In situ "artificial plasma" calibration of tokamak magnetic sensors.

A unique in situ calibration technique has been used to spatially calibrate and characterize the extensive new magnetic diagnostic set and close-fitting conducting wall of the High Beta Tokamak-Extended Pulse (HBT-EP) experiment. A new set of 216 Mirnov coils has recently been installed inside the vacuum chamber of the device for high-resolution measurements of magnetohydrodynamic phenomena including the effects of eddy currents in the nearby conducting wall. The spatial positions of these sensors are calibrated by energizing several large in situ calibration coils in turn, and using measurements of the magnetic fields produced by the various coils to solve for each sensor's position. Since the calibration coils are built near the nominal location of the plasma current centroid, the technique is referred to as an "artificial plasma" calibration. The fitting procedure for the sensor positions is described, and results of the spatial calibration are compared with those based on metrology. The time response of the sensors is compared with the evolution of the artificial plasma current to deduce the eddy current contribution to each signal. This is compared with simulations using the VALEN electromagnetic code, and the modeled copper thickness profiles of the HBT-EP conducting wall are adjusted to better match experimental measurements of the eddy current decay. Finally, the multiple coils of the artificial plasma system are also used to directly calibrate a non-uniformly wound Fourier Rogowski coil on HBT-EP.

[1]  D. Naujoks.  Contributions to Plasma Physics , 2022 .

[2]  M. Mauel,et al.  The high beta tokamak-extended pulse magnetohydrodynamic mode control research program , 2011 .

[3]  Magnetic Diagnostics for Equiibrium Reconstruction at W7‐X , 2010 .

[4]  J. Moret,et al.  Measurement of the magnetic field errors on TCV , 2010 .

[5]  M. Mauel,et al.  Feedback suppression of rotating external kink instabilities in the presence of noise , 2008 .

[6]  L. Zakharov,et al.  Magnetic probe response function calibrations for plasma equilibrium reconstructions of CDX-U , 2006 .

[7]  E. J. Strait,et al.  Magnetic diagnostic system of the DIII-D tokamak , 2006 .

[8]  G. A. Navratil,et al.  Dynamics and control of resistive wall modes with magnetic feedback control coils: experiment and theory , 2005 .

[9]  M. Mauel,et al.  Suppression of rotating external kink instabilities using optimized mode control feedback , 2005 .

[10]  N. Lam,et al.  Design of the new magnetic sensors for Joint European Torus , 2004 .

[11]  M. Mauel,et al.  Dynamical plasma response of resistive wall modes to changing external magnetic perturbations , 2004 .

[12]  A..  Fusion Engineering and Design A volumetric neutron source for fusion nuclear technology testing and development , 2004 .

[13]  L. C. Woods.  Physics of plasmas , 2003 .

[14]  Participant Teams,et al.  Magnetic diagnostics for ITER/BPX plasmas (invited) , 2003 .

[15]  Gerald A. Navratil,et al.  Modeling of active control of external magnetohydrodynamic instabilities , 2001 .

[16]  Gerald A. Navratil,et al.  Suppression of resistive wall instabilities with distributed, independently controlled, active feedback coils , 2000 .

[17]  F. Hofmann,et al.  Magnetic measurements on the TCV tokamak , 1998 .

[18]  M. Mauel,et al.  Active control of 2/1 magnetic islands in a tokamak , 1998 .

[19]  P. Stott,et al.  Plasma Physics and Controlled Fusion Conference: Focussing on Tokamak Research , 1995 .

[20]  T.K. Fowler,et al.  Nuclear fusion , 1989, IEEE Potentials.

[21]  I. Hutchinson.  Principles of Plasma Diagnostics , 1987 .

[22]  L. Lao,et al.  Reconstruction of current profile parameters and plasma shapes in tokamaks , 1985 .

[23]  J. L. Luxon,et al.  Magnetic analysis of non-circular cross-section tokamaks , 1982 .

[24]  S. WEINTROUB,et al.  A Review of Scientific Instruments , 1932, Nature.