A New OTR Based Beam Emittance Monitor for the Linac of LURE

An electron beam emittance diagnostic has been designed and built at the Linear Accelerator of Orsay, injector of Super-ACO and DCI Storage Rings. It is based on the Optical Transition Radiation produced at the interface of a 15 µm aluminium foil, which is located in the beam path. Measurement of the energy, divergence and transverse profiles of the beam can be done in a single shot, thanks to two cooled cameras. 1D and 2D methods for fitting the data are used. Emittance measurement results for a 10 nC beam at 25 Hz and 200 MeV are given, and then compared with those obtained with the “three gradients” method. We conclude that the 1D method, although attractive, is incompatible with a precision better than 100 %.