Optimization of cylindrical ion trap is to be done for testing low mass ions such as H2+, H3+ ,He+. The principle of optimization is reducing the higher order fields, not the “-10% compens- ation” rule introduced by R.Graham Cooks. The model of CIT is built by CST. The best z0 is obtained when r0=10mm. At last, the MS of Hydrogen and Helium shows the optimization is successful.
