1887
banner image
No data available.
Please log in to see this content.
You have no subscription access to this content.
No metrics data to plot.
The attempt to load metrics for this article has failed.
The attempt to plot a graph for these metrics has failed.
High confinement/high radiated power H-mode experiments in Alcator C-Mod and consequences for International Thermonuclear Experimental Reactor (ITER) QDT = 10 operationa)
a)Paper JI2 5, Bull. Am. Phys. Soc. 55, 149 (2010).
Rent:
Rent this article for
USD
10.1063/1.3567547
/content/aip/journal/pop/18/5/10.1063/1.3567547
http://aip.metastore.ingenta.com/content/aip/journal/pop/18/5/10.1063/1.3567547

Figures

Image of FIG. 1.
FIG. 1.

(Color online) Modelled power flux entering the divertor and deposited onto the divertor target vs distance to the separatrix mapped to the outer midplane, for typical QDT = 10 conditions in ITER (Ref. 9): q||x-pt is the parallel plasma power flux entering the divertor along the field line, qx-pt→div is the projection of q||x-pt onto the divertor target normal to the surface, qdiv-tot is the total perpendicular power flux deposited onto the divertor by both the plasma in contact with the divertor target (qdiv-pls) and by deposition of electromagnetic radiation (qdiv-rad). For typical conditions in ITER, radiation in the divertor decreases the peak power flux carried by the plasma by a factor of ≥5 from that entering the divertor target. The total peak heat flux is reduced by a smaller amount (∼3–4) due to the deposition of some of the radiated power onto the divertor target.

Image of FIG. 2.
FIG. 2.

(Color online) Plasma equilibrium reconstruction for the EDA H-mode discharges described in this paper.

Image of FIG. 3.
FIG. 3.

(Color online) Typical plasma parameters for the impurity seeded EDA H-modes discharges considered in this study vs time. From top to bottom: (a) central electron density and waveforms of the seeded impurities (N2, Ne, and Ar), (b) central electron temperature, (c) plasma total input power (Ohmic + ICRH) and radiated power in the plasma core, (d) normalized energy confinement (H98), and (e) measured power to the outer divertor target.

Image of FIG. 4.
FIG. 4.

(Color online) Normalized energy confinement vs net power crossing the separatrix (Pnet) normalized to the H-mode threshold power (Pth) for EDA H-modes in Alcator C-Mod with extrinsic impurity seeding (N2, Ne, and Ar) and with intrinsic impurities (unseeded). The normalized energy confinement in L-mode discharges is shown for comparison.

Image of FIG. 5.
FIG. 5.

(Color online) Normalized energy confinement vs pedestal electron temperature for EDA H-modes in Alcator C-Mod with extrinsic impurity seeding (N2, Ne, and Ar) and with intrinsic impurities (unseeded).

Image of FIG. 6.
FIG. 6.

(Color online) Pedestal electron density versus pedestal electron temperature for EDA H-modes in Alcator C-Mod with extrinsic impurity seeding (N2, Ne, and Ar) and with intrinsic impurities (unseeded) showing that for the same pedestal temperature low Z impurity seeded H-modes have higher pedestal densities.

Image of FIG. 7.
FIG. 7.

(Color online) Normalized energy confinement vs radiated power fraction, as estimated from measurements of heating power and power flow to the outer divertor target for EDA H-modes in Alcator C-Mod with extrinsic impurity seeding (N2, Ne, and Ar) and with intrinsic impurities (unseeded) showing a higher energy confinement for low Z impurity seeded H-modes for a given radiated fraction level.

Image of FIG. 8.
FIG. 8.

(Color online) Electron plasma density and temperature profiles in EDA H-modes in Alcator C-Mod with intrinsic impurities (unseeded) and with extrinsic impurity seeding (N2, Ne, and Ar) vs normalized poloidal flux for discharges with similar pedestal temperatures.

Image of FIG. 9.
FIG. 9.

(Color online) Measured power exhausted (Ploss,out) by the plasma by conduction/convection to the divertor and electromagnetic radiation for N2 and Ne seeded discharges vs the effective total input power into the plasma (Ploss,in). The lines 1:1 and those corresponding to the ±20% error are shown for comparison.

Image of FIG. 10.
FIG. 10.

(Color online) Normalized energy confinement vs radiated power fraction, as estimated from measurements of heating power and power flow to the outer divertor target (open symbols) and radiated power measurements (closed symbols) for EDA H-modes in Alcator C-Mod with extrinsic impurity seeding (N2, Ne, and Ar) and with intrinsic impurities (unseeded).

Image of FIG. 11.
FIG. 11.

(Color online) Measured parallel heat flux at the outer divertor target vs distance to the separatrix mapped to the outer midplane for a series of discharges with impurity seeding and similar normalized energy confinement showing the large decrease of the peak heat flux and the total power deposited at the outer divertor with decreasing Z of the seeded impurity. The net power normalized to the H-mode threshold power for these discharges is Pnet/Pth = 1.10 (unseeded), 0.93 (Ar), 0.97 (Ne), and 1.0 (N2). For comparison, the dashed line corresponds to an Ar-seeded plasma with lower confinement H98 = 0.78 and detached divertor conditions (as is the case for the Ne and N2 plasmas). This detached Ar-seeded plasma had Pnet/Pth = 0.76.

Image of FIG. 12.
FIG. 12.

(Color online) Measured electron temperature at the outer divertor target vs distance to the separatrix mapped to the outer midplane for the same discharges as in Fig. 11 showing the achievement of very low plasma temperatures at the divertor for low Z (N2 and Ne) seeding with high confinement (H98 ≥ 1). For comparison, the dashed line corresponds to an Ar-seeded plasma in Fig. 11, which also achieves a very low divertor temperature but with lower confinement (H98 = 0.78).

Image of FIG. 13.
FIG. 13.

(Color online) Measured VUV emission by N4+ (124 nm) along various chords in the divertor region of Alcator C-Mod for a N2 seeded EDA H-mode showing the large peak of emission near the X-point. The electron temperature profiles measured at the midplane mapped to the divertor are shown for comparison. For this, discharge H98 ∼1 and Pnet/Pth ∼ 1.

Image of FIG. 14.
FIG. 14.

(Color online) Normalized energy confinement vs normalized power to the outer divertor for EDA H-modes in Alcator C-Mod with extrinsic impurity seeding (N2, Ne, and Ar) and with intrinsic impurities (unseeded). The typical range expected for ITER QDT = 10 operation is shown for comparison.

Image of FIG. 15.
FIG. 15.

(Color online) Ratio of the measured Zeff in the EDA H-modes in Alcator C-Mod with extrinsic impurity seeding (N2, Ne, and Ar) and with intrinsic impurities (unseeded) to the Zeff multimachine scaling in Ref. 44 vs radiated power fraction. The value for the previous nitrogen seeded radiative EDA H-modes in Alcator C-Mod with deteriorated confinement is shown for comparison Ref. 20.

Tables

Generic image for table
Table I.

Measured neutron rate and central electron density for a set of EDA H-mode discharges with intrinsic impurities (unseeded) and with extrinsic impurity seeding (Ar, Ne, and N2) and similar electron temperature profiles (see Fig. 8).

Loading

Article metrics loading...

/content/aip/journal/pop/18/5/10.1063/1.3567547
2011-04-22
2014-04-19
Loading

Full text loading...

This is a required field
Please enter a valid email address
752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: High confinement/high radiated power H-mode experiments in Alcator C-Mod and consequences for International Thermonuclear Experimental Reactor (ITER) QDT = 10 operationa)
http://aip.metastore.ingenta.com/content/aip/journal/pop/18/5/10.1063/1.3567547
10.1063/1.3567547
SEARCH_EXPAND_ITEM