Measurement and adjustment of CIAE medical cyclotron magnet

A 30 MeV compact cyclotron used for medical radioactive isotope production is in construction. A program controlled mapping instrument with accuracy 10-4 was developed. Its probe moves automatically in the 30 mm gap covering a circular area more than 1600 mm in diameter. It makes the mapping efficiency and accuracy. An iteration method was used for both hamonic and average field shimming. The results were so good that made the first hamonic decrease from more than 10 guass to about 5 guass in most of the radius and from 70 guass to about 10 guass in the central region. Meanwhile the total phase shift which represents the isochronous, decrease from more than ±90 degrees to about ±20 degrees