Advanced neutral gas diagnostics for magnetic confinement devices

Wenzel, U.; Kremeyer, T.; Schlisio, G.; Marquardt, M.; Pedersen, T. S.; Schmitz, O.; Mackie, Bill; Maisano-Brown, Jeannette

doi:10.1088/1748-0221/12/09/c09008

Cited by 15 publications

(14 citation statements)

References 6 publications

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“…This curve was extrapolated to lower temperatures since the heating current at the operational point of the pressure gauge was below the measuring range. First tests were made with the original potential distribution of the APGs without magnetic field [4]. Electron currents between 250 and 320 µA were measured at the anode, confirming that the LaB 6 rod was properly working in the pressure gauge.…”

Section: Introductionmentioning

confidence: 76%

“…We observed a moderate pressure increase up to 7 × 10 −6 mbar as measured by the Penning gauge. After conditioning, the LaB 6 pressure gauge was operated in feedback mode with the standard APG potentials at the electrodes: cathode 20V, control grid 105 V and anode 250 V (see [4] for details of the potential settings). The heating current was hardwarelimited to 3 A.…”

Section: Potential Settingsmentioning

confidence: 99%

“…ASDEX Upgrade [2] or DIII-D [3] and stellarators as e.g. W7-X [4]. APGs are also foreseen for the ITER facility [5].…”

Section: Introductionmentioning

confidence: 99%

“…During operation of APGs in the Wendelstein 7-X stellarator it was observed that some cathodes were bent, some were even damaged to the point of fail- ure. The loops appear to be the cause of failure [4]. When the cathodes are deformed, a higher heating current is needed for the same electron current at the anode, increasing the Lorentz forces and the temperature of the filament, which can lead to further deformation.…”

Section: Introductionmentioning

confidence: 99%

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An ionization pressure gauge with LaB6 emitter for long-term operation in strong magnetic fields

Wenzel

Pedersen

Marquardt

et al. 2018

Review of Scientific Instruments

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We report here on a potentially significant improvement in the design of neutral pressure gauges of the so-called ASDEX-type which were first used in the Axially Symmetric Divertor EXperiment (ASDEX). Such gauges are considered state-of-the-art and are in wide use in fusion experiments, but they nonetheless suffer from a relatively high failure rate when operated at high magnetic field strengths for long times. This is therefore a significant concern for long-pulse, high-field experiments such as Wendelstein 7-X (W7-X) and ITER. The new design is much more robust. The improvement is to use a LaB 6 crystal instead of a tungsten wire as the thermionic emitter of electrons in the gauge. Such a LaB 6 prototype gauge was successfully operated for a total of 60 hours in B = 3.1 T, confirming the significantly improved robustness of the new design, and qualifying it for near-term operation in W7-X. With the LaB 6 crystal, an order of magnitude reduction in heating current is achieved, relative to the tungsten filament based gauges, from 15-20 A to 1-2 A. This reduces the Lorenz forces and the heating power by an order of magnitude also and is presumably the reason for the much improved robustness. The new gauge design, test environment setup at the superconducting magnet, and results from test operation are described.

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Section: Introductionmentioning

confidence: 76%

Section: Potential Settingsmentioning

confidence: 99%

“…ASDEX Upgrade [2] or DIII-D [3] and stellarators as e.g. W7-X [4]. APGs are also foreseen for the ITER facility [5].…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

An ionization pressure gauge with LaB6 emitter for long-term operation in strong magnetic fields

Wenzel

Pedersen

Marquardt

et al. 2018

Review of Scientific Instruments

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“…For OP1.2 13 additional pressure gauges have been mounted behind the divertor targets and baffles. Together with the five pressure gauges in midplane positions from OP1.1 [23], the neutral compression ratio of the divertor can be studied. One of the midplane pressure gauges had to be repaired after OP1.1.…”

Section: Neutral Pressure Gaugesmentioning

confidence: 99%

Upgrades of edge, divertor and scrape-off layer diagnostics of W7‐X for OP1.2

Hathiramani

Ali

Anda

et al. 2018

Fusion Engineering and Design

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Wendelstein 7-X (W7-X) is the world's largest superconducting nuclear fusion experiment of the optimized stellarator type. In the first Operation Phase (OP1.1) helium and hydrogen plasmas were studied in limiter configuration. The heating energy was limited to 4 MJ and the main purpose of that campaign was the integral commissioning of the machine and diagnostics, which was achieved very successfully. Already from the beginning a comprehensive set of diagnostics was available to study the plasma. On the path towards high-power, high-performance plasmas, W7-X will be stepwise upgraded from an inertially cooled (OP1.2, limited to 80 MJ) to an actively cooled island divertor (OP2, 10 MW steady-state plasma operation). The machine is prepared for OP1.2 with 10 inertially cooled divertor units, and the experimental campaign has started recently.The paper describes a subset of diagnostics which will be available for OP1.2 to study the plasma edge, divertor and scrape-off layer physics including those already available for OP1.1, plus modifications, upgrades and new systems. The focus of this summary will be on technical and engineering aspects, like feasibility and assembly but also on reliability, thermal loads and shielding against magnetic fields.

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