Abstract This paper presents the breakdown studies carried out in the framework of JET Enhancement Projects for Plasma Control Upgrade (PCU) and Enhanced Radial Field Amplifier (ERFA), to obtain plasma formation with different sets of coil turns in the radial field circuit. The electromagnetic conditions to reach the plasma breakdown in the JET machine are strongly dependent on the properties of JET iron core and the effects of the eddy currents driven by the transient electric field on the present passive structures. The study has been carried out by using a linearized dynamic model of JET provided by 2D axisymmetric finite element code CREATE-L [R. Albanese, et al., Nucl. Fusion 38 (1998) 723–738]. The dynamic simulations have been compared with the experimental data. A new fast visible camera has been installed and has been used for the first time at JET for studies of plasma breakdown. The images show, coherently with the model, that the avalanche evolves dynamically towards a region where the stray field is perpendicular to the first wall.
[1]
S. R. Shaw,et al.
The installation, testing and performance on the jet coils of the enhanced radial field amplifier (ERFA)
,
2011
.
[2]
V. Toigo,et al.
Conceptual design of the enhanced radial field amplifier for plasma vertical stabilisation in JET
,
2007
.
[3]
Massimiliano Mattei,et al.
Prediction of the growth rates of VDEs in JET
,
2004
.
[4]
P. Gąsior,et al.
34th European Physical Society Conference on Plasma Physics
,
2007
.
[5]
R. Albanese,et al.
The linearized CREATE-L plasma response model for the control of current, position and shape in tokamaks
,
1998
.
[6]
Alfredo Portone,et al.
Overview of modelling activities for Plasma Control Upgrade in JET
,
2011
.
[7]
Gianmaria De Tommasi,et al.
First plasma operation of the enhanced JET vertical stabilisation system
,
2011
.