Fast field mapping device for cyclotron magnets

The S.I.N. ring injector cyclotron has four sector magnets. For fast and accurate magnetic field measurements a new type of measuring system has been developed. The magnetic field of the sector magnets is measured in polar coordinates. The standard field map covers a range in radial direction from 240 mm to 3800 mm and in azimuthal direction from - 47 deg. to + 47 deg. in steps of 20 mm and 1/4 deg., respectively. (Corresponding to approx. 70'000 measurement points). Two Hall probes are mounted on a carriage which follows a meandric track. The data are taken in the "flying" mode, i.e. two fast DVM's read the values while the carriage is moving at an average speed of approx. 25 cm/ sec. The measuring procedure is controlled on line by small computer system and is carried through fully automatically within roughly 2 1/2 hours. The process control software contains diagnostic routines for surveying the system operation as well as routines for a smoothing check of the measured data which are written on a magnetic tape at the end of each radial track. The achieved measurement accuracy lies at approx. 1 Gauss at the field level (in the air gap) of 11 kGauss, while the positioning accuracy of the probes is in the order of ± 0.1 mm (radial and vertical) and ± 0.01 deg. (azimuthal).