Observation of coherent synchrotron radiation from a 1 mm electron bunch at the MAX-I storage ring

The coherent generation of synchrotron radiation by an electron storage ring is predicted for wavelengths equal to or longer than the electron bunch length. With typical bunch lengths of approximately 1 cm, diffraction and chamber-screening effects have so-far blocked observation of coherent radiation from a conventional radiation beam line. In the low-energy, second-generation light source MAX-I, the magnet lattice has been tuned to a small momentum compaction factor, allowing rms bunch lengths as short as 1 mm. Here we report the coherent emission phenomena observed from such a bunch at the infrared beam line attached to the MAX-I ring.