We are proposing a small electron storage ring dedicated to the production of coherent far-infrared and THz radiation at the ALS. We have been exploring coherent synchrotron radiation (CSR) and have determined conclusively that such a machine is entirely feasible. CIRCE (Coherent InfraRed CEnter) will be a revolutionary source for a traditionally difficult spectral region at the border between optics and electronics, namely the THz-gap.

Most synchrotron light sources require a large floor space outside the main ring to accommodate long x-ray beamlines. However, IR beamlines require relatively little space and prefer to be located as close to the source as possible. Given the layout of the ALS facility as shown above, the ideal location for an IR ring is on top of the booster shielding. The minimum circumference of a ring that fits on the existing shielding is about 65 m. Full energy injection to the ring can be done from the booster without interfering with injection to the main ring, even under continuous top-off operation.