ITER-like antenna capacitors voltage probes: Circuit/electromagnetic calculations and calibrations

The analyses illustrated in this manuscript have been performed in order to provide the required data for the amplitude-and-phasecalibration of the D-dot voltage probes used in the ITER-likeantenna at the Joint European Torus tokamak. Their equivalent electrical circuit has been extracted and analyzed, and it has been compared to the one of voltage probes installed in simple transmission lines. A radio-frequencycalibration technique has been formulated and exact mathematical relations have been derived. This technique mixes in an elegant fashion data extracted from measurements and numerical calculations to retrieve thecalibration factors. The latter have been compared to previouscalibration data with excellent agreement proving the robustness of the proposed radio-frequencycalibration technique. In particular, it has been stressed that it is crucial to take into account environmental parasitic effects. A low-frequencycalibration technique has been in addition formulated and analyzed in depth. The equivalence between the radio-frequency and low-frequency techniques has been rigorously demonstrated. The radio-frequencycalibration technique is preferable in the case of the ITER-likeantenna due to uncertainties on the characteristics of the cables connected at the inputs of the voltage probes. A method to extract the effect of a mismatcheddata acquisition system has been derived for bothcalibration techniques. Finally it has been outlined that in the case of the ITER-likeantenna...

Source: Review of Scientific Instruments - October 11, 2016 Category: Physics Authors: W. Helou, P. Dumortier, F. Durodi é, G. Lombard, K. Nicholls and JET Contributors Source Type: research