Electron density measurements from cutoff of electron cyclotron emission in the DIII-D tokamak

Lohr, J.

doi:10.1063/1.1140161

Cited by 8 publications

(7 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Discharges were operated at B T = 2.05-2.17 T with I P = 1.60-1.97 MA and heated through NBI with power P NBI = 8-14 MW. Employing 2nd harmonic X-mode electron cyclotron heating (ECH) is not possible in SH due to the high densities, which are above the ECH reflection limit [25,26]. The plasma shape was chosen to be LSN in order to measure heat fluxes with a dedicated IR camera viewing the lower divertor, with a high average triangularity (δ = 0.5 − 0.6) and elongation (κ = 1.8-1.9).…”

Section: Discharge Evolutionmentioning

confidence: 99%

See 1 more Smart Citation

On the stability and stationarity of the Super H-mode combined with an ion transport barrier in the core

Knölker

Evans

Snyder

et al. 2021

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

The Super H-mode, a regime with high pedestal pressure and stored energy, is explored on DIII-D and combined with an ion transport barrier in the plasma core to increase performance. A significant improvement of ion temperatures and confinement is facilitated by favorable conditions such as high rotational shear and high ion pedestal temperatures. As a result of a rise in density and simultaneous decrease in rotation, the ion transport barrier disappears during the discharge evolution, leading to a transition from a very high confinement state at early times, to a reduced but still high confinement phase. Additionally, in many discharges, a global magnetohydrodynamic (MHD) event consistent with the coupling of a destabilized internal mode to an edge localized mode causes a large energy loss and leads to a reorganization of the plasma into a lower temperature, higher density state. Depending on the magnitude of the global MHD event, the plasma edge collisionality can increase significantly and shift the operational boundary from the peeling to the ballooning side, which can be understood as a drop out of the Super H-mode channel into standard H-mode. Hence, in Super H-mode discharges with ion transport barriers, both the improved pedestal height and rotational shear contribute to the high stored energy. At very low levels of rotation, the confinement factor for SH modes is still expected to exceed standard H-mode by 20%–30%. With their overall stationarity and high-performance levels, Super H-mode discharges provide an attractive regime for ITER and may enable a more compact design of future fusion power plants.

show abstract

Section: Discharge Evolutionmentioning

confidence: 99%

“…SH discharges with hot ion modes show a transition from an early and short very high confinement phase (duration of 0.5 s ≈ 1-2 τ E ) with high stored energy (2.9-3.4 MJ) and pedestal pressure (22)(23)(24)(25)(26)(27)(28)(29)(30) to a stationary phase with improved confinement (H ~1.0-1.6) and stored energy (2.0-2.6 MJ).…”

Section: Introductionmentioning

confidence: 99%

On the stability and stationarity of the Super H-mode combined with an ion transport barrier in the core

Knölker

Evans

Snyder

et al. 2021

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…ECE can be reflected by the plasma and effectively cutoff when the right handed x-mode nth harmonic cutoff frequency [26] exceeds the cyclotron frequency of interest:…”

Section: Limitations Of Tq Measurementsmentioning

confidence: 99%

Measurements of hard x-ray emission from runaway electrons in DIII-D

et al. 2011

View full text Add to dashboard Cite

The spatial distribution of runaway electron (RE) strikes to the wall during argon pellet-initiated rapid shutdown of diverted and limited plasma shapes in DIII-D is studied using a new array of hard x-ray (HXR) scintillators.Two plasma configurations were investigated: an elongated diverted H-mode, and a low-elongation limited L-mode. HXR emission from MeV level REs generated during the argon pellet injection is observed during the thermal quench (TQ) in diverted discharges from REs lost into the divertor. In limiter discharges, this prompt TQ loss is reduced, suggesting improved TQ confinement of REs in this configuration. During the plateau phase when the plasma current is carried by REs, toroidally symmetric HXR emission from remaining confined REs is seen.Transient HXR bursts during this RE current plateau suggest the presence of a small level of wall losses due to the presence of an unidentified instability.Eventually, an abrupt final loss of the remaining RE current occurs. This final loss HXR emission shows a strong toroidal peaking and a consistent spatiotemporal evolution that suggests the development of a kink instability.

show abstract

“…The radial resolution varies from 1 to 2.5 cm. The interferometer measured the density along the central chord and the ECE-the radial coordinate for which the cutoff occurred [20,21]. The experimental points are shown in figure 4, and, assuming a quasi-parabolic profile with exponent α, the best fits to the data are represented.…”

Section: Radial Profilesmentioning

confidence: 99%

Plasma confinement using biased electrode in the TCABR tokamak

et al. 2005

View full text Add to dashboard Cite

Experimental data obtained on the TCABR tokamak (R = 0.61 m, a = 0.18 m) with an electrically polarized electrode, placed at r = 0.16 m, is reported in this paper. The experiment was performed with plasma current of 90 kA (q = 3.1) and hydrogen gas injection adjusted for keeping the electron density at 1.0 × 1019 m−3 without bias. Time evolution and radial profiles of plasma parameters with and without bias were measured. The comparison of the profiles shows an increase of the central line-averaged density, up to a maximum factor of 2.6, while Hα hydrogen spectral line intensity decreases and the C III impurity stays on the same level. The analysis of temporal behaviour and radial profiles of plasma parameters indicates that the confined plasma enters the H-mode regime. The data analysis shows a maximum enhanced energy confinement factor of 1.95, decaying to 1.5 at the maximum of the density, in comparison with predicted Neo–Alcator scaling law values. Indications of transient increase of the density gradient near the plasma edge were obtained with measurements of density profiles. Calculations of turbulence and transport at the Scrape-Off-Layer, using measured floating potentials and ion saturation currents, show a strong decrease in the power spectra and transport. Bifurcation was not observed and the decrease in the saturation current occurs in 50 µs.

show abstract

Electron density measurements from cutoff of electron cyclotron emission in the DIII-D tokamak

Cited by 8 publications

References 3 publications

On the stability and stationarity of the Super H-mode combined with an ion transport barrier in the core

On the stability and stationarity of the Super H-mode combined with an ion transport barrier in the core

Measurements of hard x-ray emission from runaway electrons in DIII-D

Plasma confinement using biased electrode in the TCABR tokamak

Contact Info

Product

Resources

About