Compensation of bend-plane emittance growth in a 180 degree bend

Emittance preservation in beam bending systems is vitally important in the production of bright, high-current electron microbunches. Generally, the emittance increase occurs in the bend plane and results from changes in the microbunch energy distribution as the beam transits the bend. This redistribution of electron energies increases the beam´s divergence, and hence the emittance, by spoiling the achromatic transport of the bending system. In this paper we investigate the correlated emittance growth in a 180 degree isochronous bend due to coherent synchrotron radiation (CSR). Introducing sextupole fields in the high dispersion region of the bend partially cancels the CSR-induced correlation thereby reducing the bend plane emittance growth. The generalization of this emittance compensation scheme is discussed