Impact of the ITER-like wall on divertor detachment and on the density limit in the JET tokamak

Huber, A.; Brezinsek, S.; Groth, M.; Vries, P. C. de; Riccardo, V.; Rooij, G.J. van; Sergienko, G.; Arnoux, G.; Boboc, A.; Bílková, P.; Calabrò, G.; Clever, M.; Coenen, J. W.; Beurskens, M.; Eich, T.; Jachmich, S.; Lehnen, M.; Lerche, E.; Marsen, S.; Matthews, G. F.; McCormick, K.; Meigs, A.; Mertens, Philippe; Philipps, V.; Rapp, J.; Samm, U.; Stamp, M.; Wischmeier, M.; Wiesen, S.

doi:10.1016/j.jnucmat.2013.01.022

Cited by 79 publications

(103 citation statements)

References 26 publications

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“…We note that, since the outermost spectroscopic chords are susceptible to reflections, direct n e and T e measurements at R>2.86 m at the OSP were not possible. At t =19.86 s, shortly before the density limit disruption, both the outer and inner divertor are completely detached and the density peak increases further, consistent with the radiation pattern during MARFE formation(see e.g., [2]), while density along the outer leg continues to fall. Changes in the T e profile are less pronounced compared to relatively strong shaping in the density profile.…”

Section: L-mode Detached Plasma Measurementssupporting

confidence: 69%

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Inferring divertor plasma properties from hydrogen Balmer and Paschen series spectroscopy in JET-ILW

et al. 2015

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract.A parametrised spectral line profile model is formulated to investigate the diagnostic scope for recovering plasma parameters from hydrogenic Balmer and Paschen series spectroscopy in the context of JET-ILW divertor plasmas. The separate treatment of Zeeman and Stark contributions in the line model is tested against the PPP-B code which accounts for their combined influence on the spectral line shape. The proposed simplified model does not fully reproduce the Stark-Zeeman features for the α and β transitions, but good agreement is observed in the line width and wing profiles, especially for n >5. The line model has been applied to infer radial density profiles in the JET-ILW divertor with generally good agreement between the D 5→2, 5→3, 6→2, 7→2 and 9→2 lines for high recycling and detached conditions. In an L-mode detached plasma pulse the Langmuir probe measurements typically underestimated the density by a factor 2-3 and overestimated the electron temperature by a factor of 5-10 compared to spectroscopically derived values. The line model is further used to generate synthetic high-resolution spectra for low-n transitions to assess the potential for parameter recovery using a multi-parametric fitting technique. In cases with 4 parameter fits with a single Maxwellian neutral temperature component the D 4→3 line yields the best results with parameter estimates within 10% of the input values. For cases with 9 parameter fits inclusive of a multi-component neutral velocity distribution function the quality of the fits is degraded. Simultaneous fitting of the D 3→2 and 4→3 profiles improves the fit quality significantly, highlighting the importance of complementary spectroscopic measurements for divertor plasma emission studies.

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Section: L-mode Detached Plasma Measurementssupporting

confidence: 69%

“…Observations of increased detachment stability and extended MARFE lifetime have recently been reported in JET-ILW detachment experiments [2] and present increased opportunity for feedback control to stabilise the detached operating regime (see e.g. [3] for previous attempts using edge density as feedback signal).…”

Section: L-mode Detached Plasma Measurementsmentioning

confidence: 91%

Inferring divertor plasma properties from hydrogen Balmer and Paschen series spectroscopy in JET-ILW

et al. 2015

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“…In figure 29, one can see a bifurcation-like change of the electron temperature at the outer strike point as the separatrix plasma density in DIII-D increases (McLean et al 2015). On the contrary, in JET with the ITER-like wall (ILW), a gradual evolution of the plasma flux on both the inner and outer divertor targets along with the increase of the core plasma density is observed (Huber et al 2013), figure 30.…”

Section: Transition To the Detached Divertor Regimementioning

confidence: 99%

“…Relatively slow, mesoscale FIGURE 30. Evolution of the plasma parameters in JET-ILW (Huber et al 2013).…”

Section: Transition To the Detached Divertor Regimementioning

confidence: 99%

Physics of ultimate detachment of a tokamak divertor plasma

Krasheninnikov¹,

2017

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The basic physics of the processes playing the most important role in divertor plasma detachment is reviewed. The models used in the two-dimensional edge plasma transport codes that are widely used to address different issues of the edge plasma physics and to simulate the experimental data, as well as the numerical schemes and convergence issues, are described. The processes leading to ultimate divertor plasma detachment, the transition to and the stability of the detached regime, as well as the impact of the magnetic configuration and divertor geometry on detachment, are considered. A consistent, integral physical picture of ultimate detachment of a tokamak divertor plasma is developed.

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“…Therefore it is necessary that the line emissions of both transitions weakly depend on the electron density. For example, this is routinely done at TEXTOR by measuring helium line ratios [26] or at JT-60U and JET by measuring Balmer line ratios [27,28]. With the spectrometers used for this work, it is possible to measure the Balmer D δ and D ǫ lines simultaneously.…”

Section: Spectroscopic Determination Of Volume Recombinationmentioning

confidence: 99%

A new experimental classification of divertor detachment in ASDEX Upgrade

et al. 2013

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Abstract. In this article a new experimental classification of divertor detachment in ASDEX Upgrade is presented. For this purpose a series of Ohmic and L-mode density ramp discharges at different heating powers, magnetic field directions and plasma species were carried out. For the first time at ASDEX Upgrade the electron density in the divertor volume and the occurrence of volume recombination were measured by means of spectroscopy. It is shown that detachment is not a continuously evolving process but rather undergoes three distinct states while the characteristics of the inner and outer divertor are strongly coupled. Before the complete detachment of the inner and outer divertor, radiative fluctuations occur in the inner divertor close to the Xpoint, observed for the first time via new fast diode bolometers. Finally, the effect of an externally applied magnetic perturbation field on the detachment process is investigated.

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Impact of the ITER-like wall on divertor detachment and on the density limit in the JET tokamak

Cited by 79 publications

References 26 publications

Inferring divertor plasma properties from hydrogen Balmer and Paschen series spectroscopy in JET-ILW

Inferring divertor plasma properties from hydrogen Balmer and Paschen series spectroscopy in JET-ILW

Physics of ultimate detachment of a tokamak divertor plasma

A new experimental classification of divertor detachment in ASDEX Upgrade

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