MAGNETIC FIELD ANALYSIS OF PERMANENT MAGNET UNDULATOR

2 Dimensional magnetic field expression of permanent magnet undulator with gradually varied magnetization is derived. Conditions for minimizing high order harmonics are given. Three different types of permanent magnet undulator —— the "gradually varied" type, mixed type and simple type ——are compared. Upon these comparisions we conclude that "gradually varied" type is superior to mixed type except for Δh/λ0.1.