Operation of the 3.7 GHz LHCD system in JET

Lennholm, M.; Baranov, Y.; Dobbing, John; Finburg, P.; Fischer, Baruch; Gormezano, C.; Gowers, C.; Kaye, A.; Plancoulaine, J.; Rimini, F.; Romero, Jesús; Schild, P.; Sips, A. C. C.; Smits, F.; Söldner, F. X.

doi:10.1109/fusion.1995.534332

Cited by 9 publications

(3 citation statements)

References 2 publications

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“…More details on the LH system can be found in Refs. [5,6] and references therein. For safety reasons in high power shots the launcher must be always in the shadow of the protection poloidal limiter, i.e.…”

Section: Organization and Development Of The Experimentsmentioning

confidence: 99%

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Study and optimization of lower hybrid wave coupling in advanced scenario plasmas in JET

Ridolfini¹,

Erents²,

Mailloux³

et al. 2003

Plasma Phys. Control. Fusion

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A systematic study of the coupling of the Lower Hybrid (LH) power to JET plasmas has allowed us to overcome the problems of active current drive in the H-mode and ITB plasmas. As a result, LH power up to 4MW has been injected for longer than 8s in an ITB plasma. The LH coupling has been improved by fitting thepoloidal shapes of the plasma to that of the launcher, up to the degree allowed by the septum in the divertor, and by injecting deuterated methane (CD 4) from a pipe close to the LH antenna. Average values of the reflection coefficient as low as 4%, as in the previous Lmode operation are obtained. The reduced shape mismatch has strongly increased the poloidal uniformity of the plasma in front of the LH launcher and has permitted a balanced supply of the 3 grills. The major breakthrough, however, has been to puff CD 4 , which increases the density in front of the LH launcher at least by 1.5 times locally, raising it above the cutoff value. This technique does not affects the plasma performances nor contaminates the main plasma up to the maximum flow rate so far used, F CD4 >10 22 el./s. Now it is routinely applied in JET and has allowed us to modify the plasma current radial profile evolution during the ITB, producing very encouraging results. Even though CD 4 is not suitable for ITER for the large tritium retention, the possibility to control locally and safely the scrape off plasma density has been demonstrated.

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Section: Organization and Development Of The Experimentsmentioning

confidence: 99%

“…The whole matrix is 12 rows × 32 columns, and measures 89 cm in height and 35.2 cm in length [21]. More details on the LH system can be found in [22,23] and references therein.…”

Section: Organization and Development Of The Experimentsmentioning

confidence: 99%

Study and optimization of lower hybrid wave coupling in advanced scenario plasmas in JET

Ridolfini¹,

Erents²,

Mailloux³

et al. 2003

Plasma Phys. Control. Fusion

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show abstract

“…Lower hybrid (LH) waves have been used for many years on numerous tokamaks (C-MOD [1], EAST [2], HT-7 [3], JET [4], Tore Supra [5] and TRIAM-1 M [6]) to drive a toroidal current in the plasma. In superconducting machines (Tore Supra, TRIAM-1 M, EAST, HT-7), long pulse operation has been successfully demonstrated using lower hybrid current drive (LHCD), drawing benefit both from the high current drive (CD) efficiencies, well above those of other auxiliary heating systems, and the ability to drive an off axis current.…”

Section: Introductionmentioning

confidence: 99%

Advances in multi-megawatt lower hybrid technology in support of steady-state tokamak operation

et al. 2014

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It has been demonstrated that lower hybrid current drive (LHCD) systems play a crucial role for steady-state tokamak operation, owing to their high current drive (CD) efficiency and hence their capability to reduce flux consumption. This paper describes the extensive technology programmes developed for the Tore Supra (France) and the KSTAR (Korea) tokamaks in order to bring continuous wave (CW) LHCD systems into operation. The Tore Supra LHCD generator at 3.7 GHz is fully CW compatible, with RF power PRF = 9.2 MW available at the generator to feed two actively water-cooled launchers. On Tore Supra, the most recent and novel passive active multijunction (PAM) launcher has sustained 2.7 MW (corresponding to its design value of 25 MW m−2 at the launcher mouth) for a 78 s flat-top discharge, with low reflected power even at large plasma-launcher gaps. The fully active multijunction (FAM) launcher has reached 3.8 MW of coupled power (24 MW m−2 at the launcher mouth) with the new TH2103C klystrons. By combining both the PAM and FAM launchers, 950 MJ of energy, using 5.2 MW of LHCD and 1 MW of ICRH (ion cyclotron resonance heating), was injected for 160 s in 2011. The 3.7 GHz CW LHCD system will be a key element within the W (for tungsten) environment in steady-state Tokamak (WEST) project, where the aim is to test ITER technologies for high heat flux components in relevant heat flux density and particle fluence conditions. On KSTAR, a 2 MW LHCD system operating at 5 GHz is under development. Recently the 5 GHz prototype klystron has reached 500 kW/600 s on a matched load, and studies are ongoing to design a PAM launcher. In addition to the studies of technology, a combination of ray-tracing and Fokker–Planck calculations have been performed to evaluate the driven current and the power deposition due to LH waves, and to optimize the N∥ spectrum for the future launcher design. Furthermore, an LHCD system at 5 GHz is being considered for a future upgrade of the ITER Heating and Current Drive systems, with a power capability of 20 MW coupled to the plasma using a PAM launcher. An R&D programme is being conducted at CEA/IRFM to develop a BeO vacuum window which is a safety critical component of the transmission line. In addition, a mock-up of a TE10–TE30 mode converter at 5 GHz, designed for a rectangular transmission line, has been manufactured and successfully tested on Tore Supra at low RF power.

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Real time current profile control at JET

Romero

Cruz

Dobbing

et al. 1998

Fusion Engineering and Design

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A plasma current profile control system has been designed and tested at Joint European Torus (JET). The system uses the one turn loop voltage for lower hybrid current drive (LHCD) control, and the normalised second current moment of the plasma current distribution for off-axis current control. These provide relatively simple measurements and calculations suitable for real time operation. Models for the response of the loop voltage and second current moment to Lower Hybrid power input are derived and validated against JET data. Based on these models, the components of the second current moment and loop voltage control systems are designed to suit prescribed performance. Loop voltage has been controlled in 2.5 MA discharges at 66% reduction, providing the means for LHCD regulation. Second current moment control during the current rise phase has contributed to 60% improvement of the neutron yield performance of shear optimisation discharges at JET.

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Operation of the 3.7 GHz LHCD system in JET

Cited by 9 publications

References 2 publications

Study and optimization of lower hybrid wave coupling in advanced scenario plasmas in JET

Study and optimization of lower hybrid wave coupling in advanced scenario plasmas in JET

Advances in multi-megawatt lower hybrid technology in support of steady-state tokamak operation

Real time current profile control at JET

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