HIGHLY SENSITIVE BEAM SIZE MONITOR FOR pA CURRENTS AT THE MLS ELECTRON STORAGE RING

For the operation of the Metrology Light Source (MLS) [1], the electron storage ring of the PhysikalischTechnische Bundesanstalt (PTB), as a primary radiation source standard all storage ring parameters have to be known absolutely. For the measurement of the electron beam size and the control of the stability of the orbit location a new imaging system has been set up, that operates at very different intensity levels covering more than 11 decades, given by the variation of the electron beam current. The system uses a commercial zoom lens for the achromatic optical imaging of the electron beam source point onto two different camera systems. One camera system is for life-imaging of the source point at electron beam currents from 200 mA down to some μA. The second system is a cooled CCD-camera that allows imaging of the electron beam source size and location at very low currents, down to only one stored electron.