60 research outputs found
Reducing systematic errors in time-frequency resolved mode number analysis
The present paper describes the effect of magnetic pick-up coil transfer
functions on mode number analysis in magnetically confined fusion plasmas.
Magnetic probes mounted inside the vacuum chamber are widely used to
characterize the mode structure of magnetohydrodynamic modes, as, due to their
relative simplicity and compact nature, several coils can be distributed over
the vessel. Phase differences between the transfer functions of different
magnetic pick-up coils lead to systematic errors in time- and frequency
resolved mode number analysis. This paper presents the first in-situ,
end-to-end calibration of a magnetic pick-up coil system which was carried out
by using an in-vessel driving coil on ASDEX Upgrade. The effect of the phase
differences in the pick-up coil transfer functions is most significant in the
50-250 kHz frequency range, where the relative phase shift between the
different probes can be up to 1 radian (~60{\deg}). By applying a correction
based on the transfer functions we found smaller residuals of mode number
fitting in the considered discharges. In most cases an order of magnitude
improvement was observed in the residuals of the mode number fits, which could
open the way to investigate weaker electromagnetic oscillations with even high
mode numbers
Real-time equilibrium reconstruction integration into the ASDEX Upgrade control system
The real-time equilibrium reconstruction code for the ASDEX Upgrade tokamak, JANET [1], is in the process of migration to a Linux based C11++ code. This is motivated by the need for closer integration into the ASDEX Upgrade control system and the long term goal of replacing the currently used function parameterisation based control when upper divertor coils for studying advanced magnetic configurations are installed [2
Note: Internal diamagnetic flux measurements on ASDEX Upgrade
Internal diamagnetic flux measurements, with measurement loops and compensation magnetic probes inside the vacuum vessel, are now available on the ASDEX Upgrade tokamak. The measured diamagnetic flux is compared to that predicted by simulations and calculated from equilibrium reconstruction. The diamagnetic flux measured at 2 positions separated toroidally by 180 in the vacuum vessel is compared
- …