Source size and emittance monitoring on BESSY II

Three optical monitors image the transverse cross section of the electron beam at BESSY II. The emittance of the electron beam can be determined from source images generated by hard X-ray pinhole cameras without additional measurement of the energy width of the beam. Vertical emittance changes down to 3 pmrad can be detected. Typical emittance values of 5<εx<6 nmrad horizontal and of εy<1 0 0 pmrad vertical are provided in user runs with up to 300 mA ring current. These results agree with higher resolution measurements of the Bragg–Fresnel telescope. Measurements of the source size versus ring current as well as the influence of feedbacks and the relation between emittance coupling and the properties of undulator radiation are given.