Contribution to the multi-machine pedestal scaling from the COMPASS tokamak

Komm, M.; Bílková, P.; Aftanas, M.; Berta, M.; Böhm, P.; Bogar, O.; Frassinetti, L.; Grover, O.; Hacek, P.; Havlíček, J.; Hron, M.; Imríšek, M.; Krbec, J.; Mitošínková, K.; Naydenkova, D.; Pánek, R.; Peterka, M.; Snyder, P. B.; Štefániková, E.; Ştöckel, J.; Šos, M.; Urbán, J.; Varju, J.; Vondráček, P.; Weinzettl, V.

doi:10.1088/1741-4326/aa6659

Cited by 9 publications

(7 citation statements)

References 24 publications

(43 reference statements)

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“…These values did not deviate by more than 15% throughout the seeding and fuelling scans, ensuring a valid comparison between the discharges. Pedestal collisionality was observed to range from 1 to 5 and this is in good agreement with other verified experiments that have presented values between 0.8 and 5 [2,18,23].…”

Section: Resultssupporting

confidence: 92%

Pedestal structure and energy confinement studies on TCV

Sheikh

Dunne

Frassinetti

et al. 2018

Plasma Phys. Control. Fusion

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High external gas injection rates are foreseen for future devices to reduce divertor heat loads and this can influence pedestal stability. Fusion yield has been estimated to vary as strongly as T 2 e,ped so an understanding of the underlying pedestal physics in the presence of additional fuelling and seeding is required. To address this, a database scanning plasma triangularity, fuelling and nitrogen seeding rates in neutral beam (NBH) heated ELM-y H-mode plasmas was constructed on TCV. Low nitrogen seeding was observed to increase pedestal top pressure but all other gas injection rates led to a decrease. Lower triangularity discharges were found to be less sensitive to variations in gas injection rates. No clear trend was measured between plasma top Pe and stored energy which is attributed to the non-stiffness of core plasma pressure profiles. Peeling ballooning stability analysis put these discharges close to the ideal MHD stability boundary. A constant for D in the relation pedestal width w = D β P ed θ , was not found. Experimentally inferred values of D were used in EPED1 simulations and gave good agreement for pedestal width. Pedestal height agreed well for high triangularity but was overestimated for low triangularity. IPED simulations showed that relative shifts in pedestal position were contributing significantly to the pedestal height and were able to reproduce the measured profiles more accurately.

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Section: Resultssupporting

confidence: 92%

Pedestal structure and energy confinement studies on TCV

Sheikh

Dunne

Frassinetti

et al. 2018

Plasma Phys. Control. Fusion

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“…It means the spatial resolution of the edge TS system was decreasing with z position, going from 3.5 mm at z = 200 mm to 6.0 mm at 284 mm. Moreover, the field of view turned out to be not sufficient for all plasma scenarios and limited reliable pedestal observations to smaller plasmas only [6].…”

Section: Edge Ts Lensmentioning

confidence: 99%

“…This study is important for future fusion machines like ITER [3,4] and the Thomson scattering diagnostic system, measuring electron temperature and density profiles, plays a key role in it. The COMPASS tokamak already contributes to the multi-machine database of pedestal parameters [5,6]. The presented upgrades allow enlarging the operational space of plasma scenarios covered well with the TS measurements and improving the statistics of the measured data by increasing signal-to-noise ratio of the measurements and increasing the repetition rate of the TS system.…”

Section: Introductionmentioning

confidence: 99%

High resolution Thomson scattering on the COMPASS tokamak—extending edge plasma view and increasing repetition rate

et al. 2018

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The Thomson scattering (TS) diagnostic system on the COMPASS tokamak consists of separate collection optics for core and edge plasmas. Till now, the adverse orientation of the viewport available for the edge TS limited the investigated plasma scenarios to those, where H-mode plasma pedestal was possible to be observed. The vacuum vessel port has been recently modified and directed more to the plasma edge. To bridge the time for designing and manufacturing a new lens, the so far used edge TS collection lens was tilted and the fibre bundles rearranged to comply with the new geometry. However, the full potential of the new port is utilized only by the newly designed and manufactured lens. Comparison of performance of the collection lenses before and after the viewport modification is presented. Apart from the edge collection system upgrade, the laser system was extended by two lasers with parameters similar to the original two, thus increasing the repetition rate of the TS system to 120 Hz or allowing to obtain four profiles with tight timing in order to measure fast transient events in the plasma.

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“…The detection is based on filter polychromators equipped with avalanche photodiodes, allowing covering the electron temperature range from 30 eV to 5 keV. The edge TS system was upgraded recently with the aim to improve quality and extent of measured data for an H-mode pedestal analysis [34]. The first phase of the upgrade consisted of cutting the existing edge TS port and welding a new one.…”

Section: Upgrade Of Optical and Microwave Diagnostics And Plasma Tomo...mentioning

confidence: 99%