Control of Emittance Growth in a Bunch Compressor for the International Linear Collider

We present a short two-stage bunch compressor system that has been selected as an alternative design in the ILC (International Linear Collider). The designed bunch compressor system has two rf sections and two chicanes in which each chicane consists of four bending magnets. Each bunch compressor stage includes a 34 m lattice of bending magnets that is relatively short compared to the baseline design with a 150 m lattice in the ILC. Beams with bunch length of 6 mm rms and 9 mm rms can be compressed to 0.15 mm rms and 0.3 mm rms in the bunch compressor system, respectively. We show the optimized parameters of the bunch compressor system and results of transverse and longitudinal beam trackings in the compressor system. We examined the influences of coherent and incoherent synchrotron radiations in the chicanes on the transverse emittance. Control of the emittance growth due to machine errors is an important issue in the performance of the bunch compressor. Thus, we performed the lattice corrections such as corrections of orbit distortion, dispersion function and skew component to control the emittance growths due to several machine errors in the bunch compressor system. It is shown that the system is error tolerant and the lattice corrections are very effective to suppress growth of the emittance in the bunch compressor system.