In situ high-speed synchrotron X-ray beam profiling and position monitoring

To take advantage of the very low source emittance of third generation radiation sources high-resolution in situ X-ray beam monitors are required in order to keep the X-ray beam focussed and incident on the sample. We present a compact device based on a linear photodiode array. It consists of relatively few diodes that measure the spatially resolved scattered X-rays from a thin polymer foil placed in the beam path. The device is vacuum compatible, inexpensive and radiation hard. The scattered X-rays are incident on a strip of photodiodes that are connected to a dedicated multi-channel charge-sensitive read-out chip. Test experiments performed at the European Synchrotron Radiation Facility (ESRF) show, that even at a relatively low-intensity bending magnet beam line, X-ray beam position and profiles are obtained extremely fast and precise.