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Abstract

A prototype passive active multijunction (PAM) launcher for lower hybrid (LH) waves conceptually similar to that foreseen for ITER has been successfully tested on FTU at frequency f = 8 GHz. The power routinely and safely managed for the maximum time allowed by the LH power plant (0.9 s) without any fault in the transmission lines is 250 kW, corresponding to 75 MW m{-2} across the antenna active area and very close to the design value of 270 kW or 80 MW m{-2}. The achieved value is at least 1.4 times larger than the ITER request, which would be only 52 MW m{-2}, if the 33 MW m{-2} required to the ITER grill in order to couple 20 MW to the plasma, are scaled up linearly with f, from f(ITER) = 5 GHz. This linear scaling of the power handling capability of the LH antennae is indeed conservative with respect to the available data. The test results validate also the other two main expectations relevant to ITER, foreseen by the codes, namely to operate with the grill entirely in the vessel shadow and to still preserve good current drive (CD) efficiency. Even with the grill mouth retracted 2 mm inside the port shadow and with density in front of the launcher very close or even lower than the cut-off value, the PAM reflection coefficient is always up to 2.5%, if the antenna has been properly conditioned. The CD efficiency is comparable to that of a conventional grill, once the lower directivity is taken into account. Flexibility in determining the N(//) spectrum is also maintained, according to hard x-rays and electron cyclotron emission spectra. Conditioning the PAM in order to operate at the ITER equivalent power level required only one day of radio-frequency operation, without a previous baking of the waveguides.

Additional information

Authors: PERICOLI RIDOLFINI V, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);MIRIZZI F, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);APICELLA M L, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);BARBATO E, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);BURATTI P, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);CALABRÒ G, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);CARDINALI A, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);PANACCIONE L, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);PODDA S, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);TUCCILLO A A, Associazione Euratom-ENEA sulla Fusione, Centro.Richerche Energia ENEA-Frascati, Frascati (IT);BIBET PH, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);GRANUCCI G, Istituto di Fisica del Plasma, EURATOM�ENEA�CNR Association Milano (IT);SOZZI C, Istituto di Fisica del Plasma, EURATOM�ENEA�CNR Association Milano (IT)
Bibliographic Reference: An article published in: Nuclear Fusion 45 (2005), pp. 1085-1093
Availability: This article can be accessed online by subscribers, and can be ordered online by non-subscribers, at: http://dx.doi.org/10.1088/0029-5515/45/9/008
Record Number: 200719086 / Last updated on: 2007-04-11
Category: PUBLICATION
Original language: en
Available languages: en
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