On-line measurement of magnetic fields at GANIL

On-line measurement of the magnetic fields of electromagnets at GANIL (France) was studied and developed. This type of measurement is necessary for it allows the adjustment and the monitoring of the parameters which control the transport of particle beams from the accelerators to the experimental vaults. The developments were based on nuclear magnetic resonance (NMR) magnetometers and Hall-effect magnetometers. The limitations of operating NMR probes in inhomogeneous fields required particular solutions. Techniques of positioning and appropriate compensation for field gradients were put in place. NMR probes and Hall-effect probes are integrated into the electronics for monitoring and control according to the defined standards at GANIL. The unit comprises instrumentation which perfectly meets the needs, particularly from the point of view of the measurement and the monitoring of the magnetic parameters. (author)