Measurement of the plasma edge profiles using the combined probe on W7-X

Drews, P.; Liang, Yun-Feng; Liu, Shaocheng; Krämer‐Flecken, A.; Neubauer, O.; Geiger, J.; Rack, M.; Nicolai, D.; Grulke, O.; Killer, C.; Wang, Nengchao; Charl, A.; Schweer, B.; Denner, P.; Henkel, Malte; Gao, Yu; Hollfeld, K. P.; Satheeswaran, G.; Sandri, N.; Höschen, D.

doi:10.1088/1741-4326/aa8385

Cited by 26 publications

(30 citation statements)

References 19 publications

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“…The combined probe head consists of Langmuir probes, a Mach probe, and two tri-axial pick-up coils, which is able to measure the electron density, the electron temperature, the plasma potential, the radial electric field, the parallel flow velocity, and the variation of magnetic fields in the direction of (R, u, Z). 17,18 The combined probe head and the arrangement of Langmuir pins are presented in Fig. 1.…”

Section: Diagnostics Setupmentioning

confidence: 99%

Characteristics of the SOL turbulence structure in the first experimental campaign on W7-X with limiter configuration

et al. 2018

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In the first experimental campaign of Wendelstein 7-X (W7-X), a combined probe head mounted on the multipurpose manipulator has been used to measure the scrape-off layer (SOL) turbulence characteristics. The preliminary experimental results are summarized to illustrate the SOL turbulence properties in the limiter configuration on W7-X. In a standard limiter configuration, significant electrostatic fluctuations can be found in the near SOL, and the dominant frequency of fluctuation power is below 100 kHz. The auto-correlation spectrum power law decay factor is a % À1 below 40 kHz and a %-2 between 50 and 200 kHz. A broadband spectrum appears between 240 and 380 kHz with a low spectral power density, but a high cross-correlation coefficient. The statistical characteristics of turbulence are calculated by the two-point cross-correlation technique. A clear poloidal dispersion relation is found in the spectrum S(k h , f), propagating along the ion diamagnetic drift direction with a group velocity (below 100 kHz) about 0.56 km/s in the near SOL in the laboratory frame. The poloidal correlation length is around 5-10 mm in SOL. The turbulence phase velocity is about 0.5-1 km/s when close to the last closed flux surface, which is comparable with the poloidal E Â B drift speed.

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Section: Diagnostics Setupmentioning

confidence: 99%

Characteristics of the SOL turbulence structure in the first experimental campaign on W7-X with limiter configuration

et al. 2018

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“…It is not possible for the probe to measure the / 5 6 island chain directly and the = n m 5 5 island chain is supposed to be cut off by the limiter. In figure 2 the two profiles of the electron temperature and density are shown for the J and the iota 13 configuration, one can see that the shift of the magnetic axis, field line tracing [5] also suggests this shift. The / 5 5 island is also visible for the iota 13 configuration, in [5] it is also shown that the position of the island corresponds to a region of high connection length.…”

Section: Methodsmentioning

confidence: 89%

“…In conjunction with the multi-purpose manipulator (MPM), the combined probe has been installed [3,4], with it measurements of the electron temperature and density have been carried out on W7-X in the first experimental campaign. The electron temperature and density profiles obtained by these measurements found in [5] are used to calculate the radial heat flux profiles [5], also details the poincaré plots for the relevant iota configurations. The influence of the magnetic configuration on the radial transport of heat and particles can therefore be studied in respect to the modification due to scanning the iota by tuning the planar coil currents (see table 1).…”

Section: Introductionmentioning

confidence: 99%

Magnetic configuration effects on the edge heat flux in the limiter plasma on W7-X measured using the infrared camera and the combined probe

Drews

Niemann

Cosfeld

et al. 2018

Plasma Sci. Technol.

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Controlling the heat and particle fluxes in the plasma edge and on the plasma facing components is important for the safe and effective operation of every magnetically confined fusion device. This was attempted on Wendelstein 7-X in the first operational campaign, with the modification of the magnetic configuration by use of the trim coils and tuning the field coil currents, commonly named iota scan. Ideally, the heat loads on the five limiters are equal. However, they differ between each limiter and are non-uniform, due to the (relatively small) error fields caused by the misalignment of components. It is therefore necessary to study the influence of the configuration changes on the transport of heat and particles in the plasma edge caused by the application of error fields and the change of the magnetic configuration. In this paper the upstream measurements conducted with the combined probe are compared to the downstream measurements with the DIAS infrared camera on the limiter.

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“…The maximum acceleration and velocity are 3 g and 3.5 m/s, respectively. A combined probe head, which measures the radial distribution of the magnetic field with magnetic pick-up coils, the plasma temperature and density profiles with Langmuir probes and the plasma flows with a Mach probe, was mounted on the manipulator and commissioned during the campaign OP 1.1 [10]. For the next operational campaign, an improved design of the combined probe, a retarding field analyser (RFA) and a dedicated Mach probe array will be employed.…”

Section: Measurement Of Edge Upstream Plasma Profilesmentioning

confidence: 99%

Diagnostic set-up and modelling for investigation of synergy between 3D edge physics and plasma-wall interactions on Wendelstein 7-X

et al. 2017

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A group of edge diagnostics and modelling has been developed for investigation of synergy between 3D edge physics and plasma-wall interactions on Wendelstein 7-X (W7-X). Two endoscopes have been designed for visible and ultraviolet spectroscopy and tomography of the plasma edge, along with infrared thermography of the divertor tiles. Two-dimensional profiles of impurities (e.g. helium, carbon) will be measured by two endoscopes viewing the island divertor region in the plasma edge with a spatial resolution of < 2 mm. A multipurpose manipulator, which is used as the carrier either of the probe head for measuring the plasma edge profiles or of samples for plasma exposure studies, was installed at the outside midplane on W7-X in 2015. A poloidal correlation reflectometer has also been installed at W7-X. The system consists of an antenna array observing the propagation of turbulent phenomena in the mid-plane. The EMC3-EIRENE code package has been adapted for plasma edge transport in helium plasma at W7-X using a hybrid fluid-kinetic approach by enabling EMC3 to treat non-hydrogen isotopes and extending the usage of EIRENE features within EMC3-EIRENE.

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Measurement of the plasma edge profiles using the combined probe on W7-X

Cited by 26 publications

References 19 publications

Characteristics of the SOL turbulence structure in the first experimental campaign on W7-X with limiter configuration

Characteristics of the SOL turbulence structure in the first experimental campaign on W7-X with limiter configuration

Magnetic configuration effects on the edge heat flux in the limiter plasma on W7-X measured using the infrared camera and the combined probe

Diagnostic set-up and modelling for investigation of synergy between 3D edge physics and plasma-wall interactions on Wendelstein 7-X

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