为了把氘核的能量从原来的13.6MeV提高到16.0MeV，相应的中心磁感应强度应从原来的14.61kGs提高到16.00kGs。由于磁感应强度提高，磁场边缘效应显著。原来使用的垫片（外环、内环、圆盘）均应变换，需重新进行磁场填补，以满足回旋加速器对磁场的要求。

This paper describes the shimming readjustment of a 1.2 meter cyclotron as its central magnetic field was raised from 14.6kGs to 16.0kGs. Using a model magnet on the scale of 1:5 we selected the optimum sizes of shims. A table is listed for comparison of the measured results of the magnetic field drop between the model and the full scale magnet with similar shapes of shims. The magnetic field contributions by the different sizes of shims were evaluated.

The internal and external H

2

+

beams obtained were 15×100µA and 5×100µA respectively. Therefore

the result of the shimming readjustment proved satisfactory.