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19 results on '"Michelsen, P.K."'

6. Current fast ion collective Thomson scattering diagnostics at TEXTOR and ASDEX Upgrade, and ITER plans (invited)

Author

Korsholm, S.B., Bindslev, H., Meo, F., Leipold, F., Michelsen, P.K., Michelsen, S., Nielsen, S.K., Tsakadze, E.L., Woskov, P., Westerhof, E., Oosterbeek, J.W., Hoekzema, J., Leuterer, F., and Wagner, D.

Abstract

Fast ion physics will play an important role on ITER where confined alpha particles will affect plasma dynamics and overall confinement. Fast ion collective Thomson scattering (CTS) using gyrotrons has the potential to meet the need for measuring the spatially localized velocity distributions of confined fast ions in ITER. Currently, CTS experiments are performed at TEXTOR using a 150 kW, 0.2 s, 110 GHz gyrotron and a receiver upgraded at the Ris phi National Laboratory. The gyrotron and receiver optics have also been upgraded for rapid scanning during a plasma shot. The receiver consists of a nine-mirror quasioptical transmission line including a universal polarizer and a 42-channel data acquisition system, which allows complete coverage of the double sideband scattered spectrum for localized (similar to 10 cm) time resolved (4 ms) measurements of the ion velocity distribution. At ASDEX Upgrade (AUG) a similar 50-channel CTS receiver has been installed. This CTS system will use the 105 GHz frequency of a dual frequency gyrotron. The gyrotron is presently being commissioned. CTS campaigns are scheduled for the summer of 2006 with a probe power of up to 1 MW for 10 s. This report presents the alignment of the quasioptical transmission line, calibration, and gyrotron tuning of the TEXTOR and AUG CTS systems. We will also review the progress on the design of the proposed fast ion CTS diagnostic for ITER. It is envisaged that scattered radiation from two 60 GHz probe beams launched from the low field side midplane port will be received by two arrays of receivers located on the low and high field sides of the plasma. This geometry will allow the ion velocity distribution near perpendicular and near parallel to the magnetic field to be measured in ten or more spatial locations covering the full plasma cross section. The temporal resolution can be significantly better than the required 100 ms. (c) 2006 American Institute of Physics.

Published
2006

7. Modification of the collective Thomson scattering radiometer in the search for parametric decay on TEXTOR

Author

Nielsen, S.K., Salewski, M., Bongers, W., Korsholm, S.B., Leipold, F., Meo, F., Michelsen, P.K., Moseev, D., Oosterbeek, J.W., Stejner, M., Westerhof, E., Nielsen, S.K., Salewski, M., Bongers, W., Korsholm, S.B., Leipold, F., Meo, F., Michelsen, P.K., Moseev, D., Oosterbeek, J.W., Stejner, M., and Westerhof, E.

Abstract

Strong scattering of high-power millimeter waves at 140 GHz has been shown to take place in heating and current-drive experiments at TEXTOR when a tearing mode is present in the plasma. The scattering signal is at present supposed to be generated by the parametric decay instability. Here we describe the heterodyne detection system used to characterize the newly discovered signal measured at TEXTOR, and we present spectral shapes in which the signal can appear under different conditions. The radiation is collected by the receiver through a quasi-optical transmission line that is independent of the electron cyclotron resonance heating transmission line, and so the scattering geometry is variable. The signal is detected with 42 frequency channels ranging from 136 to 142 GHz. We demonstrate that the large signal does not originate from gyrotron spurious radiation. The measured signal agrees well with independent backscattering radiometer data.

Published
2012

8. Measurements of Intrinsic Ion Bernstein Waves in a Tokamak by Collective Thomson Scattering

Author

Korsholm, S.B., Stejner, M., Bindslev, H., Furtula, V., Leipold, F., Meo, F., Michelsen, P.K., Moseev, D., Nielsen, S.K., Salewski, M., de Baar, Marco, Delabie, E.G., Kantor, M., Bürger, A., Korsholm, S.B., Stejner, M., Bindslev, H., Furtula, V., Leipold, F., Meo, F., Michelsen, P.K., Moseev, D., Nielsen, S.K., Salewski, M., de Baar, Marco, Delabie, E.G., Kantor, M., and Bürger, A.

Abstract

In this Letter we report measurements of collective Thomson scattering (CTS) spectra with clear signatures of ion Bernstein waves and ion cyclotron motion in tokamak plasmas. The measured spectra are in accordance with theoretical predictions and show clear sensitivity to variation in the density ratio of the main ion species in the plasma. Measurements with this novel diagnostic demonstrate that CTS can be used as a fuel ion ratio diagnostic in burning fusion plasma devices.

Published
2011

9. Development of novel fuel ion ratio diagnostic techniques

Author

Korsholm, S.B., Stejner, M., Conroy, S., Ericsson, G., Gorini, G., Tardocchi, M., Hellermann, von, M.G., Jaspers, R.J.E., Lischtschenko, O., Delabie, E.G., Bindslev, H., Furtula, V., Leipold, F., Meo, F., Michelsen, P.K., Moseev, D., Nielsen, S.K., Salewski, M., Korsholm, S.B., Stejner, M., Conroy, S., Ericsson, G., Gorini, G., Tardocchi, M., Hellermann, von, M.G., Jaspers, R.J.E., Lischtschenko, O., Delabie, E.G., Bindslev, H., Furtula, V., Leipold, F., Meo, F., Michelsen, P.K., Moseev, D., Nielsen, S.K., and Salewski, M.

Abstract

To overcome the challenge of measuring the fuel ion ratio in the core (¿

Published
2010

10. Measurements of ion temperature and plasma hydrogenic composition by collective Thomson scattering in neutral beam heated discharges at TEXTOR

Author

Stejner, M., Salewski, M., Korsholm, S.B., Bindslev, H., Delabie, E., Leipold, F., Meo, F., Michelsen, P.K., Moseev, D., Nielsen, S.K., Burger, A., de Baar, M., team, TEXTOR, Science and Technology of Nuclear Fusion, and Control Systems Technology

Subjects
Materials science, Scattering, Thomson scattering, Cyclotron, Radius, Plasma, Condensed Matter Physics, Ion, law.invention, Nuclear Energy and Engineering, law, Physics::Plasma Physics, Physics::Space Physics, Atomic physics, Spectroscopy, Beam (structure)
Abstract

A method is developed to perform plasma composition and ion temperature measurements across the plasma minor radius in TEXTOR based on ion cyclotron structures in collective Thomson scattering spectra. By gradually moving the scattering volume, we obtain measurements across the outer midplane of the plasma. Results for the ion temperature are compared with ion temperatures measured by active charge-exchange recombination spectroscopy.

Published
2013
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17. Nonlinear evolution of whistler wave modulational instability.

Author

Karpman, V.I., Lynov, J.P., Michelsen, P.K., and Rasmussen, J. Juul

Subjects
MAGNETOHYDRODYNAMIC waves, PLASMA gases, PLASMA waves
Abstract

Investigates the nonlinear evolution of the modulational instability of whistler waves coupled to fast magnetosonic waves (FMS) and to slow magnetosonic waves (SMS). Observation of a quasi-recurrent behavior with a slow spreading of the energy to higher and higher mode numbers in FMS-coupling; Lack of recurrent behavior in SMS-coupling.

Published
1995
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19. IR and UV gas absorption measurements during NO x reduction on an industrial natural gas fired power plant

Author

Stamate, E., Chen, W., Jørgensen, L., Jensen, T.K., Fateev, A., and Michelsen, P.K.

Subjects
*ABSORPTION, *CHEMICAL reduction, *NATURAL gas, *POWER plants, *CHEMICAL kinetics, *NITROGEN oxides, *RADICALS (Chemistry)
Abstract

Abstract: NO x reduction of flue gas by plasma-generated ozone was investigated in pilot test experiments on an industrial power plant running on natural gas. Reduction rates higher than 95% have been achieved for a molar ratio O3:NO x slightly below two. Fourier transform infrared and ultraviolet absorption spectroscopy were used for spatial measurements of stable molecules and radicals along the reduction reactor. Reactions of O3 injected in the flue gas in the reduction reactor were also modeled. Experiments are in good agreement with numerical simulations. The operation costs for NO x reduction were estimated based on field tests measurements. [Copyright &y& Elsevier]

Published
2010
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