Magnetic configuration effects on the Wendelstein 7-X stellarator

Dinklage, A.; Beidler, C. D.; Helander, P.; Fuchert, G.; Maaßberg, H.; Rahbarnia, K.; Pedersen, T. S.; Turkin, Y.; Wolf, R. C.; Alonso, A.; Andreeva, T.; Blackwell, Boyd; Bozhenkov, S.; Buttenschön, B.; Czarnecka, A.; Effenberg, F.; Feng, Y.; Geiger, J.; Hirsch, M.; Höfel, U.; Jakubowski, M.; Klinger, T.; Knauer, J.; Kocsis, G.; Krämer–Flecken, A.; Kubkowska, M.; Langenberg, A.; Laqua, H. P.; Marushchenko, N. B.; Mollén, A.; Neuner, U.; Niemann, H.; Pasch, E.; Pablant, N.; Rudischhauser, L.; Smith, H. M.; Schmitz, O.; Stange, T.; Szepesi, T.; Weir, G.; Windisch, T.; Wurden, G. A.; Zhang, D.

doi:10.1038/s41567-018-0141-9

Cited by 140 publications

(153 citation statements)

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“…The minimisation of the bootstrap current was one of the main W7-X optimisation criteria. The comparison of the bootstrap evolution in different magnetic configuration verified experimentally the optimisation predictions [4]. Here any ECCD current has to be suppressed, therefore the ECRH launch was precisely to the perpendicular direction at the plasma axis, where the power is absorbed.…”

Section: Eccd and Long Pulse Operationsupporting

confidence: 68%

Overview of W7-X ECRH Results

et al. 2019

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In its second operation phase (OP1.2a) W7-X was equipped with full 3d island divertor and an upgraded ECRH-system of 10 gyrotrons with a total port through power of 7 MW. The combination of pellet fueling and high density ECRH enabled to explore density above 1 1020 m-3. In particular with the O2-polarisation combined with a multi-pass reflector tile system a density of up to 1.4 1020 m-3 was achieved. At slightly lower densities high core beta values and record values of the fusion tripple product of 0.66 1020 m-3 keVs for stellarators were reached. In addition routine plasma start-up and ECRH wall conditioning were performed. The island divertor enables to demonstrate the intrinsic steady state capabilities of W7-X, where stationary discharges of up to 30s were demonstrated being only limited by the heat capacity of the uncooled divertor. With the flexible ECRH launch system current density profile variations were used for MHD stability investigations. Here by fine-tuning of the ECCD profile different MHD activity could be triggered.

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Section: Eccd and Long Pulse Operationsupporting

confidence: 68%

Overview of W7-X ECRH Results

et al. 2019

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“…In order to isolate the effect of the magnetic configuration on the neutron rates, the plasma profiles were left unchanged between the configurations. In reality the temperature and density will differ between magnetic configurations [24].…”

Section: Conclusion and Further Workmentioning

confidence: 99%

Overview of first Wendelstein 7-X high-performance operation

Klinger¹,

Andreeva²,

Bozhenkov³

et al. 2019

Nucl. Fusion

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Demonstrating improved confinement of energetic ions is one of the key goals of the Wendelstein 7-X (W7-X) stellarator. In the past campaigns, measuring confined fast ions has proven to be challenging. Future deuterium campaigns would open up the option of using fusion-produced neutrons to indirectly observe confined fast ions. There are two neutron populations: 2.45 MeV neutrons from thermonuclear and beam-target fusion, and 14.1 MeV neutrons from DT reactions between tritium fusion products and bulk deuterium. The 14.1 MeV neutron signal can be measured using a scintillating fiber neutron detector, whereas the overall neutron rate is monitored by common radiation safety detectors, for instance fission chambers. The fusion rates are dependent on the slowing-down distribution of the deuterium and tritium ions, which in turn depend on the magnetic configuration via fast ion orbits. In this work, we investigate the effect of magnetic configuration on neutron production rates in W7-X. The neutral beam injection, beam and triton slowing-down distributions, and the fusion reactivity are simulated with the ASCOT suite of codes. The results indicate that the magnetic configuration has only a small effect on the production of 2.45 MeV neutrons from DD fusion and, particularly, on the 14.1 MeV neutron production rates. Despite triton losses of up to 50 %, the amount of 14.1 MeV neutrons produced might be sufficient for a time-resolved detection using a scintillating fiber detector, although only in high-performance discharges.

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“…During the first test operation, OP1.1, dedicated to integrated commissioning, tests of components and diagnostics, the device was equipped with five uncooled inboard carbon limiters only, which restricted the magnetic configuration and the overall energy input for a single experiment scenario to avoid uncontrolled overheating [4], [5]. Test-divertor operation started September to December 2017 (OP1.2a) and has been completed July to Oct. 2018 (OP1.2b).…”

Section: Introductionmentioning

confidence: 99%

ECE Diagnostic for the initial Operation of Wendelstein 7-X

et al. 2019

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The ECE diagnostic at W7-X in its standard mode of operation measures in X2 mode polarization with a 32 channel radiometer in the frequency band around 140 GHz for central magnetic field 2.5T. The radiometer is calibrated by a noise source and the overall system absolutely calibrated by means of a hot-cold source placed outside the torus in front of a Gaussian telescope optics with identical geometry and transmission line as it is installed for the measurements in the plasma vessel. The system is supplemented with a 16 channel zoom device with 4 GHz span for higher frequency resolution at a suitable radial range and a Michelson interferometer for the characterization of higher harmonics sharing the same line of sight.

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Magnetic configuration effects on the Wendelstein 7-X stellarator

Cited by 140 publications

References 50 publications

Overview of W7-X ECRH Results

Overview of W7-X ECRH Results

Overview of first Wendelstein 7-X high-performance operation

ECE Diagnostic for the initial Operation of Wendelstein 7-X

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