Results of Reconstruction of U400M Cyclotron Magnetic Structure

U400M isochronous cyclotron was create on the base of U300 classic cyclotron and is under operation at FLNR, JINR since 1996. U400M cyclotron is intended for accelerating the ion beams with A/Z= 2.286 – 9 to energy W = 80 – 6 MeV/nucl. Cyclotron have H-type main magnet with 4-meter pole diameter and 4 pairs of spiral type sectors. In 2022 year, the reconstruction of cyclotron magnetic structure was held on. The reconstruction included the replacement of magnet main coil, mapping and correction of cyclotron magnetic field. In the frame of the mapping, the magnetic field was corrected to improve its average radial distribution and to compensate the first harmonic. For cyclo- tron magnetic field mapping the automatic measurement system, based on 14 Hall probes, was used.