The ECRH system for JET

The ECRH system for JET

A.G.A. Verhoeven¹, W.A. Bongers¹, B.S.Q. Elzendoorn¹, M. Graswinckel¹,

P. Hellingman¹, J.J. Kamp¹, W. Kooijman¹, O.G. Kruijt¹, J. Maagdenberg¹,

D. Ronden¹, J. Stakenborg¹, A.B. Sterk¹, J. Tichler¹

S. Alberti², T. Goodman², M. Henderson², J.A. Hoekzema³, J.W. Oosterbeek³, A. Fernandez⁴, K. Likin⁴, A. Bruschi⁵, S. Cirant⁵, S. Novak⁵, B. Piosczyk⁶,

M. Thumm⁶, H. Bindslev⁷, A. Kaye⁸, C. Fleming⁸ H. Zohm⁹

1FOM-Instituut voor Plasmafysica 'Rijnhuizen', Association EURATOM-FOM; verhoeve@rijnh.nl; P.O. Box 1207, 3430 BE Nieuwegein, the Netherlands;

^{2Euratom/CRPP-Lausanne; ³Euratom/FZJ-Julich;
^{4Euratom/CIEMAT, Madrid; ⁵Euratom/CNR-Milano;
^{6Euratom/FZK-Karlsruhe; ⁷Euratom/Riso-Denmark;
^{8Euratom-JET/UKAEA Culham; ⁹Euratom/IPP-Garching;}}}}

An ECRH (electron-cyclotron resonance heating) system is being designed for JET in the frame of the JET-Enhanced Performance project (JET-EP). This project is implemented under the new European Fusion Development Agreement (EFDA). The system will consist of 6 gyrotrons, 1 MW each, in order to deliver 5 MW into the plasma. The system will especially be equipped to enable the control of neo-classical tearing modes (NTM). Furthermore, heating and current drive is foreseen in a large number of different target plasma configurations and the control of the ratio of the electron and ion temperatures. The frequency, 113.3 GHz, is selected to enable a wide range of operating toroidal magnetic fields from 3 to 4 T and at second harmonic at lower fields and also to allow for a future upgrade to 170 GHz using the same systems, including the double-disk diamond windows at the torus side.

The main elements of the ECRH system are:

* gyrotrons with a depressed collector, each 1 MW for 10 s and 0.6 MW for 30 s.

* gyrotrons will have diamond windows, with Gaussian output mode

* evacuated waveguides will transport the mm-wave power

* double disk diamond windows on the tokamak side, with a fast valve to have additional tritium barriers

* a plug-in launcher, steerable in both toroidal and poloidal angle, able to handle 8 mm-wave beams. Four steerable launching mirrors will be installed, handling each two mm-wave beams. Water cooling of the movable mirror is being considered, in order to increase the ITER relevance.

* main power supplies, 60 kV, with a solid-state crowbar to feed two gyrotrons, each

* series IGBT switches will enable independent control of each gyrotron

* body power supplies will stabilise the gyrotron output power and enable fast modulations up to 10 kHz. Solid-state devices are considered the best option.