Advances in neutral-beam-based diagnostics on the Madison Symmetric Torus reversed-field pinch (invited)

Hartog, D. J. Den; Craig, D.; Ennis, D.A.; Fiksel, G.; Gangadhara, S.; Holly, D. J.; Reardon, J. C.; Давыденко, В. И.; Ivanov, A. A.; Lizunov, A. A.; O’Mullane, M.; Summers, H. P.

doi:10.1063/1.2217920

Cited by 43 publications

(26 citation statements)

References 27 publications

(20 reference statements)

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“…One of the most significant features of the charge exchange diagnostic at TEXTOR is the modulation of the utilized neutral beam. While most other CXRS diagnostics use separate viewing lines [10,24] or complex fitting methods [12,18,44] to subtract the CXRS and bremsstrahlung background from the active signal, the diagnostic presented uses frames with and without beam signal to aquire the active and passive parts of the spectrum, a method also applied at the DIII-D Tokamaks NBI injectors. The cameras are triggered following the beam modulation, collecting emissions from active and passive phases.…”

Section: Measurement Principlesmentioning

confidence: 99%

Charge exchange recombination spectroscopy on a diagnostic hydrogen beam—measuring impurity rotation and radial electric field at the tokamak TEXTOR

Coenen

Schweer

Clever

et al. 2010

J. Phys. B: At. Mol. Opt. Phys.

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To cite this version:J W Coenen, M Clever, U Samm, O Schmitz, B Schweer, et al.. Charge exchange recombination spectroscopy on a diagnostic hydrogen beammeasuring impurity rotation and radial electric field at the tokamak TEXTOR. Journal of Physics B: Atomic, Molecular and Optical Physics, IOP Publishing, 2010, 43 (14) Abstract. In this work we present an overview on the CXRS diagnostic operated with the modulated diagnostic hydrogen beam at the Tokamak TEXTOR. The diagnostic setup combines two observation systems used for the measurement of the poloidal (v pol ) and the toroidal (v tor ) ion velocity component.At TEXTOR a differential Doppler spectroscopy approach (accurate absolute rotation scale) is combined with the high intensity and spatial resolution of a direct imaging system necessary for accurate poloidal rotation measurements on a shot by shot basis. This setup allows the full utilization of the a 2D CCD detector in the spectral and radial direction. In case of the poloidal system this allows spatial resolution in the range of mm to cm depending on the intensity requirements for the velocity. The toroidal system is comprised of a fiber-optic array. The combination of the two measurements with a low power diagnostic beam can in principal be operated during any available heating scenario without interfering with the discharge. Time resolution is limited by the necessary averaging process, typically a stable plateau of 3 s during a TETXOR pulse is used. The TEXTOR tokamak has the ability to apply momentum input with two tangential neutral beam heating injectors, allowing for measurements under various heating and momentum input scenarios. With the presented diagnostic half the plasma minor radius at a spatial resolution of ∼ 1cm is covered. With the CVI line at 529.053 nm an accuracy of 0.7km/s for the poloidal and ∼ 5 km/s for the toroidal system is given. The temperature is measured with an accuracy of a few eV. The presented work illustrates the capability of the system during a toroidal momentum scan, showing the self-consistent determination of the radial electric field from experimental CXRS data based on the radial force balance.Confidential: not for distribution.

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Section: Measurement Principlesmentioning

confidence: 99%

Charge exchange recombination spectroscopy on a diagnostic hydrogen beam—measuring impurity rotation and radial electric field at the tokamak TEXTOR

Coenen

Schweer

Clever

et al. 2010

J. Phys. B: At. Mol. Opt. Phys.

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“…and T jj in the core of MST during the reconnection heating event. A simultaneous background measurement allows radial spatial resolution of 1-2 cm and temporal resolution of 100 s [23,24]. The temperatures as a function of time from many similar events are averaged together, aligned such that t ¼ 0 is the maximum rate of change of magnetic flux during reconnection, and grouped into 3 density ranges.…”

mentioning

confidence: 99%

Anisotropic Ion Heating and Tail Generation during Tearing Mode Magnetic Reconnection in a High-Temperature Plasma

et al. 2011

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Complementary measurements of ion energy distributions in a magnetically confined high-temperature plasma show that magnetic reconnection results in both anisotropic ion heating and the generation of suprathermal ions. The anisotropy, observed in the C(+6) impurity ions, is such that the temperature perpendicular to the magnetic field is larger than the temperature parallel to the magnetic field. The suprathermal tail appears in the majority ion distribution and is well described by a power law to energies 10 times the thermal energy. These observations may offer insight into the energization process.

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“…The CHERS diagnostic technique 14 is routinely employed for localized equilibrium values of ion velocity and temperature on many plasma devices 15 including the Madison Symmetric Torus ͑MST͒. 16,17 However, measurements using CHERS with high enough bandwidth to resolve fluctuations in velocity due to tearing modes were reported only once 18 and a correlation with tearing modes was not performed. 19 The construction of a new optical spectrometer with simultaneously high throughput and large dispersion provides flow measurements localized to Ϯ1 cm with 100 kHz bandwidth yielding the spatial structure of tearing mode flows.…”

Section: Introductionmentioning

confidence: 99%

Local measurements of tearing mode flows and the magnetohydrodynamic dynamo in the Madison Symmetric Torus reversed-field pinch

et al. 2010

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The first localized measurements of tearing mode flows in the core of a hot plasma are presented using nonperturbing measurements of the impurity ion flow. Emission from charge exchange recombination is collected by a novel high optical throughput duo spectrometer providing localized ͑Ϯ1 cm͒ measurements of C +6 impurity ion velocities resolved to Ͻ500 m / s with high bandwidth ͑100 kHz͒. Poloidal tearing mode flows in the Madison Symmetric Torus reversed-field pinch are observed to be localized to the mode resonant surface with a radial extent much broader than predicted by linear magnetohydrodynamic ͑MHD͒ theory but comparable to the magnetic island width. The relative poloidal flow amplitudes among the dominant core modes do not reflect the proportions of the magnetic amplitudes. The largest correlated flows are associated with modes having smaller magnetic amplitudes resonant near the midradius. The MHD dynamo due to these flows on the magnetic axis is measured to be adequate to balance the mean Ohm's law during reduced tearing activity and is significant but does not exclude other dynamo mechanisms from contributing during a surge in reconnection activity.

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Advances in neutral-beam-based diagnostics on the Madison Symmetric Torus reversed-field pinch (invited)

Cited by 43 publications

References 27 publications

Charge exchange recombination spectroscopy on a diagnostic hydrogen beam—measuring impurity rotation and radial electric field at the tokamak TEXTOR

Charge exchange recombination spectroscopy on a diagnostic hydrogen beam—measuring impurity rotation and radial electric field at the tokamak TEXTOR

Anisotropic Ion Heating and Tail Generation during Tearing Mode Magnetic Reconnection in a High-Temperature Plasma

Local measurements of tearing mode flows and the magnetohydrodynamic dynamo in the Madison Symmetric Torus reversed-field pinch

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