Plasma start-up results with electron cyclotron assisted breakdown on Frascati Tokamak Upgrade

G. Granucci, G. Ramponi, G. Calabrò, F. Crisanti, S. Nowak, G. Ramogida, O. Tudisco, W. Bin, A. Botrugno, P. Buratti, O. D'Arcangelo, D. Frigione, G. Pucella, A. Romano

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Abstract

Several experiments aimed at optimizing plasma pre-ionization using electron cyclotron (EC) waves have been carried out on many tokamaks in recent years as the basis of a multi-machine comparison study made to define the best operation scenarios for ITER, where the plasma breakdown will have to be achieved with a toroidal electric field of only 0.3 V m-1. The FTU (Frascati Tokamak Upgrade, R = 0.935 m, a = 0.3 m) contribution to this study is the main subject of this work. A reduction in electric field, as can be obtained with pre-ionization by ECH, can lower the transformer flux consumption in the start-up phase leading to a longer plasma current flat top. This point is of particular interest in the conceptual design of the steady-state scenario of the proposed FAST tokamak and has also been addressed. In the FTU experiment the scan in pre-filling pressure has evidenced the capability of EC power to increase, by a factor 4, the range of working pressure useful for plasma start-up. Varying the breakdown a minimum electric field of 0.41 V m -1 has been found with 0.8 MW of EC in perpendicular injection. A scan in magnetic field has evidenced that plasma start-up is likely insensitive to alignment between EC resonance and null position. A total transformer flux saving of 22% has been found acting on plasma resistivity (by increasing electron temperature) and on the plasma starting point (for an internal inductance reduction). © 2011 IAEA, Vienna.
Original languageEnglish
Article number073042
Pages (from-to)-
JournalNuclear Fusion
Volume51
Issue number7
DOIs
Publication statusPublished - Jul 2011
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

Granucci, G., Ramponi, G., Calabrò, G., Crisanti, F., Nowak, S., Ramogida, G., ... Romano, A. (2011). Plasma start-up results with electron cyclotron assisted breakdown on Frascati Tokamak Upgrade. Nuclear Fusion, 51(7), -. [073042]. https://doi.org/10.1088/0029-5515/51/7/073042