle fluxes greater than 10²⁵ m⁻²s⁻¹ and heat fluxes of up to 50 MW m⁻² are obtained. Linear regression and artificial neural network analysis have been used to gain insight in the general behavior of plasma conditions as a function of these machine settings. The plasma conditions during transient plasma heat loading have also been determined. These capabilities are now being exploited to reach fluence of up to 10³⁰ particles m⁻² at ITER-relevant conditions, equivalent to a significant fraction of the divertor service lifetime for the first time.

[en] Magnum-PSI is an advanced linear plasma device uniquely capable of producing plasma conditions similar to those expected in the divertor of ITER both steady-state and transients. The machine is designed both for fundamental studies of plasma–surface interactions under high heat and particle fluxes, and as a high-heat flux facility for the tests of plasma-facing components under realistic plasma conditions. To study the effects of transient heat loads on a plasma-facing surface, a novel pulsed plasma source system as well as a high power laser is available. In this article, we will describe the capabilities of Magnum-PSI for high-heat flux tests of plasma-facing materials

[en] A comparison is made between the critical current (I_c) versus bending strain and axial strain of superconducting multi-filamentary Bi₂Sr₂Ca₂Cu₃O_x (Bi-2223) AgMg sheathed tapes. For the bending strain measurement the tape is sandwiched between a curved base and cover plate. Six sets of bending plates introduce bending strains ranging from 0% to 1.0%. The measurements show a slight decrease in I_c after the first bending step after which the degradation becomes more pronounced. The I_c in a bent conductor is calculated assuming a linear axial strain profile inside the conductor. For this calculation the I_c degradation determined in an axial compression and elongation experiment is used. The model predicts an immediate decrease of I_c, caused by the compressive strain dependence. There is a good agreement (within 5%) between the measured data and the calculated values. Based on this good agreement it can be concluded that a possible shift in the neutral line or the formation of additional cracks due to bending has no significant influence on the I_c degradation. It is concluded that the influence of thermal contraction is crucial for a good calculation. (author)

[en] Highlights: • High heat flux, high density plasmas in a highly accessible linear plasma device. • Plasma exposure of targets of different sizes under selectable plasma beam angles. • Dedicated plasma and surface diagnostics. • Differential vacuum pumping system. -- Abstract: The construction phase of the linear plasma generator Magnum-PSI at the FOM institute DIFFER has been completed and the facility has been officially opened in March 2012. The scientific program to gain more insight in the plasma–wall interactions relevant for ITER and future fusion reactors has started. In Magnum-PSI, targets of a wide range of materials and shapes can be exposed to high particle, high heat flux plasmas (>10²⁴ ions m⁻² s⁻¹; >10 MW/m²). For magnetization of the plasma, oil-cooled electromagnets are temporarily installed to enable pulsed operation until the device is upgraded with a superconducting magnet. The magnets generate a field of up to 1.9 T close to the plasma source for a duration of 6 s. Longer exposure times are available for lower field settings. Plasma characterizations were done with a variety of gases (H, D, He, Ne and Ar) to determine the machine performance and prepare for subsequent scientific experiments. Thomson scattering and optical emission spectroscopy were used to determine the plasma parameters while infrared thermography and target calorimetry were used to determine the power loads to the surface. This paper reports on the status of Magnum-PSI and its diagnostic systems. In addition, an overview of the plasma parameters that can be achieved in the present state will be given

[en] Magnum-PSI is a linear plasma generator, built at the FOM-Institute for Plasma Physics Rijnhuizen. Subject of study will be the interaction of plasma with a diversity of surface materials. The machine is designed to provide an environment with a steady state high-flux plasma (up to 10²⁴ H⁺ ions/m² s) in a 3 T magnetic field with an exposed surface of 80 cm² up to 10 MW/m². Magnum-PSI will provide new insights in the complex physics and chemistry that will occur in the divertor region of the future experimental fusion reactor ITER and reactors beyond ITER. The conditions at the surface of the sample can be varied over a wide range, such as plasma temperature, beam diameter, particle flux, inclination angle of the target, background pressure and magnetic field. An important subject of attention in the design of the machine was thermal effects originating in the excess heat and gas flow from the plasma source and radiation from the target.

[en] Highlights: • The 2.5 T superconducting high flux plasma generator Magnum-PSI is presented. • The operational status of Magnum-PSI is presented. • ITER divertor relevant steady state heat flux (>10 MW m⁻²) has been achieved. • First high fluence (>2 × 10²⁸ m⁻²) plasma exposure experiments have been performed. • Magnum-PSI has been commissioned for magnetic fields up to 1.6 T. - Abstract: The interaction of intense plasma impacting on the wall of a fusion reactor is an area of high and increasing importance in the development of electricity production from nuclear fusion. In the Magnum-PSI linear device, an axial magnetic field confines a high density, low temperature plasma produced by a wall stabilized DC cascaded arc into an intense magnetized plasma beam directed onto a target. The experiment has shown its capability to reach conditions that enable fundamental studies of plasma-surface interactions in the regime relevant for fusion reactors such as ITER: 10²³–10²⁵ m⁻²s⁻¹ hydrogen plasma flux densities at 1–5 eV for tens of seconds by using conventional electromagnets. Recently the machine was upgraded with a superconducting magnet, enabling steady-state magnetic fields up to 2.5 T, expanding the operational space to high fluence capabilities for the first time. Also the diagnostic suite has been expanded by a new 4-channel resistive bolometer array and ion beam analysis techniques for surface analysis after plasma exposure of the target. A novel collective Thomson scattering system has been developed and will be implemented on Magnum-PSI. In this contribution, the current status, capabilities and performance of Magnum-PSI are presented.

[en] Using the tape-in-rectangular tube (TIRT) process, we have made multi-core Bi-2223/Ag tapes with various numbers of filaments (10-162), and with different filament architectures and orientations. We have measured the angular dependence of the transport current of the tape samples with 'parallel' and 'perpendicular' filaments. The transversal I_c distribution obtained by spatially resolved transport measurements ('magnetic knife') illustrates that the filament quality of the TIRT tapes is better at the tape edges than in the centre. The tapes were stressed by two types of tensioning set-up (a short straight sample and a U-shaped spring) and by bending at 77 K. The I_c degradation shows different behaviour for parallel and perpendicular filaments, which is attributed to the difference in filament density and crack propagation. (author)

[en] The FOM-Institute for Plasma Physics Rijnhuizen is constructing Magnum-PSI; a magnetized (3 T), steady-state, large area (80 cm²) high-flux (up to 10²⁴ H⁺ ions m^-2 s^-1) plasma generator. Magnum-PSI will be a highly accessible laboratory experiment in which the interaction of magnetized plasma with different surfaces can be studied. This experiment will provide new insights in the complex physics and chemistry that will occur in the divertor region of the future experimental fusion reactor ITER. Here, extremely high power and particle flux densities are predicted at relatively low plasma temperatures. Magnum-PSI will be able to simulate these detached ITER divertor conditions in detail. In addition, conditions can be varied over a wide range, such as different target materials, plasma temperatures, beam diameters, particle fluxes, inclination angles of target, background pressures, magnetic fields, etc., making Magnum-PSI an excellent test bed for high heat flux components of future fusion reactors. The design phase of the Magnum-PSI device has been completed. The construction and assembly phase of the device is in progress. In this contribution, we will present the design and construction of the Magnum-PSI experiment. The status of the vacuum system, the 3 T superconducting magnet, the plasma source, the target plate and manipulator, and additional plasma heating will be presented. The plasma and surface diagnostics that will be used in the Magnum-PSI experiment will be introduced.

[en] The PSI-laboratory at FOM-Rijnhuizen includes linear plasma generators reaching the ITER relevant strongly coupled limit of PSI and a surface analysis station. The largest plasma generator, Magnum-PSI, designed to provide a 10 cm diameter beam delivering <10 MW/m² power to a target at typically Te=1-5 eV and n_e<10²¹ m^-3, is presently under construction. A smaller prototype, Pilot-PSI is operational and has achieved record plasma parameters of n_e<4.10²¹ m^-2s^-1 with Te=1-5 eV, in a 1 cm wide beam confined by B<1.6T. The plasma source used in these experiments is a cascaded arc. At 17 mm from the target (0.5 m distance from the source), n_e>10²¹ m^-2s^-1 with Te>1 eV have been measured with Thomson scattering. Initial experiments on erosion of fine-grain carbon samples showed that up to 20 μm/s could be eroded. Numerical simulations with the B2-Eirene code confirm that in Magnum-PSI a 'detached divertor'-like condition will very likely be achieved. (author)

[en] Highlights: •We have described the design and capabilities of the plasma experiment Magnum-PSI. •The plasma conditions are well suited for PSI studies in support of ITER. •Quasi steady state heat fluxes over 10 MW m⁻² have been achieved. •Transient heat and particle loads can be generated to simulate ELM instabilities. •Lithium coating can be applied to the surfaces of samples under vacuum. -- Abstract: In Magnum-PSI (MAgnetized plasma Generator and NUMerical modeling for Plasma Surface Interactions), the high density, low temperature plasma of a wall stabilized dc cascaded arc is confined to a magnetized plasma beam by a quasi-steady state axial magnetic field up to 1.3 T. It aims at conditions that enable fundamental studies of plasma–surface interactions in the regime relevant for fusion reactors such as ITER: 10²³–10²⁵ m⁻² s⁻¹ hydrogen plasma flux densities at 1–5 eV. To study the effects of transient heat loads on a plasma-facing surface, a high power pulsed magnetized arc discharge has been developed. Additionally, the target surface can be transiently heated with a pulsed laser system during plasma exposure. In this contribution, the current status, capabilities and performance of Magnum-PSI are presented