A lower hybrid current drive system for ITER

Hoang, G. T.; Bécoulet, A.; Jacquinot, J.; Artaud, J.F.; Bae, Y. S.; Beaumont, B.; Belo, J.; Berger‐By, G.; Bizarro, João P. S.; Bonoli, P. T.; Cho, MH; Decker, J.; Delpech, L.; Ekedahl, A.; García, J.; Giruzzi, G.; Goniche, M.; Gormezano, C.; Guilhem, D.; Hillairet, J.; Imbeaux, F.; Kazarian, F.; Kessel, C.; Sh, Kim; Kwak, J. G.; Jeong, J.H.; Lister, J.B.; Litaudon, X.; Magne, R.; Milora, S.L.; Mirizzi, F.; Namkung, W.; Noterdaeme, Jean-Marie; Park, Si; Parker, R.; Peysson, Y.; Rasmussen, D. A.; Sharma, P. K.; Schneider, M.; Synakowski, E. J.; Tanga, A.; Tuccillo, A. A.; Wan, Y. X.

doi:10.1088/0029-5515/49/7/075001

Cited by 119 publications

(101 citation statements)

References 32 publications

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“…Alcator CMod [4] is in a unique position to evaluate the feasibility of LHCD in reactor relevant regimes because it can operate at reactor-relevant densities and magnetic fields, albeit at lower temperatures which may have important implications for electron Landau absorption of the waves. Furthermore, its LH launcher has flexible phasing, allowing for a wide range of launched n || , and operates at a similar frequency to what is planned for the ITER LHCD system [5].…”

Section: Introductionmentioning

confidence: 99%

“…By contrast, the transport coefficients presented in this paper were deduced from hollow, off-axis inverted x-ray profiles, peaked near r/a of 0.7. Thus these measurements of fast electron transport are relevant to LHCD operation in burning plasmas, in which LH power absorption and driven current are expected to be strongly peaked in the outer half of the plasma [5].…”

Section: Introductionmentioning

confidence: 99%

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Investigation of lower hybrid physics through power modulation experiments on Alcator C-Mod

et al. 2011

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Lower hybrid current drive (LHCD) is an attractive tool for off-axis current profile control in magneticly confined tokamak plasmas and burning plasmas (ITER), because of its high current drive efficiency. The LHCD system on Alcator C-Mod operates at 4.6 GHz, with ∼ 1 MW of coupled power, and can produce a wide range of launched parallel refractive index (n || ) spectra. A 32 chord, perpendicularly viewing hard x-ray camera has been used to measure the spatial and energy distribution of fast electrons generated by LH waves. Square-wave modulation of LH power on a time scale much faster than the current relaxation time does not significantly alter the poloidal magnetic field inside the plasma and thus allows for realistic modeling and consistent plasma conditions for different n || spectra. Inverted hard x-ray profiles show clear changes in LH-driven fast electron location with differing n || . Boxcar binning of hard x-rays during LH power modulation allows for ∼ 1 ms time resolution, which is sufficient to resolve the build-up, steady-state, and slowing-down phases of fast electrons. Ray-tracing/Fokker-Planck modeling in combination with a synthetic hard x-ray diagnostic show quantitative agreement with the x-ray data for high n || cases. The time histories of hollow x-ray profiles have been used to measure off-axis fast electron transport in the outer half of the plasma, which is found to be small on a slowing down time scale.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigation of lower hybrid physics through power modulation experiments on Alcator C-Mod

et al. 2011

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“…In particular an exponential falloff of the density and temperature with a scale length of n e dn e /dx = 2 cm was used. In the following we will focus only one top part of the antenna system (12 top rows), as proposed for the first phase of the ITER LH system [20]. The design of the LH launcher is still under way and for this simulation we assumed the launcher profile to be conformal to the flux surfaces and to be located at R ANT = 8.3 mm at the midplane, 12 cm away from the LCFS.…”

Section: Simulation Resultsmentioning

confidence: 99%

Full Wave Simulation of Lower Hybrid Waves in ITER Plasmas Based on the Finite Element Method

Meneghini

Shiraiwa

2010

Plasma and Fusion Research

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The first lower hybrid (LH) full wave simulation of an ITER-scale plasma is presented. LHEAF [O. Meneghini et al., Phys. Plasmas 16, (2009)], an efficient LH full wave solver based on Finite Element Method (FEM) was used. In this study the scalability of the LHEAF approach was investigated, and the possibility of using massive parallel computer for solving extremely large problems was shown. In reactor scale plasmas, LH waves having a typical n ≈ 2 are expected to be absorbed in the periphery of the plasma. In order to exploit the spatial localization of the LH waves, LHEAF is modified to consider only the region of plasma where the wave fields are non-zero. By this approach, the size of the computational domain was reduced by more than a factor of 10. In this simulation, the magnetic equilibrium and the density and temperature profiles proposed for AT operation scenario on ITER are used. In addition, the wide SOL is supposed to play an important role in the propagation of the LH waves on ITER, and its presence was included in the simulation. For a Maxwellian plasma the power deposition profile is narrow and peaks at r/a ≈ 0.7.

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“…This objective is motivated by the need for a fusion reactor to operate in essentially steady-state conditions, where the lifetime of the components would not be unduly limited by considerations of thermo-mechanical fatigue. Lower Hybrid Current Drive (LHCD) is an attractive option for non-inductive tokamak operation on ITER due to its high current drive efficiency and ability to drive current off axis [3]. The operational parameters of the Alcator C-Mod LHCD system [4] (f 0 = 4.6 GHz, B φ 5.5 T,n e 10 20 m −3 ) are similar to the proposed LHCD system on ITER [3].…”

Section: Introductionmentioning

confidence: 99%

“…Lower Hybrid Current Drive (LHCD) is an attractive option for non-inductive tokamak operation on ITER due to its high current drive efficiency and ability to drive current off axis [3]. The operational parameters of the Alcator C-Mod LHCD system [4] (f 0 = 4.6 GHz, B φ 5.5 T,n e 10 20 m −3 ) are similar to the proposed LHCD system on ITER [3]. This paper documents advances in LHCD technology on C-Mod designed to extend pulse length, reduce reflection coefficients, and increase single-pass absorption at high density.…”

Section: Introductionmentioning

confidence: 99%

Advances in lower hybrid current drive technology on Alcator C-Mod

et al. 2013

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Abstract. Lower Hybrid Current Drive is an attractive option for non-inductive tokamak operation due to its high current drive efficiency and ability to drive current off axis. The parameters of the Alcator C-Mod LHCD system (f 0 = 4.6 GHz, B φ 5.5 T, n e 10 20 m −3 ) are similar to the proposed LHCD system on ITER. This paper will describe improvements in LHCD technology on C-Mod designed to increase single-pass absorption at high n e , extend pulse length (to > 3 s), and increase power delivered to the plasma by reducing reflection coefficients. Modeling of LH wave propagation indicates that the loss of LHCD efficiency at highern e can be mitigated by enhancing the single pass power absorption. To this end, an off mid-plane launcher has been designed combining the 4-way poloidal splitting concept of the current LH antenna on C-Mod with a toroidal bi-junction. The four rows of the launcher are located above the mid-plane in order to exploit the poloidal upshift of n || as rays propagate from the antenna into the plasma. The maximum LHCD pulse length was previously restricted to 0.5 s to prevent boiling of the klystron collector coolant. The Transmitter Protection System (TPS) was redesigned to model the coolant temperature in real time and shut off the klystron beam if the coolant is close to boiling. The TPS upgrade has been installed and operated on C-Mod for pulses up to 4.5 s into dummy loads and 1.0 s into the plasma. A new moveable local LH launcher protection limiter was designed to reduce reflection coefficients across a wide range of launcher positions while still providing effective protection from plasma heat flux. Initial high power (P net ∼ 700 kW) results show that lower reflection coefficients are achievable with the new limiter configuration as compared to the old configuration. Rapid degradation of power handling after boronization of the plasma facing surfaces, which does not occur with the fixed position limiters, highlights the need for the local protection limiter to provide sufficient protection from contamination during boronization.Advances in lower hybrid current drive technology on Alcator C-Mod 2 PACS numbers: 52.35. Hr, 52.50.Sw, 52.55.Wq Advances in lower hybrid current drive technology on Alcator C-Mod 3

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A lower hybrid current drive system for ITER

Cited by 119 publications

References 32 publications

Investigation of lower hybrid physics through power modulation experiments on Alcator C-Mod

Investigation of lower hybrid physics through power modulation experiments on Alcator C-Mod

Full Wave Simulation of Lower Hybrid Waves in ITER Plasmas Based on the Finite Element Method

Advances in lower hybrid current drive technology on Alcator C-Mod

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