P. Börner

Forschungszentrum Jülich, Jülich, North Rhine-Westphalia, Germany

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Publications (40)56.01 Total impact

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    ABSTRACT: Abstract In optical diagnostic systems of ITER, mirrors will be used to guide the light from plasma towards detectors and cameras. The mirrors will be subjected to erosion due to fast particles and to deposition of impurities from the plasma which will affect adversely the mirror reflectivity and therefore must be suppressed or mitigated at the maximum possible extent. Predictive modeling envisages the successful suppression of deposition in the diagnostic ducts with fins trapping the impurities on their way towards mirrors located in the end of these ducts. To validate modeling predictions, cylindrical and cone-shaped diagnostic ducts were exposed in TEXTOR for 3960 s of plasma operation. After exposure, no drastic suppression of deposition was observed in the cylindrical ducts with fins. At the same time, no detectable deposition was found on the mirrors located at the end of cone-shaped ducts outlining the advantages of the cone geometry. Analyses of exposure provide evidence that the contamination of exposed mirrors was due to wall conditioning discharges and not due to working plasma exposure. Cleaning by plasma sputtering was performed on molybdenum mirrors pre-coated with a 100 nm thick aluminum film. Aluminum was used as a proxy of beryllium. During exposure in electron cyclotron resonance-generated helium plasma, the entire coating was sputtered within nine hours, leaving no trace of aluminum and leading to the full recovery of the specular reflectivity without detrimental effects on the mirror surface.
    Nuclear Fusion 08/2015; 55(9):093015. DOI:10.1088/0029-5515/55/9/093015doi:10.1088/0029-5515/55/9/093015 · 3.24 Impact Factor
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    ABSTRACT: We present the application of an improved EDGE2D-EIRENE SOL transport model for the ELM phase utilizing kinetic correction of the sheath-heat-transmission coefficients and heat-flux-limiting factors used in fluid SOL modelling. With a statistical analysis over a range of similar type-I ELMy H-mode discharges performed at the end of the first JET ITER-like wall campaign, we achieved a fast (Δt = 200 μs) temporal evolution of the outer midplane ne and Te profiles and the target-heat and particle-flux profiles, which provides a good experimental data set to understand the characteristics of an ELM cycle. We will demonstrate that these kinetic corrections increase the simulated heat-flux-rise time at the target to experimentally observed times but the power-decay time at the target is still underestimated by the simulations. This longer decay times are potentially related to a change of the local recycling coefficient at the tungsten target plate directly after the heat pulse.
    Journal of Nuclear Materials 12/2014; 463. DOI:10.1016/j.jnucmat.2014.12.023 · 2.02 Impact Factor
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    A. Mekkaoui · V. Kotov · D. Reiter · P. Boerner
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    ABSTRACT: In this contribution we present results on the effect of turbulent plasma fluctuations on the transport of atoms and molecules as well as on impurities sputtered due to charge exchange atomic bombardment. These phenomena are investigated using the kinetic Monte‐Carlo particle transport code EIRENE and a statistical model of plasma fluctuations. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
    Contributions to Plasma Physics 06/2014; 54(4-6). DOI:10.1002/ctpp.201410021 · 0.98 Impact Factor
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    ABSTRACT: The Super-X divertor edge plasma of the future MAST Upgrade tokamak (Lisgo et al 2009 36th EPS Plasma Physics Conf. 33E O4-046, Katramados et al 2011 Fusion Eng. Des. 86 1595, Morris 2012 IEEE Trans. Plasma Sci. 40 682) was simulated with the B2SOLPS5.2 transport code including, for the first time, the effects of drifts due to electric field and magnetic field gradients. The previous simulations did not contain drift effects as well as an account of the external transport barrier. The expected reduction in temperatures and heat flux densities at the low-field side divertors was obtained in the simulations. However, an account of drifts and parallel currents led to an up–down asymmetry of the power to the plates in the connected double null configuration, which was not observed in the simulations without drifts.
    Plasma Physics and Controlled Fusion 02/2013; 55(3):035005. DOI:10.1088/0741-3335/55/3/035005 · 2.39 Impact Factor
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    ABSTRACT: The transport of neutral particles in turbulent plasmas is addressed from the prospect of developing coarse-grained transport models which can be implemented in code suites like B2-EIRENE, currently used for designing the ITER divertor. The statistical properties of turbulent fluctuations are described by a multivariate Gamma distribution able to retain space and time correlations through a proper choice of covariance function. We show that in the scattering free case, relevant for molecules and impurity atoms, the average neutral particle density obeys a Boltzmann equation with an ionization rate renormalized by fluctuations. This result lends itself to a straightforward implementation in the EIRENE Monte Carlo solver for neutral particles. Special emphasis is put on the inclusion of time correlations, and in particular on the ballistic motion of coherent turbulent structures. The role of these time dependent effects is discussed for D{sub 2} molecules and beryllium atoms. The sensitivity of our results to the assumptions on the statistical properties of fluctuations is investigated.
    Physics of Plasmas 12/2012; 19(12). DOI:10.1063/1.4771688 · 2.25 Impact Factor
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    ABSTRACT: A coarse-grained kinetic equation for neutral particles (atoms, molecules) in magnetized fusion plasmas, valid on time scales large compared to the turbulence correlation time, is presented. This equation includes the effects of plasma density fluctuations, described by gamma statistics, on the transport of neutral particles. These effects have so far been neglected in plasma edge modeling, in spite of the fact that the amplitude of fluctuations can be of order unity. Density fluctuations are shown to have a marked effect on the screening of neutrals and on the spatial localization of the ionization source, in particular at high density. The coarse-grained equations obtained in this work are readily implemented in edge code suites currently used for fusion plasma analysis and future divertor design (ITER, DEMO).
    Physics of Plasmas 06/2012; 19(6). DOI:10.1063/1.4725504 · 2.25 Impact Factor
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    ABSTRACT: The 2D edge plasma transport code EDGE2D-EIRENE has been upgraded to account for the actual material and geometric properties of the newly installed ITER like wall (ILW) at JET. This includes the simulation of beryllium and tungsten impurities as well as a revised treatment of sputtering by main plasma and impurity atoms and ions (including self sputtering). In this work, two L-mode density regimes, a sheath limited and a high recycling regime, are presented with a power scan from 2 to 6 MW. Tungsten is self consistently simulated with the scrape of layer (SOL) plasma by the EDGE2D–EIRENE code. A detailed analysis of the tungsten sputtering is presented, resolving the individual contributions of the different atomic and ion species in the simulations.
    Journal of Nuclear Materials 01/2012; DOI:10.1016/j.jnucmat.2013.01.098 · 2.02 Impact Factor
  • W. Dekeyser · M. Baelmans · D. Reiter · P. Börner · V. Kotov
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    ABSTRACT: Far SOL plasma flow, and hence main chamber recycling and plasma surface interaction, are today still only very poorly described by current 2D fluid edge codes, such as B2, UEDGE or EDGE2D, due to a common technical limitation. We have extended the B2 plasma fluid solver in the current ITER version of B2-EIRENE (SOLPS4.3) to allow plasma solutions to be obtained up to the “real vessel wall”, at least on the basis of ad hoc far SOL transport models. We apply here the kinetic Monte Carlo Code EIRENE on such plasma solutions to study effects of this model refinement on main chamber fluxes and sputtering, for an ITER configuration. We show that main chamber sputtering may be significantly modified both due to thermalization of CX neutrals in the far SOL and poloidally highly asymmetric plasma wall contact, as compared to hitherto applied teleportation of particle fluxes across this domain.
    Journal of Nuclear Materials 08/2011; 415(1). DOI:10.1016/j.jnucmat.2010.08.040 · 2.02 Impact Factor
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    ABSTRACT: The scaling law for carbon erosion in Tore Supra previously established by Hogan et al. [1] (ΦC(C/s)=5×1020Pcond (MW), where Pcond is the conducted power) is revisited both from the experimental and the modelling point of view. New developments with the EIRENE code, that allow relating measured CII emission intensities to the total amount of carbon sputtered from the Toroidal Pumped Limiter, are presented. Recent measurements carried out at high input power show a good agreement with the database used to establish the scaling law.
    Journal of Nuclear Materials 08/2011; 415(1). DOI:10.1016/j.jnucmat.2010.11.066 · 2.02 Impact Factor
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    ABSTRACT: The objective of this computational engineering design study is to assess whether the ITER confined plasma will be adversely affected if the diagnostic port plug and tritium breeding module plasma-facing surfaces are left as bare stainless steel or armoured with W, rather than with Be as on the rest of the main chamber first wall. The OSM-EIRENE-DIVIMP code package is employed to determine the 2D steady-state impurity distribution, after benchmarking the OSM plasma calculations against reference SOLPS simulations. For far-SOL transport, the computational domain is extended to explicitly include plasma contact with the wall. To sample a large area of the foreseen ITER parameter space, a range of boundary plasmas are assigned via OSM based on observed experimental trends, including radial decay lengths, parallel flows, and pedestal profiles. Taking core impurity limits from ASTRA simulations, the results indicate that Be cladding of the port plugs under consideration is not required, with the proviso that neutral particle injection directly in front of the ports is avoided.
    Journal of Nuclear Materials 08/2011; 415(1). DOI:10.1016/j.jnucmat.2010.11.061 · 2.02 Impact Factor
  • D. Harting · S. Wiesen · H. Frerichs · D. Reiter · P. Börner · Y. Feng
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    ABSTRACT: The 3D edge plasma transport code EMC3-EIRENE [1] was successfully adapted to the single null configuration of JET. A test bed with the well established 2D edge plasma code EDGE2D-EIRENE [2,3] was prepared to check the adaptation of the EMC3-EIRENE code and isolate any discrepancies when compared. While both codes solve essentially the same set of reduced Braginskii’s fluid equations, they use very different numerical techniques: a 3D Lagrangian Monte Carlo method in EMC3 and a 2D Eulerian finite differences scheme in EDGE2D. The results should be very similar as both codes are iteratively coupled to the same kinetic neutral particle Monte Carlo code EIRENE [4]. We show that both codes are in a fairly good quantitative agreement regarding both midplane and target plasma profiles as well as transition from low to high recycling regime with increasing core plasma density.
    Journal of Nuclear Materials 08/2011; 415(1). DOI:10.1016/j.jnucmat.2011.01.030 · 2.02 Impact Factor
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    ABSTRACT: The effect of turbulence on the transport of neutral species (atom, molecules) in plasmas is investigated. A stochastic model relying on a multivariate gamma distribution is introduced to describe turbulent fluctuations, and implemented in EIRENE. The effects of fluctuations on the neutral density and ionization source radial profiles are investigated. The role of temperature fluctuations is discussed in detail. Calculations with ITER scrape-off layer parameters are presented, and two distinct regimes with respect to the effects of temperature fluctuations are identified, depending on the far SOL mean temperature. Finally, the influence of fluctuations on impurity contamination is discussed.
    Nuclear Fusion 07/2011; 51(8):083035. DOI:10.1088/0029-5515/51/8/083035 · 3.24 Impact Factor
  • M. Baelmans · P. Börner · W. Dekeyser · D. Reiter
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    ABSTRACT: Quantifying main chamber wall recycling, erosion and resulting material migration, at least on the basis of known or empirical far scrape-off layer (SOL) processes, is still highly uncertain, despite its relevance for ITER and fusion reactor design studies. This affects, for example, the design problem of first mirror performance of many optical diagnostics in the harsh ITER environment. Poor computational access is not least due to a fundamental technical limitation in apparently all current tokamak edge plasma fluid codes, which implicates a wide computationally unresolved gap between the outermost plasma layer treated in codes and the real vessel wall. We show how the current ITER version of the B2-EIRENE code (SOLPS-4.3) can be extended to cover also this far SOL, on the same footing as the rest of the plasma transport model. We discuss consequences of this new model for estimating plasma power and particle sink terms caused by a fairly realistic wall in ITER based on the conventional Bohm criterion along all plasma–wall interfaces.Corrections were made to this article on 14 July 2011. The authors have been assigned to the correct affiliations.
    Nuclear Fusion 07/2011; 51(8):083023. DOI:10.1088/0029-5515/51/8/083023 · 3.24 Impact Factor
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    ABSTRACT: This work addresses the transport of neutral particles (atoms, molecules) in magnetized fusion plasmas, in the presence of density fluctuations with given statistics. The latter are described by a multivariate gamma distribution. The geometry is a 2D slab and turbulence is assumed to be statistically homogeneous. The average neutral density and ionization source, which are the quantities relevant for integrated simulations and diagnostic applications, are calculated analytically in the scattering free case. The boundary conditions and the ratio of the turbulence correlation length to the neutral mean free path are identified as the main control parameters in the problem. The non-trivial relationship between the average neutral density and the ionization source is investigated. Monte Carlo calculations including scattering are then presented, and the main trends obtained in the scattering free case are shown to be conserved.
    Plasma Physics and Controlled Fusion 06/2011; 53(6). DOI:10.1088/0741-3335/53/6/065001 · 2.39 Impact Factor
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    ABSTRACT: This work addresses linear transport in turbulent media, with emphasis on neutral particle (atoms, molecules) transport in magnetized fusion plasmas. A stochastic model for turbulent plasmas, based upon a multivariate Gamma distribution, is presented. The geometry is a 2D slab and turbulence is assumed to be statistically homogeneous. The average neutral density and ionization source, which are the quantities relevant for integrated simulations and diagnostic applications, are calculated analytically in the scattering free case. The boundary conditions and the ratio of the turbulence correlation length to the neutral mean free path are identified as the main control parameters in the problem. The non trivial relationship between the average neutral density and the ionization source is investigated. Monte Carlo calculations including scattering are then presented, and the main trends obtained in the scattering free case are shown to be conserved. Comment: 11 figures
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    ABSTRACT: In this work we present a statistical model aimed at retaining edge turbulence fluctuations in the EIRENE neutral transport code. The model relies on sampling a large number of plasma backgrounds, using a given 1 point PDF and a 2 points correlation function, and computing the corresponding average quantities (neutral density profile, …). Its implementation is validated using a simplified case for which the calculations can be carried out analytically. An intuitive picture of neutral transport in turbulent plasmas is presented (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    Beiträge aus der Plasmaphysik 05/2010; 50(3‐5):279 - 284. DOI:10.1002/ctpp.201010046
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    ABSTRACT: Several improvements to the MAST plant and diagnostics have facilitated new studies advancing the physics basis for ITER and DEMO, as well as for future spherical tokamaks (STs). Using the increased heating capabilities PNBI ≤ 3.8 MW H-mode at Ip = 1.2 MA was accessed showing that the energy confinement on MAST scales more weakly with Ip and more strongly with Bt than in the ITER IPB98(y, 2) scaling. Measurements of the fuel retention of shallow pellets extrapolate to an ITER particle throughput of 70% of its original designed total throughput capacity. The anomalous momentum diffusion, χ, is linked to the ion diffusion, χi, with a Prandtl number close to P ≈ χ/χi ≈ 1, although χi approaches neoclassical values. New high spatial resolution measurements of the edge radial electric field, Er, show that the position of steepest gradients in electron pressure and Er (i.e. shearing rate) are coincident, but their magnitudes are not linked. The Te pedestal width on MAST scales with rather than ρpol. The edge localized mode (ELM) frequency for type-IV ELMs, new in MAST, was almost doubled using n = 2 resonant magnetic perturbations from a set of four external coils (n = 1, 2). A new internal 12 coil set (n ≤ 3) has been commissioned. The filaments in the inter-ELM and L-mode phase are different from ELM filaments, and the characteristics in L-mode agree well with turbulence calculations. A variety of fast particle driven instabilities were studied from 10 kHz saturated fishbone like activity up to 3.8 MHz compressional Alfvén eigenmodes. Fast particle instabilities also affect the off-axis NBI current drive, leading to fast ion diffusion of the order of 0.5 m2 s−1 and a reduction in the driven current fraction from 40% to 30%. EBW current drive start-up is demonstrated for the first time in a ST generating plasma currents up to 55 kA. Many of these studies contributed to the physics basis of a planned upgrade to MAST.
    Nuclear Fusion 10/2009; 49(10-10):104017. DOI:10.1088/0029-5515/47/10/S14 · 3.24 Impact Factor
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    ABSTRACT: The ITER Scenario Modelling Working Group (ISM WG) is organized within the European Task Force on Integrated Tokamak Modelling (ITM-TF). The main responsibility of the WG is to advance a pan-European approach to integrated predictive modelling of ITER plasmas with the emphasis on urgent issues, identified during the ITER Design Review. Three major topics are discussed, which are considered as urgent and where the WG has the best possible expertize. These are modelling of current profile control, modelling of density control and impurity control in ITER (the last two topics involve modelling of both core and SOL plasma). Different methods of heating and current drive are tested as controllers for the current profile tailoring during the current ramp-up in ITER. These include Ohmic, NBI, ECRH and LHCD methods. Simulation results elucidate the available operational margins and rank different methods according to their ability to meet different requirements. A range of 'ITER-relevant' plasmas from existing tokamaks were modelled. Simulations confirmed that the theory-based transport model, GLF23, reproduces the density profile reasonably well and can be used to assess ITER profiles with both pellet injection and gas puffing. In addition, simulations of the SOL plasma were launched using both H-mode and L-mode models for perpendicular transport within the edge barrier and in the SOL. Finally, an integrated approach was also used for the predictive modelling of impurity accumulation in ITER. This includes helium ash, extrinsic impurities (such as argon) and impurities coming from the wall (including tungsten). The relative importance of anomalous and neo-classical pinch contributions towards impurity penetration through the edge transport barrier and further accumulation in the core was assessed.
    Nuclear Fusion 07/2009; 49(7):075030. DOI:10.1088/0029-5515/49/7/075030 · 3.24 Impact Factor
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    ABSTRACT: The tokamak boundary plasma is inherently 2D/3D, which impedes the detailed validation of transport models due to the limited spatial coverage of most diagnostics. A potential method for determining the 2D profiles of ne and Te in the plasma volume is to resolve spatially the emission ratios of atomic helium, principally the lines at 667, 706 and 728 nm. Unfortunately, there are several challenges associated with this approach: the traditional use of line-of-sight spectrometer data; crowding by other impurity lines; low signal levels; reliance on accurate atomic physics; and He I meta-stables. Several of these issues are explored in the present study, which utilises tomographic reconstruction of filtered CCD camera images to measure He emission throughout the divertor. Plasma gradients are resolved and compared with results from the OSM–EIRENE code. The near-target ne and Te values agree with Langmuir probe measurements to within a factor ∼2.
    Journal of Nuclear Materials 06/2009; 390(1):1078-1080. DOI:10.1016/j.jnucmat.2009.01.292 · 2.02 Impact Factor
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    ABSTRACT: Hydrogen line radiation can be trapped in some spatial regions within magnetic fusion experiments at high density, typically when NH(∼Ne) ∼ 1015 cm−3. The corresponding photoexcitation yields a significant additional source of ionization that must be properly characterized by numerical simulations. Kinetic Monte-Carlo codes provide a capability to study this subject; however, these codes require accurate physical models for the reaction rates, including spectral line shapes. In this paper we deal with the Zeeman–Stark model used for the Lyα transition in the EIRENE code [D. Reiter, M. Baelmans, P. Börner, Fusion Sci. Technol. 47 (2005) 172; www.eirene.de] and we address the influence of ion dynamics, which can affect these line profiles. The impact theory for ions, that we first consider, is shown to be suited for description of the lateral components of the Lorentz triplet. By contrast, comparisons to numerical simulations show that this theory is not well suited for description of the central component, which is significantly affected by incomplete and non-binary collisions. A refinement of the model in the framework of the unified theory is proposed and discussed.
    High Energy Density Physics 06/2009; 5(1-2):93-96. DOI:10.1016/j.hedp.2009.03.004 · 1.52 Impact Factor

Publication Stats

216 Citations
56.01 Total Impact Points

Institutions

  • 1992–2014
    • Forschungszentrum Jülich
      • • Zentralabteilung für Chemische Analysen (ZCH)
      • • Plasma Physics (IEK-4)
      Jülich, North Rhine-Westphalia, Germany
  • 2010
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 2003
    • Max Planck Institute for Plasma Physics
      • Max Planck Institute for Plasma Physics, Greifswald
      Garching bei München, Bavaria, Germany