Miniature ionization chamber detector developed for X-ray microprobe measurements

A windowless small ionization chamber detector has been developed for monitoring the intensity of the microbeam at the ID18F microprobe end-station of the European Synchrotron Radiation Facility. The small dimensions of the ionization chamber (10 mm along the beam direction and 5 mm perpendicular to it) make it possible to place it very close to the sample. A pinhole of diameter 50 microm was used for defining the entrance window of the ionization chamber; thus the small counter can be used as an order-selecting aperture while measuring simultaneously the intensity after the aperture. In the present work the technical characteristics, such as the current-voltage curve, stability and linearity, of the small monitor have been tested.