Design of Jet Lower Hybrid Current Drive Generator and Operation of High Power Test Bed

Dobbing, John; Bosia, G.; Brandon, M.; Gammelin, M.; Gormezano, C.; Jacquinot, J.; Jessop, George A.; Lennholm, M.; Pain, M.; Sibley, A.; Wade, T.

doi:10.1016/b978-0-444-87369-9.50064-0

Cited by 3 publications

(2 citation statements)

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“…More power can be launched at the same level of the maximum permitted voltage inside the waveguides, because the reduction of the reflection at the grill mouth is much larger than the measured R c improvement at the back of the MJ. For instance, a drop in R c in the JET MJ from 10% to 4% would allow raising the power by 35% [32]. The increase of the SOL density due to CD 4 puffing, here invoked to explain the LH coupling improvement, is well documented in JET L-mode discharges with the gas box divertor, in [26].…”

Section: Discussionmentioning

confidence: 85%

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: Discussionmentioning

confidence: 85%

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

“…The large poloidal extent of the JET launcher and the variable poloidal shaping of divertor plasmas make a perfect matching of the LCFS to the launcher surface practically impossible. The JET LHCD system has a protection system that switches off the power (for ∼100 ms) on a klystron if the difference in the reflected powers in the two lines, powered by the same klystron, is too large [18]. Events that lead to local changes in the SOL electron density, for example, ELMs can lead to differences in the reflected power along the poloidal direction, and hence increases the likelihood of a klystron interrupt.…”

Section: Description Of the Lhcd System In Jetmentioning

confidence: 99%

Long distance coupling of lower hybrid waves in JET plasmas with edge and core transport barriers

et al. 2005

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Efficient coupling of Lower Hybrid (LH) waves in reactor-relevant conditions, at a distance of ~ 10 cm between the plasma and the antenna during edge localised mode (ELM) activity, has been demonstrated in advanced scenario plasmas in the JET tokamak. The key to the coupling improvement is the use of local gas injection with D 2 or CD 4 in the vicinity of the LH antenna.Current drive by Lower Hybrid (LH) waves has proven to be an efficient method of non-inductive

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Design of the Protection Crowbar for the LHCD Klystrons in Jet

Christodoulopoulos

Cross

Bertolini

et al. 1989

Fusion Technology 1988

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Design of Jet Lower Hybrid Current Drive Generator and Operation of High Power Test Bed

Cited by 3 publications

References 0 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

Long distance coupling of lower hybrid waves in JET plasmas with edge and core transport barriers

Design of the Protection Crowbar for the LHCD Klystrons in Jet

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