Electron temperature and heat load measurements in the COMPASS divertor using the new system of probes

Adámek, Jiřı́; Seidl, J.; Horáček, J.; Komm, M.; Eich, T.; Pánek, R.; Cavalier, J.; Devitre, A.; Peterka, M.; Vondráček, P.; Ştöckel, J.; Šesták, D.; Grover, O.; Bílková, P.; Böhm, P.; Varju, J.; Havránek, A.; Weinzettl, V.; Lovell, J.; Dimitrova, M.; Mitošínková, K.; Dejarnac, R.; Hron, M.

doi:10.1088/1741-4326/aa7e09

Cited by 33 publications

(59 citation statements)

References 47 publications

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“…1C). This transition was accompanied by a sudden change of temperature measured by the combined array of Langmuir and Ball-pen divertor probes [6] as shown in Fig. 3, for the discharge #13729 (HFS seeding ΓN2 = 2.0 × 10 20 s −1 ), where several such transitions were observed, since the amount of injected nitrogen was probably marginal with respect to detachment access.…”

Section: Radiation Measured By the Visible Camerasmentioning

confidence: 85%

Divertor impurity seeding experiments at the COMPASS tokamak

et al. 2019

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Partial detachment is the desired regime for the baseline burning plasma scenario in ITER and next-step devices, as it allows to convert the majority of the energy carried by charged particles through the scrape-off-layer (SOL) is dissipated and thus deposition of localized heat fluxes in the divertor region is avoided. The COMPASS tokamak is equipped with an open divertor and has a relatively short connection length, both factors being unfavourable for access to detachment. As such, it only allows to approach naturally detached operation at very high line-averaged densities (> 10 20 m −3), which are incompatible e.g. with maintaining the ELMy H-mode regime. In order to achieve the detachment at lower densities, impurities (such as nitrogen) should be injected into the plasma in the divertor region. A series of experiments with impurity injection in the range of 1-9×1020 molecules per second at different locations in the divertor were performed with the aim to cool the plasma and influence the particle and heat transport onto the divertor targets and provoke partial detachment. Previously reported results [M. Komm et al, EPS 2017, P1.118] were largely extended by injection of nitrogen at the outer divertor target.

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Section: Radiation Measured By the Visible Camerasmentioning

confidence: 85%

Divertor impurity seeding experiments at the COMPASS tokamak

et al. 2019

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“…ELM delivers huge energy (projected to the surface normal 1.2 MJ/m predicted for ITER 23 , 24 ) strongly localized around the divertor strike point within a millisecond-long pulse. This implicates the tungsten surface to heat well above recrystallization (which strongly limits the cracking lifetime 25 ) and even flash-melting 26 , 27 .…”

Section: Thermonuclear Fusion Reduction Due To Elm-induced Tungsten D...mentioning

confidence: 99%

Novel concept suppressing plasma heat pulses in a tokamak by fast divertor sweeping

Horáček

Lukes

Adámek

et al. 2022

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One of the remaining challenges in magnetic thermonuclear fusion is survival of the heat shield protecting the tokamak reactor vessel against excessive plasma heat fluxes. Unmitigated high confinement edge localized mode (ELM) is a regular heat pulse damaging the heat shield. We suggest a novel concept of magnetic sweeping of the plasma contact strike point fast and far enough in order to spread this heat pulse. We demonstrate feasibility of a dedicated copper coil in a resonant circuit, including the induced currents and power electronics. We predict the DEMO ELM properties, simulate heat conduction, 3D particles motion and magnetic fields of the plasma and coil in COMSOL Multiphysics and Matlab. The dominant system parameter is voltage, feasible 18 kV yields 1 kHz sweeping frequency, suppressing the ELM-induced surface temperature rise by a factor of 3. Multiplied by other known mitigation concepts, ELMs might be mitigated enough to ensure safe operation of DEMO.

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“…To further convince the reader that the tomographic reconstruction extracts the important part of the data on more than one snapshot, we have compared the reconstructed data with signals coming from Langmuir probes. The divertor of COMPASS was recently equipped [21] with a 54 Langmuir probe array measuring ion saturation currents (-270 V applied to the probes) at a sampling frequency of 4 MHz and located at ϕ =127.5 degree from the reconstructed plane. At that location, mainly two probes are magnetically connected to the part of the reference poloidal plane visible in the camera field, so-called LPA46 and LPA47 in the COMPASS database.…”

Section: Validation With Probesmentioning

confidence: 99%

Tomographic reconstruction of tokamak edge turbulence from single visible camera data and automatic turbulence structure tracking

et al. 2019

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Following the lead of [Nguyen van Yen Nucl. Fus. 52 (2012) 013005 (11pp)], this article tackles the problem of tomographic inversion with one camera assuming a constant emissivity of light along the magnetic field lines. In this way, the 3D problem reduces to 2D by helical symmetry, allowing for the reconstruction of any poloidal plane in the field of view of the camera. It is shown in this article that the complexity of using a wavelet basis for the reconstruction, as presented by Nguyen van Yen, is not necessary. The method is also validated by confronting it to 3D numerical data coming from the TOKAM3X code, for which the emissivity is slowly varying along the field lines (up to 20 %), showing the robustness of the reconstruction. The technique is then applied to real camera data recorded during a D-shaped ohmic plasma shot realized in the COMPASS tokamak. The method is experimentally validated by comparing reconstructed data from camera and ion saturation currents measured by Langmuir probes in the divertor region. Finally, it is shown that automatic detection and tracking of structures visible in the reconstructed poloidal plane enables unique investigations of edge plasma physics and opens wide perspectives for this method.

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Electron temperature and heat load measurements in the COMPASS divertor using the new system of probes

Cited by 33 publications

References 47 publications

Divertor impurity seeding experiments at the COMPASS tokamak

Divertor impurity seeding experiments at the COMPASS tokamak

Novel concept suppressing plasma heat pulses in a tokamak by fast divertor sweeping

Tomographic reconstruction of tokamak edge turbulence from single visible camera data and automatic turbulence structure tracking

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