Study on Beam Emittance Growth Induced by Spherical Aberration of Solenoid Lens

The solenoid lens are effective for focusing the low energy beam, but the beam efficiency decreases with the beam emittance growth, which increases with the spherical aberration of solenoid lens. Emittance growth due to spherical aberration of solenoid lens was studied in both theory and simulation in this paper. The results show that emittance growth is mainly dominated by the beam envelope in lens and magnetic strength of lens. Optimizing the magnetic field uniformity of solenoid lens, which decides the aberration coefficient, can reduce the spherical aberration and enhance the quality of beam to an extent.