R1.2 MEMER SYMMETRIC DOUBLE FOCUSING HIGH MAGNETIC INDUCTION, HIGH RESOLVING POWER ANALYZING MAGNET

R 1.2 meter, 90°deflecting, symmetric double focusing high magnetic induc-tion, high resolving power analyzing magnet was bui1t, using approximateRogowski pole contour to overcome the local magnetic saturation, the max.magnetic induction>1. 8 T. The mass resolving power≥208. The non--homogeneityof the magnetic field is less than±4×10~(-4) when the magnetic induction≤1.008 T.The measured results of the extended fringing fields of this magnet indicate:When the magnetic induction changes from 0.4 to 1.5 T, the variations of thevirtual field boundaries of the extended fringing field, So, are less than 0.006 g_0(g_0=40 mm, the gap of the magnetic pole), the integrals I_1 and I_2 are less than0.028 and 0.006 respectively. The first-order corrections and second-order aberration calculations werecarried out. in the case of entrance and exit angles are equal to 27.13°, thesymmetric double focusing can be realized and by using concave shape exit poleedge with radius of 1443 mm, the second-order aberrations can be furtherreduced. The lead isotope ions ~(204)Pb~+, ~(206)Pb~+, ~(207)Pb~+ and ~(208)Pb~+ can be separatedclearly, the beam current of ~(208)Pb~+ reaches 10 μA on the target, so heavy elementisotope ion implantation is practicable.