Abstract
In order to get a short wavelength free electron laser (FEL), higher harmonic gain has been analyzed for an FEL using a hybrid planar wiggler with a period of 20 mm. This type wiggler consisting of ferromagnetics and permanent magnets is most convenient and gives the strong field including some higher harmonic components by selecting proper sizes of these magnetic materials. A certain modification of magnetic field distribution is accomplished by small gap length of the wiggler and small width of permendur as a ferromagnet. Gain analysis of FEL shows that higher harmonic gains exceed that of the fundamental for a very high magnetic field and suggests that for high wiggler field of K>1-1.6, higher harmonic gains are improved primarily dUe to its strong field and for low wiggler field of K<1-1.6, gain improvements are mainly due to the modification of the wiggler field distribution.
