Progress in quantifying the edge physics of the H mode regime in DIII-D

Groebner, R. J.; Baker, D. R.; Burrell, K.H.; Carlstrom, T. N.; Ferron, J. R.; Gohil, P.; Lao, L. L.; Osborne, T. H.; Thomas, D.M.; West, W. P.; Boedo, J.A.; Moyer, R. A.; McKee, G. R.; Deranian, R. D.; Doyle, E. J.; Rettig, C. L.; Rhodes, T. L.; Rost, J. C.

doi:10.1088/0029-5515/41/12/306

Cited by 163 publications

(166 citation statements)

References 23 publications

Supporting

Mentioning

165

Contrasting

Order By: Relevance

“…This method has already been successfully applied in a previous study 22 and by other authors 26,27 . Although the statistical uncertainties in the fitting parameters are substantially reduced using coherent averaging, some systematic errors cannot be excluded.…”

Section: B Measurements and Data Analysismentioning

confidence: 90%

Electron temperature and density profile evolution during the edge-localized mode cycle in ohmic and electron cyclotron-heated H-mode plasmas in TCV

Pitzschke

Behn

Sauter

et al. 2011

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

The dynamics of electron temperature and density profiles during quasi-stationary H-mode phases in the TCV tokamak has been investigated for type III and type I ELMs using electron cyclotron heating (ECH) to vary the collisionality. At heating power levels close to the threshold for the L-H transition, ELMs of type III were observed, with an energy loss per ELM below 10% of the total plasma energy. Electron temperature and pressure showed no significant increase during the phase before the ELM crash. ELMs of type I were characterized by a lower repetition rate, but caused fractional energy losses reaching 20%. For this ELM type, a clear increase in pedestal pressure and pressure gradient was observed before the collapse associated with the ELM event. The rapid drop in electron temperature also affected the plasma core explaining the rather large energy losses per ELM. Ideal MHD stability calculations of the edge pedestal with the KINX code showed that high-n ballooning modes restricted the achievable pressure gradient at high collisionality and ELMs of type III. With additional heating and type I ELMs, stability limits were set by medium-n kink-ballooning modes. Comparing the values of the pressure gradients and current densities obtained from experimental data with those of ideal MHD stability calculations showed good agreement. The model, however, needs to account for the radial displacement of the location of maximum pressure gradient during the ELM cycle.

show abstract

Section: B Measurements and Data Analysismentioning

confidence: 90%

Electron temperature and density profile evolution during the edge-localized mode cycle in ohmic and electron cyclotron-heated H-mode plasmas in TCV

Pitzschke

Behn

Sauter

et al. 2011

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…Fig. 3) to the modified hyperbolic function conventionally used for H-mode pedestal analysis [36]. These fits include timeslices from the I-mode campaign (Fig.…”

Section: I-mode Edge Pedestal: Profile Characteristicsmentioning

confidence: 99%

I-mode: an H-mode energy confinement regime with L-mode particle transport in Alcator C-Mod

Whyte

Hubbard

Hughes³

et al. 2010

Nucl. Fusion

289

370

View full text Add to dashboard Cite

An improved energy confinement regime, I-mode is studied in Alcator C-Mod, a compact high-field divertor tokamak using Ion Cyclotron Range of Frequencies (ICRF) auxiliary heating. I-mode features an edge energy transport barrier without an accompanying particle barrier, leading to several performance benefits. H-mode energy confinement is obtained without core impurity accumulation, resulting in reduced impurity radiation with a high-Z metal wall and ICRF heating. I-mode has a stationary temperature pedestal with Edge Localized Modes (ELMs) typically absent, while plasma density is controlled using divertor cryopumping. I-mode is a confinement regime that appears distinct from both L-mode and H-mode, combining the most favorable elements of both. The I-mode regime is obtained predominately with ion ∇B drift away from the active X-point. The transition from L-mode to I-mode is primarily identified by the formation of a high temperature edge pedestal, while the edge density profile remains nearly identical to Lmode. Laser blowoff injection shows that I-mode core impurity confinement times are nearly identical with those in L-mode, despite the enhanced energy confinement. In addition a weakly coherent edge MHD mode is apparent at high frequency ~ 100-300 kHz which appears to increase particle transport in the edge. The I-mode regime has been obtained over a wide parameter space (B=3-6 T, I p =0.7-1.3 MA, q 95 =2.5-5). In general the I-mode exhibits the strongest edge T pedestal and normalized energy confinement (H 98 >1) at low q 95 (<3.5) and high heating power (P heat > 4 MW). I-mode significantly expands the operational space of ELM-free, stationary pedestals in C-Mod to T ped~1 keV and low collisionality ν* ped~0 .1, as compared to EDA H-mode with T ped < 0.6 keV, ν* ped >1. The I-mode global energy confinement has a relatively weak degradation with heating power; W th ~ I p P heat 0.7 leading to increasing H 98 with heating power.2

show abstract

“…The stationary phases used are longer than 0.5s and at least four energy confinement times long (τ E ≈ 0.1 s-0.25 s). The pre-ELM density and temperature profiles of each stationary phase are then fitted with a modified hyperbolic tangent function [69] to estimate the pedestal height and pedestal width: The fits are performed in real space and then mapped on the poloidal flux normalized to one at the separatrix. The uncertainties in the pedestal parameters represent the errors on the parameters of the fits.…”

Section: Diagnostics For the Pedestal Structurementioning

confidence: 99%

Global and pedestal confinement and pedestal structure in dimensionless collisionality scans of low-triangularity H-mode plasmas in JET-ILW

et al. 2016

View full text Add to dashboard Cite

A dimensionless collisionality scan in low-triangularity plasmas in the Joint European Torus with the ITER-like wall (JET-ILW) has been performed. The increase of the normalized energy confinement (defined as the ratio between thermal energy confinement and Bohm confinement time) with decreasing collisionality is observed. Moreover, at low collisionality, a confinement factor H 98 , comparable to JET-C, is achieved. At high collisionality, the low normalized confinement is related to a degraded pedestal stability and a reduction in the density-profile peaking.The increase of normalized energy confinement is due to both an increase in the pedestal and in the core regions. The improvement in the pedestal is related to the increase of the stability. The improvement in the core is driven by (i) the core temperature increase via the temperature-profile stiffness and by (ii) the density-peaking increase driven by the low collisionality.Pedestal stability analysis performed with the ELITE (edge-localized instabilities in tokamak equilibria) code has a reasonable qualitative agreement with the experimental results. An improvement of the pedestal stability with decreasing collisionality is observed. The improvement is ascribed to the reduction of the pedestal width, the increase of the bootstrap current and the reduction of the relative shift between the positions of the pedestal density and pedestal temperature.The EPED1 model predictions for the pedestal pressure height are qualitatively well correlated with the experimental results. Quantitatively, EPED1 overestimates the

show abstract

Progress in quantifying the edge physics of the H mode regime in DIII-D

Cited by 163 publications

References 23 publications

Electron temperature and density profile evolution during the edge-localized mode cycle in ohmic and electron cyclotron-heated H-mode plasmas in TCV

Electron temperature and density profile evolution during the edge-localized mode cycle in ohmic and electron cyclotron-heated H-mode plasmas in TCV

I-mode: an H-mode energy confinement regime with L-mode particle transport in Alcator C-Mod

Global and pedestal confinement and pedestal structure in dimensionless collisionality scans of low-triangularity H-mode plasmas in JET-ILW

Contact Info

Product

Resources

About