DESIGN OF AN UNDULATOR FOR ACO AND ITS POSSIBLE USE AS FREE-ELECTRON LASER

An undulator is under construction to be installed on the A. C. O. storage ring at Orsay. This device is planned to have a short period (4 cm) with a total length of 1 m. To achieve a maximum field of 0. 4 T on the axis of the system, a superconducting system has been chosen. With A. C. O. running between 540 MeV and 140 MeV, the fundamental wavelength could be tuned from 120 A to 5300 A and the brightness of the undulator is expected to be about 500 times greater than the brightness in normal bending magnets in the same conditions. In the blue and near UV, the gain of the undulator is calculated to be of the order of 0. 3% which is a lower limit of lasing action.