THE LELA UNDULATOR : MAIN FEATURES AND PERFORMANCE

Abstract
The LELA plane undulator installed on Adone is a 20 period normal conducting electromagnet ; the wavelength is 11.6 cm and the magnetic field can be as high as 5.0 kG on axis. It is tunable over the entire field range. The measured field has an almost ideal cosine-like behaviour longitudinally ; the large transverse dimension of the poles (34.8 cm) ensures a large magnetic field flat top radially. The excellent field quality is confirmed by the measured spontaneous radiation spectral lines which exihit a purely homogeneous bradening. An other important feature is the possibility of rearranging the field pattern to produce for instance an Optical Klystron configuration by simply reversing the current flow in some of the coils. All the above advantages are obtained at the expense of a rather high power consumption at the normal operating point : 500 kW at B = 4.5 kG. The consequent thermal drift causes a drift in the field that has to be compensated by means of a feed-back system. The system utilizing a Hall plate has demonstrated to work satisfactory and allows the magnetic field setting to be accurately reproduced and kept constant to within the required precision.