• F. Ewald
  ESRF, Grenoble

An additional electron beam emittance measurement at the ESRF storage ring is now installed that uses X-ray radiation from an undulator. The method consists in detecting the monochromatic spatial profile of the fifth harmonic of the undulator spectrum. The photon energy is roughly 30 keV, selected with a single bounce (3,1,1) Si monochromator. The X-rays are converted to visible light using a scintillating screen which is then imaged to a CCD camera. The emittance value is deduced from the image size, source distance, and the beta-function at the source point, taking into account the precisely known photon beam divergence. The direct use of undulator radiation is advantageous in terms of the precise knowledge of the source position and lattice parameters in the straight section. For this reason this device will find its main application as a horizontal emittance monitor with improved absolute precision compared to that of the pinhole cameras which are making use of bending magnet radiation. This paper will present the details of the method, the setup and the obtained results.