Temporal and spatial analysis of fields generated by eddy currents in superconducting magnets: optimization of corrections and quantitative characterization of magnet/gradient systems.

摘要: We propose methods for the spatial and temporal characterization of time-dependent magnetic fields generated by eddy currents after switching gradients. For an on-line determination variations fields, we extract two terms from unresolved signal extended sample, describing time evolution a frequency shift γΔB(z)(t) decay constant k(t). This procedure allows us to optimize interactively multiexponential pre-emphasis as well any spectral volume selection method with respect currents. Additionally, suggest imaging sequence which determine distribution current at chosen time-point gradient be tested. Expansion these into spherical harmonic functions proves existence higher order terms, cannot corrected standard device, where constants amplitudes are adjusted on X, Y, Z, Z0 coils. The proposed numerical analysis gives tool characterize magnet/gradient system quantitatively performance.