Abstract: A NMR-CT magnet model with scale 1/6 is now being assembled at our laboratory.3.5kG central field is generated by permanent magnet and evenness of field within the cylinder of 0.02083m radius is 1426×10^-6. In order to improve the field evenness,we changed the shape of magnetic pole,increased the iron content at the edge of pole face. Consequently,the evenness of field in the same range increases by a factor of 16.5,i.e. 86.4×10^-6 is obtained.Comparing with other methods,it is very simple and showes a significant improvement in the evenness.

Key words: magnet, field evenness