Bunch-lengthening theory including wiggler effects

The bunch-lengthening phenomenon results from one of the most severe single-bunch instabilities in electron storage rings. There are many theories explaining the bunch-lengthening and the associated longitudinal microwave instability. But none of them are totally satisfactory. In this paper, based on one bunch-lengthening theory, a new bunch-lengthening formula is established, where the wiggler's effect is taken into account. The effectiveness of this formula is checked on the CESR ring and then applied to the International Linear Collider damping ring.