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At FOM Rijnhuizen, linear plasma generators are used to investigate plasma-material interactions under high-density (≤1021 m -3), low-temperature (≤5 eV) plasma bombardment. Research into carbon-based materials has been focused on chemical erosion by hydrogen plasmas. Results from plasma exposure to high-flux (>1023 H +/m2 s) and low-temperature hydrogen plasma indicate silicon carbide has a lower relative rate of gross erosion than other carbon-based materials (e.g. graphite, diamond, carbon-fiber composites) by a factor of 7-10. Hydrogenic retention is the focus of research on tungsten and molybdenum. For target temperatures of 700-1600 K, the temperature dependence of hydrogenic retention is the dominant factor. Damage to the surface by heavy ion irradiation has shown to enhance retention by a factor of 2.5-4.1. Thermal stressing of W via. e-beam thermal cycling also enhances hydrogenic retention by a factor of 2.1 ± 0.2, likely due to the introduction of thermal defects, which act as trapping sites for implanted hydrogenic isotopes.

New linear plasma devices are currently being constructed or planned in the Trilateral Euregio Cluster (TEC) to meet the challenges with respect to plasma surface interactions in DEMO and ITER: i) MAGNUM-PSI (FOM), a high particle and power flux device with super-conducting magnetic field coils which will reach ITER-like divertor conditions at high magnetic field, ii) the newly proposed linear plasma device JULE-PSI (FZJ), which will allow to expose toxic and neutron activated target samples to ITER-like fluences and ion energies including in vacuo analysis of neutron activated samples, and iii) the plasmatron VISION I. a compact plasma device which will be operated inside the tritium lab at SCK-CEN Mol, capable to investigate tritium plasmas and moderately activated wall materials. This contribution shows the capabilities of the new devices and their forerunner experiments (Pilot-PSI at FOM and PSI-2 Julich at FZJ) in view of the main objectives of the new TEC program on plasma surface interactions. (C) 2011 Forschungszentrum Julich, Institut fur Energieforschung-Plasmaphysik. Published by Elsevier B.V. All rights reserved.

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 1 024 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. © 2010.

The FOM-Institute for Plasma Physics Rijnhuizen is preparing the construction of 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. The aim of the linear plasma device Magnum-PSI is to provide a controlled, highly accessible laboratory experiment in which the interaction of a magnetized plasma with different surfaces can be studied in detail. Plasma parameters can be varied over a wide range, in particular covering the high-density, low-temperature conditions expected for the detached divertor plasma of ITER. The target set-up will be extremely flexible allowing the investigation of different materials under a large variety of conditions (temperatures, inclination, biasing, coatings, etc.). A range of target materials will be used, including carbon, tungsten and other metals, and mixed materials. Because of the large plasma beam of 10 cm diameter and spacious vacuum tank, even the test of whole plasma-facing component mock-ups will be possible. In this article, we will present the pre-design of the Magnum-PSI experiment. We will focus on the requirements of the vacuum system and the 3 T superconducting magnet. We briefly introduce some of the other sub-systems on Magnum-PSI such as the target and target manipulator.

FOM-Rijnhuizen is building, in cooperation with its Trilateral Euregio Cluster (TEC) partners, a PSI-laboratory to study plasma surface interaction (PSI) under extreme, ITER relevant plasma conditions. The largest linear plasma generator of PSI-lab is Magnum-PSI, and is designed to deliver up to 10 MW m-2 power over a 10 cm diameter hydrogen plasma beam with an electron density (ne) up to 1021 m-3 and electron-temperature (Te) between 1–5 eV. Magnum-PSI is presently under construction and its predesign is presented. Its forerunner is Pilot-PSI, in which record plasma parameters of ne=4×1021 m-3 at Te=2 eV in a ~1 cm wide hydrogen beam confined by a magnetic field (B) =1.6 T were measured at 40 mm downstream the source nozzle. At 17 mm in front of a target (located at 0.56 m distance from the source nozzle), ne>1021 m-3 and Te= 4 eV have been demonstrated. Initial experiments on exposing fine-grain carbon samples are presented that showed up to 20 µm s-1 erosion as a demonstration of the extreme plasma conditions. Spectroscopy was applied to compare chemical erosion yields for flux densities up to 5.0×1024 m-2 s-1.

The decreasing availability of energy and the concern about climate change necessitate the development of novel sustainable energy sources. Fusion energy is such a source. The ultimate potential of fusion energy is very high and badly needed. A major step forward in the development of fusion energy is the decision to construct the experimental test reactor ITER. ITER will stimulate research in many areas of science. This article discusses research opportunities in the context of plasma–surface interaction. The fusion plasma with a typical temperature of 10 keV has to be brought into contact with a physical wall in order to remove the helium produced and drain the excess energy in the fusion plasma. The fusion plasma is far too hot to be brought into direct contact with a physical wall. It would degrade the wall and the debris from the wall would extinguish the plasma. Therefore, schemes are developed to cool down the plasma. The resulting plasma–surface interaction concerned in ITER is facing several challenges including surface erosion, material redeposition and tritium retention. In this article we introduce how plasma–surface interaction relevant for ITER can be studied in a smaller scale experiment: Magnum-PSI.

The direct simulation Monte Carlo (DSMC) method was used to investigate the efficiency of differential pumping in linear plasma generators operating at high gas flows. Skimmers are used to separate the neutrals from the plasma beam, which is guided from the source to the target by a strong axial magnetic field. In this way, the neutrals are prevented to reach the target region. The neutral flux to the target must be lower than the plasma flux to enable ITER relevant plasma-surface interaction (PSI) studies. It is therefore essential to control the neutral gas dynamics. The DSMC method was used to model the expansion of a hot gas in a low pressure vessel where a small discrepancy in shock position was found between the simulations and a well-established empirical formula. Two stage differential pumping was modeled and applied in the linear plasma devices Pilot-PSI and PLEXIS. In Pilot-PSI a factor of 4.5 pressure reduction for H2 has been demonstrated. Both simulations and experiments showed that the optimum skimmer position depends on the position of the shock and therefore shifts for different gas parameters. The shape of the skimmer has to be designed such that it has a minimum impact on the shock structure. A too large angle between the skimmer and the forward direction of the gas flow leads to an influence on the expansion structure. A pressure increase in front of the skimmer is formed and the flow of the plasma beam becomes obstructed. It has been shown that a skimmer with an angle around 53° gives the best performance. The use of skimmers is implemented in the design of the large linear plasma generator Magnum-PSI. Here, a three stage differentially pumped vacuum system is used to reach low enough neutral pressures near the target, opening a door to PSI research in the ITER relevant regime. © 2009 American Institute of Physics. U7 - Export Date: 24 March 2010 U7 - Source: Scopus U7 - Art. No.: 063307

A new cascaded arc containing three separate discharge channels at 15 mm distance from each other was constructed to produce intense and wide hydrogen plasma beams and first tests were carried out at Pilot-PSI. Current and voltage measurements as well as calorimetry on the cooling water of the source demonstrated that these channels operated independently. Thomson scattering measurements showed that, depending on the nozzle geometry, the three outputs merge to one beam if the source is operated at argon in magnetic fields up to 1.6T densities. In hydrogen operation, the individual outputs did not merge or interact. Also a first test was performed in argon on the use of a remote ring anode to induce beam mixing due to rotation driven by cross-B currents. (C) 2009 Elsevier B.V. All rights reserved.

A high flux cascaded arc hydrogen plasma source is being developed for the linear plasma generator Magnum-PS I (magnetised plasma generator and numerical modeling for plasma surface interaction studies). Magnum-PSI will be the heart of the PSI-lab at the FOM-Institute for Plasma Physics Rijnhuizen and is being developed to investigate PSI issues for ITER. Especially the wall material of the so-called divertor of ITER, which is the region where plasma and impurities are neutralized and pumped off, will receive unprecedented particle and power loads. The expected numbers are: particle fluxes of up to 1024 ions/m2s and power loads of up to 10 MW/m2. We have demonstrated that it is possible to produce such conditions in a linear plasma generator with a cascaded arc in a magnetic field of 1.6 T2. The diameter of the plasma beam in these experiments was typically 20 mm. For Magnum-PSI, we envisage a beam diameter of 10 cm in order to enter the strongly coupled regime of PSI research. In this contribution we investigate the production of larger beam diameters by combining the output of several discharge channels. A new arc consisting of three separate arc channels with a common cylinder anode was constructed for this purpose. Thomson scattering, high resolution Doppler spectroscopy and calorimetry were applied to measure the performance of and interaction between the three channels.

A highly sensitive imaging Thomson scattering system was developed for low temperature (0.1-10 eV) plasma applications at the Pilot-PSI linear plasma generator. The essential parts of the diagnostic are a neodymium doped yttrium aluminum garnet laser operating at the second harmonic (532 nm), a laser beam line with a unique stray light suppression system and a detection branch consisting of a Littrow spectrometer equipped with an efficient detector based on a "Generation III" image intensifier combined with an intensified charged coupled device camera. The system is capable of measuring electron density and temperature profiles of a plasma column of 30 mm in diameter with a spatial resolution of 0.6 mm and an observational error of 3% in the electron density (n(e)) and 6% in the electron temperature (T-e) at n(e)=4 x 10(19) m(-3). This is achievable at an accumulated laser input energy of 11 J (from 30 laser pulses at 10 Hz repetition frequency). The stray light contribution is below 9 x 10(17) m(-3) in electron density equivalents by the application of a unique stray light suppression system. The amount of laser energy that is required for a n(e) and T-e measurement is 7 x 10(20)/n(e) J, which means that single shot measurements are possible for n(e)>2 x 10(21) m(-3). (C) 2008 American Institute of Physics.

The FOM-Institute for Plasma Physics Rijnhuizen has started the construction of Magnum-PSI, a magnetized (3 T), steady-state, large area (80cm(2)) high-flux (up to 10(24) H(+)ions m(-2) s(-1)) plasma generator. The aim of this linear plasma device is to provide a controlled, highly accessible laboratory experiment facility in which the interaction of a magnetized plasma with different surfaces can be studied in detail. Magnum-PSI consists of several subsystems including vacuum, cooling, plasma source, target station, and a number of diagnostic systems. The safety, Control, Data Acquisition and Communication (CODAC) system integrates these subsystems and provides an interface for the Magnum-PSI users. The CODAC system is designed in parallel with the Magnum-PSI hardware to maximize compatibility and usability. The CODAC system must handle the step-by-step construction and expansion of the Magnum-PSI system without compromising human and system safety in each step, combine manual and remote control, and provide a central data storage and implement automated experiment execution. Key features of the CODAC system are a layered, modular and distributed design, the use of intelligent devices (e.g. commercial computer controlled cooling units), a centralized data storage built on HDF5, and a communication layer built on ZeroC (TM) Ice (TM). A significant part of the design is based on existing open source software components, integrated using C and Python code. (c) 2008 Elsevier B.V. All rights reserved.

Magnum‐PSI [1] (under construction) and Pilot‐PSI [2, 3] are linear plasma machines. The former is designed to study plasma‐surface interactions in conditions relevant to the ITER divertor. To generate the power flux required by these studies, radio‐frequency heating has been planned. Around typical Magnum‐PSI conditions (B0 = 3 T, ne = 1020–1021 m−3, T = 1–5 eV), after low frequency [4], higher‐frequency schemes are investigated. These range from below the lower‐hybrid frequency to the helicon wave range with a preference for 2.45 GHz where equipment is easily available. First experiments have been performed on the smaller machine Pilot‐PSI (B0 = 0.4–1.6 T). In this paper the conditions for wave propagation and absorption are investigated for both machines in broad parameter ranges to determine the most favourable heating conditions. The importance of choosing suitable wave polarization and launched k∥‐spectrum is discussed. A spectral code was developed to compute the coupling of a rectangular wave‐guid...

An advanced Thomson scattering system has been built for a linear plasma generator for plasma surface interaction studies. The Thomson scattering system is based on a Nd:YAG laser operating at the second harmonic and a detection branch featuring a high etendue (f /3) transmission grating spectrometer equipped with an intensified charged coupled device camera. The system is able to measure electron density (ne) and temperature (Te) profiles close to the output of the plasma source and, at a distance of 1.25 m, just in front of a target. The detection system enables to measure 50 spatial channels of about 2 mm each, along a laser chord of 95 mm. By summing a total of 30 laser pulses (0.6 J, 10 Hz), an observational error of 3% in ne and 6% in Te (at ne = 9.4 × 1018 m-3) can be obtained. Single pulse Thomson scattering measurements can be performed with the same accuracy for ne > 2.8 × 1020 m-3. The minimum measurable density and temperature are ne

A robust and sensitive Thomson scattering (TS) system has been developed for the high density low temperature plasma in the linear plasma generator Pilot-PSI, which routinely and reproducibly measures electron density and temperature profiles along a detection chord of 25 mm with a spatial resolution of 0.6 mm. The capabilities of the system are illustrated in this paper by a selection of new results from the research program at Pilot-PSI. TS data are presented that demonstrate the present plasma density record in Pilot-PSI: 5 x 10(21) m(-3) at a temperature of 3 eV. TS measurements in front of the target are combined with ion saturation current data to determine plasma velocities of 4-5 km s(-1), which shows that heat convection is dominating over conduction. Single shot operation of TS is also possible, which is demonstrated by measurements revealing a rotating filamentary return current channel to the source anode. Finally, the TS system upgrade that will provide real time feedback of electron density and temperature in the larger plasma generator Magnum-PSI is discussed.