Higher order momentum compaction in electron storage rings and capabilities for the generation of coherent synchrotron radiation

Various electron storage rings undertake strong efforts to create very short bunches. This serves the generation of coherent synchrotron radiation (CSR) and the use of extremely short pulses in time resolved X-ray spectroscopy. Recently built machines explore the capabilities arising from controlling higher orders of the momentum compaction factor (α=α0+α1δ+α2δ2..) that strongly dominates the longitudinal beam dynamics. The Metrology Light Source (MLS) is the first electron storage ring that uses additional sextupoles and octupoles to control the three leading terms of α. The resulting possibilities and some first experimental results are given.