Effect of low magnetic shear induced by lower hybrid current drive on high performance internal transport barriers in the Joint European Torus (JET)

2002 ◽  
Vol 9 (8) ◽  
pp. 3205-3208 ◽  
Author(s):  
C. Castaldo ◽  
R. Cesario ◽  
A. Cardinali ◽  
X. Litaudon ◽  
J. Mailloux ◽  
...  
Keyword(s):  
High Performance ◽  
Current Drive ◽  
Lower Hybrid ◽  
Magnetic Shear ◽  
Transport Barriers ◽  
Internal Transport Barriers ◽  
Lower Hybrid Current Drive ◽  
Internal Transport

Heat transport analysis of the improved confinement discharge with LHW in the HT-7 tokamak

2009 ◽  
Vol 76 (2) ◽  
pp. 229-237 ◽  
Author(s):  
X. M. ZHANG ◽  
X. SHEN ◽  
B. N. WAN ◽  
Z. W. WU ◽  
J. FU ◽  
...  
Keyword(s):  
Heat Transport ◽  
Current Drive ◽  
Lower Hybrid ◽  
Ion Temperature ◽  
Hybrid Wave ◽  
Lower Hybrid Wave ◽  
Transport Barriers ◽  
Internal Transport Barriers ◽  
Transport Analysis ◽  
Internal Transport

AbstractIn the HT-7 tokamak, heat transport analysis is carried out for the lower hybrid current drive (LHCD) experiments. Electrons and ions are coupled and good confinement can be obtained by properly optimizating LHCD and plasma parameters. Under the conditions that the plasma current is about 220 kA, the lower hybrid wave (LHW) power is about 300 kW and the central line-averaged density is about 1.5×1013 cm−3, lower hybrid wave power deposition is off-axis. Local transport analysis illustrated that both electron and ion thermal diffusivities are decreased during the LHW phase, and the electron internal transport barriers (eITBs) are formed while been accompanied by the ion internal transport barriers (iITBs) during LHW phase. Ions are heated by electron-ion collision in the region of the barriers although the ohmic power and the LHW power were absorbed by the electrons. Both electron temperature and ion temperature are increased during the LHW phase, and in the confinement region, the electron-to-ion temperature ratio, Te/Ti varies from 2.0 ~ 2.5 during OH phase to 1.3 ~ 1.6 during LHW injected into the plasma, which shows that electron confinement is not degraded by the electron–ion collisions meanwhile ions are also confined. The energy confinement is increased from 13 ms to 25 ms due to the formation of electron and ion internal transport barries after the LHW is injected into the plasma. LHW driven current and bootstrap current contribute to 60% of the total current.

The ITB dynamics controlled by internal kink modes on HL-2A tokamak

2021 ◽  
Author(s):  
Xiaoxue He ◽  
Longwen Yan ◽  
Deliang Yu ◽  
Wei Chen ◽  
Liming Yu ◽  
...  
Keyword(s):  
High Performance ◽  
Fusion Reactor ◽  
Rotation Velocity ◽  
Plasma Current ◽  
Ion Temperature ◽  
Lower Plasma ◽  
Transport Barriers ◽  
Internal Transport Barriers ◽  
Foot Position ◽  
Internal Transport

Abstract The active control of internal transport barriers (ITBs) is an important issue to achieve high performance plasma in a fusion reactor. A critical challenge of ITB control is to increase the ITB position. The ITBs with internal kink modes (IKMs), such as fishbone instability and long-live mode (LLM) with mode number of m/n = 1/1 are frequently observed on HL-2A tokamak in neutral beam heated discharges. The correlation of fishbone instability/LLM with ITBs is analyzed in order to extend the ITB radius. It has been revealed that fishbone instability and LLM are often excited after the ITB formation. Therefore, fishbone instability and LLM play no role in triggering ITBs on HL-2A tokamak. On the other hand, they may slow down the outward radial expansion and then shrink the foot position of ITB, and damp the gradient growth of ion temperature and rotation velocity. Since the perturbation of LLM is weaker than that of fishbone instability, the shrinking effect of ITB foot and braking effect on gradient growth are slighter than those of fishbone instability. Compared with the LLM, fishbone instability routinely appears in plasmas with lower density, higher heating power and lower plasma current. In addition, large ITBs without IKMs are also discussed on HL-2A tokamak. The large ITB is the largest one, the fishbone ITB is the strongest one and the LLM ITB is the widest one in three ITBs, where the ‘large’, ‘strong’ and ‘wide’ qualifications correspond to ITB position ρITB, the normalized temperature gradient R/LT, and its width W/a. Therefore, the large ITB position may be obtained if the IKMs are effectively controlled in a tokamak.

scholarly journals Suppressing electron turbulence and triggering internal transport barriers with reversed magnetic shear in the National Spherical Torus Experiment

2012 ◽  
Vol 19 (5) ◽  
pp. 056120 ◽  
Author(s):  
J. L. Peterson ◽  
R. Bell ◽  
J. Candy ◽  
W. Guttenfelder ◽  
G. W. Hammett ◽  
...  
Keyword(s):  
Spherical Torus ◽  
Magnetic Shear ◽  
Transport Barriers ◽  
Internal Transport Barriers ◽  
Internal Transport

Progress in internal transport barrier plasmas with lower hybrid current drive and heating in JET (Joint European Torus)

2002 ◽  
Vol 9 (5) ◽  
pp. 2156-2164 ◽  
Author(s):  
J. Mailloux ◽  
B. Alper ◽  
Y. Baranov ◽  
A. Becoulet ◽  
A. Cardinali ◽  
...  
Keyword(s):  
Current Drive ◽  
Lower Hybrid ◽  
Transport Barrier ◽  
Lower Hybrid Current Drive ◽  
Internal Transport Barrier ◽  
Internal Transport

Improved confinement through internal transport barrier formation with lower hybrid current drive in the Hefei Tokamak-7

2002 ◽  
Vol 9 (12) ◽  
pp. 4996-5000 ◽  
Author(s):  
Bojiang Ding ◽  
Guangli Kuang ◽  
Yuexiu Liu ◽  
Jiafang Shan ◽  
Weici Shen ◽  
...  
Keyword(s):  
Current Drive ◽  
Lower Hybrid ◽  
Transport Barrier ◽  
Barrier Formation ◽  
Lower Hybrid Current Drive ◽  
Internal Transport Barrier ◽  
Internal Transport

Toroidal equilibrium states with reversed magnetic shear and parallel flow in connection with the formation of Internal Transport Barriers

2015 ◽  
Vol 81 (4) ◽  
Author(s):  
Ap. Kuiroukidis ◽  
G. N. Throumoulopoulos
Keyword(s):  
Magnetic Field ◽  
Linear Stability ◽  
Current Density ◽  
Sufficient Condition ◽  
Magnetic Shear ◽  
Transport Barriers ◽  
Internal Transport Barriers ◽  
The Stability ◽  
The Magnetic Field ◽  
Internal Transport

We construct nonlinear toroidal equilibria of fixed diverted boundary shaping with reversed magnetic shear and flows parallel to the magnetic field. The equilibria have hole-like current density and the reversed magnetic shear increases as the equilibrium nonlinearity becomes stronger. Also, application of a sufficient condition for linear stability implies that the stability is improved as the equilibrium nonlinearity correlated to the reversed magnetic shear gets stronger with a weaker stabilizing contribution from the flow. These results indicate synergetic stabilizing effects of reversed magnetic shear, equilibrium nonlinearity and flow in the establishment of Internal Transport Barriers (ITBs).

Lower hybrid current drive in experiments for transport barriers at high β[sub N] of JET (Joint European Torus)

2007 ◽  
Author(s):  
R. C. Cesario ◽  
C. Castaldo ◽  
A. Fonseca ◽  
R. De Angelis ◽  
V. Parail ◽  
...  
Keyword(s):  
Current Drive ◽  
Lower Hybrid ◽  
Transport Barriers ◽  
Lower Hybrid Current Drive
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