Zhu, JB (reprint author), CAS, Inst High Energy Phys, Beijing 100049, Peoples R China.
Short and ultra-short bunch length measurement technique is one of the key techniques used to develop the short wavelength FEL and advanced accelerators. Off-line test experiment on a newly-developed bunch-length diagnostic device was implemented with the far-IR radiation emitted from a black body radiator instead of far-IR to mm wave coherent transition radiation generated by a train of micro-bunches, and got a good antocorrelation interferogram. The experiment showed that its hard and soft-ware worked as good as expected. Through a fine collimation, the well-modulated interferogram can be obtained. Further improvements are put forward.