R. Jaspers

Eindhoven University of Technology

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Co-Authors

B. Unterberg

Forschungszentrum Jülich

A. Krämer-Flecken

Forschungszentrum Jülich

H. R. Koslowski

Forschungszentrum Jülich

K.H. Finken

Heinrich Heine University Düsseldorf

I. G. J. Classen

Dutch Institute for Fundamental Energy Research

W. Biel

Forschungszentrum Jülich

M. Lehnen

ITER

U. Samm

Royal Military Academy

M. Jakubowski

Max Planck Institute for Plasma Physics - Greifswald

A. Messiaen

Royal Military Academy

Cooperative Institutions

Max Planck Institute for Plasma Physics

380

Max Planck Society

313

Culham Science Centre

234

Max Planck Institute for Plasma Physics - Greifswald

204

Forschungszentrum Jülich

189

Royal Military Academy

182

Culham Centre for Fusion Energy

165

CEA Cadarache

162

École Polytechnique Fédérale de Lausanne

118

Princeton Plasma Physics Laboratory

107

Author Statistics

Papers

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A forward model for the helium plume effect and the interpretation of helium charge exchange measurements at ASDEX Upgrade

Plasma Physics and Controlled Fusion (2018)

A. Kappatou R. M. McDermott T. Pütterich R. Dux B. Geiger

The analysis of the charge exchange measurements of helium is hindered by an additional emission contributing to the spectra, the helium 'plume' emission (Fonck et al 1984 Phys. Rev. A 29 3288), which complicates the interpretation of the measurements. The plume emission is indistinguishable from the active charge exchange signal when standard analysis of the spectra is applied and its intensity is of comparable magnitude for ASDEX Upgrade conditions, leading to a significant overestimation of the He2+ densities if not properly treated. Furthermore, the spectral line shape of the plume emission is non-Gaussian and leads to wrong ion temperature and flow measurements when not taken into account. A kinetic model for the helium plume emission has been developed for ASDEX Upgrade. The model is benchmarked against experimental measurements and is shown to capture the underlying physics mechanisms of the plume effect, as it can reproduce the experimental spectra and provides consistent values for the ion temperature, plasma rotation, and He2+ density.

ASDEX Upgrade

10.1088/1361-6587/aab25a

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Citations (16)

Electron Cyclotron Resonance Heating on TEXTOR: results from the preliminary 110 GHz system

E. Westerhof G. M. D. Hogeweij J.A. Hoekzema F. C. Schüller Clemens Barth

Electron cyclotron resonance

Cyclotron resonance

Ion cyclotron resonance

10.1142/9789812705082_0060

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Citations (0)

The Radiative Improved Mode in TEXTOR: Power Exhaust and Improved Confinement at High Density

Fusion Science & Technology (2005)

B. Unterberg U. Samm M. Z. Tokaŕ A. Messiaen J. Ongena

The concept of a cold radiating plasma boundary has been proposed as a solution to the problem of power exhaust in magnetically confined fusion plasmas. We describe experiments to study the impact of the radiating impurities on transport processes in the plasma boundary and the plasma core in the tokamak TEXTOR.The injection of impurities (neon, silicon, or argon) leads to the formation of a radiating plasma boundary where up to 90% of the input power can be distributed to large wall areas, thereby strongly reducing the convective heat flux density onto the plasma-facing components. At high plasma densities the impurity seeding leads to a transition to an improved confinement state termed the radiative improved mode. This operational scenario combines high density and high confinement with power exhaust by radiation under quasi-stationary discharge conditions.The confinement improvement can be explained by a reduction of transport caused by the ion temperature gradient mode. This reduction is initiated by the impurity content and amplified by a characteristic steepening of the density profiles of the background plasma. The extrapolation of the results obtained in TEXTOR, based on experiments in larger devices, is discussed.

Radiative Cooling

Effective radiated power

Fusion power

10.13182/fst05-a699

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Citations (17)

Spatial Heterodyne Spectro-Polarimetry Systems for Imaging Key Plasma Parameters in Fusion Devices

Plasma and Fusion Research (2010)

J. Howard A. Diallo R. Jaspers Jinil Chung

Imaging diagnostics systems are very important to aid the understanding of core and edge confinement in 3D helical magnetic devices. In this paper we consider recent developments in optical “coherence imaging” interferometric systems that open new diagnostic capabilities for next generation devices, with particular focus on Motional Stark Effect (MSE) imaging. We present preliminary results obtained using a hybrid spatio-temporal heterodyne snapshot imaging polarimeter-interferometer for motional Stark effect imaging of the q-profile in the TEXTOR tokamak.

Polarimeter

Microwave Imaging

10.1585/pfr.5.s1010

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Citations (9)

Motional Stark effect diagnostic on TEXTOR

Review of Scientific Instruments (2004)

K. Jakubowska M. De Bock R. Jaspers M. von Hellermann Л. А. Шмаенок

A motional Stark effect diagnostic at the tokamak TEXTOR has been constructed and brought recently into operation. In contrast to diagnostics used on other tokamaks, this diagnostic reveals the direction of the magnetic field from the intensity ratio of the π and σ components of the emitted Balmer-α and not from a polarization measurement of a single line. Moreover, the complete spectrum is measured which allows determining the radial position of the measurement, and in principle the radial electric field.

Balmer series

10.1063/1.1784535

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Citations (19)

Density measurements using coherence imaging spectroscopy based on Stark broadening

Review of Scientific Instruments (2010)

O. Lischtschenko K. Bystrov G. De Temmerman J. Howard R. Jaspers

A coherence imaging camera has been set up at Pilot-PSI. The system is to be used for imaging the plasma density through the Stark effect broadening of the Hγ line. Local density values are then obtained by the Abel inversion of the measured interferometric fringe contrast. This report will present the instrument setup and proof-of-principle demonstration. The inverted spatial electron density profiles obtained near the cascaded arc source of Pilot-PSI in discharges with axial magnetic field of B=0.4 T are compared with an independent measurement of electron density by Thomson scattering and good agreement is found.

Thomson scattering

Electron temperature

10.1063/1.3490023

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Citations (11)

Disruption generated runaway electrons in TEXTOR and ITER

Nuclear Fusion (1996)

R. Jaspers N.J. Lopes Cardozo F. C. Schüller K.H. Finken T Grewe

Runaway generation during a major disruption has been observed in TEXTOR. Measurements of the synchrotron radiation yielded number, energy and pitch angle of the runaways. A simple model, which assumes that the runaways take over the current density in the centre of the discharge, successfully describes these measurements. This model is applied to JET and ITER. One interesting result of the model is that it could be favourable for ITER to have a high runaway production. This leads to a lower runaway energy and less runaway damage. Quantitative predictions are sensitive to the value of the runaway parameter = E/Ecrit, which is determined by the post-disruption temperature. The present estimate for ITER gives = 0.02, which results in a maximum runaway energy of 300 MeV in a runaway beam with a total energy of 500 MJ. However, if is enhanced, these values will be reduced. An increase to = 0.04 is sufficient to decrease the maximum runaway energy to 55 MeV and the total beam energy to 130 MJ. Secondary generation plays an important role in these predictions

10.1088/0029-5515/36/3/i09

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Citations (75)

Measuring one-dimensional and two-dimensional impurity density profiles on TEXTOR using combined charge exchange-beam emission spectroscopy and ultrasoft x-ray tomography

Review of Scientific Instruments (2004)

M. De Bock K. Jakubowska M. von Hellermann R. Jaspers A. J. H. Donné

Two techniques are presented that allow us to measure impurity density profiles in the TEXTOR tokamak plasma. The one-dimensional profiles are gathered by charge exchange recombination spectroscopy (CXRS) in combination with beam emission spectroscopy (BES). Combining CXRS and BES eliminate the need for absolute calibration. For two-dimensional profiles an ultrasoft x-ray tomography system has been developed. The system is spectrally resolved and produces local emissivity profiles of several ionization stages of impurities. Both systems are presently being commissioned. They are complementary and give an insight into the impurity distribution and transport in plasmas.

X-Ray Spectroscopy

10.1063/1.1787600

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Citations (7)

Erratum: Plasma Filamentation in the Rijnhuizen Tokamak RTP [Phys. Rev. Lett. 73, 256 (1994)]

Physical Review Letters (2003)

N.J. Lopes Cardozo I. G. J. Classen Clemens Barth C. C. Chu A. J. H. Donné

Filamentation

10.1103/physrevlett.90.149901

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Citations (3)

Wendelstein 7-Xにおける電荷交換再結合分光法【JST・京大機械翻訳】