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Journal Articles

Determination of tungsten and molybdenum concentrations from an X-ray range spectrum in JET with the ITER-like wall configuration

Nakano, Tomohide; Shumack, A.*; Maggi, C. F.*; Reinke, M.*; Lawson, K.*; Coffey, I.*; P$"u$tterich, T.*; Brezinsek, S.*; Lipschultz, B.*; Matthews, G. F.*; et al.

Journal of Physics B; Atomic, Molecular and Optical Physics, 48(14), p.144023_1 - 144023_11, 2015/07

 Times Cited Count:27 Percentile:84.61(Optics)

The $$mbox{W}^{45+}$$ and $$mbox{W}^{46+}$$ 3p-4d inner shell excitation lines in addition to $$mbox{Mo}^{32+}$$ 2p-3s lines have been identified from the spectrum taken by an upgraded high-resolution X-ray spectrometer. It is found from analysis of the absolute intensities of the $$mbox{W}^{46+}$$ and $$mbox{Mo}^{32+}$$ lines that W and Mo concentrations are in the range of $$sim10^{-5}$$ and $$sim10^{-6}$$, respectively, with a ratio of $$sim$$ 5% for ELMy H-mode plasmas with a plasma current of 2.0- 2.5 MA, a toroidal magnetic field of 2.7 T and a neutral beam injection power of 14-18 MW. For the purpose of checking self-consistency, it is confirmed that the W concentration determined from the $$mbox{W}^{45+}$$ line is in agreement with that from the $$mbox{W}^{46+}$$ line within 20% and that the plasma effective charge determined from the continuum of the first order reflection spectrum is also in agreement with that from the second order within 50%. Further, the determined plasma effective charge is in agreement with that determined from a visible spectroscopy, confirming that the sensitivity of the X-ray spectrometer is valid and that probably the W and the Mo concentrations are also valid.

Journal Articles

Progress at JET in integrating ITER-relevant core and edge plasmas within the constraints of an ITER-like wall

Giroud, C.*; Jachmich, S.*; Jacquet, P.*; J$"a$rvinen, A.*; Lerche, E.*; Rimini, F.*; Aho-Mantila, L.*; Aiba, Nobuyuki; Balboa, I.*; Belo, P.*; et al.

Plasma Physics and Controlled Fusion, 57(3), p.035004_1 - 035004_20, 2015/03

 Times Cited Count:51 Percentile:96.77(Physics, Fluids & Plasmas)

This paper reports the progress made at JET-ILW on integrating the requirements of the reference ITER baseline scenario with normalized confinement factor of 1, at a normalized pressure of 1.8 together with partially detached divertor whilst maintaining these conditions over many energy confinement times. The 2.5 MA high triangularity ELMy H-modes are studied with two different divertor configurations with D-gas injection and nitrogen seeding. The power load reduction with N seeding is reported. The relationship between an increase in energy confinement and pedestal pressure with triangularity is investigated. The operational space of both plasma configurations is studied together with the ELM energy losses and stability of the pedestal of unseeded and seeded plasmas.

Journal Articles

Determination of tungsten and molybdenum concentrations from an X-ray range spectrum in JET

Nakano, Tomohide; Shumack, A. E.*; Maggi, C.*; Reinke, M.*; Lawson, K. D.*; P$"u$tterich, T.*; Brezinsek, S.*; Lipschultz, B.*; Matthews, G.*; Chernyshova, M.*; et al.

Europhysics Conference Abstracts (Internet), 38F, p.P1.019_1 - P1.019_4, 2014/06

no abstracts in English

Journal Articles

Integrated modelling of a JET type-I ELMy H-mode pulse and predictions for ITER-like wall scenarios

Wiesen, S.*; Brezinsek, S.*; J$"a$rvinen, A.*; Eich, T.*; Fundamenski, W.*; Huber, A.*; Parail, V.*; Corrigan, G.*; Hayashi, Nobuhiko; JET-EFDA Contributors*

Plasma Physics and Controlled Fusion, 53(12), p.124039_1 - 124039_12, 2011/12

 Times Cited Count:22 Percentile:71.68(Physics, Fluids & Plasmas)

Journal Articles

Flux dependence of carbon erosion and implication for ITER

Roth, J.*; Kirschner, A.*; Bohmeyer, W.*; Brezinsek, S.*; Cambe, A.*; Casarotto, E.*; Doerner, R.*; Gauthier, E.*; Federici, G.*; Higashijima, Satoru; et al.

Journal of Nuclear Materials, 337-339, p.970 - 974, 2005/03

 Times Cited Count:95 Percentile:98.93(Materials Science, Multidisciplinary)

In the frame work of the EU Task Force on Plasma-Wall Interaction and the International Tokamak Physics Activity an attempt was made to establish a possible dependence of the chemical erosion yield of carbon on the ion flux, $$Phi$$, involving ion beam experiments, plasma simulators, and fusion devices. After data normalization a fit using Bayesian probability analysis was performed yielding a decrease of the erosion yield with $$Phi$$$$^{-0.54}$$ at high ion fluxes. With this dependence on ion flux a comprehensive description is available for chemical erosion as function of energy, temperature and ion flux. Using this dependence the erosion and redeposition of carbon in the ITER divertor can be calculated using the ERO code and the steady-state plasma scenario given by the ITER team. The resulting gross and net erosion rates are compared to previous estimates using a constant erosion yield of 1.5%. The use of the complete parameter dependence results in an order of magnitude lower erosion, most strongly determined by the temperature dependence and the reduction at the highest fluxes.

Journal Articles

Flux dependence of carbon chemical erosion by deuterium ions

Roth, J.*; Preuss, R.*; Bohmeyer, W.*; Brezinsek, S.*; Cambe, A.*; Casarotto, E.*; Doerner, R.*; Gauthier, E.*; Federici, G.*; Higashijima, Satoru; et al.

Nuclear Fusion, 44(11), p.L21 - L25, 2004/11

 Times Cited Count:93 Percentile:91.38(Physics, Fluids & Plasmas)

Chemical erosion of carbon has been studied in ion beam experiments, and the yield values are available as a function of ion energy and surface temperature. ITER divertor condition, however, cannot be simulated by ion beam. For extrapolating to ITER, the erosion must be investigated in plasma simulators and in SOL or divertors of present fusion devices. In the past, erosion values were reported, but the values showed a wide scatter as a function of ion flux, $$Phi$$. Therefore, a joint attempt was made through the EU Task Force on Plasma-Wall Interaction and the International Tokamak Physics Activity (ITPA) to clarify the flux dependence. For each data point the local plasma conditions were normalized to impact energy of 30 eV, the data were selected for a surface temperature close to the maximum yield or to room temperature, and the diagnostic was calibrated in-situ. Through this procedure, the previous large scatter could be drastically reduced. A fit using Bayesian probability analysis was performed yielding a decrease of the erosion yield with $$Phi$$$$^{-0.54}$$ at high ion fluxes.

Oral presentation

Determination of tungsten and molybdenum concentrations from an X-ray range spectrum in JET

Nakano, Tomohide; Shumack, A.*; Maggi, C. F.*; Reinke, M.*; Lawson, K.*; P$"u$tterich, T.*; Brezinsek, S.*; Lipschultz, B.*; Matthews, G. F.*; Chernyshova, M.*; et al.

no journal, , 

In an European tokamak device, JET, an existing high-resolution X-ray crystal spectrometer was upgraded together with installation of the W divertor for the purpose of monitoring the W density in the core plasma. We have identified W$$^{46+}$$, W$$^{45+}$$ and Mo$$^{32+}$$ lines by comparing the spectrum observed by this spectrometer and that calculated by an atomic structure code. Further, from the intensities of these spectral lines, the W density and the Mo density over an electron density were determined to be $$10^{-5}$$ and $$10^{-7}$$, respectively. The determined W density was in good agreement with that from another spectrometer. In addition, the plasma effective charge evaluated from the continuum intensity observed by the X-ray spectrometer was in agreement with that from a visible spectrometer within a factor of three. From these agreements, it is probable that the determined W and Mo density are valid. In contrast, the determined W density is only 15% compared with that from an soft X-ray array measurement. This inconsistency will be investigated in the near future.

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