Lau, W.K. Chou, M.C. Huang, N.Y. Lee, A.P. Wu, J. JACoW Geneva, Switzerland 978-3-95450-179-3 10.18429/JACoW-FEL2017-TUP031 English 309-312 TUP031 ion electron linac dipole FEL Contribution to a conference proceedings 2018 2018-02 https://doi.org/10.18429/JACoW-FEL2017-TUP031 http://jacow.org/fel2017/papers/tup031.pdf A nonlinear bunch compressor has been designed for the proposed NSRRC VUV FEL facility. It is a double dog-leg configuration that provides a first order longitudinal dispersion function (i.e. R56) with a sign opposite to that of a conventional four-dipole chicane. A large variation in the bunch length or the peak current for various operation conditions can be done by tuning R56. This can be realized by changing the longitudinal positions of the outside dipoles and adjusting the quadrupoles and sextupoles settings for desired bunch compression. Residual energy chirp left after bunch compression as revealed from ELEGANT simulation can be corrected by a capacitive dechirper structure when the bunch is slightly over-compressed.