TCV experiments towards the development of a plasma exhaust solution

Reimerdes, H.; Duval, B.P.; Harrison, James R.; Labit, B.; Lipschultz, B.; Lunt, T.; Theiler, C.; Tsui, C.; Verhaegh, K.; Vijvers, W.A.J.; Boedo, J.A.; Calabrò, G.; Crisanti, F.; Innocente, P.; Maurizio, R.; Pericoli, V.; Sheikh, U.; Spolare, M.; Vianello, N.

doi:10.1088/1741-4326/aa82c2

Cited by 41 publications

(64 citation statements)

References 27 publications

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“…As shown in figure 13, with the small difference in separatrix density ∆~4%, the SF+ configuration exhibited a similar parameter profiles at the outer target as the SN, even though there is a secondary X point in private region and the connection length between midplane and target ∥ is much higher for SF+ as shown in figure 9 (e). As expected from 2-point model, equation (6,7), the scales ∝ ∥ 6/7 and the scales as ∝ ∥ −4/7 . However, the expected reduction of and increase in for SF+ plasma is absent, figure 13(b,c,d).…”

Section: Impact On Heat Flux At the Outer Targetsupporting

confidence: 70%

“…4]. Due to the tremendous challenge of heat and particle exhaust in future tokamak fusion reactors, detachment is being extensively studied in a number of tokamaks, such as JET [5], TCV [6,7], ASDEX Upgrade [8], DIII-D [9], JT-60U [10], C-Mod [11] and many others. Although detachment has an advantage in terms of heat flux and erosion issues on target, pushing detachment too far can lead to degradation of the pedestal pressure in H-mode and lower the overall confinement [12].…”

Section: Introductionmentioning

confidence: 99%

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Impact of an alternative divertor configuration on plasma detachment: pure deuterium simulations using the SOLEDGE2D-EIRENE edge transport code for HL-2M scenarios

Mao¹,

Fedorczak²,

Ciraolo³

et al. 2019

Nucl. Fusion

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The SOLEDGE-EIRENE edge plasma code provides solutions for particle & energy transport in the plasma edge within complex and realistic 2D geometries [1]. In this work, divertor detachment is simulated on the HL-2M alternative magnetic configurations in pure Deuterium plasma. Starting from typical HL-2M low single-null (SN) configuration, the snowflake plus (SF+) and snowflake minus (SF-) configurations have been investigated. Detachment of the outer target is studied in these configurations during plasma density ramps controlled by a fueling source, at constant input power and constant radial transport coefficients. Some typical characteristics of detachment, like threshold, depth and upstream window of detachment are investigated. In the three geometries, detachment onset and evolution with upstream plasma density is characterized by the gradual displacement of a radiation front from the outer target to the main X-point, as observed in experiments. It is found that, whatever the detachment in terms of particle, momentum or power dissipation, the detachment threshold is dominated primarily by the geometrical structure of divertor plate and it does not exhibit dependence on the magnetic configuration of the diverted plasma volume. In particular, the parallel connection length in the divertor is not found to affect the detachment threshold, in contrast with simple expectations from the 2-point model, but in agreement with experimental findings.

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Section: Impact On Heat Flux At the Outer Targetsupporting

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Impact of an alternative divertor configuration on plasma detachment: pure deuterium simulations using the SOLEDGE2D-EIRENE edge transport code for HL-2M scenarios

Mao¹,

Fedorczak²,

Ciraolo³

et al. 2019

Nucl. Fusion

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show abstract

“…Implicitly, it is assumed then that the temperature at the excitation/recombination emission location is the same [34,36,37], which may not be necessarily true. 3) In literature, it is sometimes assumed that Balmer line ratios indicative of recombinative emission imply that the plasma is 'recombination dominant' [15,37,38]. The number of expected photons per recombination/ionisation is, however, much different for recombination and ionisation and can be strongly dependent on the electron density.…”

Section: Introductionmentioning

confidence: 99%

Novel inferences of ionisation and recombination for particle/power balance during detached discharges using deuterium Balmer line spectroscopy

Verhaegh¹,

Lipschultz²,

Duval³

et al. 2019

Plasma Phys. Control. Fusion

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157

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The physics of divertor detachment is determined by divertor power, particle and momentum balance. This work provides a novel analysis technique of the Balmer line series to obtain a full particle/power balance measurement of the divertor. This supplies new information to understand what controls the divertor target ion flux during detachment.Atomic deuterium excitation emission is separated from recombination quantitatively using Balmer series line ratios. This enables analysing those two components individually, providing ionisation/recombination source/sinks and hydrogenic power loss measurements. Probabilistic Monte Carlo techniques were employed to obtain full error propagation -eventually resulting in probability density functions for each output variable. Both local and overall particle and power balance in the divertor are then obtained. These techniques and their assumptions have been verified by comparing the analysed synthetic diagnostic 'measurements' obtained from SOLPS simulation results for the same discharge. Power/particle balance measurements have been obtained during attached and detached conditions on the TCV tokamak.

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“…In addition, this provides an understanding of how detachment on TCV relates to the general experience of detachment. This is required to interpret recent experiments on TCV, which have been performed to investigate how magnetic divertor geometry influences detachment [8,9].…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic investigations of divertor detachment in TCV

Verhaegh

Lipschultz

Duval

et al. 2017

Nuclear Materials and Energy

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187

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The aim of this work is to provide an understanding of detachment at TCV with emphasis on analysis of the Balmer line emission. A new Divertor Spectroscopy System has been developed for this purpose. Further development of Balmer line analysis techniques has allowed detailed information to be extracted from the three-body recombination contribution to the n=7 Balmer line intensity. During density ramps, the plasma at the target detaches as inferred from a drop in ion current to the target. At the same time the Balmer $6\rightarrow2$ and $7\rightarrow2$ line emission near the target is dominated by recombination. As the core density increases further, the density and recombination rate are rising all along the outer leg to the x-point while remaining highest at the target. Even at the highest core densities accessed (Greenwald fraction 0.7) the peaks in recombination and density may have moved not more than a few cm poloidally away from the target which is different to other, higher density tokamaks, where both the peak in recombination and density continue to move towards the x-point as the core density is increased. The inferred magnitude of recombination is small compared to the target ion current at the time detachment (particle flux drop) starts at the target. However, recombination may be having more localized effects (to a flux tube) which we cannot discern at this time. Later, at the highest densities achieved, the total recombination does reach levels similar to the particle flux.Comment: Article accepted for publication in Journal of Nuclear Materials and Energ

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TCV experiments towards the development of a plasma exhaust solution

Cited by 41 publications

References 27 publications

Impact of an alternative divertor configuration on plasma detachment: pure deuterium simulations using the SOLEDGE2D-EIRENE edge transport code for HL-2M scenarios

Impact of an alternative divertor configuration on plasma detachment: pure deuterium simulations using the SOLEDGE2D-EIRENE edge transport code for HL-2M scenarios

Novel inferences of ionisation and recombination for particle/power balance during detached discharges using deuterium Balmer line spectroscopy

Spectroscopic investigations of divertor detachment in TCV

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