Publications (19)27.96 Total impact
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Article: Tritium control techniques in ITER by ammonia injection
Journal of Nuclear Materials 01/2011; 415(1, Supplement):S793 - S796. · 2.05 Impact Factor -
Article: Suppression of tritium retention in remote areas of ITER by nonperturbative reactive gas injection.
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ABSTRACT: A technique based on reactive gas injection in the afterglow region of the divertor plasma is proposed for the suppression of tritium-carbon codeposits in remote areas of ITER when operated with carbon-based divertor targets. Experiments in a divertor simulator plasma device indicate that a 4 nm/min deposition can be suppressed by addition of 1 Pa·m³ s⁻¹ ammonia flow at 10 cm from the plasma. These results bolster the concept of nonperturbative scavenger injection for tritium inventory control in carbon-based fusion plasma devices, thus paving the way for ITER operation in the active phase under a carbon-dominated, plasma facing component background.Physical Review Letters 10/2010; 105(17):175006. · 7.37 Impact Factor -
Article: The breakup of methane under ITER divertor hydrogen plasma conditions for carbon chemical erosion analysis with CH spectroscopy
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ABSTRACT: Methane (CH4) was injected into the high density (ne ~ 1020 m−3), low temperature (Te ~ 1 eV) hydrogen plasma in Pilot-PSI to determine the CH A–X photon efficiency in this unexplored plasma regime. The effects of particle transport and particle reflection on the emission of directly excited CH under these plasma conditions were assessed with the 3D Monte Carlo code ERO. The simulations of the inverse photon efficiency showed a difference of ~20% between full hydrocarbon sticking or no sticking (reflection). In addition it predicts that particle transport may lead to more than a factor of 10 increase. The measured inverse photon efficiency is however constant at 100 ± 30 for 0.1 < Te < 1.0 eV. The constancy is consistent with dissociative recombination of , and to produce excited CH instead of direct excitation. These results form a framework for in situ carbon erosion measurements in future fusion reactors such as ITER.Nuclear Fusion 07/2010; 50(9):095003. · 4.09 Impact Factor -
Article: Modelling of Impurity Transport in the Linear Plasma Devices PISCES‐B and Pilot‐PSI Using the Monte‐Carlo Code ERO
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ABSTRACT: The simulations for linear devices using the 3D Monte-Carlo code ERO have a number of particularities of both physical and technical nature. Many physical effects introduced and tested for these simulations (elastic collisions, population of metastable states, etc.) can be relevant for tokamaks as well. The current status of these activities is summarized. As an example some simulations reproducing the experimental observations at PISCES-B and Pilot-PSI are presented. Main deviations and ideas for their origins are discussed (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)Beiträge aus der Plasmaphysik 05/2010; 50(3‐5):432 - 438. -
Article: Chemical erosion of different carbon composites under ITER-relevant plasma conditions
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ABSTRACT: We have studied the chemical erosion of different carbon composites in Pilot-PSI at ITER-relevant hydrogen plasma fluxes (~1024 m-2 s-1) and low electron temperatures (Te~1 eV). Optical emission spectroscopy on the CH A–X band was used to characterize the chemical sputtering. Fine grain graphite (R 6650, SGL Carbon Group), ITER-reference carbon fiber composite material (SNECMA NB31 and NB41; Dunlop 3D), nano- and micro-crystalline diamond coatings on molybdenum and SiC (Silit® SKD Reaction-Bonded, Saint-Gobain Ceramics) were compared. The chemical sputtering was similar for the different composites under comparable plasma conditions, except for SiC, which produced a ten times lower rate. The CH emission was constant at electron temperatures Te>1 eV and ion fluxes ranging between 1023 and 1024 m- 2 s-1, but decreased at lower temperatures. This decrease is possibly due to changes in the excitation of CH and not due to a change in the chemical erosion rate.Physica Scripta 12/2009; 2009(T138):014017. · 1.20 Impact Factor -
Article: Thomson scattering at Pilot-PSI and Magnum-PSI
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ABSTRACT: 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 × 1021 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.Plasma Physics and Controlled Fusion 11/2009; 51(12):124037. · 2.42 Impact Factor -
Article: CH spectroscopy for carbon chemical erosion analysis in high density low temperature hydrogen plasma
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ABSTRACT: The CH A−X molecular band is measured upon seeding the hydrogen plasma in the linear plasma generator Pilot-PSI [electron temperature Te = 0.1–2.5 eV and electron density ne = (0.5–5)×1020 m−3] with methane. Calculated inverse photon efficiencies for these conditions range from 3 up to >106 due to a steeply decreasing electron excitation cross section. The experiments contradict the calculations and show a constant effective inverse photon efficiency of ∼ 100 for Te<1 eV. The discrepancy is explained as the CH A level is populated through dissociative recombination of the molecular ions formed by charge exchange. Collisional de-excitation is observed for ne>5×1020 m−3 and 0.1 eV<Te<1 eV. These results form a framework for in situ carbon erosion measurements in future fusion reactors such as ITER.Applied Physics Letters 10/2009; 95(15):151501-151501-3. · 3.84 Impact Factor -
Article: Rotation of a strongly magnetized hydrogen plasma column determined from an asymmetric Balmer-beta spectral line with two radiating distributions.
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ABSTRACT: A potential buildup in front of a magnetized cascaded arc hydrogen plasma source is explored via E x B rotation and plate potential measurements. Plasma rotation approaches thermal speeds with maximum velocities of 10 km/s. The diagnostic for plasma rotation is optical emission spectroscopy on the Balmer-beta line. Asymmetric spectra are observed. A detailed consideration is given on the interpretation of such spectra with a two distribution model. This consideration includes radial dependence of emission determined by Abel inversion of the lateral intensity profile. Spectrum analysis is performed considering Doppler shift, Doppler broadening, Stark broadening, and Stark splitting.Physical Review E 11/2008; 78(4 Pt 2):046405. · 2.26 Impact Factor -
Article: Emission spectroscopy of hydrogen lines in magnetized plasmas: Application to PSI studies under conditions foreseen in ITER
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ABSTRACT: Modelling of hydrogen line profiles in the ITER divertor plasma entails several challenges. Because of the high density (Ne>1014cm−3) low temperature (kTe<2eV) expected in the magnetized plasma close to the wall, both Stark broadening and Zeeman splitting have to be taken into account in line shape calculations, [1]. Moreover, the conditions are such that the ion dynamics has to be retained in Stark broadening calculations, the presence of a high magnetic field (B ∼ 5T) introduces couplings between Stark and Zeeman effects, which can significantly alter the profile [2,3]. We present here Balmer lines obtained by numerical simulations based on a standard Molecular Dynamics technique, of the plasma in an external magnetic field. The simulated profiles are compared to experimental ones obtained in Plasma Surface Interaction (PSI) experiments which are carried out on Pilot‐PSI of FOM.AIP Conference Proceedings. 10/2008; 1058(1):216-218. -
Article: Optimization of the output and efficiency of a high power cascaded arc hydrogen plasma source
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ABSTRACT: The operation of a cascaded arc hydrogen plasma source was experimentally investigated to provide an empirical basis for the scaling of this source to higher plasma fluxes and efficiencies. The flux and efficiency were determined as a function of the input power, discharge channel diameter, and hydrogen gas flow rate. Measurements of the pressure in the arc channel show that the flow is well described by Poiseuille flow and that the effective heavy particle temperature is approximately 0.8 eV. Interpretation of the measured I-V data in terms of a one-parameter model shows that the plasma production is proportional to the input power, to the square root of the hydrogen flow rate, and is independent of the channel diameter. The observed scaling shows that the dominant power loss mechanism inside the arc channel is one that scales with the effective volume of the plasma in the discharge channel. Measurements on the plasma output with Thomson scattering confirm the linear dependence of the plasma production on the input power. Extrapolation of these results shows that (without a magnetic field) an improvement in the plasma production by a factor of 10 over where it was in van Rooij et al. [Appl. Phys. Lett. 90, 121501 (2007) ] should be possible.Physics of Plasmas 09/2008; 15(9):093507-093507-13. · 2.15 Impact Factor -
Conference Proceeding: Multiple discharge channels in a cascaded arc to produce extreme hydrogen plasma beams
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ABSTRACT: 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/m<sup>2</sup>s 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 T<sup>2</sup>. 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.Plasma Science, 2008. ICOPS 2008. IEEE 35th International Conference on; 07/2008 -
Article: High sensitivity imaging Thomson scattering for low temperature plasma.
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ABSTRACT: 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).Review of Scientific Instruments 01/2008; 79(1):013505. · 1.37 Impact Factor -
Article: PSI research in the ITER divertor parameter range at the FOM PSI-lab
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ABSTRACT: 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.Physica Scripta 03/2007; 2007(T128):18. · 1.20 Impact Factor -
Article: Hydrogenic Retention of High-Z Refractory Metals Exposed to ITER Divertor Relevant Ion Fluxes
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Article: Hydrogenic retention of high-Z refractory metals exposed to ITER divertor relevant plasma conditions
Mateev, M.; Benova, E.: 36th European Physical Society Conference on Plasma Physics. Contributed Papers, European Physical Society (2009). -
Article: Hydrogenic retention of high-Z refractory metals exposed to ITER divertor relevant plasma conditions
Fusion Energy 2008, International Atomic Energy Agency (2009). -
Article: Materials research under ITER-like divertor conditions at FOM Rijnhuizen
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ABSTRACT: 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.Journal of Nuclear Materials. -
Article: Plasma-Facing Materials Research for Fusion Reactors at FOM Rijnhuizen
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Article: Multiple discharge channels in a cascaded arc to produce large diameter plasma beams
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ABSTRACT: 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 1.6 T 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.Fusion Engineering and Design. 84:1933-1936.
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2008
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FOM Institute AMOLF
Amsterdam, North Holland, Netherlands
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